The National Highway Traffic Safety Administration (NHTSA) has issued a final rule that makes permanent an existing requirement that trailers with antilock brake systems (ABS) be equipped with an external malfunction indicator lamp. The rule takes effect August 31.

The indicator lamp requirement, which is included in the Federal Motor Vehicle Safety Standard that governs air-braked vehicles, was originally scheduled to sunset March 1, 2009, but had previously been extended to September 1, 2009. The agency had established a sunset date for this requirement in light of the increasing numbers of post-2001 tractors that have an in-cab trailer ABS malfunction lamp, making the external trailer lamp redundant.

NHTSA officials said they are making the requirement permanent in light of additional safety purposes served by the external lamp. It not only warns the driver of a malfunctioning trailer ABS, but, unlike the in-cab lamps, also indicates which trailer in a multi-trailer train has a malfunction. The lamp also assists federal and state roadside inspectors and maintenance personnel in identifying a malfunctioning trailer ABS. This rulemaking was issued in response to petitions from the Commercial Vehicle Safety Alliance (CVSA), an international not-for-profit organization of local, State, provincial, territorial and Federal motor carrier safety officials and industry representatives from the United States, Canada, and Mexico.

CVSA’s rationale:
  • Many pre-2001 tractors were still expected to be in use when the malfunction indicator lamp requirement was set to expire (at the time, March 1, 2009). These tractors do not have the in-cab trailer ABS malfunction indicator lamp that was perceived to render the external lamp redundant.
  • For double and triple trailer applications, it will not be possible to determine, from an in-cab lamp alone, which trailer ABS is malfunctioning without external lamps.
  • Many trailer repair shops rely on the external lamp to quickly diagnose the operational status of the trailer ABS without having to couple a post-2001 tractor to the trailer. With an external indicator lamp, any age tractor can be used, making inspection significantly easier.
  • Without the external lamp, the signal from the in-cab lamp may be confusing, as it may indicate either a malfunctioning in-cab bulb, a functioning pre-1998 trailer (with no ABS), a problem with the communication circuit between the trailer and tractor, or a malfunctioning ABS. The external lamp helps to diagnose the situation further.