EVALUATION AND IMPROVEMENTS OF CONTOUR-BASED ACCESSIBILITY MEASURES PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND

uef.fi

PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND

Dissertations in Forestry and Natural Sciences

ISBN 978-952-61-2102-4ISSN 1798-5668


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XAVIER ALBACETE

EVALUATION AND IMPROVEMENTS OF CONTOUR-BASED ACCESSIBILITY MEASURES


Xavier Albacete (February 11th 1986,

Barcelona, Catalonia). The author’s interests are focused on multidisciplinary research

aiming at explaining the dynamics in the urban environment in order to promote socially and

environmentally sustainable cities.

Accessibility relates the transport network and urban space for measuring the feasibility of the citizens in reaching their destinations.

This thesis evaluates the most commonly used type of accessibility measures: contour-based

measures and proposes ways to improve them.

XAVIER ALBACETE

XAVIER ALBACETE

Evaluation andimprovements of

contour-based accessibilitymeasures

Publications of the University of Eastern FinlandDissertations in Forestry and Natural Sciences

No 221

Academic DissertationTo be presented by permission of the Faculty of Science and Forestry for public

examination in the Auditorium SN200 in Snellmania Building at the University ofEastern Finland, Kuopio, on June, 28th, 2016,

at 12 o’clock noon.

Department of Environmental and Biological Sciences

Grano

Jyväskylä, 2016

Editor: Prof. Pertti Pasanen

Distribution:

University of Eastern Finland Library / Sales of publications

[email protected]

http://www.uef.fi/kirjasto

ISBN: 978-952-61-2102-4 (printed)

ISSNL: 1798-5668

ISSN: 1798-5668

ISBN: 978-952-61-2013-1 (pdf)

ISSNL: 1798-5668

ISSN: 1798-5676

Author’s address: Xavier Albacete, M. Sc.University of Eastern FinlandDepartment of Environmental and Biological SciencesResearch Group of Environmental InformaticsP.O.Box 162770211 KUOPIOFINLANDemail: [email protected]

Supervisors: Professor Mikko Kolehmainen, Ph.D.University of Eastern FinlandDepartment of Environmental and Biological SciencesResearch Group of Environmental InformaticsP.O.Box 162770211 KUOPIOFINLANDemail: [email protected]

Reviewers: Professor Mari Vaattovaara, Ph.D.University of HelsinkiDepartment of GeographyP.O.Box 6400014 HELSINKIFINLANDemail: [email protected]

Professor Kevin Krizek, Ph.D.University of Colorado BoulderEnvironmental Studies ProgramEnvironmental Design BuildingBoulder, COLORADOUSAemail: [email protected]

Opponent: Professor Karst Geurs, Ph.D.University of TwenteCentre of Transport StudiesTWENTENETHERLANDSemail: [email protected]

Grano

Jyväskylä, 2016

Editor: Prof. Pertti Pasanen

Distribution:

University of Eastern Finland Library / Sales of publications

[email protected]

http://www.uef.fi/kirjasto

ISBN: 978-952-61-2102-4 (printed)

ISSNL: 1798-5668

ISSN: 1798-5668

ISBN: 978-952-61-2013-1 (pdf)

ISSNL: 1798-5668

ISSN: 1798-5676

Author’s address: Xavier Albacete, M. Sc.University of Eastern FinlandDepartment of Environmental and Biological SciencesResearch Group of Environmental InformaticsP.O.Box 162770211 KUOPIOFINLANDemail: [email protected]

Supervisors: Professor Mikko Kolehmainen, Ph.D.University of Eastern FinlandDepartment of Environmental and Biological SciencesResearch Group of Environmental InformaticsP.O.Box 162770211 KUOPIOFINLANDemail: [email protected]

Reviewers: Professor Mari Vaattovaara, Ph.D.University of HelsinkiDepartment of GeographyP.O.Box 6400014 HELSINKIFINLANDemail: [email protected]

Professor Kevin Krizek, Ph.D.University of Colorado BoulderEnvironmental Studies ProgramEnvironmental Design BuildingBoulder, COLORADOUSAemail: [email protected]

Opponent: Professor Karst Geurs, Ph.D.University of TwenteCentre of Transport StudiesTWENTENETHERLANDSemail: [email protected]

ABSTRACT

Accessibility measures have enjoyed increasing usage among urban plan-ners, policy makers and, more recently, ordinary citizens with real travelapplications. The decreased sedentary lifestyle among citizens, reduc-tion of air and noise pollution, economic optimization of new urbanand transport developments or optimization of the resources investedin public services are some examples of relevant goals for the urban ar-eas of the present day. Accessibility measurement describes the relationbetween land use, transportation and citizens’ use of the opportunitiesin the urban area. However, not all types of accessibility measures ap-proach that relation under the same prism, and their data and computa-tional requirements differ in the same manner.

Among accessibility measures, contour-based accessibility measuresare the most widely used. Contour-based accessibility measures are asub-type of location-based (or activity-based) measures, valued by theireasily interpretable outcome and low data requirements. However, in-dividual and temporal components have not been clearly addressed forcontour-based measures. This is to say, to adapt contour-based accessi-bility measures in order to able them to reflect these components. Ad-ditionally, several authors have pointed out the limitations from the useof threshold values in these kind of measures. An evaluation of theselimitations and potential improvements would order and optimize theirfuture usage.

This thesis firstly outlines the literature of accessibility measures andfocuses on contour-based accessibility measures. The current work eval-uates the main limitations of contour-based measures and proposes thepossibilities for integrating individual components (needs, abilities andopportunities of each individual) as well as their capability for overcom-ing the limitations from the use of threshold values.

The evaluation is done using contour-based measures in three ap-plications. These applications are reviewed and the contribution of thepapers on them is indicated. Firstly, as a tool for selecting the residentialarea. Secondly, as an indicator of sustainable transport mobility. Finally,as a tool for the spatial optimization of the services in the urban areas. Inthe first application, a cumulative index is proposed based on the livingpriorities from citizens; in the second study, the Structural Accessibility

Layer (SAL) and Public Transport and Walking Accessibility Index (PT-WAI) are compared and evaluated with local experts; and in the thirdpaper, SAL is modified in order to express accessibility categories foreach population cohort.

The current work proposes, through the practical cases presented inthe papers, how an individual component can be included in contour-based measures. The papers presented in the current thesis brings us tothe overall conclusion that the contour-based measures can express theindividual component by gathering individual level data and by merg-ing individual accessibility measures. However, individual accessibilitymeasures using contour-based measures are too constrained for dataneeds and heavy computation. Regarding the limitations from the useof threshold values in the measures, the results from the papers showthat its bias can be partially corrected by using a fine spatial resolutionof the case study area, compiling from actual travel behaviour specificthreshold values for different population groups and by using as manycategory indexes as possible within the threshold values in order to ap-proximate the measure to a potential measure.

In conclusion, the current thesis shows that although limitations incontour-based accessibility measures cannot be totally overcome, someprocedures can help to minimize its limitations while keeping its advan-tages.

ABSTRACT

Accessibility measures have enjoyed increasing usage among urban plan-ners, policy makers and, more recently, ordinary citizens with real travelapplications. The decreased sedentary lifestyle among citizens, reduc-tion of air and noise pollution, economic optimization of new urbanand transport developments or optimization of the resources investedin public services are some examples of relevant goals for the urban ar-eas of the present day. Accessibility measurement describes the relationbetween land use, transportation and citizens’ use of the opportunitiesin the urban area. However, not all types of accessibility measures ap-proach that relation under the same prism, and their data and computa-tional requirements differ in the same manner.

Among accessibility measures, contour-based accessibility measuresare the most widely used. Contour-based accessibility measures are asub-type of location-based (or activity-based) measures, valued by theireasily interpretable outcome and low data requirements. However, in-dividual and temporal components have not been clearly addressed forcontour-based measures. This is to say, to adapt contour-based accessi-bility measures in order to able them to reflect these components. Ad-ditionally, several authors have pointed out the limitations from the useof threshold values in these kind of measures. An evaluation of theselimitations and potential improvements would order and optimize theirfuture usage.

This thesis firstly outlines the literature of accessibility measures andfocuses on contour-based accessibility measures. The current work eval-uates the main limitations of contour-based measures and proposes thepossibilities for integrating individual components (needs, abilities andopportunities of each individual) as well as their capability for overcom-ing the limitations from the use of threshold values.

The evaluation is done using contour-based measures in three ap-plications. These applications are reviewed and the contribution of thepapers on them is indicated. Firstly, as a tool for selecting the residentialarea. Secondly, as an indicator of sustainable transport mobility. Finally,as a tool for the spatial optimization of the services in the urban areas. Inthe first application, a cumulative index is proposed based on the livingpriorities from citizens; in the second study, the Structural Accessibility

Layer (SAL) and Public Transport and Walking Accessibility Index (PT-WAI) are compared and evaluated with local experts; and in the thirdpaper, SAL is modified in order to express accessibility categories foreach population cohort.

The current work proposes, through the practical cases presented inthe papers, how an individual component can be included in contour-based measures. The papers presented in the current thesis brings us tothe overall conclusion that the contour-based measures can express theindividual component by gathering individual level data and by merg-ing individual accessibility measures. However, individual accessibilitymeasures using contour-based measures are too constrained for dataneeds and heavy computation. Regarding the limitations from the useof threshold values in the measures, the results from the papers showthat its bias can be partially corrected by using a fine spatial resolutionof the case study area, compiling from actual travel behaviour specificthreshold values for different population groups and by using as manycategory indexes as possible within the threshold values in order to ap-proximate the measure to a potential measure.

In conclusion, the current thesis shows that although limitations incontour-based accessibility measures cannot be totally overcome, someprocedures can help to minimize its limitations while keeping its advan-tages.

Preface

This doctoral thesis is not only the result of professional and intellectualwork but, what is important, an entire life experience of the discovery ofa new society and myself.

Like all achievements in life, the result cannot and should not be re-lated to a single ability or circumstance. I believe that this achievementis thanks to multiple contributors that have influenced and supportedme and my work. I would never have discovered the desire for knowl-edge and the curiosity about the urban environment if I had not metJoan Tort. He has been so inspiring, encouraging and supportive; with-out doubt he could be considered as the intellectually "guilty party" andpromoter of this work. So gràcies Joan! Additionally, I would like tothank my supervisor Mikko Kolehmainen for all the support, often fur-ther than the strictly professional. He bet on me and took the risk of it.Thanks too to all the colleagues that shared with me so many hours atwork; with special consideration for Jukka Saarenpää, Matti Mononenand Doina Olaru for their practical advice.

However, I would never have been able to cope without the help,support and love of those closest to me, those living far away from me,my family and friends. They have been a mirror to look at myself andkeep a reference of my own evolution. Among them, my most specialthanks, with all my love to my sister Núria Albacete and my brother-in-law Andrea Rinaldi. Life has put us in similar circumstances andsharing the experience and caring of each other has been of great helpthrough this time. This is also because and thanks to you! Gràcies,grazie! Thanks to my parents for investing in education for me, it isadmirable to be able to foresee a better future for your children whenyou did not have the same opportunity for yourself. Among all friendsand co-workers that I have met here in Finland and that I cannot nameall here; I would like to give my special thanks to three friends whohave been as brothers and sister here. These friends have shown anincredible capability for loving, they gave the fuel to carry on in manydimensions of my life. So thanks Marc Cerrada, Sirke Sormunen andMikko Miettinen. I love you. I am sure that I am here because of you

Preface

This doctoral thesis is not only the result of professional and intellectualwork but, what is important, an entire life experience of the discovery ofa new society and myself.

Like all achievements in life, the result cannot and should not be re-lated to a single ability or circumstance. I believe that this achievementis thanks to multiple contributors that have influenced and supportedme and my work. I would never have discovered the desire for knowl-edge and the curiosity about the urban environment if I had not metJoan Tort. He has been so inspiring, encouraging and supportive; with-out doubt he could be considered as the intellectually "guilty party" andpromoter of this work. So gràcies Joan! Additionally, I would like tothank my supervisor Mikko Kolehmainen for all the support, often fur-ther than the strictly professional. He bet on me and took the risk of it.Thanks too to all the colleagues that shared with me so many hours atwork; with special consideration for Jukka Saarenpää, Matti Mononenand Doina Olaru for their practical advice.

However, I would never have been able to cope without the help,support and love of those closest to me, those living far away from me,my family and friends. They have been a mirror to look at myself andkeep a reference of my own evolution. Among them, my most specialthanks, with all my love to my sister Núria Albacete and my brother-in-law Andrea Rinaldi. Life has put us in similar circumstances andsharing the experience and caring of each other has been of great helpthrough this time. This is also because and thanks to you! Gràcies,grazie! Thanks to my parents for investing in education for me, it isadmirable to be able to foresee a better future for your children whenyou did not have the same opportunity for yourself. Among all friendsand co-workers that I have met here in Finland and that I cannot nameall here; I would like to give my special thanks to three friends whohave been as brothers and sister here. These friends have shown anincredible capability for loving, they gave the fuel to carry on in manydimensions of my life. So thanks Marc Cerrada, Sirke Sormunen andMikko Miettinen. I love you. I am sure that I am here because of you

and thanks to you, so please, take it as your own success as persons andfriends.

My academic background and the living conditions have made thisexperience harder than I originally expected. I needed to start almostfrom zero and at the same time deal with rebuilding a new life in aforeign land. Through all the period of my doctoral studies there havebeen three statements in relation with the academic improvement whichhave been confirmed through time which might be useful for futurestudents to come and that I want to share here. First, one PhD studenttold me at the beginning that a PhD is "a process that you will learn on theway". That has been clearly a total truth. Second, my supervisor oncetold me "do not worry, anybody that studies the same subject for 5 years endsup being an expert in it". Even if it may sound a bit harsh, it gave me thehope to be able to achieve a certain knowledge level. Finally, a quotationfrom Socrates: "I know that I know nothing" has become my own themewhile moving forward with my studies.

On a personal level, I have learnt that "only in the total emotional,natural, soul, and cultural silence; one can listen to him(her)self and get to knowyourself better". It is a hard experience but very useful in my personalgrowth. Life and love is similar to a cactus, with its spikes. However,they store the few good moments to keep growing during the hard times.Luckily I found my source of water, thanks Joel for being the water.

Thanks to all of you!

Kuopio June 28, 2016 Xavier Albacete

LIST OF PUBLICATIONS

This thesis consists of the present review of the author’s work in thefield of the urban accessibility, focusing on contour-based accessibilitymeasures; and the following selection of the author’s publications:

I X. Albacete, K. Pasanen and M. Kolehmainen, “A GIS-based methodfor the selection of the location of residence,” Geo-Spatial Informa-tion Science , 1–6 (2012) doi: 10.1080/10095020.2012.708159.

II X. Albacete, D. Olaru, V. Paül and S. Biermann, “Measuring theAccessibility of Public Transport: a critical comparison betweenmethods in Helsinki” Applied Spatial Analysis and Policy, 1–28 (2015)doi: 10.1007/s12061-015-9177-8.

III X. Albacete, T. Toivonen, M. Salonen, P. Saarsalmi and M. Kolehmainen,“Resident group specific accessibility analysis and implications forthe Great Helsinki Region using Structural Accessibility Layer,”Case Studies on Transport Policy (2015)(submitted).

Throughout the overview, these papers will be referred to by their re-spective Roman numerals.

and thanks to you, so please, take it as your own success as persons andfriends.

My academic background and the living conditions have made thisexperience harder than I originally expected. I needed to start almostfrom zero and at the same time deal with rebuilding a new life in aforeign land. Through all the period of my doctoral studies there havebeen three statements in relation with the academic improvement whichhave been confirmed through time which might be useful for futurestudents to come and that I want to share here. First, one PhD studenttold me at the beginning that a PhD is "a process that you will learn on theway". That has been clearly a total truth. Second, my supervisor oncetold me "do not worry, anybody that studies the same subject for 5 years endsup being an expert in it". Even if it may sound a bit harsh, it gave me thehope to be able to achieve a certain knowledge level. Finally, a quotationfrom Socrates: "I know that I know nothing" has become my own themewhile moving forward with my studies.

On a personal level, I have learnt that "only in the total emotional,natural, soul, and cultural silence; one can listen to him(her)self and get to knowyourself better". It is a hard experience but very useful in my personalgrowth. Life and love is similar to a cactus, with its spikes. However,they store the few good moments to keep growing during the hard times.Luckily I found my source of water, thanks Joel for being the water.

Thanks to all of you!

Kuopio June 28, 2016 Xavier Albacete

LIST OF PUBLICATIONS

This thesis consists of the present review of the author’s work in thefield of the urban accessibility, focusing on contour-based accessibilitymeasures; and the following selection of the author’s publications:

I X. Albacete, K. Pasanen and M. Kolehmainen, “A GIS-based methodfor the selection of the location of residence,” Geo-Spatial Informa-tion Science , 1–6 (2012) doi: 10.1080/10095020.2012.708159.

II X. Albacete, D. Olaru, V. Paül and S. Biermann, “Measuring theAccessibility of Public Transport: a critical comparison betweenmethods in Helsinki” Applied Spatial Analysis and Policy, 1–28 (2015)doi: 10.1007/s12061-015-9177-8.

III X. Albacete, T. Toivonen, M. Salonen, P. Saarsalmi and M. Kolehmainen,“Resident group specific accessibility analysis and implications forthe Great Helsinki Region using Structural Accessibility Layer,”Case Studies on Transport Policy (2015)(submitted).

Throughout the overview, these papers will be referred to by their re-spective Roman numerals.

CONTRIBUTION OF THE AUTHOR

The publications included in the present dissertation are original re-search papers on accessibility measures. The research aim in all thepublications was that of the main author.

In all the publications, the author personally selected each of themethodologies used and performed all of the computational analysis.The data used for the analysis was provided by external sources andinstitutions; i.e. Statistics Finland, HSL, HSY and the University ofHelsinki.

Paper I was proposed, structured, calculated and written by XavierAlbacete, M. Sc.. Additionally, Kari Pasanen, M. Sc. collaborated forthe GIS visualization and Professor Mikko Kolehmainen had providedrelevant collaboration on the proposal of the mathematical basis for theproposed indexes in the paper.

In Paper II Professor Biermann, Dr. Paül and specially Dr. Olaruparticipated in the calculations and corrections of the paper. HSL andthe City of Helsinki offered external qualitative evaluation of the results.Xavier Albacete, M. Sc. was the main person responsible for the pro-posal, selection of methods, calculations and writing of the manuscript.

Finally, in Paper III collaboration in suggestions, data considerationsand paper corrections were provided by Professor Toivonen, Dr. Salonenand Professor Kolehmainen. Additionally, qualitative external evalua-tion was obtained from HSL and the City of Helsinki. Xavier Albacete,M. Sc. was responsible for the proposal of the paper, methods, calcula-tion and writing.

Contents

1 INTRODUCTION 11.1 Background and motivation of the study . . . . . . . . . . 11.2 Research problem and questions . . . . . . . . . . . . . . . 21.3 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 Structure of the dissertation . . . . . . . . . . . . . . . . . . 5

2 THEORETICAL CONTEXT OF CONTOUR-BASED ACCESSI-BILITY MEASURES 72.1 Accessibility definition and classification . . . . . . . . . . 7

2.1.1 Accessibility definition . . . . . . . . . . . . . . . . . 72.1.2 Accessibility classification . . . . . . . . . . . . . . . 92.1.3 Uses of accessibility . . . . . . . . . . . . . . . . . . 152.1.4 What is a good accessibility measure? . . . . . . . . 16

2.2 Contour-based accessibility measure . . . . . . . . . . . . . 182.2.1 Definition of contour-based accessibility measure . 182.2.2 Elements of contour-based accessibility measure . 192.2.3 Limitations and proposed solutions for contour-

based measures . . . . . . . . . . . . . . . . . . . . . 21

3 SUMMARY OF THE RESEARCH PAPERS 273.1 Contour-based measure for the selection of residence lo-

cation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283.2 Comparison of SAL and PTWAI as sustainable accessibil-

ity indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.3 Contour measures for management of public services . . . 31

4 CONCLUSION AND DISCUSSION 334.1 Summary of the results . . . . . . . . . . . . . . . . . . . . . 334.2 Contribution of the research . . . . . . . . . . . . . . . . . . 354.3 Evaluation of the research . . . . . . . . . . . . . . . . . . . 374.4 Future research . . . . . . . . . . . . . . . . . . . . . . . . . 37

CONTRIBUTION OF THE AUTHOR

The publications included in the present dissertation are original re-search papers on accessibility measures. The research aim in all thepublications was that of the main author.

