Analysis of design attributes and crashes on the Oregon highway system

This paper estimates the relationship between crash activity and roadway design attributes on the Oregon state highway system. Crash models are estimated from roadway segments distinguished by functional classification and location. A number of design attributes were found to be related to crash activity in the various models, including number of lanes, curve characteristics, vertical grade, surface type, median type, turning lanes, shoulder width and lane width. In selected instances, crash reduction factors (CRFs) calculated from model results are compared with those presently used to evaluate projects in the Oregon Department of Transportation's Safety Improvement Program. The number of design attributes specified in the crash models is limited in comparison with the number of CRFs presently used to evaluate safety improvement projects. However, the attributes included in the crash models represent countermeasures associated with the more costly outlays that states make to improve safety. Thus, crash models of this type provide states with an opportunity to validate the CRFs that are most important economically.