Webinar: Traffic safety on bus corridors

Traffic Safety on Bus Corridors

Nicolae Duduta, EMBARQ, World Resources Institute

ALC BRT Center of Excellence Webinar

September 27, 2013

What is the overall safety impact from implementing a BRT,

Busway, or other type of bus system?

What are the factors that impact safety performance on a

bus corridor?

How do safety countermeasures impact operational

performance?

Case studies

Summary

Depends on the configuration of the new bus system,

but also on what was there before

Here: Calz. Independencia (Guadalajara) before BRT

Overall safety impact


Reduction in the number of

lanes

Shorter

pedestrian

crossings Central

median

Existing buses and minibuses

replaced with a single

operating agency

Crashes on Macrobus corridor, before and after


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Citywide

Crashes on the BRT

Before During BRT

construction During BRT


Type of transit service Corridor and

length (km)

Safety impacts, per year, per km

(percent change in parenthesis)

City Before After Crashes Injuries Fatalities

Mexico City Informal

transit

Single lane

BRT

Metrobus

Line 3 (17

km)

+7.5 (+11%) -6.7 (-38%) - 0.3 (-38%)

Guadalajara Bus priority

lane

BRT with

overtaking

lane

Macrobus

(16 km)

-83.19 (-56%) -4.1 (-69%) -0.2 (-68%)

Bogota Busway Multi-lane

BRT

Av. Caracas

(28 km)

n/a -12.1 (-39%) -0.9 (-48%)

Ahmedabad Informal

transit

Single lane

BRT

Janmarg

system (39

km)

-2.8 (-32%) -1.5 (-28%) -1.3 (-55%)

Melbourne Conventional

bus

Queue

jumpers,

signal

priority

SmartBus

Routes 900,

903 (88.5

km)

-0.09 (-11%) -0.1 (-25%) -0.03 (-100%)


Best

estimate 95% confidence interval Source

Arterial BRT (developing world)

Fatalities -52% (-39%; -63%)

Injuries -39% (-33%; -43%) EMBARQ Analysis

All crashes -33% (-30%; -36%)

Arterial BRT (Latin America)

Fatalities -47% (-21%; -64%)

Injuries -41% (-35%; -46%) EMBARQ Analysis

All crashes -33% (-29%; -36%)

Bus priority lanes (Australia)

All crashes -18% n/a Goh et al. 2013

Peak hour bus lanes (US)

Injury crashes +12% (+4%; +21%)

Elvik and Vaa (2008) Property damage

crashes +15% (+3%; +28%)

Bus and taxi lanes (US)

Injury crashes +27% (+8%; +49%) Elvik and Vaa (2008)

Unspecified severity -4% (-8%; 0)

Peak hour bus / HOV lanes (US)

Unspecified severity +61% (+51%; +71%) Elvik and Vaa (2008)



What are the factors that impact safety performance on

a bus corridor?


performance?

Summary

Crash frequency models

Statistical models that aim to explain differences in crash

rates at different locations through variables including traffic

volumes, street geometry, land uses, etc.

The preferred probability distributions for modeling crash

data are Poisson and, more commonly, negative binomial

The same street characteristic (e.g. block sizes) will have

different impacts on crashes at different levels of severity

It is recommended to develop crash frequency models for

different types of crashes (e.g. vehicle collisions, pedestrian

crashes, severe crashes, property damage crashes, etc.)

Crash frequency model results

Variables

Severe crash

model (Poisson)

All crashes

model (negative

binomial)

Annual average daily traffic (AADT, thousands of

vehicles) 0.016* -

Total number of approaches to the intersection - 0.424***

Total length of all approaches to the intersection

(meters) 0.003** -

Average length of approaches to the intersection

(meters) - -0.008**

Average number of lanes per approach 0.334*** 0.492***

Cross street is through street (=1 if yes, =0 otherwise) 1.142** 0.820***

Major T junction (=1 if yes, =0 otherwise) 0.719** 0.748**

Constant -3.914*** -1.197**

N 133 133

LR χ2 64.62*** 135.76***

chibar2 n/a 341.99***

Log likelihood -141.58 -141.58

*0.05<p<0.1; **0.001<p<0.05; ***p<0.001; - variable not included in the model; n/a not applicable

Guadalajara


Mexico City

Vehicle collisions (NB) Pedestrian crashes (NB)

Coef. Coef.

