Bulb Outs (Curb Extensions)

In Canada, the majority of pedestrian fatalities occur on urban roads with posted speed limits of up to 70 km/h. About 70% of all pedestrians killed in urban locations were attempting to cross the road. Approximately 29% of pedestrians killed on urban roads were crossing an intersection with no traffic control. A further 27% of fatally injured pedestrians were attempting to cross an intersection with traffic controls with or without the right-of-way (Transport Canada, 2009).

Bulb-outs – also called curb extensions – extend the sidewalk or curb line out into the parking lane, which reduces the effective street width. Curb extensions significantly improve pedestrian crossings by reducing the pedestrian crossing distance, visually and physically narrowing the roadway, improving the ability of pedestrians and motorists to see each other, and reducing the time that pedestrians are in the street.

Bulb-outs were installed on a collector used by children to access a school and a park in a Cambridge, Massachusetts, neighborhood where residents were concerned about speeding. The city conducted before-and-after speed studies as part of an ongoing evaluation. The 85th percentile speed was reduced by 14% following the installation of the bulb-outs. The speed limit on the collector where the bulb-outs were installed was 48 km/h. Prior to the improvements, 39% of vehicles exceeded 40 km/h. After the bulb-outs had been installed, 14% of vehicles exceeded 40 km/h (Cambridge Community Development Department).

King (2000) conducted a before-and-after study of crash data at six intersections in New York City where curb extensions had been installed. Monthly rates for all crashes as well as vehicle-pedestrian crashes were analysed according to the criterion of severity. These numbers were compared to the crash rates of the surrounding intersections. King concluded that curb extensions reduced the overall severity rates of collisions in four out of six surveyed areas in New York City. In two of three locations, the severity of pedestrian injuries decreased, in part due to the reduced vehicle speeds that resulted from spatial limitations.

Johnson (2005) documented a case study evaluating the yielding behavior of motorists at a crosswalk in Albany, Oregon, where a curb extension had been installed to determine if the pedestrian safety improvements functioned as intended. The measures of effectiveness used to evaluate the pedestrian improvements were the average number of vehicles that passed before a pedestrian-cross, the percent of pedestrians crossing with yield, and the percent of vehicles yielding at the advance stop bar. The findings of Johnson’s research suggested that curb extensions contributed to a significant reduction in the average number of vehicles that passed rather than let pass a waiting pedestrian.

Molino et al. (2010) conducted an experiment that focused on measures that contributed to traffic calming for small rural towns during the day. The traffic calming measures that were studied included chicanes, parked cars on both sides of the road and bulb-outs. The experiment was conducted in the United States Federal Highway Administration’s (FHWA) Highway Driving Simulator. The bulb-outs were the least effective traffic-calming countermeasures, slowing drivers down by only 1 to 1.6 to 2.4 km/h through the town relative to the baseline speed.

Fernandez et al. (2012) conducted a study to better understand the environmental factors (traffic control, geometric, and land use factors) associated with pedestrian-vehicle crashes. Geometry and collision data from 1 871 signalized intersections in Montreal were studied. Geometric variables were incorporated into risk exposure models. The authors determined that pedestrian crashes were reduced by 25% at sites with curb extensions.

Scope of the Problem

• Transport Canada (2009) Fatally Injured Vulnerable Road Users in Canada, 2004-2006. Retrieved from http://www.walkinginfo.org/pedsafe/pedsafe_curb1.cfm?CM_NUM=19

Evidence

• Cambridge Community Development Department (1998). Granite Street Traffic Calming. Cambridge, Massachusetts. Retrieved from http://www.walkinginfo.org/pedsafe/casestudy.cfm?CM_NUM=19&CS_NUM=20
• King, M. (2000). Calming New York City Intersections. Transportation Research Circular. EC019: Urban Street Symposium Conference Proceedings, Dallas, TX, June 28-30, 1999. TRB, NRC: Washington, DC.
• Johnson, R.S. (2005). Pedestrian Safety Impacts of Curb Extensions: A Case Study, Final Report (Report No. SPR 304-321). Washington DC: Oregon Department of Transportation, Salem OR & Federal Highway Administration. Retrieved from http://www.oregon.gov/ODOT/td/tp_res/docs/reports/pedestrainsafetycurbext.pdf
• Molino, J.A., Katz, B.J., Hermosillo, M.B., Dagnall, E.E., & Kennedy. J.F. (2010). Simulator Evaluation of Low-Cost Safety Improvements on Rural Two-Lane Undivided Roads: Nighttime Delineation for Curves and Traffic Calming for Small Towns (Report No. FHWA-HRT-09-061). Washington, DC Retrieved from http://www.fhwa.dot.gov/publications/research/safety/09061/index.cfm
• Fernandez, D., Miranda-Moreno, L. & Morency, P. (2012). Vehicle-Pedestrian Accidents at Signalized Intersections: Exposure Measures and Geometric Designs. Transportation Research Board Annual Meeting 2012, Paper #12-3208, Washington DC.