Study Details

Study Title: Development of Crash Modification Factors for Installation of High-Tension Cable Median Barrier

Authors:

Publication Date: 2016

Abstract: Cross-median crashes are among the most hazardous collision types that can occur on freeways. These crashes can be caused by a variety of factors including drowsiness, driver distraction, impaired driving, and loss of control. The primary countermeasure to reduce the potential for such crashes is the installation of a median barrier. Several states have recently installed cable barrier as a countermeasure to reduce the number of fatalities resulting from freeway cross-median crashes. As of 2014, approximately 317 miles of cable median barrier had been installed on freeways throughout the state of Michigan. In order to determine the safety impacts of cable barrier installation, a comprehensive before-and-after crash analysis was conducted, which included a manual crash report review to identify all median-related crashes. Safety performance functions were developed for roadway segments before and after cable barrier installation, as well as for similar control segments where no median barrier had been installed. Crash modification factors were developed as a function of median width using the Empirical Bayes (EB) method, which accounts for the regression-to-the-mean (RTM) effect. The results show cable median barriers to significantly reduce the frequency of such severe crashes, though marked increases in lower severity crashes were observed. Reductions in fatalities and serious injuries are less pronounced as compared to prior research (especially for wider median widths), which has largely ignored the RTM effect. Ultimately, this study provides important guidance for transportation agencies with respect to the expected safety impacts of cable median barrier installation.

Study Citation: Russo, B., Savolainen, P., and Gates, T., "Development of Crash Modification Factors for Installation of High-Tension Cable Median Barrier." Presented at the 95th Annual Meeting of the Transportation Research Board, Washington, D.C., (2016).

Related Citations: Russo et al.


CMFs Associated With This Study

Category: Roadside

Countermeasure: Install cable median barrier (high tension)

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
2.63 -163 4 Stars Other Minor injury,Property damage only (PDO) Principal Arterial Other Freeways and Expressways
2.51 -151 4 Stars Other Minor injury,Property damage only (PDO) Principal Arterial Other Freeways and Expressways
0.97 3 4 Stars Other Minor injury Principal Arterial Other Freeways and Expressways
1.02 -2 4 Stars Other Minor injury Principal Arterial Other Freeways and Expressways
0.47 53 3 Stars Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways
0.76 24 3 Stars Other Fatal,Serious injury Principal Arterial Other Freeways and Expressways

The information contained in the Crash Modification Factors (CMF) Clearinghouse is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in the CMF Clearinghouse. The information contained in the CMF Clearinghouse does not constitute a standard, specification, or regulation, nor is it a substitute for sound engineering judgment.