Constant -1.518*** -1.857***

Number of legs 0.374*** 0.252***

Number of lanes per leg 0.374*** 0.341***

Left turns per approach 1.705*** 1.268**

Market area - 0.664***

Maximum pedestrian crossing distance (m) - 0.026**

Pedestrian overpass - -0.147

Center-lane BRT (Metrobus Line 1) -0.029 -0.299

Counterflow bus lane 0.554*** 0.389**

Curbside bus lane -0.176 -0.087

No. of observations 216 216

Log likelihood -618.475 -518.539

LR chi2 139.99 104.88

Prob > chi2 0.000 0.000

chibar2(01) 367.14 231.39

Prob >=chibar2 0.000 0.000

*0.05<p<0.1; **0.001<p<0.05; ***p<0.001, - variable not included in the model

Safety impact analysis showed statistically significant safety improvements post

BRT implementation


Removal of one

lane per

approach: -28%

crashes

Crosswalk

shortened by 10m:

-26% pedestrian

crashes

Central median:

-28% vehicle collisions

Left turn

prohibitions:

-20% all crash

types

The safest place to be on a bus corridor is inside the bus

The most dangerous place: walking to and from the station

Fatalities on bus corridors

Pedestrians 54%

Car occupants

23%

Motorcyclists 10%

Bicyclists 5% Other

8%

Delhi Busway

Traffic speeds and block sizes

For each additional 10 m (30’) between signalized

intersections:

• 2% decrease in all crashes

• 3% increase in severe crashes

TransMilenio, Av. Caracas, Bogota


TransOeste BRT, Rio de Janeiro


Av. das America, Rio de Janeiro

Speed management

Av. Caracas, Bogota

Metrobus Line 2, Mexico City

Pedestrians do not use bridges and prefer to cross under them

Crash frequency model: bridges have no statistically significant impact on pedestrian safety on urban arterials

Pedestrian bridges

Metrobus BRT, Istanbul

Pedestrian bridges are a good solution on expressways

Crash frequency model: bridges are strongly correlated with lower pedestrian crash frequencies on expressways

Pedestrian bridges

Curbside bus lane, Eje 2 Oriente, Mexico City

Mid-block signalized crosswalks



What are the factors that impact safety performance on a

bus corridor?


performance?

Summary

Case study: TransOeste BRT, Rio de Janeiro

Road safety inspection – proposed safety countermeasures targeted at speed reductions and improved pedestrian safety

Microsimulation model – test the impact of countermeasures on operational performance

Safety recommendations

Reducing speed from 70kmh to 60kmh (30 kmh at stations)

Adding mid-block signalized crossings

Reducing pedestrian signal delay

Pedestrian delay issues - TransOeste

Mid-block signalized crosswalk, Av. das Americas

Pedestrian delay issues - TransOeste

HCM recommends keeping pedestrian delay under 30 seconds (ideally under 10)

Impact on operations

* Speed variability is defined here as the ratio of the standard deviation to the mean

commercial speed, for all vehicles generated in the simulation. A lower speed

variability coefficient indicates more reliable service.

Indicator Service Baseline 60kmh 60/30kmh Complete

Speed (km/h) Express 32 31.5 29.6 29.6

Local 25.6 25.6 25.4 25.4

Travel time (min) Express 71 72 77 77

Local 89 89 89 89

Speed variance Express 37 31.3 22.33 15.6

Local 16 14.9 14.85 15.6

Speed variability* Express 0.19 0.18 0.16 0.16

Local 0.16 0.15 0.15 0.16

Slight negative impact on commercial speed (though still above 25kmh benchmark)

Slight increase in travel times (+6 min terminal to terminal)

Lower speed variability (i.e. more reliable service)

Potential for significant safety benefits

Safety and operating speed

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0 5 10 15 20 25 30 35 40 45

Op

era

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Sections along Metrobus Line 1, Av. Insurgentes

Observed operating speed Poly. (Predicted speed, current conditions) Poly. (Predicted speeds with 300m blocks)

BRT operating speed along Metrobus Line 1, Mexico City

Black dots indicate pedestrian black spots

Nicolae Duduta, [email protected]

Further reading on this topic:

EMBARQ’s safe design guidelines for BRT: http://www.embarq.org/en/traffic-safety-bus-corridors-pilot-version-road-test

A TRR paper including the crash frequency models: http://www.brt.cl/understanding-road-safety-impact-of-high-performance-bus-rapid-transit-and-busway-design-features-2/

Thank you

mailto:[email protected]

http://www.embarq.org/en/traffic-safety-bus-corridors-pilot-version-road-test
















http://www.brt.cl/understanding-road-safety-impact-of-high-performance-bus-rapid-transit-and-busway-design-features-2/






























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Webinar: Traffic safety on bus corridors