Interpretation ID: nht75-4.5

DATE: 09/30/75

FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA

TO: Wesco Truck & Trailer Sales

TITLE: FMVSS INTERPRETATION

TEXT: This responds to your recent request for a discussion of what constitutes the manufacture of a new trailer when used components from an existing trailer are utilized. As you are aware, a newly-manufactured air-braked trailer must, in all but a few cases, be equipped with an air brake system that conforms to Standard No. 121, Air Brake Systems.

The use of new components in combination with used components to assemble a complete vehicle is a common practice in both truck and trailer operations. The National Highway Traffic Safety Administration (NHTSA) has recognized this commercial practice by establishing that the use of a new body on a used "chassis" that has already been certified does not constitute the manufacture of a new vehicle. In contrast, placing a used body on a new chassis that has never been certified as a vehicle has been determined to create a newly-manufactured vehicle that must be certified. This distinction did not present difficulty to trailer manufacturers in the past, when they were only required to meet the lighting requirements of Standard No. 108, Lamps, Reflective Devices, and Associated Equipment.

Since implementation of Standard No. 121, however, manufacturers have had to determine whether the particular assembly they undertake contains a used "chassis" which would not be required to meet the air brake standard. As a general matter, the NHTSA has stated that, as a minimum, the running gear (the axles, wheels, suspension, and related components sometimes known as a bogie) and main frame of the existing vehicle must be used to qualify as a used "chassis". However, the many different types of trailer construction make it difficult to determine what constitutes the main frame of some configurations. The NHTSA has concluded that the load-bearing structural member(s) which run the length of the vehicle and support the trailer will be considered to be the "main frame".

In the case of monocoque van construction, the trailer side walls which constitute the main load-bearing members through the length of the vehicle must be reused as the main frame in addition to the running gear, or else the rebuilding operation will constitute manufacture of a new vehicle.

In the case of container chassis, the box frame that consitutes the main load-bearing member through the length of the vehicle must be reused as the main frame in addition to the running gear, or else the rebuilding operation will constitute manufacture of a new vehicle.

In the case of a platform trailer, the main frame members which run the length of the trailer must be reused in addition to the running gear, or else the rebuilding operation will constitute manufacture of a new vehicle.

In the case of a tank trailer in which the tank serves the purpose of and replaces frame rails, the tank must be reused as the main frame in addition to the running gear, or else the rebuilding operation will constitute manufacture of a new vehicle. If a separate frame serves as the load-bearing member through the length of the vehicle, the tank could be replaced without the operation constituting the manufacture of a new vehicle. An inner tank may be replaced without certification as a new vehicle if the inner tank does not serve as a main load-bearing member.

Modifications of existing trailers to increase or decrease volumetric capacity or vehicle length are generally permitted without recertification. For example, the barrel of a tank trailer may be lengthened in response to the new weight limits without recertification of the vehicle.

In closing, it should be noted that Bureau of Motor Carrier regulations may differ on modification or rebuilding of vehicles in interstate commerce.