Traffic Safety on Bus Corridors

Nicolae Duduta EMBARQ, World Resources Institute

ALC BRT Center of Excellence Webinar

September 27, 2013 11am EST

Please mute your microphones

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

Overall safety impactReduction in the number of lanes

Shorter pedestrian

crossingsCentral median

Existing buses and minibuses replaced with a single operating agency

Crashes on Macrobus corridor, before and after

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)Citywide crashes

Crashes on the BRT corridor

Before BRT

During BRT construction During BRT opera-

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Overall safety impact

  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%)

Overall safety impact

 Best

estimate95% confidence

interval SourceArterial BRT (developing world)  Fatalities -52% (-39%; -63%)  Injuries -39% (-33%; -43%) EMBARQ AnalysisAll crashes -33% (-30%; -36%)  Arterial BRT (Latin America)  Fatalities -47% (-21%; -64%)  Injuries -41% (-35%; -46%) EMBARQ AnalysisAll crashes -33% (-29%; -36%)  Bus priority lanes (Australia)  All crashes -18% n/a Goh et al. 2013Peak 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 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?

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 133LR 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

Crash frequency model results

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 - -0.147Center-lane BRT (Metrobus Line 1) -0.029 -0.299Counterflow bus lane 0.554*** 0.389**Curbside bus lane -0.176 -0.087No. of observations 216 216Log likelihood -618.475 -518.539LR chi2 139.99 104.88Prob > chi2 0.000 0.000chibar2(01) 367.14 231.39Prob >=chibar2 0.000 0.000*0.05<p<0.1; **0.001<p<0.05; ***p<0.001, - variable not included in the modelSafety impact analysis showed statistically significant safety improvements post

BRT implementation

Crash frequency model results

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

Pedes-trians54%

Car occupants23%

Motor-cyclists

10%

Bicyclists5% Other

7%

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

Traffic speeds and block sizes

TransOeste BRT, Rio de Janeiro

Traffic speeds and block sizes

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 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?

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

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 29.6Local 25.6 25.6 25.4 25.4

Travel time (min) Express 71 72 77 77Local 89 89 89 89

Speed variance Express 37 31.3 22.33 15.6Local 16 14.9 14.85 15.6

Speed variability*

Express 0.19 0.18 0.16 0.16Local 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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Observed operating speed

Sections along Metrobus Line 1, Av. Insurgentes

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BRT operating speed along Metrobus Line 1, Mexico City

Black dots indicate pedestrian black spots

Nicolae Duduta, nduduta@wri.org

EMBARQ.org

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/

Next steps