In recent years the trucking industry has developed higher capacity, short wheelbase trucks. These vehicles have capacities of 80,000 pounds, contain four to seven axles and are referred to as Specialized Hauling Vehicles (SHVs). The SHVs meet federal weight requirements (as given in Federal Bridge Formula B), but may exceed states’ legal load limits. Legal load limits have been increased in some states to allow the use of these vehicles on public roads without special permit requirements. National studies show that these trucks can cause stresses in bridge structures that significantly exceed design stresses.

In New Mexico, there have been several recent legislative proposals to increase the maximum legal load for these vehicles from 68,400 pounds to 80,000 pounds. The New Mexico Department of Transportation (NMDOT) needs to have up-to-date information regarding experience with- and the effects of SHVs in adjacent & other states where these types of vehicles are allowed to operate as legal loads. This will assist the NMDOT in the future when and if additional legislative proposals are introduced, and allow the NMDOT to make informed recommendations to the State Legislature.

Through this project, the research team will perform a literature search to identify states that allow SHV Modified Weights, and conduct a more in-depth investigation of at least 6 states to document their experiences and impacts.