Cross-median crashes frequently result in high-severity injuries and fatalities. Previous studies of contributory factors associated with cross-median crashes have typically focused on median width and average daily traffic (ADT). A few studies have looked at the influence of geometry and cross-sectional elements. Although these studies have been helpful, they did not explore many other design and operational factors that may contribute to cross-median crash frequency or severity (e.g., interchange ramps, interchange spacing, mixture of vehicle types, peak-period volumes, peak-period duration, land use, access control, driver workload, posted speed, or presence of speed transition zones).
All median-related incidents begin with a median encroachment. Reducing median encroachments will reduce both cross-median crashes and fixed-object crashes in the median. Consequently, analyzing median encroachments should provide additional insight into the causes of cross-median crashes.
There is also a knowledge gap regarding countermeasures appropriate for the various factors contributing to median encroachments and cross-median crashes. Although installing a barrier will greatly reduce cross-median crashes, it will also increase fixed-object crashes and the crash risk of maintenance personnel. Other countermeasures besides barriers exist and knowing which ones effectively address the contributory factors on a highway will allow an engineer to develop a more effective design.
In this project, MRIGlobal reviewed the literature on median encroachments and cross-median crashes. Based on a survey of states, Canadian provinces, and turnpike/toll road authorities, the team compiled a list of design and operational factors likely to contribute to median encroachments and cross-median crashes. The research team then collected data to determine the relative contribution of each of the factors to median encroachments and cross-median crashes.
Appendix D of the report provides recommended guidelines for reducing the frequency and severity of median-related crashes. This material is designed to be easily incorporated into a transportation agency's design manual.
