Working Paper on Slope Testing

There has been increased use of cable median barriers in recent years to address the growing problem of crossmedian crashes. Cable median barriers are viewed as a highly effective means to mitigate the problem at a lower cost and in a shorter time frame. This has occurred despite limited current guidance on effective use of the various designs that have emerged over the past ten years. Research has discovered that cable median barriers are more sensitive to slope effects than was previously understood. In attempting to develop better guidance for the deployment of cable barriers systems, vehicle dynamics analysis was found to provide a method to determine effective positioning of such barriers on sloped median surfaces. The research evolved from using the vehicle dynamics analysis to understanding particular cross-median events to the generation of a series of nomographs that indicate the best lateral placement locations to assure effective vehicle-to-barrier interface. In the course of these efforts it became apparent that it was possible to determine the limits for override and underride for any median configuration and to use these to evaluate the potential effectiveness for any given barrier design. Further efforts, described in this paper, developed composite limits that are not median configuration biased. The limits are shown to have usefulness for specific regimes defined for the median area and maximum side slope conditions encountered. These are believed to offer usefulness to the design of new cable median barrier systems, consideration of the relative applicability of existing barriers for particular applications, and even a potential means to be assured that a given barrier application will provide the same level of crashworthiness as determined in testing. The information generated in this effort is believed to provide a robust basis for the development of improved (simplified) guidelines for cable median barrier design and placement. Working Paper NCAC 2010-W-008 August 2010