Evaluation of the Influences of Cable Barrier Design and Placement on Vehicle to Barrier Interface

The primary purpose of longitudinal safety barriers, such as cable barriers, is to contain and/or redirect errant vehicles that depart the roadway, hence keeping them from entering opposing travel lanes or encountering terrain features and roadside objects that may cause severe impacts. In this paper, vehicle dynamics analysis is used to study the effect of median configuration and cable barrier designs on the safety performance. Median configurations vary by width, side slope and slope combinations, and crosssection. Cable designs for this effort considered the number, arrangements, and height (Note: tension, post spacing and features, cable type, and anchorages were not addressed). Vehicle dynamics analyses were conducted to compute the vehicle’s trajectory and dynamics as it crossed the sloped terrain and interfaced the barrier. Vehicle dynamics analysis allowed a range of vehicles and impact conditions to be studied. The various plots generated provide insights on the optimal placement locations for 3or 4cable systems, the differences between degree of slope, cross-section shape, and median width, and varying impact conditions. The information generated provides a robust basis for the development of improved guidelines for median barrier design and placement. Working Paper NCAC 2008-W-001 October 2008