Modeling Traffic Safety Benefits of Intelligent Transportation System Technologies at Truck Inspection Facilities: Microscopic Simulation

A microscopic simulation model was developed to capture the traffic safety benefits of using intelligent transportation system (ITS) technologies, including weigh-in-motion scales with variable message signs, at truck inspection facilities. The development of the simulation model was motivated by prevalent safety concerns at congested truck inspection facilities nationwide. Three primary safety components (roadway, driver, and vehicle) were considered in the model. The roadway component focuses on the varying size of truck queues at inspection facilities and safety implications. The driver component captures key human factor elements and their variability, including distributions for perception-reaction time, speed, gap acceptance, headway, and braking characteristics. The vehicular component incorporates the size distribution of vehicles (trucks and nontrucks), proportion of trucks with defective braking systems, and their safety implications with respect to stopping distance. The primary objective for the model is to depict variations in traffic pattern for baseline (pre-ITS) and post-ITS situations. Measures of effectiveness used for evaluating traffic benefits of using ITS technologies include percent reduction in sudden deceleration of vehicles resulting from shock wave phenomena and percent reduction in duration of truck-queue overflow resulting from a high traffic intensity. Results from simulation runs support the hypothesis that the use of ITS technologies at truck inspection facilities significantly reduces the frequency of experiencing the high-risk traffic phenomena (e.g., hard braking and truck-queue overflow). The postulation is made that the reduction in the frequency of high-risk phenomena will translate into a decrease in the likelihood of experiencing crash-related incidents in the vicinity of truck inspection facilities.