Webinar: Traffic safety on bus corridors

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2013-09-27 webinar by Nicolae Duduta

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Webinar: Traffic safety on bus corridors

  1. 1. Traffic Safety on Bus Corridors Nicolae Duduta, EMBARQ, World Resources Institute ALC BRT Center of Excellence Webinar September 27, 2013
  2. 2. 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
  3. 3. 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
  4. 4. Overall safety impact Reduction in the number of lanes Shorter pedestrian crossings Central median Existing buses and minibuses replaced with a single operating agency
  5. 5. Crashes on Macrobus corridor, before and after Overall safety impact 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 0 50 100 150 200 250 Jan-07 Mar-07 May-07 Jul-07 Sep-07 Nov-07 Jan-08 Mar-08 May-08 Jul-08 Sep-08 Nov-08 Jan-09 Mar-09 May-09 Jul-09 Sep-09 Nov-09 Jan-10 Mar-10 May-10 Jul-10 Sep-10 Nov-10 Jan-11 Mar-11 May-11 Monthlycitywidecrashes(excludingtheBRTcorridor) MonthlycrashesontheBRTcorridor Citywide Crashes on the BRT Before During BRT construction During BRT
  6. 6. 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%)
  7. 7. Overall safety impact 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)
  8. 8. 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
  9. 9. 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.)
  10. 10. 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
  11. 11. 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 - -0.147 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
  12. 12. 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
  13. 13. 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%
  14. 14. 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
  15. 15. TransMilenio, Av. Caracas, Bogota Traffic speeds and block sizes
  16. 16. TransOeste BRT, Rio de Janeiro Traffic speeds and block sizes
  17. 17. Av. das America, Rio de Janeiro Speed management Av. Caracas, Bogota
  18. 18. 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
  19. 19. 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
  20. 20. Curbside bus lane, Eje 2 Oriente, Mexico City Mid-block signalized crosswalks
  21. 21. 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
  22. 22. 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
  23. 23. Safety recommendations Reducing speed from 70kmh to 60kmh (30 kmh at stations) Adding mid-block signalized crossings Reducing pedestrian signal delay
  24. 24. Pedestrian delay issues - TransOeste Mid-block signalized crosswalk, Av. das Americas
  25. 25. Pedestrian delay issues - TransOeste HCM recommends keeping pedestrian delay under 30 seconds (ideally under 10)
  26. 26. 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
  27. 27. Safety and operating speed 0 10 20 30 40 50 60 0 5 10 15 20 25 30 35 40 45 Operatingspeedsbysection 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
  28. 28. Nicolae Duduta, nduduta@wri.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/ Thank you

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