What federal regulation governs the operation of combination vehicles?

The operation of combination vehicles is governed by federal regulations found in 49 CFR 393. This section of the Code of Federal Regulations specifically outlines standards related to the parts and accessories necessary for the safe operation of motor vehicles, particularly focusing on the motor vehicle safety regulations that apply to larger vehicles such as buses and trucks used in combination operations, including trailers and semi-trailers.

The reason this regulation is crucial is that it ensures that all components of a combination vehicle function properly and meet safety standards. This includes requirements for braking systems, lighting, and cargo securing, which are vital for the safe and efficient operation of these larger vehicles on highways.

In contrast, the other options pertain to different aspects of transportation law. For example, 48 CFR generally deals with transportation contracts and logistics, while 50 CFR addresses regulations related to wildlife and fisheries, which are not applicable to vehicle operation. Finally, 51 CFR does not exist as a recognized regulation series, thus further emphasizing why 49 CFR 393 is the relevant regulation for combination vehicles.