Evaluation of Large-Truck Transportation Alternatives with Safety, Mobility, Energy, and Emissions Analysis

During 2008, more than 5.8 million motor vehicle crashes, resulting in 37,000 fatalities and 2.3 million injuries, were reported to police in the United States. Research has identified heavy trucks as significant contributors to unsafe traveling conditions because of the different operating and maneuvering capabilities of trucks. Three safety treatments-peak hour travel restrictions, speed limiters, and lane restrictions-have been proposed to alleviate the safety risks of heavy trucks in the traffic stream. However, it is often difficult to quantify the potential safety benefits of transportation alternatives because crash occurrences, the ultimate indicators of the safety of a roadway, are sporadic, random events. A safety evaluation module was developed for the TRANSIMS microsimulator to simulate the safety of a transportation network with respect to rear-end crashes with safe headway distance used as a crash surrogate. The safety evaluation module could measure the safety benefits of competing transportation alternatives. Simulation results indicated that left-lane restrictions were the most statistically significant and beneficial treatment strategy; network-aggregated safe headway distance as an indicator of the likelihood of a rear-end crash decreased from pretreatment levels by at least 2% and 1% for the off-peak and peak hour travel periods, respectively. Supplementary analysis with the microscopic energy and emissions model from Virginia Polytechnic Institute and State University indicated that left-lane restrictions also had marginally positive effects on fuel consumption and emissions.