Effect of Speed, Flow and Geometric Characteristics on Crash Rates for DifferentTypes of Virginia Highways

摘要

Althoughn considerable progress has been made over the past several years inmaking highway travel safer, the frequency and severity of speed-related crashes on the nation's highways continue to be of concern. Understanding the factors associated with these crashes enables engineers to identify and implement effective countermeasures to reduce the probability of crashes. A number of studies have been conducted to determine the variation of crash rates as they relate to hourly traffic volumes, geometric characteristics, average speed, and speed variance. However, these studies have not established mathematical relationships that can be used to estimate changes in the crash characteristics as a result of the combined changes in speed, flow, and geometric characteristics. The establishment of direct mathematical models that describe the influence of these factors on crash characteristics would signficantly enhance the efforts of traffic engineers to determine suitable countermeasures to reduce the occurrence and severity of crashes. This project develops mathematical relationships that describe the combined influence that traffic and geometric charactristics have on crash occurrences. This study was limited to roadways in the state of Virginia with speed limits of 89 or 105 km/h (55 or 65 mph). The data were obtained from speed monitoring stations established by the Virginia Department of Transportation (VDOT) and from police accident reports from January 1993 to September 1995.