The study analyzes likely impacts of left truck lane restriction strategies on urban freeways based on a traffic simulation model. This study contains two main parts. The first part is performed to develop feasible alternatives as well as provide insights into conditions under left truck lane restrictions would be effective based on the analysis of two representative hypothetical highways. Different levels of O-D demands and truck percentage is at least restrictions would work when maximum rate of flow is more than 1,300vphpl or truck percentage is at least over loft of the total traffic. The second part of our study concerns a case study on a region with perhaps the highest truck volumes in the U.S. - a northbound section of Interstate 710 corridor in Los Angeles County, Southern California. The results show that restricting the two leftmost lanes under congested traffic with heavy ruck use, provides the most positive impacts in terms of improving the flow of traffic and saving fuel. In addition, our study demonstrates that in general, the number of lanes restricted is a crucial factor in the success of this strategy.