In all the publications, the author personally selected each of themethodologies used and performed all of the computational analysis.The data used for the analysis was provided by external sources andinstitutions; i.e. Statistics Finland, HSL, HSY and the University ofHelsinki.

Paper I was proposed, structured, calculated and written by XavierAlbacete, M. Sc.. Additionally, Kari Pasanen, M. Sc. collaborated forthe GIS visualization and Professor Mikko Kolehmainen had providedrelevant collaboration on the proposal of the mathematical basis for theproposed indexes in the paper.

In Paper II Professor Biermann, Dr. Paül and specially Dr. Olaruparticipated in the calculations and corrections of the paper. HSL andthe City of Helsinki offered external qualitative evaluation of the results.Xavier Albacete, M. Sc. was the main person responsible for the pro-posal, selection of methods, calculations and writing of the manuscript.

Finally, in Paper III collaboration in suggestions, data considerationsand paper corrections were provided by Professor Toivonen, Dr. Salonenand Professor Kolehmainen. Additionally, qualitative external evalua-tion was obtained from HSL and the City of Helsinki. Xavier Albacete,M. Sc. was responsible for the proposal of the paper, methods, calcula-tion and writing.

Contents

1 INTRODUCTION 11.1 Background and motivation of the study . . . . . . . . . . 11.2 Research problem and questions . . . . . . . . . . . . . . . 21.3 Methodology . . . . . . . . . . . . . . . . . . . . . . . . . . 31.4 Structure of the dissertation . . . . . . . . . . . . . . . . . . 5

2 THEORETICAL CONTEXT OF CONTOUR-BASED ACCESSI-BILITY MEASURES 72.1 Accessibility definition and classification . . . . . . . . . . 7

2.1.1 Accessibility definition . . . . . . . . . . . . . . . . . 72.1.2 Accessibility classification . . . . . . . . . . . . . . . 92.1.3 Uses of accessibility . . . . . . . . . . . . . . . . . . 152.1.4 What is a good accessibility measure? . . . . . . . . 16

2.2 Contour-based accessibility measure . . . . . . . . . . . . . 182.2.1 Definition of contour-based accessibility measure . 182.2.2 Elements of contour-based accessibility measure . 192.2.3 Limitations and proposed solutions for contour-

based measures . . . . . . . . . . . . . . . . . . . . . 21

3 SUMMARY OF THE RESEARCH PAPERS 273.1 Contour-based measure for the selection of residence lo-

cation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283.2 Comparison of SAL and PTWAI as sustainable accessibil-

ity indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . 293.3 Contour measures for management of public services . . . 31

4 CONCLUSION AND DISCUSSION 334.1 Summary of the results . . . . . . . . . . . . . . . . . . . . . 334.2 Contribution of the research . . . . . . . . . . . . . . . . . . 354.3 Evaluation of the research . . . . . . . . . . . . . . . . . . . 374.4 Future research . . . . . . . . . . . . . . . . . . . . . . . . . 37

LIST OF FIGURES

2.1 Schematic diagram of the classification of accessibility mea-sures proposed by Geurs and van Wee (2004). Made bythe author. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.2 Marginal costs of accessibility for three location-based ac-cessibility measure. Made by the author. . . . . . . . . . . 18

4.1 Schematic diagram of the research questions presented inthe current thesis, papers and findings. Made by the author. 35

LIST OF TABLES

1.1 Summary of the approach of the research questions in thecurrent thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Accessibility classifications -: Measure not used in theclassification; ?: Measure not specified in the classifica-tion; and *: Measure used in the classification with one ofthe terminologies. . . . . . . . . . . . . . . . . . . . . . . . . 11

1 Introduction

1.1 BACKGROUND AND MOTIVATION OF THE STUDY

Ensuring a sustainable environment has become one of the main goalsin urban areas. A sustainable environment includes a sustainable socio-economic environment where all citizens have access to services; as wellas sustainable mobility where emissions could be reduced.

Accessibility measures have been used to describe access to servicesand promote sustainable mobility in urban areas. Accessibility calcu-lation is based on the spatial distribution of opportunities and a costmatrix to achieve them. Based on these two elements, accessibility mea-sures quantify the feasibility for citizens to attain the services by differ-ent transport modes.

Among accessibility measures, contour-based measures are widelyused due to their easy interpretation, low computing and data require-ments, while they deliver easy explanatory results (Baradaran and Ram-jerdi, 2001; Silva, 2008; Geurs and van Wee, 2004). Contour-based mea-sures are a sub-type of location-based (or activity-based) accessibilitymeasures. Location-based accessibility focuses on the spatial distribu-tion of the opportunities and the demand/costs of attaining them.

However, contour-based measures present three major limitations.Firstly, temporal and individual accessibility components are not inte-grated in the measure (Geurs and van Eck, 2001). As Geurs and van Wee(2004) and Wegener and Fürst (1999) have pointed out that the measureis not capable to reflect the previously mentioned components, and thisrepresents its main drawback. The lack of a direct integration of indi-vidual and temporal components, forces a generalization of accessibilitymeasures which might not correspond with the real travel behaviour ofthe population. The individual component is based on the needs, abili-ties and opportunities of each individual; while the temporal componentis based on the times when the opportunities are available and the abilityof the citizen to utilize them.

Secondly, the pre-established threshold value for travel cost assumeshomogeneity in travel behaviour among the group of citizens and through

Dissertations in Forestry and Natural Sciences No 221 1

LIST OF FIGURES

2.1 Schematic diagram of the classification of accessibility mea-sures proposed by Geurs and van Wee (2004). Made bythe author. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.2 Marginal costs of accessibility for three location-based ac-cessibility measure. Made by the author. . . . . . . . . . . 18

4.1 Schematic diagram of the research questions presented inthe current thesis, papers and findings. Made by the author. 35

LIST OF TABLES

1.1 Summary of the approach of the research questions in thecurrent thesis . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 Accessibility classifications -: Measure not used in theclassification; ?: Measure not specified in the classifica-tion; and *: Measure used in the classification with one ofthe terminologies. . . . . . . . . . . . . . . . . . . . . . . . . 11

1 Introduction

1.1 BACKGROUND AND MOTIVATION OF THE STUDY

Ensuring a sustainable environment has become one of the main goalsin urban areas. A sustainable environment includes a sustainable socio-economic environment where all citizens have access to services; as wellas sustainable mobility where emissions could be reduced.

Accessibility measures have been used to describe access to servicesand promote sustainable mobility in urban areas. Accessibility calcu-lation is based on the spatial distribution of opportunities and a costmatrix to achieve them. Based on these two elements, accessibility mea-sures quantify the feasibility for citizens to attain the services by differ-ent transport modes.

Among accessibility measures, contour-based measures are widelyused due to their easy interpretation, low computing and data require-ments, while they deliver easy explanatory results (Baradaran and Ram-jerdi, 2001; Silva, 2008; Geurs and van Wee, 2004). Contour-based mea-sures are a sub-type of location-based (or activity-based) accessibilitymeasures. Location-based accessibility focuses on the spatial distribu-tion of the opportunities and the demand/costs of attaining them.

However, contour-based measures present three major limitations.Firstly, temporal and individual accessibility components are not inte-grated in the measure (Geurs and van Eck, 2001). As Geurs and van Wee(2004) and Wegener and Fürst (1999) have pointed out that the measureis not capable to reflect the previously mentioned components, and thisrepresents its main drawback. The lack of a direct integration of indi-vidual and temporal components, forces a generalization of accessibilitymeasures which might not correspond with the real travel behaviour ofthe population. The individual component is based on the needs, abili-ties and opportunities of each individual; while the temporal componentis based on the times when the opportunities are available and the abilityof the citizen to utilize them.

Secondly, the pre-established threshold value for travel cost assumeshomogeneity in travel behaviour among the group of citizens and through


Evaluation and improvements of contour-based accessibility measures

time (Geurs and van Wee, 2004). The False Assumption of Older Co-hort Homogeneity (Davies and James, 2011) can be extrapolated for allpopulation cohorts; which questions the robustness of the accessibilityanalysis.

The third limitation is related to the selection of the threshold values.The accessibility measure is based on a threshold value obtained fromobserved travel behaviour, which inevitably partially contains a com-ponent of adaptation to the existing transportation infrastructure. Thisendogeneity makes the task of identifying deficiencies of the transportsystem more difficult. Additionally, this approach is based on an uni-directional flow of data; the value is obtained based on travel behaviourand then is transformed into the contour measure, leading to biases inthe results.

Therefore, it is expected that if temporal and individual componentswere integrated and if the limitations related with the threshold valuewould be overcome, contour measures would provide more robust re-sults.

The aim of this thesis is to investigate different alternatives to includethe individual component in contour-based measures, and to proposeways to overcome the limitations that stem from the usage of thresholdvalues. The methodology proposed in the different papers contemplatesthe integration of the individual component, as well as evaluating theeffects of the use of threshold values. Additionally, contour-based ac-cessibility measures are applied as a contribution for the three differentpurposes presented in each of the papers (see Figure 4.1).

1.2 RESEARCH PROBLEM AND QUESTIONS

The goal of this thesis is to contribute to the knowledge of contour-basedmeasures and propose alternatives for improving it. The empirical set-ting of the thesis is on contour-based measures as sustainable mobilityindicators; contour-based measures as a tool for selecting the place ofresidence; and contour-based measures as a tool for public services pol-icy.

In the current thesis, accessibility has been evaluated under a quanti-tative and qualitative focus. As exposed by several authors (e.g. Handyand Niemeier (1997); Tillema et al. (2003); Bertolini et al. (2005) or Páez

2 Dissertations in Forestry and Natural Sciences No 221

Introduction

et al. (2012)), there exists an objective accessibility which can be quanti-fied and a subjective accessibility which can be evaluated through qual-itative research. In that sense, the results presented in this thesis havebeen contrasted with socio-demographic data and with the opinions oflocal experts so that both approaches can be covered respectively.

This thesis addresses two main research questions, elaborated inmore detail below.

RQ 1 How to integrate the individual component into contour-basedaccessibility measures?

The first question focuses on the integration of the individual com-ponent into contour measures. This integration is based on adapt-ing the contour-based accessibility measure so that is able to reflectthe needs, abilities and opportunities of the citizen. The focus isplaced on evaluating previous integration proposals through ourapplied research. The evaluation is done based on external eval-uation and, additionally, by comparing the results to the generalcharacteristics for a good accessibility measure, extracted from theliterature.

RQ 2 Can the limitations from the usage of threshold values be over-come in contour-based accessibility measures?

The second research question aims at evaluating the limitations de-rived from the use of threshold values in contour-based accessibil-ity measures. Special focus is placed on overcoming the thresholdhomogeneity for population cohorts and on the use of observedtravel behaviour for fixing the threshold value. The evaluation ofthe research question is done through a review of the limitationsand proposals in the literature, and it is solved by proposing adap-tations in the papers presented in the thesis.

1.3 METHODOLOGY

The two research questions are tackled within three research papers.Table 1.1 presents the link between the research questions and the papersthat aimed at answering them.



time (Geurs and van Wee, 2004). The False Assumption of Older Co-hort Homogeneity (Davies and James, 2011) can be extrapolated for allpopulation cohorts; which questions the robustness of the accessibilityanalysis.

The third limitation is related to the selection of the threshold values.The accessibility measure is based on a threshold value obtained fromobserved travel behaviour, which inevitably partially contains a com-ponent of adaptation to the existing transportation infrastructure. Thisendogeneity makes the task of identifying deficiencies of the transportsystem more difficult. Additionally, this approach is based on an uni-directional flow of data; the value is obtained based on travel behaviourand then is transformed into the contour measure, leading to biases inthe results.

Therefore, it is expected that if temporal and individual componentswere integrated and if the limitations related with the threshold valuewould be overcome, contour measures would provide more robust re-sults.

The aim of this thesis is to investigate different alternatives to includethe individual component in contour-based measures, and to proposeways to overcome the limitations that stem from the usage of thresholdvalues. The methodology proposed in the different papers contemplatesthe integration of the individual component, as well as evaluating theeffects of the use of threshold values. Additionally, contour-based ac-cessibility measures are applied as a contribution for the three differentpurposes presented in each of the papers (see Figure 4.1).

1.2 RESEARCH PROBLEM AND QUESTIONS

The goal of this thesis is to contribute to the knowledge of contour-basedmeasures and propose alternatives for improving it. The empirical set-ting of the thesis is on contour-based measures as sustainable mobilityindicators; contour-based measures as a tool for selecting the place ofresidence; and contour-based measures as a tool for public services pol-icy.

In the current thesis, accessibility has been evaluated under a quanti-tative and qualitative focus. As exposed by several authors (e.g. Handyand Niemeier (1997); Tillema et al. (2003); Bertolini et al. (2005) or Páez


Introduction

et al. (2012)), there exists an objective accessibility which can be quanti-fied and a subjective accessibility which can be evaluated through qual-itative research. In that sense, the results presented in this thesis havebeen contrasted with socio-demographic data and with the opinions oflocal experts so that both approaches can be covered respectively.

This thesis addresses two main research questions, elaborated inmore detail below.

RQ 1 How to integrate the individual component into contour-basedaccessibility measures?

The first question focuses on the integration of the individual com-ponent into contour measures. This integration is based on adapt-ing the contour-based accessibility measure so that is able to reflectthe needs, abilities and opportunities of the citizen. The focus isplaced on evaluating previous integration proposals through ourapplied research. The evaluation is done based on external eval-uation and, additionally, by comparing the results to the generalcharacteristics for a good accessibility measure, extracted from theliterature.

RQ 2 Can the limitations from the usage of threshold values be over-come in contour-based accessibility measures?

The second research question aims at evaluating the limitations de-rived from the use of threshold values in contour-based accessibil-ity measures. Special focus is placed on overcoming the thresholdhomogeneity for population cohorts and on the use of observedtravel behaviour for fixing the threshold value. The evaluation ofthe research question is done through a review of the limitationsand proposals in the literature, and it is solved by proposing adap-tations in the papers presented in the thesis.

1.3 METHODOLOGY

The two research questions are tackled within three research papers.Table 1.1 presents the link between the research questions and the papersthat aimed at answering them.



Regarding the inclusion of the individual component, Paper I re-searched the creation of individualized accessibility maps for residentsbased on their individual priorities. The study proposed the use of in-dividual priorities as a proxy for measuring the self-perceived needs,abilities and opportunities of the citizens. The method for calculationin Paper I is based on multi-criteria decision analysis where each of theopportunities was weighted by the citizen in different categories basedon the individual relevance that the service had for him/her. In Pa-per III, inclusion of the individual component is done by adapting apre-existing approach for categorizing potential accessibility (SAL) forpopulation age groups and comparing the results with the global ac-cessibility categories obtained for the city. Additionally, the obtainedaccessibility categories were compared with socio-economic data andthe results were discussed with local experts in order to validate the re-sults and the technical procedure to obtain them. Qualitative evaluationon the inclusion of the individual component in the measure is done inPaper III via interviews with local experts.

The answer to the second research question was approached in Pa-per I and Paper II. In Paper I, the proposed tool uses a self-selectionof the threshold value by the citizen based on a multi-criteria decisionanalysis. In Paper II, two different threshold values are computed foreach of the methods (PTWAI 1 and SAL 2). The two threshold values are,on the one hand, the one proposed by Mavoa et al. (2012) and the aver-age commuting times found for the Helsinki study area. The suitabilityof the threshold values and their effect on the outcome accessibility cat-egory was later discussed with the local experts and their opinions arereflected in Paper II.

1Public Transport and Walking Accessibility Index2Structural Accessibility Layer


Introduction

Table 1.1: Summary of the approach of the research questions in thecurrent thesis

RESEARCHQUESTION

PAPERS RESEARCHMETHOD

SAMPLE/DATA

1. How tointegrate theindividual com-ponent intocontour-basedaccessibilitymeasures?

I, III -Literature review-Methodologicalstudy (own con-tour measure andmodification of SAL)-Case study (HelsinkiMetropolitan Area)-Cross valida-tion with socio-demographic data-Interview with localexperts

-Service points-Commuting timematrix for car,PT and walk-Socio-economicdata of the area-Qualitative eval-uation frominterviews

2. Can the lim-itations fromthe usage ofthreshold valuesbe overcome incontour-basedaccessibilitymeasures?

I, II -Literature review-Methodologicalcomparison(SAL vs PTWAI)-Case study (Kuo-pio and HelsinkiMetropolitanArea (Finland))-Cross valida-tion with socio-demographic data-Interview with localexperts

-Service points-Noise leveland forestdensity data-Commuting timematrix for car,PT and walk-Socio-economicdata of the area-Qualitative eval-uation frominterviews

1.4 STRUCTURE OF THE DISSERTATION

This dissertation consists of three research papers and a summary. PaperI has been published, Paper II has been published, and Paper III has



Regarding the inclusion of the individual component, Paper I re-searched the creation of individualized accessibility maps for residentsbased on their individual priorities. The study proposed the use of in-dividual priorities as a proxy for measuring the self-perceived needs,abilities and opportunities of the citizens. The method for calculationin Paper I is based on multi-criteria decision analysis where each of theopportunities was weighted by the citizen in different categories basedon the individual relevance that the service had for him/her. In Pa-per III, inclusion of the individual component is done by adapting apre-existing approach for categorizing potential accessibility (SAL) forpopulation age groups and comparing the results with the global ac-cessibility categories obtained for the city. Additionally, the obtainedaccessibility categories were compared with socio-economic data andthe results were discussed with local experts in order to validate the re-sults and the technical procedure to obtain them. Qualitative evaluationon the inclusion of the individual component in the measure is done inPaper III via interviews with local experts.

The answer to the second research question was approached in Pa-per I and Paper II. In Paper I, the proposed tool uses a self-selectionof the threshold value by the citizen based on a multi-criteria decisionanalysis. In Paper II, two different threshold values are computed foreach of the methods (PTWAI 1 and SAL 2). The two threshold values are,on the one hand, the one proposed by Mavoa et al. (2012) and the aver-age commuting times found for the Helsinki study area. The suitabilityof the threshold values and their effect on the outcome accessibility cat-egory was later discussed with the local experts and their opinions arereflected in Paper II.

1Public Transport and Walking Accessibility Index2Structural Accessibility Layer


Introduction

Table 1.1: Summary of the approach of the research questions in thecurrent thesis

RESEARCHQUESTION

PAPERS RESEARCHMETHOD

SAMPLE/DATA

1. How tointegrate theindividual com-ponent intocontour-basedaccessibilitymeasures?

I, III -Literature review-Methodologicalstudy (own con-tour measure andmodification of SAL)-Case study (HelsinkiMetropolitan Area)-Cross valida-tion with socio-demographic data-Interview with localexperts

-Service points-Commuting timematrix for car,PT and walk-Socio-economicdata of the area-Qualitative eval-uation frominterviews

2. Can the lim-itations fromthe usage ofthreshold valuesbe overcome incontour-basedaccessibilitymeasures?

I, II -Literature review-Methodologicalcomparison(SAL vs PTWAI)-Case study (Kuo-pio and HelsinkiMetropolitanArea (Finland))-Cross valida-tion with socio-demographic data-Interview with localexperts

-Service points-Noise leveland forestdensity data-Commuting timematrix for car,PT and walk-Socio-economicdata of the area-Qualitative eval-uation frominterviews

1.4 STRUCTURE OF THE DISSERTATION

This dissertation consists of three research papers and a summary. PaperI has been published, Paper II has been published, and Paper III has



been submitted and is currently under review.The thesis consists of four chapters. The first chapter presents the

background of the research and the motivation of the study, the researchquestions to be answer in this thesis, the methodology followed in theresearch papers in order to answer the proposed research questions andfinally the structure of the summary. The second chapter contains aliterature review on measures of accessibility. It includes the definition,classification and application of accessibility; along with the benefits andlimitations of their use. This is followed by a more detailed presentationof the contour accessibility measures, which represent the focus of thisdissertation. The third chapter shows the main structure and summaryof the research papers included in this dissertation. Finally, the fourthchapter presents the conclusion regarding the research questions, thecontribution of this dissertation to scientific knowledge, an evaluation ofthe research and proposals for future research based on the findings.


