Effect of Truck Lane Restriction and Differential Speed Limit on Traffic Characteristics of Four-Lane Rural Freeways

Trucks play a significant role in highway safety and operation because of their different operating characteristics. To mitigate the impact of truck traffic on operation and safety, some states, including Louisiana, have resorted to policies that restrict trucks in terms of lane use and speed limit on specific freeway segments. In this study, an investigation was conducted to measure the effectiveness of the implemented policies on an 18-mile four-lane elevated segment of I-10, where trucks are restricted to the right lane with a speed limit of 55 mph. One of the primary objectives of the research study was to examine the traffic characteristics and truck compliance to the restrictions over the study section. Traffic data was collected and analyzed for four different sites along the freeway corridor using the statistical methods presented in this paper. The basic statistical analysis showed that the speed in the left lane was much higher than it was in the right lane as a result of the imposed differential speed limit. The results also showed more trucks in the right lane than in the left lane, with a compliance rate in the range of 60 % to 80 % most of the time. To further evaluate more detailed aspects of the compliance of trucks to the differential speed limit policy, linear regression models were applied to determine the variables with the most significant effect on speed.