A Study of the Relationship between Crash Rate, Geometric Alignment and Freeway Safety

A safety evaluation method for freeway segments is proposed in this study by analyzing the relationship between crash rates and road geometric alignment.First,the relationship between crash rates and road geometric features including radius of horizontal curves,deflections of horizontal curves,length of tangents,radius of vertical curves,longi-tudinal gradient is analyzed through linear regression.Then,the relationship between a combination of different alignment features and crash rates is studied.Further,the alignment factors analyzed over the first two steps are used to evaluate the impacts of geometric alignment features on crash rates and the method is then proposed to evaluate the safety of freeway. The results of a case study indicated that up to 81% of"dangerous highway sections" identified by proposed method are confirmed by the crash data.The proposed highway safety evaluation method is practical to identify collision prone sec-tions of freeways.