2 Theoretical context ofcontour-based accessibilitymeasures

This chapter sets the theoretical context of contour-based accessibilitymeasures. The aim of this chapter is to bring the reader the researchcontext of accessibility and accessibility measures; with a special focuson contour-based accessibility measures.

The structure of the chapter is as follows. The first section is basedon a short introduction to the definition and classification of accessibilityand classification of accessibility measures. The second section is basedon the definition and elements of contour-based accessibility measuresand limitations of contour-based accessibility measures. The theoreticalcontext presented in this section is based on the most commonly sharedrationale on accessibility measures, rather than an extended literaturereview.

2.1 ACCESSIBILITY DEFINITION AND CLASSIFICATION

2.1.1 Accessibility definition

As proposed by Wegener and Fürst (1999) in their well-known land-usetransport feedback cycle, accessibility enables the linking of transportand land use. Accessibility is determined by the spatial distributionof potential destinations, the ease of reaching each destination, and themagnitude, quality, and character of the activities found there (Handyand Niemeier, 1997). The greater the number of potential destinationswithin some defined time or distance range and the closer such choicedestinations are within this maximum range, the higher the level of ac-cessibility (Church and Marston, 2003).

However, the definition of accessibility does not enjoy of much con-sensus in the literature. It can often be found in many research papers



been submitted and is currently under review.The thesis consists of four chapters. The first chapter presents the

background of the research and the motivation of the study, the researchquestions to be answer in this thesis, the methodology followed in theresearch papers in order to answer the proposed research questions andfinally the structure of the summary. The second chapter contains aliterature review on measures of accessibility. It includes the definition,classification and application of accessibility; along with the benefits andlimitations of their use. This is followed by a more detailed presentationof the contour accessibility measures, which represent the focus of thisdissertation. The third chapter shows the main structure and summaryof the research papers included in this dissertation. Finally, the fourthchapter presents the conclusion regarding the research questions, thecontribution of this dissertation to scientific knowledge, an evaluation ofthe research and proposals for future research based on the findings.


2 Theoretical context ofcontour-based accessibilitymeasures

This chapter sets the theoretical context of contour-based accessibilitymeasures. The aim of this chapter is to bring the reader the researchcontext of accessibility and accessibility measures; with a special focuson contour-based accessibility measures.

The structure of the chapter is as follows. The first section is basedon a short introduction to the definition and classification of accessibilityand classification of accessibility measures. The second section is basedon the definition and elements of contour-based accessibility measuresand limitations of contour-based accessibility measures. The theoreticalcontext presented in this section is based on the most commonly sharedrationale on accessibility measures, rather than an extended literaturereview.

2.1 ACCESSIBILITY DEFINITION AND CLASSIFICATION

2.1.1 Accessibility definition

As proposed by Wegener and Fürst (1999) in their well-known land-usetransport feedback cycle, accessibility enables the linking of transportand land use. Accessibility is determined by the spatial distributionof potential destinations, the ease of reaching each destination, and themagnitude, quality, and character of the activities found there (Handyand Niemeier, 1997). The greater the number of potential destinationswithin some defined time or distance range and the closer such choicedestinations are within this maximum range, the higher the level of ac-cessibility (Church and Marston, 2003).

However, the definition of accessibility does not enjoy of much con-sensus in the literature. It can often be found in many research papers



the statement of Gould (1969, pp. 64), who defines accessibility as "...aslippery notion...one of those common terms which everyone uses until facedwith the problem of defining and measuring it".

The evolution of the definition of accessibility follows the evolutionof the concept itself and the addition of new components that shouldbe considered. Based on the most cited definitions of accessibility, theconcept has shifted from a basic mathematical relation of people, dis-tances and opportunities (Hansen, 1959) to a perception of the ease ofthe population to reach the desired opportunities (including here the in-dividual component of accessibility)(Wachs and Kumagi, 1973; Bertoliniand le Clercq, 2003; Litman, 2003). Later on, it was proposed that accessi-bility represents the utility of reaching those opportunities, consideringthe individual and temporal components. Again, the definitions evolvedfrom "consumer surplus or net benefit", (Leonardi, 1978) to utility, whichrepresents the overall effect of reaching the activity at the destination, ac-counting for the individual choices of activity type, location, mode, andtime (Bhat et al., 2000; SEU, 2003). Furthermore, Ross (2000) and Haldenet al. (2005) in their definitions introduced the differentiation of real andperceived costs and accessibility; emphasizing in this way the need to fo-cus on the perceived accessibility and therefore look for more individuallevel measures.

Other authors have emphasized in more specific aspects that acces-sibility may consider. In this direction, Hack (1976) introduced the "rela-tiveness" distance in the measures; and Pirie (1979) defined accessibilityas a "condition (a vacancy) in an activity routine", this is to say, accessibilityis one condition affecting daily routines. Following the same direction,Bertolini et al. (2005) focused on the definition of a sustainable accessi-bility that indirectly introduces the idea of the need for an egalitarianaccessibility level for all citizens. This concept was later applied in thestudy of social exclusion based on differences in mobility (Larsen et al.,2006; Jiron, 2010; Urry and Grieco, 2011).

Additionally, there are authors that differentiate between access andaccessibility based on the subject of the evaluation of accessibility. Inthis regard, Geurs and van Wee (2004, p.128) stated that "access is usedwhen talking about a person’s perspective, accessibility when using a location’sperspective.". Similarly Tillema et al. (2003) differentiate between objectiveaccessibility and subjective accessibility. In the current work, these differ-


Theoretical context of contour-based accessibility measures

ences were not taken into consideration, although, as will be revealed insection 4.4, it is an element to be considered in the future. Finally, someresearchers differentiate accessibility to some place(s) from accessibilityfrom some place(s) (Ingram, 1971).

In conclusion, the concept of accessibility and its definition haveshifted from a more spatial general level where distance costs and spa-tial distribution of opportunities only were considered; towards moreindividual-based measures where the cost of reaching opportunities goesfurther than the spatial dimension. This shift in vision implies an evo-lution of the mathematical methods applied for accessibility measuresand a higher dependency on data requirements for the most advancedmeasures. In the current thesis and papers we used the definition fromGeurs and van Wee (2004, p. 128) where accessibility is defined as "theextent to which land-use and transport systems enable (groups of) individu-als to reach activities or destinations by means of a (combination of) transportmode(s)".

2.1.2 Accessibility classification

Previous reviews on accessibility measures and existing applicationshave been undertaken by Handy and Niemeier (1997), Bhat et al. (2000),Baradaran and Ramjerdi (2001), Geurs and van Eck (2001), Church andMarston (2003), Tillema et al. (2003), Halden et al. (2005), Silva (2008),Lei and Church (2010), van Wee et al. (2012) and more recently, Bröm-melstroet et al. (2014).

Among all these authors the classification of accessibility is fairlysimilar with some nominal changes in the categories. Most of the au-thors classify accessibility into five main groups: infrastructure-based;cumulative opportunities; gravity measure; utility measure; and time-space measure. There are, nevertheless, several differences among them.Handy and Niemeier (1997) and Bhat et al. (2000) did not observe the in-frastructure (also called travel-cost) measure, while Baradaran and Ram-jerdi (2001) used the classification introduced by Miller (1998) and addeda composite approach as a new fifth category. Church and Marston(2003) proposed seven types of measures for accessibility: 1) counting;2) total sums of distances; 3) closest available; 4) gross interaction poten-tial; 5) probabilistic choice, 6) net and maximum benefit; and 7) absolute.Comparing this classification with the one proposed by Geurs and van



the statement of Gould (1969, pp. 64), who defines accessibility as "...aslippery notion...one of those common terms which everyone uses until facedwith the problem of defining and measuring it".

The evolution of the definition of accessibility follows the evolutionof the concept itself and the addition of new components that shouldbe considered. Based on the most cited definitions of accessibility, theconcept has shifted from a basic mathematical relation of people, dis-tances and opportunities (Hansen, 1959) to a perception of the ease ofthe population to reach the desired opportunities (including here the in-dividual component of accessibility)(Wachs and Kumagi, 1973; Bertoliniand le Clercq, 2003; Litman, 2003). Later on, it was proposed that accessi-bility represents the utility of reaching those opportunities, consideringthe individual and temporal components. Again, the definitions evolvedfrom "consumer surplus or net benefit", (Leonardi, 1978) to utility, whichrepresents the overall effect of reaching the activity at the destination, ac-counting for the individual choices of activity type, location, mode, andtime (Bhat et al., 2000; SEU, 2003). Furthermore, Ross (2000) and Haldenet al. (2005) in their definitions introduced the differentiation of real andperceived costs and accessibility; emphasizing in this way the need to fo-cus on the perceived accessibility and therefore look for more individuallevel measures.

Other authors have emphasized in more specific aspects that acces-sibility may consider. In this direction, Hack (1976) introduced the "rela-tiveness" distance in the measures; and Pirie (1979) defined accessibilityas a "condition (a vacancy) in an activity routine", this is to say, accessibilityis one condition affecting daily routines. Following the same direction,Bertolini et al. (2005) focused on the definition of a sustainable accessi-bility that indirectly introduces the idea of the need for an egalitarianaccessibility level for all citizens. This concept was later applied in thestudy of social exclusion based on differences in mobility (Larsen et al.,2006; Jiron, 2010; Urry and Grieco, 2011).

Additionally, there are authors that differentiate between access andaccessibility based on the subject of the evaluation of accessibility. Inthis regard, Geurs and van Wee (2004, p.128) stated that "access is usedwhen talking about a person’s perspective, accessibility when using a location’sperspective.". Similarly Tillema et al. (2003) differentiate between objectiveaccessibility and subjective accessibility. In the current work, these differ-



ences were not taken into consideration, although, as will be revealed insection 4.4, it is an element to be considered in the future. Finally, someresearchers differentiate accessibility to some place(s) from accessibilityfrom some place(s) (Ingram, 1971).

In conclusion, the concept of accessibility and its definition haveshifted from a more spatial general level where distance costs and spa-tial distribution of opportunities only were considered; towards moreindividual-based measures where the cost of reaching opportunities goesfurther than the spatial dimension. This shift in vision implies an evo-lution of the mathematical methods applied for accessibility measuresand a higher dependency on data requirements for the most advancedmeasures. In the current thesis and papers we used the definition fromGeurs and van Wee (2004, p. 128) where accessibility is defined as "theextent to which land-use and transport systems enable (groups of) individu-als to reach activities or destinations by means of a (combination of) transportmode(s)".

2.1.2 Accessibility classification

Previous reviews on accessibility measures and existing applicationshave been undertaken by Handy and Niemeier (1997), Bhat et al. (2000),Baradaran and Ramjerdi (2001), Geurs and van Eck (2001), Church andMarston (2003), Tillema et al. (2003), Halden et al. (2005), Silva (2008),Lei and Church (2010), van Wee et al. (2012) and more recently, Bröm-melstroet et al. (2014).

Among all these authors the classification of accessibility is fairlysimilar with some nominal changes in the categories. Most of the au-thors classify accessibility into five main groups: infrastructure-based;cumulative opportunities; gravity measure; utility measure; and time-space measure. There are, nevertheless, several differences among them.Handy and Niemeier (1997) and Bhat et al. (2000) did not observe the in-frastructure (also called travel-cost) measure, while Baradaran and Ram-jerdi (2001) used the classification introduced by Miller (1998) and addeda composite approach as a new fifth category. Church and Marston(2003) proposed seven types of measures for accessibility: 1) counting;2) total sums of distances; 3) closest available; 4) gross interaction poten-tial; 5) probabilistic choice, 6) net and maximum benefit; and 7) absolute.Comparing this classification with the one proposed by Geurs and van



Wee (2004) measures 1 - 3 can be considered location-based measures; 4and 5 can be considered gravity measures; while measures 6 and 7 canbe classified as individual-based measures.

Later on, Lei and Church (2010) proposed six categories for accessmetrics: system accessibility, facilitated accessibility, integral accessibil-ity, space-time geography, utility theory and relative accessibility. Sys-tem accessibility focuses on the influence area of certain infrastructureover citizens. System-facilitated accessibility adds a cost or decay func-tion to the access to the transport infrastructure. The integral accessibil-ity joints proximity-based and activity-based measures, where there is acertain distance or cost and the amount or diversity of activities reach-able within that maximum cost value is calculated. The categories arethe same as the classification proposed by Geurs and van Wee (2004).Additionally Lei and Church (2010) added relative accessibility, whichis based on comparing access between modes or types of users (Church andMarston, 2003) (see Table 2.1)



MEA

SUR

ESG

eurs

and

van

Wee

(200

4)

Han

dyan

dN

iem

eier

(199

7)

Bha

tet

al.

(200

0)B

arad

aran

and

Ram

-je

rdi

(200

1)

Chu

rch

and

Mar

ston

(200

3)Le

ian

dC

hurc

h(2

010)

Infr

astr

uctu

re,

trav

el-

cost

orpr

oxim

ity-

base

d

*-

--

-?

Loca

tion

-or

acti

vity

-ba

sed

Loca

tion

or acti

vity

-ba

sed

*C

umul

ativ

eop

port

unit

yor

mea

sure

*1.

Cou

ntin

g2.

Tota

lsu

ms

ofdi

stan

ces

3.C

los-

est

avai

labl

e

Inte

gral

acce

ssi-

bilit

y

Gra

vity

orpo

tent

ial

Loca

tion

or acti

vity

-ba

sed

**

*4.

Gro

ssin

tera

c-ti

onpo

tent

ial

5.Pr

obab

ilist

icch

oice

Syst

emfa

cili-

tate

d

Uti

lity

orin

divi

dual

-ba

sed

**

**

6.N

etan

dm

ax-

imum

bene

fit7.

Abs

olut

e

?

Tim

e-sp

ace

orpe

rson

-ba

sed

**

**

-?

Oth

erpr

opos

edm

ea-

sure

s-

--

Com

posi

teA

p-pr

oach

-R

elat

ive

acce

ssi-

bilit

y

Tabl

e2.

1:A

cces

sibi

lity

clas

sific

atio

ns-:

Mea

sure

notu

sed

inth

ecl

assi

ficat

ion;

?:M

easu

reno

tspe

cifie

din

the

clas

sific

atio

n;an

d*:

Mea

sure

used

inth

ecl

assi

ficat

ion

wit

hon

eof

the

term

inol

ogie

s.



Wee (2004) measures 1 - 3 can be considered location-based measures; 4and 5 can be considered gravity measures; while measures 6 and 7 canbe classified as individual-based measures.

Later on, Lei and Church (2010) proposed six categories for accessmetrics: system accessibility, facilitated accessibility, integral accessibil-ity, space-time geography, utility theory and relative accessibility. Sys-tem accessibility focuses on the influence area of certain infrastructureover citizens. System-facilitated accessibility adds a cost or decay func-tion to the access to the transport infrastructure. The integral accessibil-ity joints proximity-based and activity-based measures, where there is acertain distance or cost and the amount or diversity of activities reach-able within that maximum cost value is calculated. The categories arethe same as the classification proposed by Geurs and van Wee (2004).Additionally Lei and Church (2010) added relative accessibility, whichis based on comparing access between modes or types of users (Church andMarston, 2003) (see Table 2.1)



MEA

SUR

ESG

eurs

and

van

Wee

(200

4)

Han

dyan

dN

iem

eier

(199

7)

Bha

tet

al.

(200

0)B

arad

aran

and

Ram

-je

rdi

(200

1)

Chu

rch

and

Mar

ston

(200

3)Le

ian

dC

hurc

h(2

010)

Infr

astr

uctu

re,

trav

el-

cost

orpr

oxim

ity-

base

d

*-

--

-?

Loca

tion

-or

acti

vity

-ba

sed

Loca

tion

or acti

vity

-ba

sed

*C

umul

ativ

eop

port

unit

yor

mea

sure

*1.

Cou

ntin

g2.

Tota

lsu

ms

ofdi

stan

ces

3.C

los-

est

avai

labl

e

Inte

gral

acce

ssi-

bilit

y

Gra

vity

orpo

tent

ial

Loca

tion

or acti

vity

-ba

sed

**

*4.

Gro

ssin

tera

c-ti

onpo

tent

ial

5.Pr

obab

ilist

icch

oice

Syst

emfa

cili-

tate

d

Uti

lity

orin

divi

dual

-ba

sed

**

**

6.N

etan

dm

ax-

imum

bene

fit7.

Abs

olut

e

?

Tim

e-sp

ace

orpe

rson

-ba

sed

**

**

-?

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In the current study, the classification proposed by Geurs and vanWee (2004) will be used since it is the most easily understandable andcommunicative. In their classification, accessibility is divided into fourtypes of accessibility perspectives with four components to consider.

The four perspectives proposed by Geurs and van Wee (2004) are:infrastructure-based or proximity-based, utility-based, person-based andlocation-based (or activity-based). Infrastructure or proximity-based mea-sures focus on times, congestion and operating speed in the transportnetwork. Utility-based measures are based on the principle that thecitizen aims at maximizing his/her individual benefit. Person-basedmeasures focus on the availability of activities under some given con-ditions of the available and personal time budget and transport. Finally,location-based measures focus on the spatial distribution of the oppor-tunities and the demand for them. See Bhat et al. (2000) for a completereview of the mathematical models of accessibility measures.

Among all types of accessibility measures, location-based accessi-bility measures are the most commonly used among researchers sincetheir output is easier to communicate and maximizes the cost-benefitbetween the data and computing costs and the obtained information.Consequently, in recent years, a large range of models of these typesof measures have been proposed with multiple potential applications,which in some cases have not been fully explored.

The location-based accessibility measures have been at the same timesubdivided into four sub-types. Namely, distance measure, contourmeasure, potential accessibility measure and balancing factors of poten-tial interaction. Tillema et al. (2003) provided a complete review of thecharacteristics and mathematical linkage between these measures. Notethat some authors classify the person (or time-space) based measure as asubtype of location- (or activity-) based measure (see for example Geursand van Eck (2001)).

The four accessibility perspectives combine different dimensions ofthe measure that are called "accessibility components" (Geurs and vanWee, 2004). As Geurs and van Wee (2004) stated, the four componentsinteract with each other and they are not necessarily present in eachof the accessibility perspectives. The four components proposed are





In the current study, the classification proposed by Geurs and vanWee (2004) will be used since it is the most easily understandable andcommunicative. In their classification, accessibility is divided into fourtypes of accessibility perspectives with four components to consider.

The four perspectives proposed by Geurs and van Wee (2004) are:infrastructure-based or proximity-based, utility-based, person-based andlocation-based (or activity-based). Infrastructure or proximity-based mea-sures focus on times, congestion and operating speed in the transportnetwork. Utility-based measures are based on the principle that thecitizen aims at maximizing his/her individual benefit. Person-basedmeasures focus on the availability of activities under some given con-ditions of the available and personal time budget and transport. Finally,location-based measures focus on the spatial distribution of the oppor-tunities and the demand for them. See Bhat et al. (2000) for a completereview of the mathematical models of accessibility measures.

Among all types of accessibility measures, location-based accessi-bility measures are the most commonly used among researchers sincetheir output is easier to communicate and maximizes the cost-benefitbetween the data and computing costs and the obtained information.Consequently, in recent years, a large range of models of these typesof measures have been proposed with multiple potential applications,which in some cases have not been fully explored.

