EFFECT OF LANE WIDTH, SHOULDER WIDTH, AND SHOULDER TYPE ON HIGHWAY SAFETY

Accident experience on rural highways is a complex function of many factors, including not only those associated with physical aspects of the roadway and the roadside but also a multitude of others related to driver, vehicle, traffic, and environmental conditions. Among the many roadway-related features of importance--estimated by one 1978 study to total at least 50--three that are often underscored as being among those having the greatest impact include lane width, shoulder width, and shoulder type. The purpose of this investigation was to critically review relevant literature and develop a model for estimating the effect of lane width, shoulder width, and shoulder type on motor vehicle accidents on two-lane, rural highways. Preliminary issues considered important to this task include (a) criteria for selecting and evaluating useful studies, and (b) definitional issues.