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Safety Evaluation of Cable Barriers Installation on Some Highways in British Columbia

Author(s): Sowers, Elesawey; Sengupta

Slidedeck Presentation Only (no paper submitted):

6C - Sowers

Abstract:

Median and roadside cable barriers have been proven to prevent crossover crashes which are usually associated with high-severity injury or fatality. In 2004, the British Columbia Ministry of Transportation and Infrastructure (BC MOTI) developed a policy to include the use of 4-cable barrier systems as a treatment option for median and roadside barriers on provincial highways. The safety effectiveness of cable barriers in the province has yet to be evaluated following its implementation. To undertake a safety evaluation of cable barriers installation on the following highway sections in BC: Highway 1 Southern Railway of BC U/P 2624 to Sign: Exit 123/Prest Rd; Highway 97 from Deer Park Mobile Home Park to Brauns Road; Highway 97 from Lakehead Campsite Road to Road 21; Highway 99 from 8th Avenue to Hydro Powerline Crossing; Highway 99 from Emergency U-Turn to Sign Bridge for Exits 41 A-B. Data - Evaluation Sites: Five sites on three corridors. One site on Highway 1 (total length of 2.9 km), two sites on Highway 97 (total length of 4.6 km), and two sites on Highway 99 (total length of 45 km). Collision Data: Serious collisions only (fatal + injury) before and after cable barrier installation. The before data covered 3 years before and after cable barrier installation. Traffic Volumes: Annual average of daily traffic volumes on each site for both the before and after periods. Methods - An Empirical Bayes (EB) method was utilized to undertake the safety assessment. The method made use of Safety Performance Functions (SPFs) and a reference group. The evaluation was undertaken for each location separately due to the significant differences in attributes of the three corridors. The evaluation was also done for all collision types as well as off-road collisions. The evaluation showed safety benefits in terms of collision reductions; however, the safety gains differed in magnitude from one location to another. The results of this study give insight to practitioners on the safety effects of cable barriers installation on road sections. The safety impact differed from one location to another. The majority of vehicles to have impact with the cable median barriers were redirected or contained. Cable barriers in BC were found to reduce the number of serious collisions as well as off-road collisions and high-severity head-on collisions. The use of cable barriers is recommended for road segments which are experiencing a greater than average number of off-road right or left collisions in British Columbia.