The "Lowboy Auto Hauler Fairness Act of 2025" aims to standardize and increase the permissible length for certain commercial vehicle combinations across states. It specifically addresses truck tractor-lowboy trailer combinations , defining a lowboy trailer as a semitrailer with a depressed section used for transporting assembled highway vehicles. The bill prohibits states from imposing a vehicle length limitation of less than 80 feet on these combinations, provided the front overhang is less than 4 feet and the rear overhang is less than 6 feet. This length allowance applies regardless of whether the truck-tractor is capable of carrying cargo. Furthermore, it grants an exemption for lowboy trailers from the rear overhang flag requirements specified in section 393.87 of title 49, Code of Federal Regulations.