The location-based accessibility measures have been at the same timesubdivided into four sub-types. Namely, distance measure, contourmeasure, potential accessibility measure and balancing factors of poten-tial interaction. Tillema et al. (2003) provided a complete review of thecharacteristics and mathematical linkage between these measures. Notethat some authors classify the person (or time-space) based measure as asubtype of location- (or activity-) based measure (see for example Geursand van Eck (2001)).

The four accessibility perspectives combine different dimensions ofthe measure that are called "accessibility components" (Geurs and vanWee, 2004). As Geurs and van Wee (2004) stated, the four componentsinteract with each other and they are not necessarily present in eachof the accessibility perspectives. The four components proposed are



Figure 2.1: Schematic diagram of the classification of accessibility mea-sures proposed by Geurs and van Wee (2004). Made by the author.

transport, land-use, temporal and individual component. The transportcomponent consists of the objective impedance of the transport network(distance, travel time, costs and effort between origin and destination);and a perception of the impedance of the transport. The land-use com-ponent consists of spatial distribution of services, the demand for themand the competition effects within the supply and demand for such ser-vices. The temporal component of accessibility is based on the timeswhen the opportunities are available and that an individual can makeuse of certain opportunities. Finally, the individual component is basedon the needs, abilities and opportunities of each individual.

The contour-based accessibility measures are, like many of the location-based type measures, do not directly integrate all the accessibility com-



ponents.1. Contour-based measures only explicitly contain the transportlimited by isolines (i.e. the line formed by all the points in the spacelocated in the same distance, travel time or cost); and the land-use com-ponent (since it considers the spatial distribution of the opportunitieswithin the isochrones). This second characteristic differentiates themfrom the distance measure where only the transport component is con-sidered. However, as the main difference from the rest of the location-based measures, contour measures do not explicitly take into accountthe individual and temporal components. In section 2.2.3 I will revealproposed solutions to fill this gap.

Selecting the type of accessibility measure to be modelled and/orcalculated is often a multi-criteria decision based on the goal that it isaimed to answer and data availability. In this sense, Wilson (1973) pro-posed that selection of the accessibility measure should be based on fourcriteria: 1) the degree and type of disaggregation desired, 2) the defini-tion of origins and destinations, 3) measurement of the attraction, and4) the impedance measure. In the current study, the focus is only oncontour-based accessibility, which is a subtype of location or activity-based accessibility.

2.1.3 Uses of accessibility

The review undertaken by Bhat et al. (2000) showed different uses fordifferent accessibility measures (see Table 2.1). Infrastructure-based mea-sures (spatial separation measure in Bhat et al. (2000)) have been usedfor categorizing links into strong or weak, evaluating changes in thetransport system and as a measure for trip generation.

Location-based measures are differentiated by Bhat et al. (2000) as cu-mulative measures (also known as distance measure) and gravity-basedmeasures (also known as potential measure). Cumulative opportunities,location-based measures with a linear accessibility decay function, areapplied for monitoring changes in accessibility due to changes in landuse, transportation system or growth; and a data source for other trans-portation models. A gravity-based measure, a non-linear accessibilitydecay function, is applied for evaluating access to particular types of ac-tivities, comparing different transport configurations, tracking changes

1see Table 1 in Albacete et al. 2015 for a complete view



Figure 2.1: Schematic diagram of the classification of accessibility mea-sures proposed by Geurs and van Wee (2004). Made by the author.

transport, land-use, temporal and individual component. The transportcomponent consists of the objective impedance of the transport network(distance, travel time, costs and effort between origin and destination);and a perception of the impedance of the transport. The land-use com-ponent consists of spatial distribution of services, the demand for themand the competition effects within the supply and demand for such ser-vices. The temporal component of accessibility is based on the timeswhen the opportunities are available and that an individual can makeuse of certain opportunities. Finally, the individual component is basedon the needs, abilities and opportunities of each individual.

The contour-based accessibility measures are, like many of the location-based type measures, do not directly integrate all the accessibility com-



ponents.1. Contour-based measures only explicitly contain the transportlimited by isolines (i.e. the line formed by all the points in the spacelocated in the same distance, travel time or cost); and the land-use com-ponent (since it considers the spatial distribution of the opportunitieswithin the isochrones). This second characteristic differentiates themfrom the distance measure where only the transport component is con-sidered. However, as the main difference from the rest of the location-based measures, contour measures do not explicitly take into accountthe individual and temporal components. In section 2.2.3 I will revealproposed solutions to fill this gap.

Selecting the type of accessibility measure to be modelled and/orcalculated is often a multi-criteria decision based on the goal that it isaimed to answer and data availability. In this sense, Wilson (1973) pro-posed that selection of the accessibility measure should be based on fourcriteria: 1) the degree and type of disaggregation desired, 2) the defini-tion of origins and destinations, 3) measurement of the attraction, and4) the impedance measure. In the current study, the focus is only oncontour-based accessibility, which is a subtype of location or activity-based accessibility.

2.1.3 Uses of accessibility

The review undertaken by Bhat et al. (2000) showed different uses fordifferent accessibility measures (see Table 2.1). Infrastructure-based mea-sures (spatial separation measure in Bhat et al. (2000)) have been usedfor categorizing links into strong or weak, evaluating changes in thetransport system and as a measure for trip generation.

Location-based measures are differentiated by Bhat et al. (2000) as cu-mulative measures (also known as distance measure) and gravity-basedmeasures (also known as potential measure). Cumulative opportunities,location-based measures with a linear accessibility decay function, areapplied for monitoring changes in accessibility due to changes in landuse, transportation system or growth; and a data source for other trans-portation models. A gravity-based measure, a non-linear accessibilitydecay function, is applied for evaluating access to particular types of ac-tivities, comparing different transport configurations, tracking changes

1see Table 1 in Albacete et al. 2015 for a complete view



over time and as an input to other modelling.Utility-based measures are used for modelling mobility and travel.

Finally, uses for person-based accessibility measures (time-space mea-sure in Bhat et al. (2000)) are focused on evaluating multiple case studies,including changes in the transportation system and in opportunities.

From a global point of view, accessibility measurement has been tra-ditionally focused towards studying the changes in trip generation andtravel behaviour (Vickerman, 1974; Bhat et al., 2000); as an indicator ofsocial inequalities (Wachs and Kumagi, 1973; Wachs, 1978; Bhat et al.,2000; Geurs and van Eck, 2001; Halden et al., 2005); and as a quality-of-life index (Bhat et al., 2000). These applications remain nowadays themain interest (directly or as a background motivation) for transport andurban planners.

2.1.4 What is a good accessibility measure?

The qualitative evaluation of a good accessibility measure is not straight-forward since the quality of accessibility is relative to its capacity toanswer the goal of the research. As an example, the needs regardingthe measure would differ a lot if we were trying to measure potentialphysical mobility in a region rather than measuring the accessibility toeducational facilities in the city. The first one would integrate multipleopportunities and the educational facilities may be one more compo-nent integrated in the final calculation; whereas the second one mighttake into account much more detailed data (different walking speed fordifferent ages of students, school capacities and opening hours).

Nevertheless, there are some common assumptions in the literaturethat define the main lines of what would be a good accessibility mea-sure. Firstly, many authors (Weibull, 1976; Davidson, 1977; Geurs andvan Eck, 2001; Geurs and van Wee, 2004; Curtis and Scheurer, 2010)required, based on the basic concept of accessibility, that accessibilityshould reflect the changes in transportation and land use. Secondly,Weibull (1976) and Geurs and van Wee (2004) agree that the accessibilityshould be somehow weighted by the demand for the opportunities, i.e.the opportunities that have zero value should not contribute to the finalmeasure. Thirdly, Morris et al. (1979), Geurs and van Wee (2004) andBertolini et al. (2005) emphasize the personal capabilities, and the setof desired opportunities and perceptions as elements that accessibility



measures should consider. Finally, the definitions of Morris et al. (1979)and Bertolini et al. (2005) emphasize the need for being technically fea-sible and understandable, respectively.

In conclusion, accessibility measures should be based on the rela-tion between the transportation system and land use. The individualpriorities should be considered in the measure by weighting the oppor-tunities or by integrating the mobility constraints of the citizens; and themeasure has to be technically feasible and understandable.

Many authors have considered that contour-based accessibility mea-sures are the type of measure that better emphasizes those requirements.Contour-based measures, a sub-type of location-based accessibility mea-sure, are specially valued for being understandable while keeping lowtechnical requirements. A short review of this type of location-basedmeasure is presented in the following section.



over time and as an input to other modelling.Utility-based measures are used for modelling mobility and travel.

Finally, uses for person-based accessibility measures (time-space mea-sure in Bhat et al. (2000)) are focused on evaluating multiple case studies,including changes in the transportation system and in opportunities.

From a global point of view, accessibility measurement has been tra-ditionally focused towards studying the changes in trip generation andtravel behaviour (Vickerman, 1974; Bhat et al., 2000); as an indicator ofsocial inequalities (Wachs and Kumagi, 1973; Wachs, 1978; Bhat et al.,2000; Geurs and van Eck, 2001; Halden et al., 2005); and as a quality-of-life index (Bhat et al., 2000). These applications remain nowadays themain interest (directly or as a background motivation) for transport andurban planners.

2.1.4 What is a good accessibility measure?

The qualitative evaluation of a good accessibility measure is not straight-forward since the quality of accessibility is relative to its capacity toanswer the goal of the research. As an example, the needs regardingthe measure would differ a lot if we were trying to measure potentialphysical mobility in a region rather than measuring the accessibility toeducational facilities in the city. The first one would integrate multipleopportunities and the educational facilities may be one more compo-nent integrated in the final calculation; whereas the second one mighttake into account much more detailed data (different walking speed fordifferent ages of students, school capacities and opening hours).

Nevertheless, there are some common assumptions in the literaturethat define the main lines of what would be a good accessibility mea-sure. Firstly, many authors (Weibull, 1976; Davidson, 1977; Geurs andvan Eck, 2001; Geurs and van Wee, 2004; Curtis and Scheurer, 2010)required, based on the basic concept of accessibility, that accessibilityshould reflect the changes in transportation and land use. Secondly,Weibull (1976) and Geurs and van Wee (2004) agree that the accessibilityshould be somehow weighted by the demand for the opportunities, i.e.the opportunities that have zero value should not contribute to the finalmeasure. Thirdly, Morris et al. (1979), Geurs and van Wee (2004) andBertolini et al. (2005) emphasize the personal capabilities, and the setof desired opportunities and perceptions as elements that accessibility



measures should consider. Finally, the definitions of Morris et al. (1979)and Bertolini et al. (2005) emphasize the need for being technically fea-sible and understandable, respectively.

In conclusion, accessibility measures should be based on the rela-tion between the transportation system and land use. The individualpriorities should be considered in the measure by weighting the oppor-tunities or by integrating the mobility constraints of the citizens; and themeasure has to be technically feasible and understandable.

Many authors have considered that contour-based accessibility mea-sures are the type of measure that better emphasizes those requirements.Contour-based measures, a sub-type of location-based accessibility mea-sure, are specially valued for being understandable while keeping lowtechnical requirements. A short review of this type of location-basedmeasure is presented in the following section.



2.2 CONTOUR-BASED ACCESSIBILITY MEASURE

2.2.1 Definition of contour-based accessibility measure

A contour measure is also called "an ’isochronic measure’, ’cumulativeopportunities’, ’proximity distance’ or ’proximity count’". It "indicatesthe number of opportunities reachable within a given travel time or dis-tance" (Geurs and van Eck, 2001).

Additional definitions of a contour-based accessibility measure havebeen proposed. Bhat et al. (2000, p. 19) defined it as "the simplest acces-sibility measure that takes account of both distance and the objective of a trip.This measure defines a travel time or distance threshold and uses the numberof potential activities within that threshold as the accessibility for that spatialunit." Therefore, contour-based accessibility are often used as accumu-lative measures, this is to say, counting the amount of total services orthe amount of different services within a threshold value (Pirie, 1979).

Figure 2.2: Marginal costs of accessibility for three location-based acces-sibility measure. Made by the author.

Therefore, from a methodological point of view, contour-based mea-sures could also be defined as measures accounting for the transport andland use component without having a continuous decay function. This



observation, and as it can be easily interpreted from Figure 2.2, doesthat mathematically, a contour measure subdivided into infinite valueswould tend to a continuous decay function (a potential accessibility mea-sure).

This observation is of special relevance for evaluating the limitationsderived from the use of threshold values (Research Question 2), whichis handled in section 4.1.

Figure 2.2 compares the marginal cost of accessibility function for thesubtypes of location-based accessibility measures. The figure helps invisualizing the mathematical differences between distance, contour andpotential accessibility measures. Please note that the subtype "balancingfactors of potential interaction" has not been included in the graphic dueto its complexity. As it can be seen in Figure 2.2, the marginal cost ofaccessibility (loss of accessibility per incremented unit of cost) is constantfor distance measures whereas contour measures are defined by partialcumulative functions depending on the selected threshold commutingvalues. Moreover, in potential measures, where the cost function followsan exponential or logarithmic function, the marginal cost for increasingaccessibility is growing at a constant rate.

These kinds of measures present some limitations that are pointedout by different authors throughout the literature which are analysed inmore detail in subsection 2.2.3. Nevertheless, contour-based accessibilitymeasures are still the most commonly used accessibility measures dueto their simplicity which warrants an easy communication of the resultswith relatively low data requirements (Tillema et al., 2003; Halden et al.,2005; Silva, 2008; Curl et al., 2011) and does not require assumptionsabout a person’s perception of transport (Bertolini et al., 2005).

2.2.2 Elements of contour-based accessibility measure

In the literature there is no common agreement about the elementsthat comprise contour-based accessibility measures. In this section wegrouped the elements that constitute the contour-based measures basedon the discussions found in the literature about ways to improve thistype of accessibility measure.

Based on the literature, we found that the measure consisted of fourelements. These elements are origins, links, destinations or opportuni-ties, and the mathematical relation between origins and destinations. In



2.2 CONTOUR-BASED ACCESSIBILITY MEASURE

2.2.1 Definition of contour-based accessibility measure

A contour measure is also called "an ’isochronic measure’, ’cumulativeopportunities’, ’proximity distance’ or ’proximity count’". It "indicatesthe number of opportunities reachable within a given travel time or dis-tance" (Geurs and van Eck, 2001).

Additional definitions of a contour-based accessibility measure havebeen proposed. Bhat et al. (2000, p. 19) defined it as "the simplest acces-sibility measure that takes account of both distance and the objective of a trip.This measure defines a travel time or distance threshold and uses the numberof potential activities within that threshold as the accessibility for that spatialunit." Therefore, contour-based accessibility are often used as accumu-lative measures, this is to say, counting the amount of total services orthe amount of different services within a threshold value (Pirie, 1979).

Figure 2.2: Marginal costs of accessibility for three location-based acces-sibility measure. Made by the author.

Therefore, from a methodological point of view, contour-based mea-sures could also be defined as measures accounting for the transport andland use component without having a continuous decay function. This



observation, and as it can be easily interpreted from Figure 2.2, doesthat mathematically, a contour measure subdivided into infinite valueswould tend to a continuous decay function (a potential accessibility mea-sure).

This observation is of special relevance for evaluating the limitationsderived from the use of threshold values (Research Question 2), whichis handled in section 4.1.

Figure 2.2 compares the marginal cost of accessibility function for thesubtypes of location-based accessibility measures. The figure helps invisualizing the mathematical differences between distance, contour andpotential accessibility measures. Please note that the subtype "balancingfactors of potential interaction" has not been included in the graphic dueto its complexity. As it can be seen in Figure 2.2, the marginal cost ofaccessibility (loss of accessibility per incremented unit of cost) is constantfor distance measures whereas contour measures are defined by partialcumulative functions depending on the selected threshold commutingvalues. Moreover, in potential measures, where the cost function followsan exponential or logarithmic function, the marginal cost for increasingaccessibility is growing at a constant rate.

These kinds of measures present some limitations that are pointedout by different authors throughout the literature which are analysed inmore detail in subsection 2.2.3. Nevertheless, contour-based accessibilitymeasures are still the most commonly used accessibility measures dueto their simplicity which warrants an easy communication of the resultswith relatively low data requirements (Tillema et al., 2003; Halden et al.,2005; Silva, 2008; Curl et al., 2011) and does not require assumptionsabout a person’s perception of transport (Bertolini et al., 2005).

2.2.2 Elements of contour-based accessibility measure

In the literature there is no common agreement about the elementsthat comprise contour-based accessibility measures. In this section wegrouped the elements that constitute the contour-based measures basedon the discussions found in the literature about ways to improve thistype of accessibility measure.

Based on the literature, we found that the measure consisted of fourelements. These elements are origins, links, destinations or opportuni-ties, and the mathematical relation between origins and destinations. In



the following paragraphs we will detail the main discussions aroundeach of the elements.

1.Origin of the measure. The origins of the contour measure refer tothe reference point where the physical travel starts. In this subject, sev-eral authors have pointed out two main aspects to consider about theorigins in contour-based measures: spatial resolution and trip chains.The importance of the spatial resolution of the map throughout the ac-cessibility calculation represents a relevant limitation (Silva, 2008). Basedon the spatial resolution of the original data, results may differ even ifusing the same calculation method. This is due to the discriminatory ca-pacity of the threshold travel cost which is better defined when there is ahigher resolution. The other side of the coin is that too fine a resolutionmay increase the computational and data requirements but it does notguarantee robustness and realism in the result. The debate of findingan optimal spatial resolution and limit of the study area remains underdiscussion. On the other hand, the importance of trip chains is gain-ing relevance among researchers since it has been shown to have a realimpact on the decision for choosing between travel modes (Hamed andOlaywah (2000), Dong et al. (2006) or Walle and Steenberghen (2006)).Consequently, the origin point is not static but dynamic after each tripof a trip chain.

2.Links of the measure. A link refers to the unit in which origins anddestinations are linked through a cost matrix. Travel time is the mostwidely used unit, but in other instances travel distance, economic costsor a combination of these three units (for example translating travel timeinto monetary cost and adding it to the transportation cost) have beenused. There are three aspects of the link that may strongly affect thefinal outcome. Firstly, the unit has to be carefully selected in advancein order to deliver the right message to the audience and to be reusedfor future calculations. Secondly, the transformation between units (forexample time to money, money to space or space to time) has to be care-fully done since its transformation indirectly includes information aboutthe existing transport network, urban fabric and monetary value for thepopulation. And thirdly, the level of detail of the available data willdeliver more feasible results without adding any computational costs to



the calculations; therefore it is important to obtain as defined originaldata about the links as possible. Church and Marston (2003) and Yigit-canlar et al. (2007) revealed the need for incluing in the travel time thewaiting times, changes in speed during rush hours and to consider howthe transportation works at different hours of the day.

3.Destinations or opportunities of the measure. Destinations or op-portunities refer to the set of services considered reachable (and there-fore included in the accessibility calculation). For some authors likeSilva (2008), the accessibility index is conditional on the total percentageof frequency of trips on foot. The inclusion of services is specific forevery case study and dependent on the purpose of the study. Anotherdiscussion related with the destinations arises around the inclusion ofcompetition effects between opportunities (Bhat et al., 2000; Geurs andvan Eck, 2001). Integrating the competition effects is one of the main lim-itations of contour-based measures as will be discussed in the followingsection.

4.Mathematical relation of the measure. Finally, the mathematical re-lation of attractiveness and/or repulsion between the origins and thedestinations (opportunities) is a fourth element of debate. The debatearound this relation is focused on the threshold value. Although theprinciple assumes that all services within the threshold value are la-belled with the same accessibility index, several authors have proposeda final composed accessibility index based on different threshold values(see for example the PTWAI index from Mavoa et al. (2012)). Bhat et al.(2000) presented different approximations for cumulative accessibility.

