Development of a system to prioritize sites for the installation of automated truck rollover warning systems in Tennessee

The goal of this thesis is to produce a system by which Tennessee highway officials can assign priority to sites for the installation of automated truck rollover warning systems. A need for this ranking system has emerged as more intelligent transportation systems (ITS) technology is developed to combat the costly occurrence of heavy truck rollovers.

To conduct this study, a thorough study of heavy truck rollover crashes on the Tennessee Interstate Highway system is conducted using data obtained from the Tennessee Department of Transportation's TRIMS database. Once general crash trends are established from this data, crashes occurring on Interstate 75 are subjected to a more complex analysis From data collected in the field, various geometric features are linked to the occurrence of heavy truck rollovers.

A number of findings result from the analysis of the crash database. These findings include. typical truck rollover crashes involve a single vehicle, non-rollover crashes involve and average of two vehicles, the truck occupants are much more likely to be injured or killed in a rollover crash than in a non-rollover incident, rollover crashes occur at a much higher rate on freeway ramps than do other truck crashes; and the majority of rollover crashes occur at night. From the analysis of Interstate 75 crashes, it was determined that the following roadway characteristics increased the potential for truck rollover a speed differential of 25 miles per hour between ramp and highway speed limits; long, steep downgrades, and curves with a maximum ball bank reading of five degrees or more on the main lanes (ten degrees or more on ramp curves). Furthermore, rollover crashes are more likely to occur on curves to the left than curves to the right when all other factors are equal.

The final product of the study is a system to rank potential sites for the installation of rollover warning systems. The system is based first on the number of crashes occurring at a site during a five-year study period. For sites with a single rollover crash during the study period, priority is determined by comparing a variety of geometric factors to the thresholds identified in the study of Interstate 75 rollover crashes. Finally, for sites that have no rollover crashes within the study period, a qualitative comparison of risk factors is used to determine rank.