Effects of Geometric Design Features on Truck Crashes on Limited-Access Highways

Freight can be transported between most points in the country quite efficiently using trucks. However, involvement of large trucks in crashes can cause much damage and serious injuries, due to their large sizes and heavy weights. Large truck crashes occurring on limited-access highways may be more severe than crashes occurring on other roadways due to high speed limits, and traffic- and geometric-related characteristics. The purpose of this study is to describe the relationships between large truck crash probability, and traffic and geometric characteristics. Crash data from 2005 to 2010 were obtained from the Kansas Department of Transportation (KDOT), which included 5,378 large track crashes that occurred on Kansas limited-access highway sections. The traffic- and geometric-related details of highways were obtained from the Control Section Analysis System (CANSYS) database, which is maintained by KDOT as a highway inventory system. Homogeneous road sections in terms of speed limit, AADT, percent of trucks, horizontal curvature, horizontal grade, lane width, shoulder width, median width, and existence of rumble strips were identified. The total number of crashes occurring within each segment from 2005 to 2010 was determined, resulting in 7,273 analysis segments used in the modeling. A Poisson regression model and a negative binomial regression model were developed for identifying the relationships between the occurrence of truck crashes, and traffic and geometric characteristics. According to the models, highway design features such as horizontal curvature, vertical grade, lane width, and shoulder width are factors which can be used to change the occurrence of large truck crashes. Identifying the effect of traffic and geometric characteristics is important to promote safety treatments through engineering improvements.