2.2.3 Limitations and proposed solutions for contour-based measures

Throughout the literature, many authors agree that the contour measurepresents some important limitations compared with other accessibilitymeasures. The method limitations most widely commented on the liter-ature and proposed solutions are presented in the following section.

Threshold value is based on subjective perceptions. The thresholdvalue is controversial since it is based on subjective perceptions. Its value



the following paragraphs we will detail the main discussions aroundeach of the elements.

1.Origin of the measure. The origins of the contour measure refer tothe reference point where the physical travel starts. In this subject, sev-eral authors have pointed out two main aspects to consider about theorigins in contour-based measures: spatial resolution and trip chains.The importance of the spatial resolution of the map throughout the ac-cessibility calculation represents a relevant limitation (Silva, 2008). Basedon the spatial resolution of the original data, results may differ even ifusing the same calculation method. This is due to the discriminatory ca-pacity of the threshold travel cost which is better defined when there is ahigher resolution. The other side of the coin is that too fine a resolutionmay increase the computational and data requirements but it does notguarantee robustness and realism in the result. The debate of findingan optimal spatial resolution and limit of the study area remains underdiscussion. On the other hand, the importance of trip chains is gain-ing relevance among researchers since it has been shown to have a realimpact on the decision for choosing between travel modes (Hamed andOlaywah (2000), Dong et al. (2006) or Walle and Steenberghen (2006)).Consequently, the origin point is not static but dynamic after each tripof a trip chain.

2.Links of the measure. A link refers to the unit in which origins anddestinations are linked through a cost matrix. Travel time is the mostwidely used unit, but in other instances travel distance, economic costsor a combination of these three units (for example translating travel timeinto monetary cost and adding it to the transportation cost) have beenused. There are three aspects of the link that may strongly affect thefinal outcome. Firstly, the unit has to be carefully selected in advancein order to deliver the right message to the audience and to be reusedfor future calculations. Secondly, the transformation between units (forexample time to money, money to space or space to time) has to be care-fully done since its transformation indirectly includes information aboutthe existing transport network, urban fabric and monetary value for thepopulation. And thirdly, the level of detail of the available data willdeliver more feasible results without adding any computational costs to



the calculations; therefore it is important to obtain as defined originaldata about the links as possible. Church and Marston (2003) and Yigit-canlar et al. (2007) revealed the need for incluing in the travel time thewaiting times, changes in speed during rush hours and to consider howthe transportation works at different hours of the day.

3.Destinations or opportunities of the measure. Destinations or op-portunities refer to the set of services considered reachable (and there-fore included in the accessibility calculation). For some authors likeSilva (2008), the accessibility index is conditional on the total percentageof frequency of trips on foot. The inclusion of services is specific forevery case study and dependent on the purpose of the study. Anotherdiscussion related with the destinations arises around the inclusion ofcompetition effects between opportunities (Bhat et al., 2000; Geurs andvan Eck, 2001). Integrating the competition effects is one of the main lim-itations of contour-based measures as will be discussed in the followingsection.

4.Mathematical relation of the measure. Finally, the mathematical re-lation of attractiveness and/or repulsion between the origins and thedestinations (opportunities) is a fourth element of debate. The debatearound this relation is focused on the threshold value. Although theprinciple assumes that all services within the threshold value are la-belled with the same accessibility index, several authors have proposeda final composed accessibility index based on different threshold values(see for example the PTWAI index from Mavoa et al. (2012)). Bhat et al.(2000) presented different approximations for cumulative accessibility.

2.2.3 Limitations and proposed solutions for contour-based measures

Throughout the literature, many authors agree that the contour measurepresents some important limitations compared with other accessibilitymeasures. The method limitations most widely commented on the liter-ature and proposed solutions are presented in the following section.

Threshold value is based on subjective perceptions. The thresholdvalue is controversial since it is based on subjective perceptions. Its value



is decided based on the subjective perceptions of the author or travelbehaviour data. However, this involves an adaptation to the given trans-port infrastructure and land use which cannot be neglected in the giventravel behaviour. Additionally, those given threshold values fall into afalse homogeneity of behaviour for different population ages (Daviesand James, 2011) and an assumption that travel behaviour does notchange through time, given the same transport infrastructure (Bhat et al.,2000). These two main assumptions might create bias in the final results.

Authors such as Handy and Niemeier (1997), Silva (2008), Baradaranand Ramjerdi (2001), Halden et al. (2005) or Bertolini et al. (2005) pointedout how the previously mentioned limitations related to the thresholdvalue affect the accessibility measure. Some of the proposed solutionsfor the threshold value are based on splitting the values into many con-tours and making them as specific to different population groups as pos-sible (Silva, 2008); (Pirie, 1979). With this application, the contour mea-sure is approximated to a potential accessibility measure and the dis-crimination between contours and population groups is reduced. Otherproposed solutions, also approaching the approximation to potential ac-cessibility measures, are based on considering a more gradual decreasein travel time or cost utility (Bertolini et al., 2005); (Pirie, 1979). Finally,(Silva and Pinho, 2010) use external qualitative evaluations on the decayfunctions and their results as a way to calibrate their functions, calcula-tions and the optimal threshold value of the accessibility index.

All opportunities are treated equally. Several authors have pointedout that all the services or opportunities are treated equally if they arewithin the threshold value and this might not correspond with the ac-tual relevance of the opportunities for the citizens (Voges and Naudé,1983; Curtis and Scheurer, 2010). This factor limits the output of theaccessibility index since it does not reflect real travel behaviour wherecertain services have a higher usage frequency than others.

Proposed solutions are focused on bringing some weight to servicesor opportunities. Weights can be directly based on pre-observed fre-quency of use of the opportunities (Silva, 2008) and calibrated to ob-served travel choices (Handy, 1992) or based on the travel cost as Tillemaet al. (2003) proposed to multiply the travel time by the value of time.Other authors have focused on the influence area of the opportunity as



the attribute for weighting. In this way, Weibull (1976) proposed weight-ing attractions by the number of jobs in a zone and including car own-ership. However, it is worth noticing that all these proposed solutionsassume certain behavioural homogeneity. The frequency of use of op-portunities or the travel mode choices are assumed to be homogeneousamong each population group.

Exclusion of competition effects. The exclusion of competition effectsbetween origins and destinations decreases the reliability of the measure.Competition effects can only then be included by approximating spatialdensities of the opportunities to competition effects. As an example, vanWee et al. (2001) and van Wee et al. (2012) proposed a combination ofvolume of opportunities and competition between working places usingcontour-based measures for measuring the accessibility to work.

Spatial definition of area of analysis. The spatial definition of the areaof analysis strongly affects the final result. In those cases where the mea-sure is based on relative values among citizens or sub-areas of the regionthe effect is stronger (Baradaran and Ramjerdi, 2001). In the cases wherethe study area is big, the relative results of accessibility will tend tooverestimate the accessibility level since areas with very low accessibil-ity have been included in the calculation. The opposite may occur whenthe study area is small with a high density of optimal transportationservices.

Moreover, for certain extensions of the area of the case study, theinterest of reaching those opportunities could be neglected. In that sense,the study area will be determined by the extension of influence of theactivity we are trying to measure. Unfortunately, this extension cannotbe easily determined since it differs among individuals and this maycreate bias in the accessibility measure.

In order to overcome this limitation, Silva (2008) proposed using anextension such that the region must be wide enough to encompass the main po-tential mobility patterns of an urban agglomeration. However, this proposaldoes not totally solve the limitation.

Comparability of results. Differences between travel cost matrixes be-tween case studies make results incomparable. Contour measures can



is decided based on the subjective perceptions of the author or travelbehaviour data. However, this involves an adaptation to the given trans-port infrastructure and land use which cannot be neglected in the giventravel behaviour. Additionally, those given threshold values fall into afalse homogeneity of behaviour for different population ages (Daviesand James, 2011) and an assumption that travel behaviour does notchange through time, given the same transport infrastructure (Bhat et al.,2000). These two main assumptions might create bias in the final results.

Authors such as Handy and Niemeier (1997), Silva (2008), Baradaranand Ramjerdi (2001), Halden et al. (2005) or Bertolini et al. (2005) pointedout how the previously mentioned limitations related to the thresholdvalue affect the accessibility measure. Some of the proposed solutionsfor the threshold value are based on splitting the values into many con-tours and making them as specific to different population groups as pos-sible (Silva, 2008); (Pirie, 1979). With this application, the contour mea-sure is approximated to a potential accessibility measure and the dis-crimination between contours and population groups is reduced. Otherproposed solutions, also approaching the approximation to potential ac-cessibility measures, are based on considering a more gradual decreasein travel time or cost utility (Bertolini et al., 2005); (Pirie, 1979). Finally,(Silva and Pinho, 2010) use external qualitative evaluations on the decayfunctions and their results as a way to calibrate their functions, calcula-tions and the optimal threshold value of the accessibility index.

All opportunities are treated equally. Several authors have pointedout that all the services or opportunities are treated equally if they arewithin the threshold value and this might not correspond with the ac-tual relevance of the opportunities for the citizens (Voges and Naudé,1983; Curtis and Scheurer, 2010). This factor limits the output of theaccessibility index since it does not reflect real travel behaviour wherecertain services have a higher usage frequency than others.

Proposed solutions are focused on bringing some weight to servicesor opportunities. Weights can be directly based on pre-observed fre-quency of use of the opportunities (Silva, 2008) and calibrated to ob-served travel choices (Handy, 1992) or based on the travel cost as Tillemaet al. (2003) proposed to multiply the travel time by the value of time.Other authors have focused on the influence area of the opportunity as



the attribute for weighting. In this way, Weibull (1976) proposed weight-ing attractions by the number of jobs in a zone and including car own-ership. However, it is worth noticing that all these proposed solutionsassume certain behavioural homogeneity. The frequency of use of op-portunities or the travel mode choices are assumed to be homogeneousamong each population group.

Exclusion of competition effects. The exclusion of competition effectsbetween origins and destinations decreases the reliability of the measure.Competition effects can only then be included by approximating spatialdensities of the opportunities to competition effects. As an example, vanWee et al. (2001) and van Wee et al. (2012) proposed a combination ofvolume of opportunities and competition between working places usingcontour-based measures for measuring the accessibility to work.

Spatial definition of area of analysis. The spatial definition of the areaof analysis strongly affects the final result. In those cases where the mea-sure is based on relative values among citizens or sub-areas of the regionthe effect is stronger (Baradaran and Ramjerdi, 2001). In the cases wherethe study area is big, the relative results of accessibility will tend tooverestimate the accessibility level since areas with very low accessibil-ity have been included in the calculation. The opposite may occur whenthe study area is small with a high density of optimal transportationservices.

Moreover, for certain extensions of the area of the case study, theinterest of reaching those opportunities could be neglected. In that sense,the study area will be determined by the extension of influence of theactivity we are trying to measure. Unfortunately, this extension cannotbe easily determined since it differs among individuals and this maycreate bias in the accessibility measure.

In order to overcome this limitation, Silva (2008) proposed using anextension such that the region must be wide enough to encompass the main po-tential mobility patterns of an urban agglomeration. However, this proposaldoes not totally solve the limitation.

Comparability of results. Differences between travel cost matrixes be-tween case studies make results incomparable. Contour measures can



differ from the simplest cost measure between two areas (e.g. straightdistance between two points), to the most sophisticated ones (e.g. traveltimes considering commuting to the public transport stations and wait-ing for the service). It seems obvious that the more realistic the data, thehigher the chances to obtain representative results. However, obtainingsuch data is often very complicated, if not impossible and results cannotbe compared even if they calculate accessibility using the same method.

Bertolini et al. (2005) proposed using a unit of time or cost sensitive tothe travel purpose and to individual socio-demographic characteristics.However, this remains a vague recommendation. It is to be expected,however, that with the new software available and common platformsfor accessibility calculations the quality and characteristics of the datawill become progressively more standardized among study areas.

Temporal and individual components are not included. The temporalcomponent of accessibility is not included. Authors such as Geurs andvan Eck (2001), Silva (2008) and van Wee et al. (2012) have pointed outthat the lack of temporal components represents a major limitation forcontour-based measures. Common strategies for overcoming this limi-tation are based on creating contour measures for different time laps ofthe day. However, this approach increases the computational work anddata is often unavailable at that level of detail.

The individual component of accessibility is not included. All indi-viduals of a certain group are assumed to have the same travel behaviourand use the same set of opportunities. Contour-based measures are notable to make individual differentiation among citizens (Baradaran andRamjerdi, 2001).

The measure does not correspond to the travel behaviour. The contour-based accessibility measure does not necessarily correspond to the travelbehaviour. Many authors have calculated the spatial and individualcharacteristics that seem to affect travel behaviour (Voges and Naudé,1983) and the choice of transport mode. Therefore, the assumption oftravel behaviour based only on a travel cost matrix may be misleading ifthose other components are not taken into account.

Research shows that the total amount of trips depends on externalvariables from the land use and transport network, such as gender (Tim-



mermans et al., 2003), mixed land use (Handy, 1992; Kitamura et al.,1997; Ewing and Cervero, 2001; Krizek, 2003; Timmermans et al., 2003),location of the transport stations (Handy, 1992; Timmermans et al., 2003),population density (Kitamura et al., 1997; Ewing and Cervero, 2001)and short distances between opportunities (Handy, 1992; Boarnet andSarmiento, 1998; Timmermans et al., 2003).

Additionally, findings show that the use of different transport modesis also influenced by socio-economic variables and spatial variables. Us-age of cars depends on income (Kitamura et al., 1997; Boarnet and Sarmiento,1998; Ryley, 2006), car ownership (Kitamura et al., 1997), children in thehousehold (Kitamura et al., 1997; Hamed and Olaywah, 2000; Dielemanet al., 2002), mixed land use (Cervero and Kockelman, 1997; Boarnet andSarmiento, 1998; Dieleman et al., 2002), population density (Cervero andKockelman, 1997) and the presence of parking lots (O´Fallon et al., 2004).The use of public transportation depends on the presence of children inthe household (Cervero and Kockelman, 1997; Hamed and Olaywah,2000), mixed land use (Cervero and Kockelman, 1997), population den-sity (Cervero and Kockelman, 1997; Ewing and Cervero, 2001) and shortdistances to opportunities (Cervero and Kockelman, 1997). Finally, mo-bility on foot or by bike seems to be correlated to gender (Ryley, 2006),bike ownership (Ryley, 2006), presence of children in the household(Cervero and Kockelman, 1997), mixed land use (Cervero and Kock-elman, 1997), population density (Cervero and Kockelman, 1997; Kita-mura et al., 1997; Ewing and Cervero, 2001) and short distances betweenopportunities (Cervero and Kockelman, 1997; Kingham et al., 2001).

The inclusion of those variables in the cost matrix of contour-basedaccessibility measures should provide more realistic results. However, itremains unclear which weight those variables should have in the finaldecision of choosing a specific transport mode.

Lack of papers comparing accessibility indexes. The lack of paperscomparing the proposed accessibility indexes in the literature makes itmore difficult to identify optimal indexes. Additionally, many indexesare done by and for a specific case study, where threshold values cannotbe extrapolated to other urban areas. Furthermore, the extension of thearea of study and the characteristics of the commuting time databasemake the comparison more difficult.



differ from the simplest cost measure between two areas (e.g. straightdistance between two points), to the most sophisticated ones (e.g. traveltimes considering commuting to the public transport stations and wait-ing for the service). It seems obvious that the more realistic the data, thehigher the chances to obtain representative results. However, obtainingsuch data is often very complicated, if not impossible and results cannotbe compared even if they calculate accessibility using the same method.

Bertolini et al. (2005) proposed using a unit of time or cost sensitive tothe travel purpose and to individual socio-demographic characteristics.However, this remains a vague recommendation. It is to be expected,however, that with the new software available and common platformsfor accessibility calculations the quality and characteristics of the datawill become progressively more standardized among study areas.

Temporal and individual components are not included. The temporalcomponent of accessibility is not included. Authors such as Geurs andvan Eck (2001), Silva (2008) and van Wee et al. (2012) have pointed outthat the lack of temporal components represents a major limitation forcontour-based measures. Common strategies for overcoming this limi-tation are based on creating contour measures for different time laps ofthe day. However, this approach increases the computational work anddata is often unavailable at that level of detail.

The individual component of accessibility is not included. All indi-viduals of a certain group are assumed to have the same travel behaviourand use the same set of opportunities. Contour-based measures are notable to make individual differentiation among citizens (Baradaran andRamjerdi, 2001).

The measure does not correspond to the travel behaviour. The contour-based accessibility measure does not necessarily correspond to the travelbehaviour. Many authors have calculated the spatial and individualcharacteristics that seem to affect travel behaviour (Voges and Naudé,1983) and the choice of transport mode. Therefore, the assumption oftravel behaviour based only on a travel cost matrix may be misleading ifthose other components are not taken into account.

Research shows that the total amount of trips depends on externalvariables from the land use and transport network, such as gender (Tim-



mermans et al., 2003), mixed land use (Handy, 1992; Kitamura et al.,1997; Ewing and Cervero, 2001; Krizek, 2003; Timmermans et al., 2003),location of the transport stations (Handy, 1992; Timmermans et al., 2003),population density (Kitamura et al., 1997; Ewing and Cervero, 2001)and short distances between opportunities (Handy, 1992; Boarnet andSarmiento, 1998; Timmermans et al., 2003).

Additionally, findings show that the use of different transport modesis also influenced by socio-economic variables and spatial variables. Us-age of cars depends on income (Kitamura et al., 1997; Boarnet and Sarmiento,1998; Ryley, 2006), car ownership (Kitamura et al., 1997), children in thehousehold (Kitamura et al., 1997; Hamed and Olaywah, 2000; Dielemanet al., 2002), mixed land use (Cervero and Kockelman, 1997; Boarnet andSarmiento, 1998; Dieleman et al., 2002), population density (Cervero andKockelman, 1997) and the presence of parking lots (O´Fallon et al., 2004).The use of public transportation depends on the presence of children inthe household (Cervero and Kockelman, 1997; Hamed and Olaywah,2000), mixed land use (Cervero and Kockelman, 1997), population den-sity (Cervero and Kockelman, 1997; Ewing and Cervero, 2001) and shortdistances to opportunities (Cervero and Kockelman, 1997). Finally, mo-bility on foot or by bike seems to be correlated to gender (Ryley, 2006),bike ownership (Ryley, 2006), presence of children in the household(Cervero and Kockelman, 1997), mixed land use (Cervero and Kock-elman, 1997), population density (Cervero and Kockelman, 1997; Kita-mura et al., 1997; Ewing and Cervero, 2001) and short distances betweenopportunities (Cervero and Kockelman, 1997; Kingham et al., 2001).

The inclusion of those variables in the cost matrix of contour-basedaccessibility measures should provide more realistic results. However, itremains unclear which weight those variables should have in the finaldecision of choosing a specific transport mode.

Lack of papers comparing accessibility indexes. The lack of paperscomparing the proposed accessibility indexes in the literature makes itmore difficult to identify optimal indexes. Additionally, many indexesare done by and for a specific case study, where threshold values cannotbe extrapolated to other urban areas. Furthermore, the extension of thearea of study and the characteristics of the commuting time databasemake the comparison more difficult.



In the current study I aim to explore these limitations and throughthe papers presented in the thesis, support some of the proposals forimprovement that have been put forward previously.


3 Summary of the researchpapers

In this thesis, contour-based accessibility was calculated in three differ-ent applications. The first application focused on the citizen, analysing asuitable area of residence based on his/her own personal criteria (PaperI and Paper III). For the second application, accessibility was used asan indicator of transport sustainability and potential mobility inequal-ities were discussed (Paper II and Paper III). The output of this studywas targeted for urban and transport planners and policy makers. Fi-nally, the third application was focused on identifying potential mobilityinequalities and supporting policies for transport sustainability (PaperII and Paper III). In all three papers, policy makers from the respec-tive cities were informed about the results so that they could use themin their investment or operation decisions. Their qualitative evaluationwas collected through interviews.

