Jersey barriers and guardrails

Crashworthy concrete barriers are designed to redirect, slow, or stop errant vehicles from causing a more severe crash. Jersey barriers are the original and most widely used safety shape concrete barriers (U.S. Department of Transportation, 2006). Jersey median barriers are often used in narrow highway medians to prevent vehicle crossovers into oncoming traffic.

Zein et al. (2003) carried out a study that identified the most effective road engineering improvements that had been introduced in North America in the four previous decades. They included rigid barriers in their list of improvements, but also noted that these structures contributed to a higher frequency of crashes, because barriers were fixed-object hazards. However, serious head-on and off-road crashes were usually reduced or eliminated following their introduction.

The authors summary of the literature findings of Zein et al. (1999) estimated that the introduction of median barriers would result in a 30% increase in total crashes, but a 40% reduction in fatalities and a 20% decrease in injuries due to median-related crashes. Zein et al. (1999) also provided estimates of casualty reductions following the introduction of rigid roadside barriers. They concluded that fatal and injury crashes would be reduced by 52% and 44%, respectively.

A comparative Full Bayesian before-and-after analysis of the impact of the installation of raised medians on two-lane urban collectors and arterial roads in New Jersey with speed limits less than 45 mph determined that all crashes had decreased by 14% (Yanmaz-Tuzel et al., 2010).

Yang et al. (2013) used Empirical Bayesian methodology to evaluate the safety effect of removing eleven mainline barrier toll plaza booths and retrofitting the highway with two express toll collector lanes in either direction of the median-divided multilane expressway in New Jersey. Multiple-year traffic and crash data before and after the removals of the barrier toll plazas were used in the analysis. The removal of the barrier tollbooths and retro fitment of the expressway resulted in 47.2% decrease in total crashes and a 40.3% reduction in casualty collisions.

Scope of the Problem

• U.S. Department of Transportation (2006). Concrete Barriers. U.S. Department of Transportation, Federal Highway Administration, Washington D.C. Retrieved from http://safety.fhwa.dot.gov/roadway_dept/policy_guide/road_hardware/ctrmeasures/concrete_barriers/concrt_barriers.pdf

Evidence

• Zein, S.R. and Montufar, J. (2003). Road Safety Benchmarks Over Time. (Report No.  TP 14328 E). Prepared for Transport Canada. Retrieved from http://www.tc.gc.ca/media/documents/roadsafety/tp14328e.pdf
• Zein, S. and Rocchi, S, (1999). Traffic Safety Barriers and Rumble Strips: Overview of the Potential for System-Wide Implementation, Hamilton Associates for the Insurance Corporation of British Columbia, Vancouver, BC.
• Yanmaz-Tuzel, O. and Ozbay, K. (2010). A comparative Full Bayesian before-after analysis and application to urban road safety countermeasures in New Jersey." Accident Analysis and Prevention, Vol. 42, No. 6, Oxford, N.Y., Pergamon Press, (2010) pp. 2099-2107. Retrieved from http://www.cmfclearinghouse.org/study_detail.cfm?stid=246
• Yang, H.; Ozbay, K.; Bartin, B.; and Ozturk, O. (2013). Effect of Removing Freeway Mainline Barrier Toll Plazas on Safety. Presented at the Transportation Research Board 92nd Annual Meeting, Paper No. 13-5001, January 13-17, 2013, Washington, DC. Retrieved from http://www.cmfclearinghouse.org/detail.cfm?facid=4958