Traffic Behavior and Compliance to Truck-Restriction Policies on Four-Lane Rural Freeways

This study examined the overall traffic characteristics and truck compliance behavior under truck-lane-restriction and differential speed limit policies on an 18-mile rural four-lane elevated segment of I-10. Traffic data was collected at four different sites along the freeway corridor and analyzed using statistical methods. The results show that the overall traffic speed decreased as the percentage of trucks in the traffic stream increased and that trucks had the tendency to increase their speed in the absence of other types of vehicles. The results also showed a compliance rate of 60% to 80% to the truck-lane restriction. Linear regression models showed significant differences in speed between the right and left lane at each site, implying some compliance to the reduced speed limit by trucks. In addition, the pairwise comparison results indicated that for mixed traffic conditions truck speeds were within a 5-mph range above the imposed truck speed limit on the right lane and 5 mph above the truck speed limit on the left lane. The study concluded that the truck compliance to both policies seemed somewhat acceptable, but higher compliance rates could be attained by increasing the level of enforcement along the corridor.