Impacts of Left Lane Truck Restriction on Urban Freeways

This paper examines the impacts of truck lane restriction on urban freeways using traffic simulation models. The study includes three main parts: Part (1) provides insights into conditions under which truck lane restrictions would work well; Part (2) identifies the best number of lanes to restrict and shows that this is an important factor in the success of lane restriction; Part (3) investigates potential impacts of truck lane restriction through a case study using a region with some of the highest truck volumes in the U.S., the I-710 corridor in Los Angeles County, California. The study begins by examining the potential impacts of truck lane restrictions using two representative hypothetical freeways. This is because the impacts of truck lane restrictions will vary with differing traffic and geometric conditions. Results suggest that truck lane restriction could work well when the rate of flow is more than 1300 vehicles per hour per lane and where trucks make up at least 10 percent of the total traffic. Three scenarios are developed. These are do-nothing (no strategy implemented), alternative I (the one leftmost lane restricted from trucks), and alternative II (the two leftmost lanes restricted from trucks). These are examined in a pair-wise manner. Results show that determining the best number of restricted lanes is very important. Through the I-710 case study we find that alternative II would have the most positive effects on traffic congestion and travel time variance. Based on these results, we conclude that truck lane restriction strategies, which are very simple and cost-effective to implement, may contribute to improved traffic flow on urban freeways.