REPRINT

STINA

Project for the Application of the AASHO

Road Results in the Nordic Countries

FINAL REPORT

The Secretariat of the Nordic Council

of Ministers, Oslo, Dec 1976

Projekt Organization

Coordinator:

Magnus Holmgren

National representatives:

Denmark Mogens Rasmussen

Erik Bärenholdt

Finland Esko Kankare

Jon Skulason

Rasmus Nordal

Iceland

Norway

Geir Refsdal

Sweden Olle Andersson

Note

This booklet is a reprint of the English summary

of the project technical report, included in NU

A 1977:3 4, published by the Nordic Council, Gamla

Riksdagshuset, Stockholm, Sweden.

The Secretariat of the Nordic Council of Mi-

nisters, Oslo, Norway

Public Roads Administration, Copenhagen

The National Danish Road Laboratory, Ros-

kilde _

Technical Research Centre of Finland. Road

and Traf c Laboratory, Otaniemi

Public Roads Administration, Reykjavik

Norwegian Institute of Technology, Trond-

heim

Public Roads Administration, Norwegian

Road Research Laboratory, Oslo

Royal Institute of Technology, Stockholm in

the STINA project representing Swedish Road

and Traf c Research Institute, Linköping

9. Summary

Background, purpose and planning

The design specifications for road pavements

which are in use in different countries are

mostly based on accumulated experience

during all the time heavy vehicles have been

in use. For quanti cation of the relation be-tween the traf c load ( ow and axle weight)

and the design parameters of the pavement

the American road association AASHO took

in 1946 the initiative of the most compre-

hensive road experiment ever made. To illu-

strate the extent of the experiment it can

be mentioned that the total cost was $27

million, it lasted from 1958 till 1960, and

resulted in 300 million data which were ana-

lyzed. The results comprise relations be-

tween serviceability, number of axle passa-

ges, axle load and pavement design para-

meters.

Quite naturally the results have been re-

ceived with great interest, not only in the

US but also in Europe. Thus the applicabili-

ty of the results at other locations than the

site of the experiment has been debated.

Especially differences in the composition of

the traf c and differences in climate and

subgrade properties have been payed atten-

tion to. Also in the Nordic countries the

AASHO results have naturally been studied

and to some extent applied, although syste-

matic applicability test on a large scale have

not been performed. Against this back-

ground, and due to the common interest in

176

the question, a Nordic cooperative project,

named by the acronym STINA, was started.

The purpose of the project was to give an

improved base for pavement design, especial-

ly with respect to in uence of subgrade,

traf c load and climate, and to illustrate the

in uence of traf c load on investment and

operation costs.

No appraisal of the AASHO road test and

its results was included in the STINA pro-

ject.

After programming the work started in

the spring of 1974 and was concluded in the

fall of 1976. Sponsored by the Nordic Coun-

cil of Ministers, who also employed the pro-

ject coordinator, the work was done in the

member countries by national project

groups, each led by a national project leader.

The work was divided into ve main activiti-

es, and each main activity was assigned to

one national project group for detailed plan-

ning, coordination and reporting. The main

acitivities were

inventory abroad

inventory in the Nordic countries

eld trials and sampling

laboratory investigations

analyses

The rst two acitivites were accounted for

in a progress report, published as two parts

of Nordisk utredningsserie , denoted NU

1975:Il and NU 1975:12.

NU A 1977:3

[i-wentory abroad

The purpose of this inventory was to find

out by literature surveys and by visits to se-

lected countries, how application and deve-

lopment of the AASHO road test results had

progressed during the last few years. Visits

were paid to the US and Canada and to

Europe, where interviews were made at road

research institutions and road authorities.

The subgrade is in many countries intens-

ly studied with respect to stress-strain be-

haviour and fatigue properties. The influence

of the subgrade upon road pavement failure

was however found to be incomplete.

During the study visits special attention

was given to the way in which the AASHO

load equivalency factors were used in treat-

ing traf c load in the different countries. It

then appeared that the equivalency factors

according to the four power law had been

largely accepted, lacking other alternatives.

An important finding was the vehicle equi-

valency factors, based on traffic load ana-

lyses and differential traffic counting. Such

factors have also been used in Finland for

several years. The influence of Climate was

in writing the AASHO interim guides ac-

counted for by assigning regional factors to

different areas, representing the average

climatic influence of the area. Considerable

skepticism against these factors was met,

since they account for only part of the

climatic influence upon road design.

