Investigating Large Truck-Passenger Vehicle Interactions

An analysis of truck-passenger car interactions was performed for Missouri urban and rural freeways. Trucks were found to travel 2 mph slower than other vehicles on urban interstates and 3.5 mph slower on rural interstates. These speed differences between trucks and passenger vehicles were not very large. Thus, there was no evidence that, on the average, trucks were traveling much faster than passenger cars. An implementation of differential speed limits could increase significantly the speed differences between trucks and passenger vehicles. In terms of lane usage, trucks concentrated mainly in the middle lanes and avoided the slow and fast lanes in situations with 5 and 6 lanes. The application of truck lane restrictions could alter the current truck lane usage significantly and increase the truck usage in the lane nearest the shoulder. In terms of number of crashes, trucks accounted for a smaller percentage of crashes as compared to passenger vehicles. However, an analysis of RSEC ratios showed that on urban freeways, the percentage of truck crashes is disproportionately larger when considering the volume or exposure of trucks. In contrast, the rural data in general shows that truck crashes are not as disproportional to the crash rates of passenger vehicles. These results point to a greater safety concern in truck-passenger vehicle interactions on urban freeways.