This study is an examination of the safety and operational performance of the high tension median cable barrier (HTCB) installed between January and May 2007 on a 10.75 km section of Deerfoot Trail, a six-lane divided freeway with a depressed median in Calgary, Alberta, carrying 150,000 vehicles per day. It was the first major HTCB in Canada and a discussion of its design elements and preliminary safety impacts have been reported before. This paper presents the results of a rigorous analysis of nearly three years of detailed collision and operational data. The study of the barrier’s performance reported here makes this HTCB installation one of the most robustly studied in North America, and should therefore be of interest to highway safety professionals. The main objectives of this study were to examine the safety performance of the HTCB in terms of collision severity reduction, effects on the numbers of median collisions, severity distribution of the HTCB collisions compared to median collisions without the HTCB, and the operational and maintenance characteristics of the barrier. The results of a comprehensive benefit-cost analysis are also presented. The main steps of the study were: 1) Collect and review collision data; 2) Analyse median collisions before and after the installation of HTCB; 3) Compare the rate and severity of median collisions before and after HTCB installation; 4) Obtain feedback from maintenance contractor, RCMP and emergency responders; 5) Evaluate safety effects of HTCB on Deerfoot Trail using AASHTO Highway Safety Manual (2010); and 6) Conduct a benefitcost analysis. The before and after analyses of the safety performance of the HTCB revealed that the rate and severity of median-related severe collisions dropped significantly after the installation of the barrier (severe collisions are defined as collisions resulting in fatalities and major injuries). After the installation of the HTCB, the percentage of median related fatal collisions dropped from 4.4% to 0%, and the percentage of injury collisions dropped from 21.1% to 11.8%. The analyses also showed that although there was an increase in property damage only collisions the frequency of severe collisions dropped by 25% and the rate of severe collisions dropped by 40% after the installation of the HTCB. Application of Empirical Bayes method according AASHTO Highway Safety Manual (2010) shows that the safety performance on the study section of Deerfoot Trail improved by 27.92% with respect to reduction in severity (fatal and injury collisions) and by 32.46% with respect to reduction in fatality (fatal collisions). The benefit-cost analysis (with a 20-year analysis period, and taking into account the construction and maintenance costs and the monetary benefits of the reduction in severe collisions) indicated a benefit-cost ratio of 11.1 and a payback period of less than one year which are strong indications of the safety benefits of the HTCB. This study concludes that the HTCB on Deerfoot Trail has been performing well with respect to safety and operation, and can serve as a model for applicability in other jurisdictions.
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