Methodology to Estimate Percent of Overweight Trucks Without Proper Permits

All state agencies have truck size and weight restrictions on their roadways based on federal and state legislation. However, drivers can typically apply for special permits allowing those limits to be exceeded, particularly when the load is non-divisible. The permit application includes the origin and destination of the load, as well as characteristics about the truck’s size and weight. This information is used by state highway agencies to evaluate the impact of the loading on the roads and bridges that the vehicle will cross to determine a preferred route and the need for a police escort. Unfortunately, drivers with non-divisible loads do not always take the time or spend the money to obtain a permit. Furthermore, it is commonplace for drivers with divisible loads to haul overweight to maximize profit. For those individuals, the reward for hauling oversize and overweight outweighs the risk of being caught. The West Virginia Division of Highways initiated a project to quantify the percentage of overweight trucks on its highways that are not properly permitted. If there is a significant problem identified, further action will be taken to address the issue. This paper describes the methodology that was used to combine data from the state’s weigh-in-motion (WIM) data collection program and oversize/overweight permit database in order to estimate the percentage of trucks not obtaining proper permits. The percentages are estimated on both a macroscopic level by examining summary statistics and a microscopic level by trying to match individual permits with records in the WIM database. The route information in the permit database is processed in geographic information system (GIS) to determine which WIM stations the vehicle should have crossed. Preliminary macroscopic results from a single WIM station indicate only 6% of the overweight vehicles likely have permits for the period analyzed.