Abstract Manager

High Tension Cable Barriers (HTCB) have seen increasing usage as median barriers in recent years. However, most implementations and assessments of HTCB revolve around high-speed rural facilities, and there is limited data for using HTCB in the urban context. The design considerations for HTCB in urban areas include lower roadway operating speeds, higher traffic volumes, presence of curbed medians, and lack of shoulders causing limited offset between barriers and travel lanes. In 2024, The City of Calgary retained MORR Transportation Consulting to conduct a two-phase study on the effectiveness of HTCB installed both in Calgary and other jurisdictions. The results of this study provided guidance on future installations of cable barriers on Calgary’s urban and semi-urban environments.  

The initial study phase culminated in a knowledge base report summarizing the available assessments of HTCB in North America. The safety performance of HTCB was synthesized through literature review and jurisdictional surveys. The reviewed Collision Modification Factors (CMFs), as well as Safety Performance Functions (SPFs), predominantly indicated a reduction in severe injury collisions and an increase in Property-Damage Only (PDO) collisions. The overall safety performance and benefit-cost ratio was found to be net positive for HTCB on rural roadways. However, the synthesis of findings revealed few CMFs and SPFs were available for urban and semi-urban roadways like those that exist in Calgary.

The second study phase determined the collision impacts of HTCB along three urban corridors in Calgary. This was done through a comparison of the normalized frequency of off-road collisions before and after HTCB installation. On corridors with narrower curbed medians, injury rates for off-road collisions were three times higher without HTCB involvement than when the HTCB is contacted. On corridors with wider medians and shoulders, injury rates for off-road collisions were similar regardless of HTCB involvement. No head-on median-crossover collisions have been reported after HTCB installation on any corridor. Across all corridors there was an increase in reported PDO collisions after HTCB installation.

The results of this two-phase study indicate that HTCB can become an effective safety countermeasure in the urban context. The most effective application of HTCB is along roadways that experience a high proportion of off-road collisions causing injury. The presence of curbs and lack of median shoulders do not necessarily reduce the effectiveness of HTCB, as these factors may contribute to the initially high proportion of injury collisions prior to HTCB implementation. These findings validated The City’s decision to proceed with HTCB installation on another urban corridor in the coming year. Lessons learned from Calgary’s study could also inform other jurisdictions that have installed or are considering installing HTCBs in an urban context.