Interpretation ID: nht78-4.30

DATE: 06/09/78

FROM: LAWRENCE W. HENNEBGERGER; ROBERT L. GREEN -- ARENT FOX

TO: JOSEPH J. LEVIN -- CHIEF COUNSEL NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION

COPYEE: Z. TAYLOR VINSON, GERALD M. BLOOM; JOSEPH WALSH, ROBERT BRENNER

TITLE: NONE

ATTACHMT: ATTACHED TO LETTER DATED 08/31/78 FROM JOSEPH J. LEVIN -- NHTSA TO LAWRENCE F. HENNEBERGER AND ROBERT W. GREEN; REDBOOK A26(3); STANDARD 108

TEXT: Dear Mr. Levin:

Our client, Jacobs Manufacturing Company, has manufactured and distributed its well-known diesel engine retarder (the "Jake brake") for a number of years. The Jake R brake is sold both in the OEM market as original engine equipment (by such companies as Cummins Engine Co. and Mack Truck, among others) and as an aftermarket installation. This retarder provides auxiliary retarding capabilities independent of the vehicle's foundation brakes and perm[Illegible Words] a heavy truck to travel at normal traffic speeds on long downgrades, under full control, as well as extending the service life of the foundation brakes.

In recent years, the retarding force generated by current-design engine retarders has increased considerably, and electric driveline retarders with markedly greater retarding horsepower have become available. For example, Jacobs is now marketing an electric retarder (the "Jake ERR"), rated at some two to three times the retarding force of a typical large diesel engine equipped with the Jake R brake.

Because retarding forces of this magnitude are capable of producing significant deceleration of a large truck so equipped, Jacobs believe that some means should be provided to warn following vehicles when a retarder is in use. In addition, since a truck tractor equipped with a retarder may be used to pull a variety of different semi-trailers, the warning system must utilize existing vehicle equipment and operate both on the tractor alone ("bob-tail" configuration) and with any semi-trailer that may be hooked up.

After careful analysis and based upon a meeting with NHTSA and BMCS representatives on June 6, 1978, Jacobs has concluded that use of the existing hazard warning flasher system would best provide such warning to following drivers. Many states now require trucks moving less than 40 m.p.h. on limited access highways to use their hazard warning flashers to alert other motorists that they are slow-moving.

In order to provide this retarder warning signal automatically, Jacobs proposes to connect the retarder activation switch to the hazard warning system when a retarder is installed, either at the OEM or aftermarket level. Accordingly, the Company requests an advisory opinion that such use and connection of the hazard warning system is permissive and will not violate the requirements of FMVSS 108, nor will it violate the "antitampering" provisions set out in section 108 (a) (2) (A) of the National Traffic and Motor Vehicle Safety Act of 1966, as amended.

Sincerely,