NHVR says use Suzi on the semi but rubber on Dollys, Dogs or Pigs

The NHVR has issued a Safety Bulletin on the use of coiled air hoses (“Suzi” coils).  The issuing of the safety bulletin has been prompted by several incidents where trailers have disconnected, and the air hoses have remained attached.

This allowed the trailer to unnecessarily wander behind the prime mover. On one occasion, the trailer moved into on coming traffic and the use of a Suzi coil was seen as a significant contributor to the ensuing fatal accident.

HVIA strongly recommends that Suzi coils should not be fitted where an A coupling is used to couple trailers. Suzi coils will stretch considerably before the air hoses disconnect.

This causes the trailer to travel down the road completely uncontrolled for a lot longer than is absolutely necessary, before the air leaks out the trailer’s brake system and the emergency brakes apply.

In fact, in some cases Suzi coils stretch, pinch and disconnect in such a way that when disconnection occurs, air does not get dumped from the trailer’s brake system and the emergency brakes do not activate.

Where an A coupling is used, rubber brake hoses meeting the SAE J1402, FMVSS 106 or other equivalent standard, which do not stretch, should be used. This will ensure that in the event of a break away, the trailer’s emergency brakes will apply quickly.  

The NHVR’s safety bulletin may be found here.