The serviceability concept was another

important product of the AASHO road test.

The serviceability index is a quantitative

measure of the state of the road as experi-enced by the motorist and is used as a meas-

ure of the state of the road as experienced

by the motorist and is used as a measure of

the state of the road also in analysis of road

failure.

The failure model concept is used to

quantify the progress of the failure of the

road in relation to the variables causing fail-

ure. Several failure models developed abroad

were recorded for use in analysis of road fail-

ure in Nordic countries.

NU A 1977:3

Inventory ofNordic conditions

The purpose of this inventory was to com-

pile data from the Nordic countries required

for examination of the applicability of

AASHO road test results and other results

derived therefrom.

The inventory comprised road structures,

rheology, climate, traffic load, failure data

and test road data. The data collection was

made by sending questionnaires to road au-

thorities and research institutions. In addi-

tion road appraisal for determination of serv-

iceability was performed in the member

countries and on a number of test sections

in the member countries and on a number of

test sections in the vicinity of Stockholm

International Airport (Arlanda). These sec-

tions were also used for roughness measure-

ments in order to establish correlation with

data from subjective ranking.

These inventories gave an account of the

occurence of different subgrade materials

in the road networks and the permitted

traf c loads in different countries. The

climate inventory resulted in maps of the

Nordic countries showing zones of mean

temperature, mean precipitation and mean

freezing index.

Rz'deabz'lity ranking and roughness meas-

urements of selected test sections resulted

in a serviceability index formula (equiva-

lent to the AASHO PSI formula) and a re-

lated Nordic terminal serviceability index.

The road damage inventory gave an indi-

cation of the occurrence of damages, their

kind and causes.

In conjunction with development of a

Nordic serviceability index formula, atten-

tion was directed towards the existence of

different roughness meters in the Nordic

countries and the possible use of other

meters than the CHLOE meter for service-

ability assessment. Correlation studies were

therefore performed using the CHLOE me-

ter, the bump integrator and the towed

straight-edge. All instruments were used at

the same time for measurements on the test

sections near Stockholm International Air-

177

port.

These measurements resulted in empirical

formulae for conversion of data from the

other two instruments into CHLOE data

and in serviceability formulae bases upon

these other two instruments.

Field tests and sampling

The purpose of the field tests was to start

an inventory of road engineering properties,

predominantly bearing capacity, of Nordic

subgrades and their seasonal variation. The

measurements also comprised moisture con-

tent, temperature, water table and frost

depth and were performed ten times in

1975, beginning at frost break. Bearing ca-

pacity was measured by conventional static

plate loading on the subgrade and on the

surface of the road adjecent to the eld

station.

During recent years it has become more

and more customary to simulate the traffic

load in bearing capacity measurements by

using a dynamic type of measurement. Dur-

ing planning of the STINA project, however,

equipment for such measurements was not

available at resonable cost, and therefore all

the measurements were made by using con-

ventional static plate bearing equipment.

The measurements were made at field

stations prepared for this particular purpose.

Between measurements the subgrade at these

stations was provided with a thin pavement

structure, which was thermally and hydrolo-

gically equivalent to the specified pavement

structure required by such a subgrade. Two

subgrade types were selected in each country

(in Iceland only one), selection being made

on the basis of most trafficked subgrade

under the public road network.

A multipurpose sample was taken from

each field station for geotechnical analysis

and classification. Sampling was also made

for deformation and fatigue testing. From

stations with friction material this sampling

was done once and for all and from stations

with cohesive material the sampling was

done in connection with each field testing.

178

The winter 1974 75 was unusually mild

in all Nordic countries except Iceland, and

therefore there was practically no frost

break period. A few more measurements

were therefore made in the spring and early

summer of 1976. This winter was however

also milder than average.

In plate bearing testing a procedure was

used which was specially developed for the

purpose, This implied loading from zero to

each load level three times, the level being

increased step-wise until a predetermined

deflectiOn was reached.The results of these field tests was report-

ed as static eleastic moduli, computed from

the total deflection and from the rebound

de ection (Et and Ee), since both moduli

are used in road design in the Nordic coun-

tries. Regression analysis of the two moduli

gives linear relationships with very high cor-

relation coefficients, the analysis being done

separately from each field stations. The in-

tercept of each linear relation is however

considerable, which illustrates that the mo-duli are not mutually interchangable, The

intercept reflects the permanent de ection,

which is exceptionally great with the Ice-

landic lava. This reflects the high porosity

of the lava material.

The moduli showed at several places a

considerable variation with load level, which

illustrates the non-linear properties of these

materials and also to some extent the bedd-

ing effect of the plate load test.

The seasonal variation of bearing capacity

at each field station was reviewed by draw-

ing a curve showing modulus against time,

the modulus value being selected at the

loading level corresponding to the weight of

the pavement required by that subgrade type

according to the local design specification.

In spite of the mild winters a fairly normal

course of each seasonal curve was obtatin-

ed, having low bearing capacity in the spring

and high values during the later half of the

year. At some stations the bearing capacity

ofthe adjacent road showed a minimum dur-

ing late summer. This is a natural result of

the softening of thick bitumen bound pave-

NU A 197723

ment layers during the summer months,

whereas the softening during the spring

period was not very pronounced after the

mild winters. _

As an inventory of the bearing capacity

of Nordic subgrades the work done has to be

considered as a-start. However, a common

method for measurement has been develop-

ed, and it is recommended that the measure-

ments are pursued for a considerably pro-

longed period.

Laboratory in vcstigations

The laboratory investigations of subgrade

materials aimed at deformation and fatigue

properties comprised undisturbed samples

from cohesion materials and laboratory com-

pacted samples of friction material, compac-

tion then being made at moisture contents

and to bulk densities prevailing during eld

tests. The measurements on cohesion materi-

als were made by applying haversine shaped

loads in a triaxial cell, whereas friction ma-

terials were tested also by applying haversine

shaped loads in a triaxial cell, whereas fric-

tion materials were tested also by applying

haversine shaped loads but in an open-face

cylinder with a dead load on the free soil

surface.

Undisturbed tube samples were also im

ported from three places outside Scandi-

navia, namely 100p number 1 of the AASHO

road test site, the Alconbury Hill test road

in England and the Hiltpoltstein test road in

West Germany. Alconbury Hill is a test sec-

tion on the London-Edinburgh motorway

used for follow-up studies of the AASHO

road test, and Hiltpoltstein is the site of an

extensive road test in Germany.

A sampling technique adapted for these

and the Nordic field stations had to be devel-

oped. Altogether 128 tube samples were col-

lected. Some of them were cancelled and

some were stored for future research, while

69 samples were analysed at the road labo-

ratory at Roskilde, Denmark, and at the In-

stitute of Technology at Trodheim, Norway.

The friction material investigations were

NU A 1977:3

made at the Swedish Road and Traf c Re-

search lnstitute at Linköping, Sweden.

The undisturbed samples were also sub-

jected to CBR testing and static testing in

a triaxial cell. These tests were used predoni-

mantly for determining the strength pro-

perties of the undisturbed samples under

static conditions. Dynamic testing consist-

ed in applying 20000 load pulses at each

stress amplitude in a stepwise increasing

sequence of amplitudes.

During testing the rebound de ection and

the permanent de ection of the samples

were recorded continously. The former was

used for computation of the rebound mo-

dulus Mr, which was recorded as a function

of the stress amplitude.

No systematic variation of Mr with mois-

ture content could be established except at

frost break, and therefore the rebound mo-

dulus was reported as a function of stress

amplitude, showing the mean curve and the

envelopes generated by the standard devia-

tion. The frost break curves were reported

separately, where necessary.

The modulus curves can mathematically

be represented by a power law, where the ex-

ponent lies in the interval Olo 0.57 for all

materials tested. The modulus value corre-

sponding to the stress 0.1 athmospheres was

denoted material modulus and was de-

signated by the synbol M0. It was consider-

ed as a parameter expressing the dynamic

properties of the material. This quantity

showed a noteworthy correlation with the

CBR value, the factor of prOportionality

beting 100, if the modulus is expressed in

kg/cm2. This is an interesting con rmation

of earlier work in this field. The present re-

sult is however confined to undisturbed

cohesive soil samples.

The permanent de ection has been fitted

into a power function, comprising the num-

ber of load applications. the stress amplitude

and the rebound modulus. From this equa-

tion it is possible to derive a stress equival-

ency factor for comparison of different

stress amplitudes, which in contrast to the

AASHO load equivalency factor has expo-

179

nent values in the interval 15-~20.

This equation of the permanent deflec-

tion can be interpreted in the following way:

- there exists a critical stress level in

cohesive subgrade materials

- at stresses below this level, failure seldom

occurs in cohesive subgrades

- at stresses above this level failure occurs

after only a very limited number of load

applications

-- - it is not realistic to use load equivalency

factors for cohesive subgrade failure

__ the subgrade criterion should be based

upon the maximum permitted stress

(Which of course varies with season)

Equivalency factors should on the other

hand be used in treatment of the contribu-

tions of the pavement itself to the failure of

the road, but it is then not dependent upon

the failure process in the subgrade.

At the analysis of corresponding measure-

ments on friction subgrade materials a simi-

lar arithmetic expression was used. The cor-

relations were however rather weak, and an

equivalency factor of the same kind could

not be derived. In order to give more con-

clusive results these measurements require a

considerable extension beyond what was

availabe within the limits of the STINA pro-

ject.

The studies of subgrade materials was

combined with the field tests. searching a re-

lation between the modulus values found in

laboratory tests and those found in the field

tests. The stress dependent field moduli

could be fitted into a power relation similar

to that of the laboratory rebound moduli.

The factors of proportionality found in

these analyses differed rom one another

(field and laboratory) by a factor of 2 or

more. Consindering dissimilarities in the

tests such as temperature and depth under

the subgrade surface this agreement can be

considered satisfactory.

A nalyscs

Improved basis for analytical pavement de-

180

sign was one of the main purposes of the

STINA project, and this implied predomi-

nantly load equivalency factors and the con-

tribution from the subgrade to road failure

criteria. Analyses of these factors were part-

ly made hand in hand, and the results were

checked against oneanother.

Traffic load

By consideration of the wearing wourse, the

pavement or the subgrade separately or in

combination it is possible to derive equiva-

lency functions with a wide range of expo?

nents. The most extreme exponent values,

pertaining to choesive soils, can as explain-

ed above be ascribed to a fracture process

and can be replaced by a critical stress

criteriOn instead of a fatigue criterion.

Exponents derived in other ways remain in

the region 2.5 - 5, the low end of the range

being derived from permanent de ections

of the road surface. Considerations of the

whole road structure lead to exponent

values in the range 3 5. Such values are

obtained eg from a linear elastic model

using the exponent value 4 and modification

of this model by assuming non-linear pro-

perties of the pavement materials.

A conservative conclusion from these

observations is that the exponent value of4

as derived from the AASHO road test has

not been seriously contradicted under

Nordic conditions. A range of3 5 or possib-

ly 3.5 4.5 can be stated a applicable. On

the other hand computations of the equiva-

lent number of 10 ton axles based on real

axle load distributions show a moderate

in uence of the magnitude of the expo-

nent. ln analyses of the traffic load in con-

junction with pavement design therefore, the

assumption of the magnitude of the expo-

nent is unimportant as long as its value is

limited to the interval 3 5.

Subgrade criteria

Determination of the critical values of the

subgrade has earlier been made by calcula-

NU A l977:3

tion of the subgrade strains during the

various phases of the AASHO road test and

therefore determining a relation between the

number of load applications to failure and

the subgrade strain amplitude (sometimes

referred to as the Shell criterion). Failure

was then defined as the occurrence of ter-

minal serviceability index.

In the STINA project a similar approach

was tried but not applied to the AASHO

road test but to the road pavements built

according to standard speci cations. This

procedure was applied to the specifications

in Finland, Norway and Sweden. Iceland

has the same specifications as Norway and

the Danish specifications are based upon

an analytical approach, which would make

the proposed test inadequate.

A design period of 10 20 years was

assumed, which in combination with known

traffic flows gave a basis for the number of

passages to failure. The pavement layer

parameters were taken from experience in

the various countries.

This procedure implies quite a few simpli-

fications and hence the high and low ex-

tremes were computed in each combination

of inputs. These extremes defined limiting

lines of the computed relation between

subgrade strain and number of passes of

equivalent standard axles. The subgrade

criterion diagram therefore was represented

by a band rather than a curve. In two-sided

logarithmic representation the limiting lines

are straight and have a slope of 1/4, confirm-

ing the existence of an exponent value near

4.

Between the extreme curves derived from

the Swedish standard specifications the

corresponding curve derived from the

AASHO road test can be drawn. The Nor

weigian and the Finnish specifications

gave a similar result, although the agree-

ment with the Shell criterion was not in

all cases quite so good.

The Shell criterion is based upon sub-

grade strain, whereas there are other criteria

systems based Upon subgrade stress. The

basic difference between these criteria is

NU A 197713

not considerable but can be of importance

when non-linear elasticity is assumed.

Climate

The influence of the climate upon pavementdesign has been given some attention in theSTINA project. The AASHO test site repre-sents only one climate, but the change ofclimatic conditions during the test was ac-counted for by using a set of seasonal weighting factors, based upon deflection measure-ments of the untrafficked lOOp number 1.Similar weighting factors have been calculat-ed from the field station results in theSTINA project (adjacent roads). The season

curves then obtained were at some stations

not similar to those obtained at the AASHO

road test. This is partly due to the absence

of typical frost break periods during the

course of the STINA project. It should also

be noted that the sections underlying the

AASHO seasonal weighting function curve

did not contain thick bitumen stabilized

layers. Since no serviceability measurementswere made at the test stations the usefulness

of the method cannot be checked but such

measurements are recommended in the fu

ture. Tests of the regional factors recom-

mended in the AASHO interim guides were

not checked within the STINA project.

Failure models

The AASHO pavement design system is

based on the semi-empirical failure model

derived in conjunction with analyses of the

AASHO road test data. The model gives by

a system of formulae an arithmetic relation

between serviceability index, number of

passes. axle load and the bearing capacity

of the pavement. Later on the AASHO

model was extended to taking care of the

properties of the subgrade and the non-

traffic load influenced pavement failure.

Other models but of different arithmetical

structure have been developed in other areas

in North America. These models, including

a British failure model (based on Alconbury

Hill test road data) of quite different compo-

181

sition, were tested within the STINA project

by application to data from Nordic test

roads.

The inventory of Nordic test road data

gave a rather limited set of data in view of

this purpose, predominantly because traffic

load data were missing and data for assess

ment of serviceability were missing at many

test roads. Swedish test road traffic data

could largely be aquired afterwards by traf-

fic counting and be extrapolation back-

wards in time. The test roads included in the

analysis were those at Edsvalla, NykrOppa

and Barkarby-Staket. The later is not actual-

ly a test road but has been subjected to ex-

tensive measurements by the CHLOE meter

for a number of years. In addition the Vorm-

sund test road in Norway could be included

in the analysis.

The Vormsund test road data could be

fitted to three of the models tested, namely

the AASHO, Ontario and Alconbury Hill

Models. To the data from the Nykroppa test

road only a modi cation of the British Al-

conbury Hill model could be fitted, whereas

to the other Swedish test road data the

AASHO Texas and Ontario models could

be fitted.

The Texas and Ontario models (one being

a modification of the other) both have a

component which is independent of traffic

load and describes mainly climate induced

failure. This is also true for a later modifi-

cation of the AASHO model. Fitting of

Swedish test road data required such a load

independent component. A factor applied

to the time variable in these models can be

used as a climate parameter which describes

the failure directly induced by the climate.

The goodness of fit to Nordic test roads was

similar to that in the home areas in spite of

the rather limited amount of data.

These models are expected to find their

use in development of rehabilitation strategi-

es and in calculation of the cost responsibili-

ty of different types of vehicles.

182

Rehabilitation strategies

In order to include in a rational way all the

factors entering into Optimization of rehabi

litation strategies the methods of systems

engineering have been taken into considera-

tion during later years. These strategies re-

quire quantification of the state of failure

of the road, and for this purpose the AASHO

serviceability concept has been very helpful.

An American system denoted SAMP has

been treated within the STINA project.

It has been adapted for Nordic conditions

and extended for wider application. The re-

sulting system, denoted by the acronym

SYLVIA is comprehensive and contains

a separable part, named SUSANN, which

treats regular maintenance. These systems

could not be developed further than to

principles, but for implementation the

SAMP 5 system was adapted to Nordic

conditions and is offered as a FORTRAN

program (denoted NSAMP) ready for test-

ing by Nordic agencies.

Vehicle equivalenqv factors

In analyses of the traffic load spectrum it

has been found that the number of vehicle

types running on the roads is quite limited.

Each vehicle type usually has a miximum

nominal axle load. It has therefore been

tried at some places to assign to each vehicle

type a vehicle equivalent factor, being the

number of equivalent standard axles per

vehicle. In this way the expensive traffic

load analyses could be replaced by differen-

tial traffic counting for assessment of the

number of vehicles of each type.

This method has been in use in Finland

since 1964. It has also been tried in Minne-

sota, where however the correlation between

the number of standard axles found by the

two methods was rather weak. A similar

analysis has been made within the STINA

project, using a very comprehensive traffic

analysis made by the Swedish Road Ad-

ministration in the middle of the sixties.

The analysis was limited to a small selec-

NU A l977:3

tion of roads of different types and loca-

tions. lt comprised, however. all vehicle

types except passanger cars whose contribu-

tion to the total traf c load was found to be

negligible. The vehicle equivalence factor

(VEF) is identical with the truck factor

which has been in use for a long time, but

the truck factor averages all heavy vehicles.

VEF was found to vary not only with the

vehicle types but also with region and type

of road. The exponent of the equivalency

factor formula is however quite unimportent

within the range 3.5 5. ln road design the

exponent value is therefore unimportant. if

VEF is used. A fair agreement between Fin-

nish and Swedish VEF :s was found.

Cost respons!!)l'lify

The structure of rehabilitation strategies

shows that there is quite a strong relation-

ship between certain road operation costs

and traffic load. Within the STINA project

therefore the possibilities have been studied

to use these relationships for allocation of

the traffic load dependent part of the Opera-

tions costs to vehicles of different axle loads.

Thereby a certain rehabilitation strategy was

assumed and the decrease in annual cost

caused by exclusion of one vehicle type (or

axle load) was computed. Repetition ofthis

computation excluding one vehicle type (or

axle load) at a time and comparing the cost

reductions was assumed to re ect the cost

responsibility of the component excluded.

lt can then be assumed, that the original

strategy is maintained except for a change

(i.e. cost) of the treatment due to the ex-

clusion of one traffic component. The calcu-

lations, all inputs considered, become rather

involved, but a few examples, based upon

drastic simplifications. were performed. The

two alternatives of excluding one vehicle

type at a time and excluding one axle load

at a time were tried. The former alternative

inplies the use of vehicle equivalency factors.

As expected the influence of the magnitude

of the exponent of the equivalency factor

formula is much less if the vechicle approach

NU A 19773

is used. On the other hand, in the present

work great differences were found between

vehicle types that are very similar.

Pursuit of this approach could certainly

give important contributions in this problem

area, but this would require a considerable

reseach effort.

Future aspects

In the final chapter of the report there is a

list of possible follow-up projects. which

could be carried out by all or a few of the

member countries. One of these projects has

already gone into operation and will be

finishedby the end ofJune 1977.

The STINA project has Opened up new

varieties of c00peration in Nordic road re-

search and has contributed to the progress

in this field on the same time as it has sti-

mulated further cooperation of a similar

kind. '

List of results

Subdivided according to the declared pur-

poses of the STINA project the results may .

be condensed in the following manner.

Subgrade

0 The start of an inventory of road engi

neering prOperties, covering nine typical

Nordic subgrades during one climate

season.

' Experimental technique for seasonal as-

sessment of subgrade bearing capacity.

. Experimental technique for determination

of road engineering properties, especially

those important for bearing capacity, by

sampling and laboratory testing of sub-

grade materials.

0 Improved knowledge of the deformation

and fatigue properties of subgrades and

subgrade materials, including non-linear

elasticity.

0 Check of subgrade criteria used for ana-

lytical pavement design.

0 Procedure for assessment of permitted

183

stresses in cohesive subgrade soils.

O lilucidation of the relation between sub-

grade properties determinad by field and

laboratory testing.

Traffic load, road failure

O Establishment of the influence of sub-

grade properties on the failure of roads

built on cohesive soils.

0 Analysis of vehicle equivalency factors

based on axle arrangements.

0 Elucidation of the applicability of the

four power rule in the Nordic countries.

O Elucidation of the applicability of road

failure models in Nordic countries.

0 Serviceability formula applicable in the

Nordic countries.

O Inventory of road failure mechanisms in

the Nordic countries including pertinent

road engineering data.

Climate

O The seasonal variations of road bearing

capacity. documented examples.

G Illustration of the use of the climate

parameter in failure models for quanti -

cation of the climate induced road failure.

0 Inventory of climate data in the Nordic

countries.

Cost Optimization

0 Test of a new approach to calculation of

the cost responsibility of different vehicle

types in road failure. based on rehabilita-

tion strategies.

0 Suggestions for design and rehabilitation

strategies in the Nordic countries.

0 Modification of an American design and

rehabilitation system. prepared for testing

and implementation in the Nordic coun-

tries (NSAMP).

184 NU A l977:3