ANALYSIS OF HIGHWAY MEDIAN SAFETY IN PENNSYLVANIA

Traffic safety is a key concern for both users and resources in the United States. On high functional class roadways such as interstates and expressways, the consequences of cross-median collisions are significant because of their social and economic impact on the community. To enhance safety among highway users, median barriers are often considered. The need for median barriers in Pennsylvania is based on but not limited to several factors, including median width, average daily traffic and crash history. From 1994 through 1998, Pennsylvania's Interstates and expressways experienced 267 crossover crashes and 55 of them had fatalities. Many of these cross median crashes occurred on full-width, transversable medians. Research was conducted to evaluate the relationship between median crossover crashes and median widths on Interstates and expressways in Pennsylvania. The objective of this paper is to outline the research methodology of the median safety study in Pennsylvania and to summarize the results. It includes a state-of-the-art literature review of sate department of transportation median safety issues. A Delphi-type survey instrument was used to gather expert knowledge on median safety issues. The opinions gathered from 23 experts complemented the numerical data analysis to make the research approach more comprehensive. Lastly, PennDOT's accident and geometric data were analyzed to develop an understanding of median safety which included: (1) The relationship between median crossover crashes and current median widths on Interstates and expressways; (2) The relationship between median crossover crashes and current average daily traffic (ADT) levels on Interstates and expressways, (3) The characteristics of Pennsylvania's cross median crashes; (4) The relationship between cross median crashes in Pennsylvania's current median warrant criteria (five-year ADT projection criteria, and width and ADT thresholds).