Impacts of Specialized Hauling Vehicles on Highway Infrastructure, the Economy, and Safety: Renewed Perspective

In the United States, the Federal Bridge Formula (FBF) has been used to set the Gross Vehicle Weight (GVW) limit and axle weight limit for various vehicle configurations. Further, the American Association of State Highway and Transportation Officials (AASHTO) developed a set of legal loads that closely match the FBF in the short, medium, and long truck length ranges and are used to evaluate the need for bridge weight limit posting. Specialized Hauling Vehicles (SHVs) were developed in recent years and they play an important role in the trucking industry. Typically, SHVs refer to single unit (SU) vehicles with closely spaced multiple axles that can carry up to 80,000 pounds. Even though SHVs meet the requirement under FBF, these newer axle configurations were not considered in the original development of the FBF and AASHTO legal loads. As such, FBF does not adequately restrict SHVs and most likely overstress the bridges. This study was conducted to examine the current knowledge related to the impact of SHVs on highway infrastructures, economy, and safety. The key findings from the study include: (1) Relative to conventional trucks, SHVs may not induce significant damage to asphalt pavements and can potentially induce additional damage to concrete pavements; (2) Relative to conventional trucks, SHVs can induce significant damage to short span bridges particularly to short span timber and steel bridges; (3) Bridge weight limit posting is expected to increase with the allowance of SHVs; and (4) SHVs are likely to benefit economy and safety. Findings of the study will contribute to environmentally sustainable highway infrastructure in the presence of SHVs.