In the current work, I have used the definition of accessibility pro-posed by Geurs and van Eck (2001) since their definition proposed theaccessibility components which are very useful for evaluating and com-paring accessibility measures in our research papers and discussing themathematical background between measures. This thesis is focused onaccessibility, based on physical travel, and consequently other types ofmobilities proposed by Larsen et al. (2006) and Urry and Grieco (2011)are not pursued in the current work. Additionally, our measurement ofaccessibility is based on reaching a minimal diversity of services or op-portunities within a travel time. Therefore, land use is considered as anindividual system where ideally a pattern or set of services is repeatedfor each spatial unit. The limit of the spatial unit is marked by the valueof the threshold travel time used in the measure.

The contour measures used in the papers have been chosen and/ormodified from those previously proposed. The calculations consideredthe transport network, in the form of expected travel times and the spa-tial distribution of the opportunities. The opportunities were preselected



In the current study I aim to explore these limitations and throughthe papers presented in the thesis, support some of the proposals forimprovement that have been put forward previously.


3 Summary of the researchpapers

In this thesis, contour-based accessibility was calculated in three differ-ent applications. The first application focused on the citizen, analysing asuitable area of residence based on his/her own personal criteria (PaperI and Paper III). For the second application, accessibility was used asan indicator of transport sustainability and potential mobility inequal-ities were discussed (Paper II and Paper III). The output of this studywas targeted for urban and transport planners and policy makers. Fi-nally, the third application was focused on identifying potential mobilityinequalities and supporting policies for transport sustainability (PaperII and Paper III). In all three papers, policy makers from the respec-tive cities were informed about the results so that they could use themin their investment or operation decisions. Their qualitative evaluationwas collected through interviews.

In the current work, I have used the definition of accessibility pro-posed by Geurs and van Eck (2001) since their definition proposed theaccessibility components which are very useful for evaluating and com-paring accessibility measures in our research papers and discussing themathematical background between measures. This thesis is focused onaccessibility, based on physical travel, and consequently other types ofmobilities proposed by Larsen et al. (2006) and Urry and Grieco (2011)are not pursued in the current work. Additionally, our measurement ofaccessibility is based on reaching a minimal diversity of services or op-portunities within a travel time. Therefore, land use is considered as anindividual system where ideally a pattern or set of services is repeatedfor each spatial unit. The limit of the spatial unit is marked by the valueof the threshold travel time used in the measure.

The contour measures used in the papers have been chosen and/ormodified from those previously proposed. The calculations consideredthe transport network, in the form of expected travel times and the spa-tial distribution of the opportunities. The opportunities were preselected



in the case of specific accessibility analysis for different population agegroups; and for the case of SAL (Silva and Pinho, 2010), the catego-rization included a weight based on the sum frequency of use of thoseactivities that cannot be reached by public transport or on foot. 1

The aim of the scientific papers presented in the current thesis is,based on the applications described above, to analyse and propose solu-tions for integrating the individual component in the measure and waysto overcome the limitations presented from the use of threshold values.In the following sections, a summary for each of the papers is presented.

3.1 CONTOUR-BASED MEASURE FOR THE SELECTION OF RES-IDENCE LOCATION

Paper I uses the city of Kuopio (Finland) as a case study area to im-plement a contour-based accessibility tool for selecting the location ofresidence. Previous studies considered local opinions as an informationsource for future urban development; however none of them examinedthe relation between the location of residence and the perception of theliving environment. The decision support tool presented in Paper I is forthe first time developed for ordinary people rather than for city plannersand delivers one tool to the debate about a stronger public participationin the urban development processes. The paper uses the principles ofmulti-criteria decision analysis (see for example Malczewski (2006)) forweighting the characteristics of opportunities in living areas. The qualityof the services is based on contour distance following the road network.The user could select (as described in the case studies) the requiredlevel of quality for each of the services and the resulting intersectionareas closer to his/her requirements would be shown to him/her. Addi-tionally, dwellings found in the selected areas would also be ranked sothat the final output were dwellings fulfilling the housing requirementsranked according to the living area requirements.

Paper I explores the usage of contour measures as a multi-criteriadecision analysis tool for selecting the location of residence. This par-ticipatory GIS tool, which is based on contour-based measures, would

1See Albacete et al. 2015 and Albacete et al. 2015b for a more detailed explanation ofthe services used for the study and frequent destinations in the case study area.


Summary of the research papers

be a useful method for linking better the interests of customers, real es-tate companies and city planning. This approach is relevant because itshows that multi-criteria decision analysis could be useful for two rea-sons: firstly, to integrate individual components into contour measures;and secondly, to collect individual data in a mutually beneficial situationbetween the customers, real estate companies and city administration.

The main contribution from the study run in Paper I presents a wayto integrate the individual component in the contour-based accessibil-ity measure. Additionally it examines the relation between the locationof residence and the perceived living environment. In this case, theapproach is done by integrating the individual priorities into an acces-sibility map. This is to say, the proposed tool advocates that the inte-gration of individual components could be done by the automation ofsuch tools and collecting the individual priorities from the system. Thecriteria selected by the user is proposed as a proxy for measuring theself-perceived needs, abilities and opportunities of the citizens. Addi-tionally, the integration of the data from the individual to the collectivemeasure allows one to overcome the need to fix a single threshold value,since the final output is based on a combination of variables with sixdifferent levels and a threshold value for each of them. Additionally, thethreshold value for each level was not the same for each variable, in-creasing even more the diversity of potential outputs and the adaptationto the citizen’s requirements.

3.2 COMPARISON OF SAL AND PTWAI AS SUSTAINABLE AC-CESSIBILITY INDICATORS

In Paper II, two contour-based accessibility measures, SAL and PTWAI,were compared. These measures had been created by Silva (2008) andMavoa et al. (2012) respectively as a suitable tool for measuring acces-sibility by public transport. In our paper, the Helsinki Capital Regionwas used as a case study and socio-demographic data was afterwardscomposed with the calculated indexes. Finally, our results were vali-dated through interviews with local experts in transportation and urbanplanning.

The goal of the study was to validate the utility of both measuresas indicators of accessibility by public transport and on foot. Results



in the case of specific accessibility analysis for different population agegroups; and for the case of SAL (Silva and Pinho, 2010), the catego-rization included a weight based on the sum frequency of use of thoseactivities that cannot be reached by public transport or on foot. 1

The aim of the scientific papers presented in the current thesis is,based on the applications described above, to analyse and propose solu-tions for integrating the individual component in the measure and waysto overcome the limitations presented from the use of threshold values.In the following sections, a summary for each of the papers is presented.

3.1 CONTOUR-BASED MEASURE FOR THE SELECTION OF RES-IDENCE LOCATION

Paper I uses the city of Kuopio (Finland) as a case study area to im-plement a contour-based accessibility tool for selecting the location ofresidence. Previous studies considered local opinions as an informationsource for future urban development; however none of them examinedthe relation between the location of residence and the perception of theliving environment. The decision support tool presented in Paper I is forthe first time developed for ordinary people rather than for city plannersand delivers one tool to the debate about a stronger public participationin the urban development processes. The paper uses the principles ofmulti-criteria decision analysis (see for example Malczewski (2006)) forweighting the characteristics of opportunities in living areas. The qualityof the services is based on contour distance following the road network.The user could select (as described in the case studies) the requiredlevel of quality for each of the services and the resulting intersectionareas closer to his/her requirements would be shown to him/her. Addi-tionally, dwellings found in the selected areas would also be ranked sothat the final output were dwellings fulfilling the housing requirementsranked according to the living area requirements.

Paper I explores the usage of contour measures as a multi-criteriadecision analysis tool for selecting the location of residence. This par-ticipatory GIS tool, which is based on contour-based measures, would

1See Albacete et al. 2015 and Albacete et al. 2015b for a more detailed explanation ofthe services used for the study and frequent destinations in the case study area.



be a useful method for linking better the interests of customers, real es-tate companies and city planning. This approach is relevant because itshows that multi-criteria decision analysis could be useful for two rea-sons: firstly, to integrate individual components into contour measures;and secondly, to collect individual data in a mutually beneficial situationbetween the customers, real estate companies and city administration.

The main contribution from the study run in Paper I presents a wayto integrate the individual component in the contour-based accessibil-ity measure. Additionally it examines the relation between the locationof residence and the perceived living environment. In this case, theapproach is done by integrating the individual priorities into an acces-sibility map. This is to say, the proposed tool advocates that the inte-gration of individual components could be done by the automation ofsuch tools and collecting the individual priorities from the system. Thecriteria selected by the user is proposed as a proxy for measuring theself-perceived needs, abilities and opportunities of the citizens. Addi-tionally, the integration of the data from the individual to the collectivemeasure allows one to overcome the need to fix a single threshold value,since the final output is based on a combination of variables with sixdifferent levels and a threshold value for each of them. Additionally, thethreshold value for each level was not the same for each variable, in-creasing even more the diversity of potential outputs and the adaptationto the citizen’s requirements.

3.2 COMPARISON OF SAL AND PTWAI AS SUSTAINABLE AC-CESSIBILITY INDICATORS

In Paper II, two contour-based accessibility measures, SAL and PTWAI,were compared. These measures had been created by Silva (2008) andMavoa et al. (2012) respectively as a suitable tool for measuring acces-sibility by public transport. In our paper, the Helsinki Capital Regionwas used as a case study and socio-demographic data was afterwardscomposed with the calculated indexes. Finally, our results were vali-dated through interviews with local experts in transportation and urbanplanning.

The goal of the study was to validate the utility of both measuresas indicators of accessibility by public transport and on foot. Results



from this comparison would help decision makers such as urban andtransport planners to identify which method is more suitable for thatpurpose. There is a lack of comparative studies between accessibilityindexes that has been often pointed out in the literature (see for exampleCurl et al. (2011) and Mavoa et al. (2012)); but few comparative studieshad been done till the moment in that direction (Kwan, 1998; Kim andKwan, 2003; Lei and Church, 2010; Páez et al., 2012). The contributionof Paper II was directed to overcome the lack.

Although the method for calculating the measures was similar be-tween the methods, the concept of accessibility which was assumed dif-fered between them. In SAL (Silva and Pinho, 2010), accessibility isbased on the Diversity of Activities previously proposed by Cervero andKockelman (1997). It assumes that accessibility increases when the diver-sity of activities reachable within a given threshold value increases. Incontrast, in PTWAI (Mavoa et al., 2012), the accessibility index is basedon weighting the opportunities based on the category of the contourwhere they are located (the closer they are, the higher their weighting inthe final score).

Paper II underlined the differences in methodology and performancebetween the methods. SAL (Silva and Pinho, 2010) presented a singlethreshold value for its calculation whereas PTWAI (Mavoa et al., 2012)presented multiple threshold values which are combined for its calcu-lation. This difference explained the more fine-grained analysis of PT-WAI. Additionally, interviews with the local experts supported our find-ings. Therefore, PTWAI is recommended when the goal of the accessi-bility measure is to evaluate access to public transportation and walking(which is often related to the concept of sustainable mobility). On theother hand, since SAL is an index created for the categorization of ac-cessibility in urban areas based on multiple travel modes (walking, carand public transport), we found that this index is more suitable whenthe goal is to categorize an urban area and identify transportation in-frastructure needs.

The findings from Paper II showed that bias from the threshold valuerather than the assumption of homogeneity within population cohorts,or the establishment of threshold values based on observed travel be-haviour can be partially overcome when the measure is based on mul-tiple threshold values. The diversity of threshold values increases the



robustness of the measure and increases the definition of the results.Therefore, our findings tackled the strategies to follow to overcome thelimitation from the use of threshold value in contour-based accessibil-ity measures. Our findings proved that the subdivision of the thresholdvalue into sub-thresholds and adding a weight improves the final defi-nition of the measure without significantly increasing the computationalrequirements.

3.3 CONTOUR MEASURES FOR MANAGEMENT OF PUBLIC SER-VICES

Although previous studies assessed the accessibility for elderly popu-lation (Love and Lindquist, 1995; Mercado et al., 2010; Frändberg andVilhelmson, 2011; Horner et al., 2015); no previous studies have been as-sessing the potential accessibility categories for each population cohort.

The Paper III approaches accessibility categories for specific pop-ulation cohorts based on a modification of the Structural AccessibilityLayer (SAL) (Silva and Pinho, 2010). It was modified in order to calcu-late categories of potential accessibility for specific population cohorts.SAL was originally developed to assess accessibility categories in urbanareas based on combinations of the different levels of the dissimilarityindex reached by each transport mode. This type of measure is espe-cially useful since it allows the selection of services to be included in thecalculation and their weighting based on the frequency of usage. Theaccessibility categories obtained from this approach indicates potentialtransport modes feasible to be used for reaching the set of services in-cluded in the measure. This represents a calculation and visualization ofpotential mobility based on the spatial distribution of the services andthe characteristics of the transport network.

The goal of Paper III was by using SAL for specific services for eachpopulation age group in the Helsinki area; to identify potential gapsin accessibility and additionally, propose potential zones of the city forurban development which were already providing good accessibility onfoot and by public transport. The contribution of the paper was notonly directed to improve contour-based accessibility measures but alsoto point out the lack of provision of transportation and services for thedifferent population cohorts. Results from the study show that a high



from this comparison would help decision makers such as urban andtransport planners to identify which method is more suitable for thatpurpose. There is a lack of comparative studies between accessibilityindexes that has been often pointed out in the literature (see for exampleCurl et al. (2011) and Mavoa et al. (2012)); but few comparative studieshad been done till the moment in that direction (Kwan, 1998; Kim andKwan, 2003; Lei and Church, 2010; Páez et al., 2012). The contributionof Paper II was directed to overcome the lack.

Although the method for calculating the measures was similar be-tween the methods, the concept of accessibility which was assumed dif-fered between them. In SAL (Silva and Pinho, 2010), accessibility isbased on the Diversity of Activities previously proposed by Cervero andKockelman (1997). It assumes that accessibility increases when the diver-sity of activities reachable within a given threshold value increases. Incontrast, in PTWAI (Mavoa et al., 2012), the accessibility index is basedon weighting the opportunities based on the category of the contourwhere they are located (the closer they are, the higher their weighting inthe final score).

Paper II underlined the differences in methodology and performancebetween the methods. SAL (Silva and Pinho, 2010) presented a singlethreshold value for its calculation whereas PTWAI (Mavoa et al., 2012)presented multiple threshold values which are combined for its calcu-lation. This difference explained the more fine-grained analysis of PT-WAI. Additionally, interviews with the local experts supported our find-ings. Therefore, PTWAI is recommended when the goal of the accessi-bility measure is to evaluate access to public transportation and walking(which is often related to the concept of sustainable mobility). On theother hand, since SAL is an index created for the categorization of ac-cessibility in urban areas based on multiple travel modes (walking, carand public transport), we found that this index is more suitable whenthe goal is to categorize an urban area and identify transportation in-frastructure needs.

The findings from Paper II showed that bias from the threshold valuerather than the assumption of homogeneity within population cohorts,or the establishment of threshold values based on observed travel be-haviour can be partially overcome when the measure is based on mul-tiple threshold values. The diversity of threshold values increases the



robustness of the measure and increases the definition of the results.Therefore, our findings tackled the strategies to follow to overcome thelimitation from the use of threshold value in contour-based accessibil-ity measures. Our findings proved that the subdivision of the thresholdvalue into sub-thresholds and adding a weight improves the final defi-nition of the measure without significantly increasing the computationalrequirements.

3.3 CONTOUR MEASURES FOR MANAGEMENT OF PUBLIC SER-VICES

Although previous studies assessed the accessibility for elderly popu-lation (Love and Lindquist, 1995; Mercado et al., 2010; Frändberg andVilhelmson, 2011; Horner et al., 2015); no previous studies have been as-sessing the potential accessibility categories for each population cohort.

The Paper III approaches accessibility categories for specific pop-ulation cohorts based on a modification of the Structural AccessibilityLayer (SAL) (Silva and Pinho, 2010). It was modified in order to calcu-late categories of potential accessibility for specific population cohorts.SAL was originally developed to assess accessibility categories in urbanareas based on combinations of the different levels of the dissimilarityindex reached by each transport mode. This type of measure is espe-cially useful since it allows the selection of services to be included in thecalculation and their weighting based on the frequency of usage. Theaccessibility categories obtained from this approach indicates potentialtransport modes feasible to be used for reaching the set of services in-cluded in the measure. This represents a calculation and visualization ofpotential mobility based on the spatial distribution of the services andthe characteristics of the transport network.

The goal of Paper III was by using SAL for specific services for eachpopulation age group in the Helsinki area; to identify potential gapsin accessibility and additionally, propose potential zones of the city forurban development which were already providing good accessibility onfoot and by public transport. The contribution of the paper was notonly directed to improve contour-based accessibility measures but alsoto point out the lack of provision of transportation and services for thedifferent population cohorts. Results from the study show that a high



percentage of the groups of Children from 0 to 7 years old and Studentswere located in areas with medium or low accessibility whereas a veryhigh percentage of the Pensioners group were living in areas with goodaccess by public transport.2 When looking at areas with good acces-sibility on foot and public transport but with low population density,in some cases urban development was not possible since the area wasoccupied by a park, but for the other areas, they matched the zones ofinterest for development established by the local urban planners.

Categorization of the accessibility for each of the population groupswas handled by a pre-selection of the services targeted for each of thepopulation groups.

Findings from Paper III showed that when the opportunities in-cluded in the contour-based accessibility measures are split, the outcomeaccessibility maps fit with the socio-dynamics observed by the local ex-perts. This is to say, with the obtained accessibility categories, when con-trasted with the living locations for the different population cohorts, themeasure is well-adjusted to the local residential dynamics. Therefore,the current paper proved that the individual component can partially beimplemented in contour-based accessibility measures by splitting the setof opportunities included into each of the population cohorts.

2see Table 3 in Paper III for more detailed results


4 Conclusion and discussion

4.1 SUMMARY OF THE RESULTS

The aim of this thesis is to contribute to finding improvements for contour-based measures as well as a better identification of their limitations. Themain focus is placed on identifying ways to include the individual com-ponent and overcome the limitations related to the use of threshold val-ues in the measure.

The results presented in Paper I and Paper III suggest possibilitiesfor integrating the individual component into contour-based accessi-bility measures. Individual characteristics can be better integrated inthese types of accessibility measures by using mostly two approaches.The first approach in my work is based on creating a compound in-dex which customises the accessibility index for every type of citizen orwhatever it is desired to split the population into. The second approachis based on splitting the value given to the contour measurement intoas many threshold values as we can ensure or where there is some pre-vious knowledge of the level of quality for the citizens. By doing so,we are approximating the contour measure to a potential accessibilitymeasure without increasing significantly the computation requirementsor sacrificing the easy interpretation of the results.

Paper I showed how individual priorities from the population aboutthe characteristics of their residential area could be combined usingcontour-based measures (in some cases the travel cost was in terms ofdistance and for other variables it was the impediment of pollution andnoise level). Nevertheless, this approach reinforces the findings of thefirst research question; only the opportunities can be pre-established (setof services the citizen chooses from) but we still need to assume that thecitizen makes his/her own utility calculation for the different alterna-tives where the needs and abilities are counted.

Paper III showed that splitting the contour measure by pre-selectingthe set of opportunities to be included in the measure seems to deliveraccessibility results better fitted to the social dynamics in the urban area.Therefore, although this strategy increases the computational require-



percentage of the groups of Children from 0 to 7 years old and Studentswere located in areas with medium or low accessibility whereas a veryhigh percentage of the Pensioners group were living in areas with goodaccess by public transport.2 When looking at areas with good acces-sibility on foot and public transport but with low population density,in some cases urban development was not possible since the area wasoccupied by a park, but for the other areas, they matched the zones ofinterest for development established by the local urban planners.

Categorization of the accessibility for each of the population groupswas handled by a pre-selection of the services targeted for each of thepopulation groups.

