Raised median treatment

Midblock locations, where vehicle travel speeds are higher, account for more than 70% of pedestrian fatalities. (Federal Highway Administration, 2012). Raised medians are usually installed on multilane arterial streets with high traffic volumes or on multi-lane roadways that are too wide for some pedestrians to cross safely. The median breaks up the crossing into smaller more manageable distances. Installing a median can be especially helpful for children, older adults and persons with mobility challenge who need more time to cross.

Elvik and Vaa, (2004) found that providing a raised median on principal arterial roads in urban areas reduced all crashes by 39%, reduced serious and minor injury crashes on principal arterial roads in urban areas by 22%, and reduced serious and minor injury crashes on principal arterial roads in rural areas by 12% and property damage only crashes on principal arterial roads in rural areas by 18%.

Zegeer et al. (2005) conducted a study to determine whether marked crosswalks at uncontrolled locations were safer than unmarked crosswalks under various traffic and roadway conditions. The study involved an analysis of 5 years of pedestrian crashes at 1,000 marked crosswalks and 1,000 matched unmarked comparison sites. No sites in this study had traffic signal or stop sign on the approaches. Detailed data were collected on traffic volume, pedestrian exposure, number of lanes, median type, speed limit, and other site variables. The authors found that on multilane roads (3 to 8 lanes) with average daily traffic (ADT) greater than 15,000 vehicles, the pedestrian crash rate per million crossings at marked crossings with raised medians was 46% lower than the crash rate at locations with the same ADT without raised medians, while the crash rate at unmarked crossings on multilane roads with raised medians and ADT greater than 15,000 vehicles was 39% lower than that of unmarked crossings with the same traffic level without raised medians.

Shultz et al. (2011) used a hierarchical Bayesian model to analyze the effectiveness of raised median installations on overall and severe crash frequency in the state of Utah by determining the effect each had on crash frequency and frequency of severe crashes at study locations before and after the installation of raised medians. Several sites where raised medians had been installed during the previous 10 years were evaluated using available crash data. The results of the study showed that the overall crash frequency decreased by 39% while severe crashes decreased by 44% along corridors where raised medians were installed.

Alluri et al. (2012) conducted a before-after analysis to evaluate the impact of median conversion from two-way left-turn lanes to raised medians at 18 locations in Florida. The results showed a 30.3% decrease in the total crash rate following median conversion. Median conversion was especially effective in reducing rear-end, angle, left-turn, and right-turn crash rates. Of the 2,436 crashes that occurred at the 18 locations following median conversion, only 1.8% involved pedestrians. None of the pedestrians were struck while standing on the raised median.

The Federal Highway Administration (2013) in the United States cited the results of research on crash modification factors by Gan et al. (2005) which indicated that the installation of raised medians would reduce all pedestrian crashes by 25%.

A study on raised median treatments by Pécheux et al. (2009) produced mixed results. The authors evaluated the safety and mobility impacts of the installation of a median refuge island at two intersection locations in San Francisco, California and at one midblock location in Las Vegas, Nevada. Measures of effectiveness included the percentage of pedestrians trapped in the roadway, the percentage of pedestrians diverted to the crosswalk, the percentage of pedestrian-vehicle conflicts, the percent of drivers yielding to pedestrians, and the average pedestrian delay. The results of the analysis did not show any measurable changes in the percentage of pedestrians trapped in the roadway, the percentage of pedestrians that were diverted to the crosswalk, or the percentage of pedestrian-vehicle conflicts. In San Francisco, there was no significant change in the percent of turning drivers that yielded to pedestrians at intersections where refuge islands were installed. However, in Las Vegas there was a significant 24% increase (from 22% to 46%) in driver yielding at the midblock crosswalk where the refuge island was installed.

Scope of the Problem

• U.S. Department of Transportation (2012). Proven Safety Countermeasures, Medians and Pedestrian Crossing Islands in Urban and Suburban Areas. U.S. Department of Transportation Federal Highway Administration. Report No. FHWA-SA-12-011. Retrieved from http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_011.htm

Evidence

• Elvik, R. and Vaa, T. (2004), Handbook of Road Safety Measures. Oxford, United Kingdom, Elsevier. Retrieved from http://www.cmfclearinghouse.org/study_detail.cfm?stid=14
• Zegeer, C. V., Stewart, J. R. and Huang, H. and Lagerwey, P., Feaganes, J., & Campbell, B.J. (2005). Safety effects of marked vs. unmarked crosswalks at uncontrolled locations: Final Report and Recommended Guidelines. (Report No. FHWA-HRT-04-100). University of North Carolina Highway Safety Research Center, Chapel Hill, N.C. Retrieved from http://www.fhwa.dot.gov/publications/research/safety/04100/04100.pdf
• Schultz, G., Thurgood, D., Olsen, A., Reese, C.S. (2011) Analyzing Raised Median Safety Impacts Using Bayesian Methods. Transportation Research Record: Journal of the Transportation Research Board, Washington, D.C. Retrieved from http://trid.trb.org/view.aspx?id=1091849
• Alluri, P., Gan, A., Haleem, K., Miranda, S., Echezabal, E., Diaz, A., Ding, S. (2012). Before-and-after safety study of roadways where new medians have been added. Florida Department of Transportation. Retrieved from http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_PL/FDOT-BDK80-977-18-rpt.pdf
• Federal Highway Administration (2013). Tool Box of Countermeasures and Their Potential Effectiveness for Pedestrian Crashes. (Report No. FHWA-SA-014). US Department of Transportation. Retrieved from http://www.pedbikeinfo.org/collateral/PSAP%20Training/gettraining_references_pedToolboxofCountermeasures2013.pdf
• Gan, A., Shen, J., & Rodriguez, A. (2005). Update of Florida Crash Reduction Factors and Countermeasures to improve the Development of District Safety Improvement Projects.” Florida Department of Transportation. Retrieved from http://www.dot.state.fl.us/research-center/Completed_Proj/Summary_SF/FDOT_BD015_04_rpt.pdf
• Pécheux, K., Bauer, J., & McLeod, P. (2009).Pedestrian Safety Engineering and ITS-Based Countermeasures Program for Reducing Pedestrian Fatalities, Injury Conflicts, and Other Surrogate Measures Final System Impact Report. U.S. Department of Transportation, Washington, DC. Retrieved from http://safety.fhwa.dot.gov/ped_bike/tools_solve/ped_scdproj/sys_impact_rpt/sys_impact_rpt.pdf