Truck Delay and Traffic Conflicts Around Weigh Stations: A Case Study in Illinois

Truck weight enforcement helps protect infrastructure and improve traffic safety. However, requiring all trucks to stop at all weigh stations reduces productivity and increases enforcement costs. This pilot study was conducted at the Williamsville weigh station in Springfield, Ill., to quantify the delay and traffic conflicts experienced by trucks around weigh stations. The quantification is needed to evaluate the effectiveness of automatic vehicle identification/weigh in motion (AVI/WIM) systems for electronic screening of trucks at weigh stations. The main emphasis of this project is to examine potential benefits of intelligent transportation system (ITS) technologies for intrastate commercial vehicle operations (CVO) applications. Reducing the number of traffic conflict incidents due to the merging and diverging movements of trucks would increase traffic safety. In the case study, without the AVI/WIM system, on the average, 30 percent of all trucks could not be weighed because the weigh station was temporarily closed to prevent a queue backup. The average delay was 4.95 min/truck and varied from 3.56 to 6.59 min/truck. The maximum delay varied from 8.69 to 137.62 min/truck. There were significant numbers of conflicts even under light-volume conditions. Models to predict the number of conflicts were developed. The number of diverge conflicts depends on car and truck volumes, and the number of merge conflicts depends on the truck volume on the ramp and the car volume in the right and middle lanes of a six-lane interstate.