Findings from Paper III showed that when the opportunities in-cluded in the contour-based accessibility measures are split, the outcomeaccessibility maps fit with the socio-dynamics observed by the local ex-perts. This is to say, with the obtained accessibility categories, when con-trasted with the living locations for the different population cohorts, themeasure is well-adjusted to the local residential dynamics. Therefore,the current paper proved that the individual component can partially beimplemented in contour-based accessibility measures by splitting the setof opportunities included into each of the population cohorts.

2see Table 3 in Paper III for more detailed results


4 Conclusion and discussion

4.1 SUMMARY OF THE RESULTS

The aim of this thesis is to contribute to finding improvements for contour-based measures as well as a better identification of their limitations. Themain focus is placed on identifying ways to include the individual com-ponent and overcome the limitations related to the use of threshold val-ues in the measure.

The results presented in Paper I and Paper III suggest possibilitiesfor integrating the individual component into contour-based accessi-bility measures. Individual characteristics can be better integrated inthese types of accessibility measures by using mostly two approaches.The first approach in my work is based on creating a compound in-dex which customises the accessibility index for every type of citizen orwhatever it is desired to split the population into. The second approachis based on splitting the value given to the contour measurement intoas many threshold values as we can ensure or where there is some pre-vious knowledge of the level of quality for the citizens. By doing so,we are approximating the contour measure to a potential accessibilitymeasure without increasing significantly the computation requirementsor sacrificing the easy interpretation of the results.

Paper I showed how individual priorities from the population aboutthe characteristics of their residential area could be combined usingcontour-based measures (in some cases the travel cost was in terms ofdistance and for other variables it was the impediment of pollution andnoise level). Nevertheless, this approach reinforces the findings of thefirst research question; only the opportunities can be pre-established (setof services the citizen chooses from) but we still need to assume that thecitizen makes his/her own utility calculation for the different alterna-tives where the needs and abilities are counted.

Paper III showed that splitting the contour measure by pre-selectingthe set of opportunities to be included in the measure seems to deliveraccessibility results better fitted to the social dynamics in the urban area.Therefore, although this strategy increases the computational require-



ments, if the calculation is automated, the gain of fitting of the resultsis higher than the additional required computational costs. This strat-egy allows a better fitting of the individual components of the citizens(threshold values adapted to their capacities and constraints).

However, the approximation still does not include all the elementsfrom the individual component. Theoretically, it could be possible toinclude the needs, abilities and opportunities (elements comprising theindividual component); but the computational cost would be high and,what is more important, combining the individual models would be ahard task which may have potential fuzziness in the results. Utility ortime-space accessibility measures seem to deliver better results for thatpurpose.

The second research question is related to the limitations as a conse-quence of the use of threshold values. In order to assess the question,Paper I and Paper II explored two ways for overcoming the usage ofthreshold values based on observed travel behaviour and the false as-sumption of cohort homogeneity when applying one single thresholdvalue for the same population cohort.

Results from Paper I show that categorization of opportunities withmultiple threshold values based on observed/recommended distancesis a valid approach for delivering individualized accessibility measuresand overcoming the false principle of cohort homogeneity. Additionally,although the initial threshold values are based on observed travel be-haviours, the possibility for the citizen to select intermediate thresholdvalues overcomes this limitation.

Paper II supports the findings from Paper I regarding the splitting ofthreshold values into subcategories. The usage of multiple contours inPTWAI and its validation by local experts, proved that usage of multiplethreshold values, their categorization and integration of the categoryvalues improve the robustness of the measure. Regardless of the usageof threshold values based on observed travel behaviour, Paper II didnot approach the limitation of assuming the same threshold value forall the population. However, current new data delivered more discretethreshold values for smaller cohorts. It is expected that, in future, moreprecise threshold values and more complete data sets will allow morerealistic calculations.

In conclusion, research question 1 has been answered in Paper I and


Conclusion and discussion

Paper III; while research question 2 from the current thesis has beenanswered in Paper I and Paper II. Although the fields of applicationdiffer between papers, the methods used and the quality of their outputhave been comparable and useful for answering the questions in thedissertation.

Figure 4.1: Schematic diagram of the research questions presented in thecurrent thesis, papers and findings. Made by the author.

4.2 CONTRIBUTION OF THE RESEARCH

The results from the articles included in this thesis showed the possi-bilities of including individual components in contour-based accessibil-ity measures. As previously pointed out by Geurs and van Eck (2001)and others, the inclusion can only be done implicitly through data im-provements, by approximating the measure to a potential accessibilitymeasure by splitting its decay function or by integrating the weighting



ments, if the calculation is automated, the gain of fitting of the resultsis higher than the additional required computational costs. This strat-egy allows a better fitting of the individual components of the citizens(threshold values adapted to their capacities and constraints).

However, the approximation still does not include all the elementsfrom the individual component. Theoretically, it could be possible toinclude the needs, abilities and opportunities (elements comprising theindividual component); but the computational cost would be high and,what is more important, combining the individual models would be ahard task which may have potential fuzziness in the results. Utility ortime-space accessibility measures seem to deliver better results for thatpurpose.

The second research question is related to the limitations as a conse-quence of the use of threshold values. In order to assess the question,Paper I and Paper II explored two ways for overcoming the usage ofthreshold values based on observed travel behaviour and the false as-sumption of cohort homogeneity when applying one single thresholdvalue for the same population cohort.

Results from Paper I show that categorization of opportunities withmultiple threshold values based on observed/recommended distancesis a valid approach for delivering individualized accessibility measuresand overcoming the false principle of cohort homogeneity. Additionally,although the initial threshold values are based on observed travel be-haviours, the possibility for the citizen to select intermediate thresholdvalues overcomes this limitation.

Paper II supports the findings from Paper I regarding the splitting ofthreshold values into subcategories. The usage of multiple contours inPTWAI and its validation by local experts, proved that usage of multiplethreshold values, their categorization and integration of the categoryvalues improve the robustness of the measure. Regardless of the usageof threshold values based on observed travel behaviour, Paper II didnot approach the limitation of assuming the same threshold value forall the population. However, current new data delivered more discretethreshold values for smaller cohorts. It is expected that, in future, moreprecise threshold values and more complete data sets will allow morerealistic calculations.

In conclusion, research question 1 has been answered in Paper I and



Paper III; while research question 2 from the current thesis has beenanswered in Paper I and Paper II. Although the fields of applicationdiffer between papers, the methods used and the quality of their outputhave been comparable and useful for answering the questions in thedissertation.

Figure 4.1: Schematic diagram of the research questions presented in thecurrent thesis, papers and findings. Made by the author.

4.2 CONTRIBUTION OF THE RESEARCH

The results from the articles included in this thesis showed the possi-bilities of including individual components in contour-based accessibil-ity measures. As previously pointed out by Geurs and van Eck (2001)and others, the inclusion can only be done implicitly through data im-provements, by approximating the measure to a potential accessibilitymeasure by splitting its decay function or by integrating the weighting



of the opportunities in the process of the creation of a compound acces-sibility index. The papers included in this thesis and the evaluation oftheir results with local experts confirm the previous suggestions. The ap-plication of these suggestions does not make contour-based accessibilitymeasures explicitly include the individual component, but they approx-imate it more while keeping the computing and data costs down, as wellas providing easy interpretation as the main advantages in comparisonwith other types of measures.

Previous knowledge about the threshold values (as specific as possi-ble) and having a fine working resolution for the spatial analysis seemto be constant factors that constrain the quality of accessibility indexes.The results from the presented papers support the suggestion that calcu-lation of a final compound index may help to approximate the availabledata to the logic followed by citizens when taking their mobility deci-sion; but as explained in section 4.1, only opportunities can be explicitlyincluded in the calculation.

The current thesis supports the suggestions proposed by Pirie (1979),Silva (2008) and Silva and Pinho (2010) in order to overcome the subjec-tivity of the applied threshold value for the calculation. Additionally,Paper II and Paper III support the proposals from Handy (1992) andSilva (2008) on using an observed travel pattern in order to calibrate theweighting of the alternatives. This approximation was supported espe-cially with the findings in Paper II where PTWAI gives more realisticresults when compared with SAL because of its weighting based on thecontour distance. Finally, this thesis clearly contributed to the need pro-posed by Mavoa et al. (2012) and others to compare different accessibilityindexes and discuss their utility based on their purpose.

Additionally, on the practical side, the papers presented in the thesisshow that the applications of contour accessibility measures could stillbenefit from a wider range of fields of usage. In the current work, thecontribution was done using a wide range applications; from selectionof residential location, as tool for managing service locations, and as anindex for measuring the quality of public transport. It can be concludedthat contour-based measures could be used for any type of applicationwhere we want to estimate the priorities (individually or collectively)with low computing and data costs.

In conclusion, this thesis supports the idea that improving the refine-



ment of travel behaviour data, splitting the decay function, integratingsome weighting to the opportunities and refining threshold values arevalid ways to obtain more realistic accessibility indexes without losingthe advantages of contour-based accessibility measures.

4.3 EVALUATION OF THE RESEARCH

The evaluation of the current research has been done through two sources.On the one hand, the academic quality of the findings has been re-viewed in peer-reviewed journals and international conferences wherethis research was submitted. In that sense, the scientific community hasshown its interest in the results described in this thesis and the appli-cations that are proposed. On the other hand, this research has alsobeen evaluated by local experts on transportation and urban planning,who at the same time have quality evaluations from the citizens. Thissecond evaluation has been useful for contrasting the academic findingswith the real perception of the local population as well as seeing that theproposed applications are of use to local experts.

It was not the aim of the current thesis to cover all the potentialapplications that contour-based accessibility measures can offer, nor tocompare all the contour-based accessibility indexes that have been pre-viously proposed since such work would be beyond the scope and ca-pacities of this thesis. However, the presented work supports previouslyproposed improvements on the contour-based measures and suggestsnew applications which, given their low computing cost compared toother type of measures, would be useful if applied in real cases.

4.4 FUTURE RESEARCH

The research on accessibility measures is developing quickly and is widen-ing their usage while creating a higher complexity in the proposed mod-els. As discovered in this work, contour-based measures depend greatlyon the amount of threshold values that could be extracted from the ob-served travel behaviour. In that sense the development of mobile appli-cations for collecting individual data on travel behaviour, as well as thedevelopment of software for that, which is now taking place, anticipatesthe relevant development of accessibility measures in the future. There



of the opportunities in the process of the creation of a compound acces-sibility index. The papers included in this thesis and the evaluation oftheir results with local experts confirm the previous suggestions. The ap-plication of these suggestions does not make contour-based accessibilitymeasures explicitly include the individual component, but they approx-imate it more while keeping the computing and data costs down, as wellas providing easy interpretation as the main advantages in comparisonwith other types of measures.

Previous knowledge about the threshold values (as specific as possi-ble) and having a fine working resolution for the spatial analysis seemto be constant factors that constrain the quality of accessibility indexes.The results from the presented papers support the suggestion that calcu-lation of a final compound index may help to approximate the availabledata to the logic followed by citizens when taking their mobility deci-sion; but as explained in section 4.1, only opportunities can be explicitlyincluded in the calculation.

The current thesis supports the suggestions proposed by Pirie (1979),Silva (2008) and Silva and Pinho (2010) in order to overcome the subjec-tivity of the applied threshold value for the calculation. Additionally,Paper II and Paper III support the proposals from Handy (1992) andSilva (2008) on using an observed travel pattern in order to calibrate theweighting of the alternatives. This approximation was supported espe-cially with the findings in Paper II where PTWAI gives more realisticresults when compared with SAL because of its weighting based on thecontour distance. Finally, this thesis clearly contributed to the need pro-posed by Mavoa et al. (2012) and others to compare different accessibilityindexes and discuss their utility based on their purpose.

Additionally, on the practical side, the papers presented in the thesisshow that the applications of contour accessibility measures could stillbenefit from a wider range of fields of usage. In the current work, thecontribution was done using a wide range applications; from selectionof residential location, as tool for managing service locations, and as anindex for measuring the quality of public transport. It can be concludedthat contour-based measures could be used for any type of applicationwhere we want to estimate the priorities (individually or collectively)with low computing and data costs.

In conclusion, this thesis supports the idea that improving the refine-



ment of travel behaviour data, splitting the decay function, integratingsome weighting to the opportunities and refining threshold values arevalid ways to obtain more realistic accessibility indexes without losingthe advantages of contour-based accessibility measures.

4.3 EVALUATION OF THE RESEARCH

The evaluation of the current research has been done through two sources.On the one hand, the academic quality of the findings has been re-viewed in peer-reviewed journals and international conferences wherethis research was submitted. In that sense, the scientific community hasshown its interest in the results described in this thesis and the appli-cations that are proposed. On the other hand, this research has alsobeen evaluated by local experts on transportation and urban planning,who at the same time have quality evaluations from the citizens. Thissecond evaluation has been useful for contrasting the academic findingswith the real perception of the local population as well as seeing that theproposed applications are of use to local experts.

It was not the aim of the current thesis to cover all the potentialapplications that contour-based accessibility measures can offer, nor tocompare all the contour-based accessibility indexes that have been pre-viously proposed since such work would be beyond the scope and ca-pacities of this thesis. However, the presented work supports previouslyproposed improvements on the contour-based measures and suggestsnew applications which, given their low computing cost compared toother type of measures, would be useful if applied in real cases.

4.4 FUTURE RESEARCH

The research on accessibility measures is developing quickly and is widen-ing their usage while creating a higher complexity in the proposed mod-els. As discovered in this work, contour-based measures depend greatlyon the amount of threshold values that could be extracted from the ob-served travel behaviour. In that sense the development of mobile appli-cations for collecting individual data on travel behaviour, as well as thedevelopment of software for that, which is now taking place, anticipatesthe relevant development of accessibility measures in the future. There



is a call therefore for utility and time-space accessibility measures to bedeveloped more strongly than they have been so far, but the commu-nicative and easy computational advantages of contour measures sug-gest that they will be used (as explained in our papers for some specificapplications) more widely than they are at the present. Additionally,such software development would allow comparison between measuresand among study areas as suggested, for example in SNAMUTS (Curtisand Scheurer, 2010).

However, the limitation for integrating the individual and temporalcomponent as well as their capacity for integrating the competition ef-fects between opportunities remain in the nature of contour measure.However, in the future research is expected to have available a big-ger amount and more detailed individual data on travel behaviour andsocio-economic characteristics. Aggregation of the observed weightingof opportunities and travel behaviour contrasted with some individualdata could describe the needs and limitations of the citizens.

Finally, a very promising research direction for transport and urbanplanners is towards a more cognitive accessibility. The relative accessi-bility proposed by Páez et al. (2010) based on the expansion models ofCasetti (1972) has shown that travel behaviour has a strong componentof the individual perception of the distances that can be travelled by eachtransport mode and the will to expend certain time or monetary costson them. Therefore, if the goal for urban planners is to influence travelbehaviour, there seems to be room for modifying it by influencing theperception of the population (for example by campaigns) without theneed for much modification of the existing transportation system northe distribution of services in the region.


Bibliography

Baradaran, S. and Ramjerdi, F. (2001). Performance of accessibilitymeasures in Europe. Journal of Transportation and Statistics, (Septem-ber/December).

Bertolini, L. and le Clercq, F. (2003). Urban development without moremobility by car? lessons from Amsterdam, a multimodal urban region.Environment and Planning A, 35:575–589.

Bertolini, L., le Clercq, F., and Kapoen, L. (2005). Sustainable acces-sibility: a conceptual framework to integrate transport and land useplan-making. two test-applications in the Netherlands and a reflectionon the way forward. Transport Policy, 12:207–220.

Bhat, C., Handy, S., Kockelman, K., Mahmassani, H., Chen, Q., andWeston, L. (2000). Development of an urban accessibility index: Liter-ature review. research project conducted for the Texas Department ofTransportation. Technical report.

Boarnet, M. G. and Sarmiento, S. (1998). Can land-use policy really affecttravel behaviour? A Study of the Link between Non-work Travel andLand-use Characteristics. Urban Studies, 35(7):1155–1169.

Brömmelstroet, M., Silva, C., and Bertolini, L. (2014). COST ActionTU1002 Assessing Usability of Accessibility Instruments. COST. ISBN:978-90-9028212-1.

Casetti, E. (1972). Generating models by the expansion method: appli-cations to geographic research. Geographical Analysis, 28:281–298.

Cervero, R. and Kockelman, K. (1997). Travel demand and the 3Ds:Density, diversity and design. Transport Research Part D: Transport andEnvironment, 2:199–219.

Church, R. L. and Marston, J. R. (2003). Measuring accessibility for peo-ple with a disability. Geographical Analysis, 35(1):83. M3: Article.



is a call therefore for utility and time-space accessibility measures to bedeveloped more strongly than they have been so far, but the commu-nicative and easy computational advantages of contour measures sug-gest that they will be used (as explained in our papers for some specificapplications) more widely than they are at the present. Additionally,such software development would allow comparison between measuresand among study areas as suggested, for example in SNAMUTS (Curtisand Scheurer, 2010).

However, the limitation for integrating the individual and temporalcomponent as well as their capacity for integrating the competition ef-fects between opportunities remain in the nature of contour measure.However, in the future research is expected to have available a big-ger amount and more detailed individual data on travel behaviour andsocio-economic characteristics. Aggregation of the observed weightingof opportunities and travel behaviour contrasted with some individualdata could describe the needs and limitations of the citizens.

Finally, a very promising research direction for transport and urbanplanners is towards a more cognitive accessibility. The relative accessi-bility proposed by Páez et al. (2010) based on the expansion models ofCasetti (1972) has shown that travel behaviour has a strong componentof the individual perception of the distances that can be travelled by eachtransport mode and the will to expend certain time or monetary costson them. Therefore, if the goal for urban planners is to influence travelbehaviour, there seems to be room for modifying it by influencing theperception of the population (for example by campaigns) without theneed for much modification of the existing transportation system northe distribution of services in the region.


Bibliography

Baradaran, S. and Ramjerdi, F. (2001). Performance of accessibilitymeasures in Europe. Journal of Transportation and Statistics, (Septem-ber/December).

Bertolini, L. and le Clercq, F. (2003). Urban development without moremobility by car? lessons from Amsterdam, a multimodal urban region.Environment and Planning A, 35:575–589.

Bertolini, L., le Clercq, F., and Kapoen, L. (2005). Sustainable acces-sibility: a conceptual framework to integrate transport and land useplan-making. two test-applications in the Netherlands and a reflectionon the way forward. Transport Policy, 12:207–220.

Bhat, C., Handy, S., Kockelman, K., Mahmassani, H., Chen, Q., andWeston, L. (2000). Development of an urban accessibility index: Liter-ature review. research project conducted for the Texas Department ofTransportation. Technical report.

Boarnet, M. G. and Sarmiento, S. (1998). Can land-use policy really affecttravel behaviour? A Study of the Link between Non-work Travel andLand-use Characteristics. Urban Studies, 35(7):1155–1169.

Brömmelstroet, M., Silva, C., and Bertolini, L. (2014). COST ActionTU1002 Assessing Usability of Accessibility Instruments. COST. ISBN:978-90-9028212-1.

Casetti, E. (1972). Generating models by the expansion method: appli-cations to geographic research. Geographical Analysis, 28:281–298.

Cervero, R. and Kockelman, K. (1997). Travel demand and the 3Ds:Density, diversity and design. Transport Research Part D: Transport andEnvironment, 2:199–219.

Church, R. L. and Marston, J. R. (2003). Measuring accessibility for peo-ple with a disability. Geographical Analysis, 35(1):83. M3: Article.



Curl, A., Nelson, J. D., and Anable, J. (2011). Does accessibility planningaddress what matters? a review of current practice and practitionerperspectives. Research in Transportation Business & Management, 2(0):3–11.

Curtis, C. and Scheurer, J. (2010). Planning for sustainable accessibility:Developing tools to aid discussion and decision-making. Progress inPlanning, 74(2):53–106.

Davidson, K. B. (1977). Accessibility in transport/land-use modellingand assessment. Environment and Planning A, 9:1401–1416.

