• The federal regulations governing parts and accessories consist of nine subparts that cover most of the systems and components found on a CMV.
• The standards required of manufacturers when building a CMV must be maintained after the vehicle enters service.

The parts and accessories regulations in Part 393 are broken into 10 Subparts, 9 of which cover most of the systems and components found on a commercial motor vehicle (CMV).

These systems and components include:

• Lamps, reflective devices, and electrical wiring (Subpart B)
• Brakes (Subpart C)
• Glazing and window construction (Subpart D)
• Fuel systems (Subpart E)
• Coupling devices and towing methods (Subpart F)
• Miscellaneous parts and accessories (Subpart G)
• Emergency equipment (Subpart H)
• Protection against shifting and falling cargo (Subpart I)
• Frames, cab, and body components, wheels, steering, and suspension systems (Subpart J)

The Federal Motor Carrier Safety Administration (FMCSA) is not the only agency within the Department of Transportation (DOT) issuing vehicle-related regulations. Another DOT agency, the National Highway Traffic Safety Administration (NHTSA) issues the Federal Motor Vehicle Safety Standards (FMVSS), found in Part 571. The FMVSS are the regulations that the manufacturers must meet when building a CMV. The FMVSS regulations matter to the maintenance manager of a fleet because a CMV must be maintained in such a way that it continues to meet the standards that were in place when the vehicle was built.