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Traffic Calming

Urban Transportation Planning

MIT Course 1.252j/11.380j

Fall 2002

Mikel Murga, MIT Research AssociateDec 6, 2002

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Urban Transportation Planning Fall 2002

Fri Dec 6

Table of Contents

! Why traffic calming?

! Traffic calming, how?

! Techniques! Design Criteria

! The Process

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Fri Dec 6

Why Traffic Calming?

! The faster you go, the higher

the probability of an accident,as:

! Your vision focus narrows withspeed

! For a given reaction time,

distance covered is proportionalto speed

! The faster you go, the longer

the stopping distance

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Fri Dec 6


! The faster you go, the higher the

seriousness of an accident! For instance, the kinetic energy of an

automobile (1.2 tons at 35 mph) is at

least 150 times higher than for apedestrian (180 pounds) at 3 mph

! Such a collision at:! 20 mph, means bone fractures and

concussions! Between 20-30 mph, medium seriousness

! More than 30 mph, very high probability ofeither death or permanent disability

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Fri Dec 6


! To avoid segregation of publicspaces and maintain itslivability

! Underpasses, skywalks andother solutions, do notprovide eyes on the street

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Fri Dec 6

Traffic Calming: How?

! When you drive at

30 mph, you tendto focus your sightfar ahead

! And you narrowthe sight area

! You fail to see thesurroundings

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! But if you driveat 20 mph, you

start to seewhat lies onthe sides

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! The basic idea is to

change the perceptions ofthe driver through theintroduction of new

physical features! These self-enforcing

features tend to break

the infinite continuity thatencourages speed with orwithout speed warnings

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Fri Dec 6


! Raised crosswalks

! Narrower pavement widths! Chicanes through urban furniture or parking

! Changes in the pavement texture

! Mini-roundabouts

! Cul-de-sacs

! Eliminating some movements! Civilizedgreen waves

! .

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Raised crosswalks

! Double function! You accommodate to gradient:

! 7% for 40-45 km/hr

! 10% for 30 km/hr! 12% for 25 km/hr or less

! Every 60-100 meters plus proper

warning! The top needs a minimum width,

specially for buses

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Raised intersections

! The automobile

finds itself inneutral grounds

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Bulb-outs

! Pros:! Decrease

exposure

! Higher visibilityspecially forchildren

! Easyimplementation

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Narrower pavement widths

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0,15 2,5 0,3 1,7 0,15

4,80

0,15 2,5 0,2 2,5 0,15

5,5

0,3 1,7 0,8 1,7 0,3

4,80

0,6 1,7 0,9 1,7 0,6

5,5

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Nothing like abucket of paint

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Narrowing the pavement

You could

rearrange parking

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Eliminating road lanes

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Mini-roundabouts

They work!

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Or all of the above

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Eliminating some movements (i.e. in a roundabout)

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Civilized Green Waves

They need low cycles to avoidlate-comers driving fast (at night)

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CivilizedGreen Waves

Plus often changes inhorizontal

alignment, refugeislands, narrowingthe road width

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Fri Dec 6


CivilizedPedestrian signals

! Longer timing forpedestrians

!

Lower total cycles! Green waves for

pedestrianmovements

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Fri Dec 6


Narrowing the pavement

! Improving publicspaces:

! New urban furniture,including trees

! New activities

! Weather shelters toencourage people useof the streets

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Fri Dec 6


!

Not an end by itself, justthe means to an end

! It must be accompanied by

other measures to improvethe urban environment soas to encourage more

pedestrians

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Fri Dec 6

Design Criteria

! Including other

important issues:! Location

! Self-enforcement

! Liability

! Reversibility

!

Public participation! Overall traffic scheme

! Traffic deviated to other

areas

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Fri Dec 6

Location

! Sensitive areas:! Schools

! Transit stations

! Senior citizens

! Areas with highaccident rates

! High speeds

eg.transitionareas from theexpressway into

the urbannetwork

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Fri Dec 6

Some Bibliography

! Canadian Guide to

Neighbourhood TrafficCalming TAC-ATC/ITE1998

!

Civilised Streets CarmenHass-Klau et al ET&P,1992

!

Guide Les ralentisseursde type dos dane ettrapezoidal CERTU, 1994

! Guide Zone 30 CETUR,

1992! Pedestrian and City Traffic

Carmen Hass-Klau, 1990

! City Routes, City RightsConserv Law Found, 1998

! Reduire la Vitesse enAgglomeration CETUR 1989

! Voirie Urbaine CETUR 1988! plus JANE JACOBS, KEVIN

LYNCH, WHYTE, etc..

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Fri Dec 6

Bibliography http://www.ite.org/traffic/index.htm

U b T i Pl i F ll 2002

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Bibliographyhttp://www.trans.ci.portland.or.us/Traffic_Management/Trafficcalming/

U b T t ti Pl i F ll 2002

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Fri Dec 6

Traffic Calming: The Process

U b T t ti Pl i F ll 2002

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Fri Dec 6

Not an easy process at the beginning

My good friend the

city engineer...


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But once you begin...

! There is not enoughmoney toaccommodate allthe requests

! The best is the

change inbehavioral patterns


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Fri Dec 6

Look for an easy winner...

!

Nothing like a school


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Once they try...

! Bulb-outs everywhere

! Today a pedestrianized plaza


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Fri Dec 6

Always go easy at the beginning...

! Even if you have

to cheat a bit likemy good friend

Jan Gehl


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Fri Dec 6

In a nutshell, ten rules

1. Every change is hard to implement

2. Start by the easiest job3. You need allies

4. You have to minimize risks

5. Technical competence a must6. Not isolated measures, but packages

7. Short term results, a must

8. But dont forget to plant a few seeds9. Everyone sees things differently

10. Success is hard to measure

But if you want, you can!

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18 Week14a