Davies, A. and James, A. (2011). Geographies of Ageing: Social Processesand the Spatial Unevenness of Population Ageing. Ashgare.

Dieleman, F. M., Dijst, M., and Burghouwt, G. (2002). Urban form andtravel behaviour: Micro-level household attributes and residential con-text. Urban Studies (Routledge), 39(3):507–527.

Dong, X., Ben-Akiva, M. E., Bowman, J. L., and Walker, J. L. (2006). Mov-ing from trip-based to activity-based measures of accessibility. Trans-portation Research Part A: Policy and Practice, 40(2):163–180.

Ewing, R. and Cervero, R. (2001). Travel and the built environment. Asynthesis. Transportation Research Record 1780, (01-3515):87–114.

Frändberg, L. and Vilhelmson, B. (2011). More or less travel: personalmobility trends in the Swedish population focus gender and cohort.Journal of Transport Geography, 19(6):1235–1244.

Geurs, K. T. and van Eck, J. R. R. (2001). Accessibility measures: reviewand applications. evaluation of accessibility impacts of land-use trans-portation scenarios, and related social and economic impact. Bereik-baarheidsmaten: review en case studies.Beoordeling van bereikbaarheidsef-fecten van ruimtelijk-infrastructurele scenario’s, en gerelateerde sociale eneconomische effecten.

Geurs, K. T. and van Wee, B. (2004). Accessibility evaluation of land-use and transport strategies: review and research directions. Journal ofTransport Geography, 12:127–140.


Bibliography

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Hack, J. (1976). Land use transport interaction - a new approach toaccessibility, Development Plans Regional Strategies. Working Noteno 151. 2 Division, Department of the Environment. London.

Halden, D., Jones, P., and Wixey, S. (2005). Accessibility Analysis Litera-ture Review. Technical Report Working Paper 3.

Hamed, M. M. and Olaywah, H. H. (2000). Travel-related decisions bybus, service taxi, and private car commuters in the city of Amman,Jordan. Cities, 17(1):63–71.

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Handy, S. and Niemeier, D. (1997). Measuring accessibility: an ex-ploration of issues and alternatives. Environment and Planning A,29(7):1175–1194.

Hansen, W. G. (1959). How accessibility shapes land use. Jour-nal of the American Institute of Planners, 25(2):73–76. doi:10.1080/01944365908978307; 24.

Horner, M., Duncan, M., Wood, B., Valdez-Torres, Y., and Stansbury, C.(2015). Do aging populations have difdifferent accessility to activities?analyzing the spatial structure of social, professional, and businessopportunities. Travel Behaviour and Society, 2:182–191.

Ingram, D. R. (1971). The concept of accessibility: a search for an opera-tional form. Regional Studies, 5:101–107.

Jiron, P. (2010). Mobile borders in urban daily mobility practices in San-tiago de Chile. International Political Sociology, 4(1):66–79.

Kim, H. M. and Kwan, M. P. (2003). Space-time accessibility measures: ageocomputational algorithm with a focus on the feasible opportunityset and possible activity duration. Journal of Geographical Systems, 5:71–91.

Kingham, S., Dickinson, J., and Copsey, S. (2001). Travelling to work:will people move out of their cars. Transport Policy, 8(2):151–160.



Curl, A., Nelson, J. D., and Anable, J. (2011). Does accessibility planningaddress what matters? a review of current practice and practitionerperspectives. Research in Transportation Business & Management, 2(0):3–11.

Curtis, C. and Scheurer, J. (2010). Planning for sustainable accessibility:Developing tools to aid discussion and decision-making. Progress inPlanning, 74(2):53–106.

Davidson, K. B. (1977). Accessibility in transport/land-use modellingand assessment. Environment and Planning A, 9:1401–1416.

Davies, A. and James, A. (2011). Geographies of Ageing: Social Processesand the Spatial Unevenness of Population Ageing. Ashgare.

Dieleman, F. M., Dijst, M., and Burghouwt, G. (2002). Urban form andtravel behaviour: Micro-level household attributes and residential con-text. Urban Studies (Routledge), 39(3):507–527.

Dong, X., Ben-Akiva, M. E., Bowman, J. L., and Walker, J. L. (2006). Mov-ing from trip-based to activity-based measures of accessibility. Trans-portation Research Part A: Policy and Practice, 40(2):163–180.

Ewing, R. and Cervero, R. (2001). Travel and the built environment. Asynthesis. Transportation Research Record 1780, (01-3515):87–114.

Frändberg, L. and Vilhelmson, B. (2011). More or less travel: personalmobility trends in the Swedish population focus gender and cohort.Journal of Transport Geography, 19(6):1235–1244.

Geurs, K. T. and van Eck, J. R. R. (2001). Accessibility measures: reviewand applications. evaluation of accessibility impacts of land-use trans-portation scenarios, and related social and economic impact. Bereik-baarheidsmaten: review en case studies.Beoordeling van bereikbaarheidsef-fecten van ruimtelijk-infrastructurele scenario’s, en gerelateerde sociale eneconomische effecten.

Geurs, K. T. and van Wee, B. (2004). Accessibility evaluation of land-use and transport strategies: review and research directions. Journal ofTransport Geography, 12:127–140.


Bibliography

Gould, P. (1969). Spatial difussion. Resource Paper No. 17.

Hack, J. (1976). Land use transport interaction - a new approach toaccessibility, Development Plans Regional Strategies. Working Noteno 151. 2 Division, Department of the Environment. London.

Halden, D., Jones, P., and Wixey, S. (2005). Accessibility Analysis Litera-ture Review. Technical Report Working Paper 3.

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Handy, S. and Niemeier, D. (1997). Measuring accessibility: an ex-ploration of issues and alternatives. Environment and Planning A,29(7):1175–1194.

Hansen, W. G. (1959). How accessibility shapes land use. Jour-nal of the American Institute of Planners, 25(2):73–76. doi:10.1080/01944365908978307; 24.

Horner, M., Duncan, M., Wood, B., Valdez-Torres, Y., and Stansbury, C.(2015). Do aging populations have difdifferent accessility to activities?analyzing the spatial structure of social, professional, and businessopportunities. Travel Behaviour and Society, 2:182–191.

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Jiron, P. (2010). Mobile borders in urban daily mobility practices in San-tiago de Chile. International Political Sociology, 4(1):66–79.

Kim, H. M. and Kwan, M. P. (2003). Space-time accessibility measures: ageocomputational algorithm with a focus on the feasible opportunityset and possible activity duration. Journal of Geographical Systems, 5:71–91.

Kingham, S., Dickinson, J., and Copsey, S. (2001). Travelling to work:will people move out of their cars. Transport Policy, 8(2):151–160.



Kitamura, R., Mokhtarian, P., and Laidet, L. (1997). A micro-analysisof land use and travel in five neighborhoods in the San Francisco BayArea. Transportation, 24(2):125–158. J2: Transportation.

Krizek, K. J. (2003). Neighborhood services, trip purpose, and tour-basedtravel. Transportation, 30(4):387–410. J2: Transportation.

Kwan, M. P. (1998). Space-time and intregral measures of individualaccessibility: a comparative analysis using a point-based framework.Geographical Analysis, 30:191–216.

Larsen, J., Urry, J., and Axhausen, K. W. (2006). Mobilities. Mobilities,Networks, Geographies. EBSCOhost, Aldershot, England, 2006 edi-tion.

Lei, T. L. and Church, R. L. (2010). Mapping transit-based access: inte-grating GIS, routes and schedules. International Journal of GeographicalInformation Science, 24(2):283–304. M3: Article.

Leonardi, G. (1978). Optimum facility location by accessibility maximis-ing. Environment and Planning A, 10:1287–1305.

Litman, T. (2003). Accessibility: Defining, evaluating and improvingaccessibility. Victoria Transport Policy Institute.

Love, D. and Lindquist, L. (1995). The geographical accessibility of hos-pitals to the aged: a geographic information systems analysis withinIllinois. Health Services Research Journal, 29(6):629–651.

Malczewski, J. (2006). Gis-based multicriteria decision analysis: a surveyof the literature. International Journal of Geographical Information Science,20(7):703–726.

Mavoa, S., Witten, K., McCreanor, T., and O´Sullivan, D. (2012). GISbased destination accessibility via public transit and walking in Auck-land, New Zealand. Journal of Transport Geography, 20(1):15–22.

Mercado, R., Páez, A., and Newbold, K. B. (2010). Transport policy andthe provision of mobility options in an aging society: a case study onOntario, Canada. Journal of Transport Geography, 18:649–661.


Bibliography

Miller, H. J. (1998). Measuring space-time accessibility benefits withintransportation networks: Basic theory and computational procedures.In 37th annual meeting of the Western Regional Science Association, Mon-terey, California. Western Regional Science Association.

Morris, J. M., Dumble, P. L., and Wigan, M. R. (1979). Accessibilityindicators for transport planning. Transportation Research A, 13A:91–109.

O´Fallon, C., Sullivan, C., and Hensher, D. A. (2004). Constraints af-fecting mode choices by morning car commuters. Transport Policy,11(1):17–29.

Páez, A., Mercado, R. G., Farber, S., Morency, C., and Roorda, M. (2010).Relative accessibility deprivation indicators for urban settings: Def-initions and application to food deserts in Montreal. Urban Studies,47(7):1415–1438.

Páez, A., Scott, D. M., and Morency, C. (2012). Meauring accessibility:positive and normative implementations of various accessibility indi-cators. Journal of Transport Geography, 25:141–153.

Pirie, G. H. (1979). Measuring accessibility: a review and proposal. En-vironment and Planning A, (11):299–312.

Ross, W. (2000). Mobility & accessibility: the yin & yang of planning.World Transport Policy and Practice, 6(2):13–19.

Ryley, T. (2006). Use of non-motorised modes and life stage in Edin-burgh. Journal of Transport Geography, 14(5):367–375.

SEU (2003). Making the connections: Final report on transport and socialexclusion. Technical report, Social Exclusion Unit. Office of the DeputyPrime Minister.

Silva, C. (2008). Comparative Accessibility for Mobility Management. TheStructural Accessibility Layer. PhD thesis, University of Oporto.

Silva, C. and Pinho, P. (2010). The Structural Accessibility Layer (SAL):Revealing how urban structure constrains travel choice. Environmentand Planning A, 42(11):2735–2752.



Kitamura, R., Mokhtarian, P., and Laidet, L. (1997). A micro-analysisof land use and travel in five neighborhoods in the San Francisco BayArea. Transportation, 24(2):125–158. J2: Transportation.

Krizek, K. J. (2003). Neighborhood services, trip purpose, and tour-basedtravel. Transportation, 30(4):387–410. J2: Transportation.

Kwan, M. P. (1998). Space-time and intregral measures of individualaccessibility: a comparative analysis using a point-based framework.Geographical Analysis, 30:191–216.

Larsen, J., Urry, J., and Axhausen, K. W. (2006). Mobilities. Mobilities,Networks, Geographies. EBSCOhost, Aldershot, England, 2006 edi-tion.

Lei, T. L. and Church, R. L. (2010). Mapping transit-based access: inte-grating GIS, routes and schedules. International Journal of GeographicalInformation Science, 24(2):283–304. M3: Article.

Leonardi, G. (1978). Optimum facility location by accessibility maximis-ing. Environment and Planning A, 10:1287–1305.

Litman, T. (2003). Accessibility: Defining, evaluating and improvingaccessibility. Victoria Transport Policy Institute.

Love, D. and Lindquist, L. (1995). The geographical accessibility of hos-pitals to the aged: a geographic information systems analysis withinIllinois. Health Services Research Journal, 29(6):629–651.

Malczewski, J. (2006). Gis-based multicriteria decision analysis: a surveyof the literature. International Journal of Geographical Information Science,20(7):703–726.

Mavoa, S., Witten, K., McCreanor, T., and O´Sullivan, D. (2012). GISbased destination accessibility via public transit and walking in Auck-land, New Zealand. Journal of Transport Geography, 20(1):15–22.

Mercado, R., Páez, A., and Newbold, K. B. (2010). Transport policy andthe provision of mobility options in an aging society: a case study onOntario, Canada. Journal of Transport Geography, 18:649–661.


Bibliography

Miller, H. J. (1998). Measuring space-time accessibility benefits withintransportation networks: Basic theory and computational procedures.In 37th annual meeting of the Western Regional Science Association, Mon-terey, California. Western Regional Science Association.

Morris, J. M., Dumble, P. L., and Wigan, M. R. (1979). Accessibilityindicators for transport planning. Transportation Research A, 13A:91–109.

O´Fallon, C., Sullivan, C., and Hensher, D. A. (2004). Constraints af-fecting mode choices by morning car commuters. Transport Policy,11(1):17–29.

Páez, A., Mercado, R. G., Farber, S., Morency, C., and Roorda, M. (2010).Relative accessibility deprivation indicators for urban settings: Def-initions and application to food deserts in Montreal. Urban Studies,47(7):1415–1438.

Páez, A., Scott, D. M., and Morency, C. (2012). Meauring accessibility:positive and normative implementations of various accessibility indi-cators. Journal of Transport Geography, 25:141–153.

Pirie, G. H. (1979). Measuring accessibility: a review and proposal. En-vironment and Planning A, (11):299–312.

Ross, W. (2000). Mobility & accessibility: the yin & yang of planning.World Transport Policy and Practice, 6(2):13–19.

Ryley, T. (2006). Use of non-motorised modes and life stage in Edin-burgh. Journal of Transport Geography, 14(5):367–375.

SEU (2003). Making the connections: Final report on transport and socialexclusion. Technical report, Social Exclusion Unit. Office of the DeputyPrime Minister.

Silva, C. (2008). Comparative Accessibility for Mobility Management. TheStructural Accessibility Layer. PhD thesis, University of Oporto.

Silva, C. and Pinho, P. (2010). The Structural Accessibility Layer (SAL):Revealing how urban structure constrains travel choice. Environmentand Planning A, 42(11):2735–2752.



Tillema, T., Bert, V. W., and Jong, T. D. (2003). Road pricing from ageographical perspective: a literature review and implications for re-search into accessibility.

Timmermans, H., van der Waerden, P., Alves, M., Polak, J., Ellis, S.,Harvey, A. S., Kurose, S., and Zandee, R. (2003). Spatial context andthe complexity of daily travel patterns: an international comparison.Journal of Transport Geography, 11(1):37–46.

Urry, J. and Grieco, M. (2011). Does Mobility have a Future? Mobilities:New Perspectives on Transport and Society. eBook Academic Collec-tion (EBSCOhost).

van Wee, B., Chorus, C., and Geurs, K. T. (2012). Accessibility Analysisand Transport Planning. Challenges for Europe and North America, chapter3. ICT and accessibility: research synthesis and future perspectives,pages 37–53. Nectar Series on Transportation and CommunicationsNetworks Research. Edward Elgar Publishing Limited.

van Wee, B., Hagoort, M., and Annema, J. A. (2001). Accessibility mea-sures with competition. Journal of Transport Geography, 9(3):199–208.

Vickerman, R. W. (1974). Accessibility, attraction and potential: a reviewof some concepts and their use in determining mobility. Environment& Planning A, 6:675–691.

Voges, E. M. and Naudé, A. H. (1983). Accessibility in urban areas: anoverview of different indicators. Technical Report RT/21/83, NationalInsitute for Transport and Road Research, CSIR, South Africa.

Wachs, M. (1978). Accessibility, mobility and travel need. In 3rd Interna-tional Conference Behavioural Travel Modelling, Tanunda, South Australia.,London. Croom Helm.

Wachs, M. and Kumagi, T. G. (1973). Physical accessibility as a socialindicator. Socio-Economic Planning Science, 7:437–456.

Walle, S. V. and Steenberghen, T. (2006). Space and time related deter-minants of public transport use in trip chains. Transportation ResearchPart A: Policy and Practice, 40(2):151–162.


Bibliography

Wegener, M. and Fürst, F. (1999). Land-use transport interaction: Stateof the art. Technical Report 46, Institut für Raumplanung, Dortmund.

Weibull, J. W. (1976). An axiomatic approach to the measurement ofaccessibility. Regional Science and Urban Economics, 6:357–379.

Wilson, A. G. (1973). Entropy in Urban and Regional Modeling. Pion,London, England.

Yigitcanlar, T., Sipe, N. G., Evans, R., and Pitot, M. (2007). A GIS-basedland use and public transport accessibility indexing model. AustralianPlanner, 44(3):30–37.



Tillema, T., Bert, V. W., and Jong, T. D. (2003). Road pricing from ageographical perspective: a literature review and implications for re-search into accessibility.

Timmermans, H., van der Waerden, P., Alves, M., Polak, J., Ellis, S.,Harvey, A. S., Kurose, S., and Zandee, R. (2003). Spatial context andthe complexity of daily travel patterns: an international comparison.Journal of Transport Geography, 11(1):37–46.

Urry, J. and Grieco, M. (2011). Does Mobility have a Future? Mobilities:New Perspectives on Transport and Society. eBook Academic Collec-tion (EBSCOhost).

van Wee, B., Chorus, C., and Geurs, K. T. (2012). Accessibility Analysisand Transport Planning. Challenges for Europe and North America, chapter3. ICT and accessibility: research synthesis and future perspectives,pages 37–53. Nectar Series on Transportation and CommunicationsNetworks Research. Edward Elgar Publishing Limited.

van Wee, B., Hagoort, M., and Annema, J. A. (2001). Accessibility mea-sures with competition. Journal of Transport Geography, 9(3):199–208.

Vickerman, R. W. (1974). Accessibility, attraction and potential: a reviewof some concepts and their use in determining mobility. Environment& Planning A, 6:675–691.

Voges, E. M. and Naudé, A. H. (1983). Accessibility in urban areas: anoverview of different indicators. Technical Report RT/21/83, NationalInsitute for Transport and Road Research, CSIR, South Africa.

Wachs, M. (1978). Accessibility, mobility and travel need. In 3rd Interna-tional Conference Behavioural Travel Modelling, Tanunda, South Australia.,London. Croom Helm.

Wachs, M. and Kumagi, T. G. (1973). Physical accessibility as a socialindicator. Socio-Economic Planning Science, 7:437–456.

Walle, S. V. and Steenberghen, T. (2006). Space and time related deter-minants of public transport use in trip chains. Transportation ResearchPart A: Policy and Practice, 40(2):151–162.


Bibliography

Wegener, M. and Fürst, F. (1999). Land-use transport interaction: Stateof the art. Technical Report 46, Institut für Raumplanung, Dortmund.

Weibull, J. W. (1976). An axiomatic approach to the measurement ofaccessibility. Regional Science and Urban Economics, 6:357–379.

Wilson, A. G. (1973). Entropy in Urban and Regional Modeling. Pion,London, England.

Yigitcanlar, T., Sipe, N. G., Evans, R., and Pitot, M. (2007). A GIS-basedland use and public transport accessibility indexing model. AustralianPlanner, 44(3):30–37.


Paper I

X. Albacete, K. Pasanen and M. Kolehmainen

A GIS-based method for the selectionof the location of residence

Geo-Spatial Information Science,

pp. 1-6, 2012, doi: 10.1080/10095020.2012.708159.

Reprinted by permission of Taylor & Francis Ltd.

uef.fi



ISBN 978-952-61-2102-4ISSN 1798-5668


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XAVIER ALBACETE

EVALUATION AND IMPROVEMENTS OF CONTOUR-BASED ACCESSIBILITY MEASURES


Xavier Albacete (February 11th 1986,

Barcelona, Catalonia). The author’s interests are focused on multidisciplinary research

aiming at explaining the dynamics in the urban environment in order to promote socially and

environmentally sustainable cities.

Accessibility relates the transport network and urban space for measuring the feasibility of the citizens in reaching their destinations.

This thesis evaluates the most commonly used type of accessibility measures: contour-based

measures and proposes ways to improve them.

XAVIER ALBACETE

Documents

EVALUATION AND IMPROVEMENTS OF CONTOUR-BASED ACCESSIBILITY MEASURES PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND