Interpretation ID: nht94-3.40

TYPE: INTERPRETATION-NHTSA

DATE: June 16, 1994

FROM: Darlene E. Skelton, President, National Institute Of Emergency Vehicle Safety, Inc.

TO: Barry Felrice -- Asst. Administrator-NHTSA Office of Rulemaking

TITLE: NONE

ATTACHMT: ATTACHED TO 4/10/95 LETTER FROM PHILIP RECHT TO DARLENE SKELTON (A43; STD. 120; STD. 121; PART 567)

TEXT: Dear Mr. Felrice:

The National Institute of Emergency Vehicle Safety is a nonprofit organization committed to improving safety in the purchase, application, operation, and maintenance of emergency vehicles. Over the course of our work, several items have come to question .

1. We have examined vehicles that the GVW exceeds the tire rating capacity. In such cases the manufacturer places a limitation on the distance and speed the vehicle can travel.

For example, a fire truck with four rear mounted tires rated 7,000 lbs. each or a total of 28,000 lbs. are mounted on a 31,000 lb. axle. The final stage manufacturer actually acquired a letter from the tire manufacturer a. raising the air pressure from 100 to 110 or 115 psi b. placing a limit of driving no more than 55mph for a distance no greater than than seven (7) miles.

Our question is, do these practices constitute a violation of the Federal Motor Vehicle Safety Standards (FMVSS)?

2. We have also examined vehicles where the axle has been re-rated.

For example, one manufacturer increased the axle rating because fire trucks do not cycle as much as tractor trailer trucks. Because there is less cycling over the highway, they decided that the same axle in a fire truck application could be increased fr om 22,000 lbs. to 24,000 lbs.

Does this re-cycling of axles constitute a violation of the FMVSS?

3. We have knowledge of some manufacturers taking air supply for horns off of the air supply for breaks.

Does this violate the FMVSS?

Any direction you can provide regarding these issues is greatly appreciated.