This research focused on the traffic operational and safety effects of the median width of at-grade intersections on divided highways with partial or no control of access. The objective of the research was to develop and recommend on the basis of operational and safety considerations appropriate design policies for median width at rural and suburban divided highway intersections. Traffic operational field data were collected at 40 selected divided highway intersections in 10 states. In addition, a statistical analysis of relationships between median width and intersection accidents was conducted with an accident, geometric, and traffic volume data base for the California state highway system. The analysis concluded that, at rural unsignalised intersections, both accidents and undesirable driving behaviour decrease as the median width increases. In contrast, at suburban signalised and unsignalised intersections, accidents and undesirable driving behaviour increase as the median width increases. Thus, at rural unsignalised intersections, wider medians are generally preferable to narrower medians, unless future signalisation or suburban development can be anticipated at a particular intersection. The median at a suburban intersection generally should not be wider than necessary to accommodate the appropriate median left-turn treatment needed to serve current and anticipated traffic volumes. (A)
Abstract