Interpretation ID: nht89-3.28

TYPE: INTERPRETATION-NHTSA

DATE: 11/01/89

FROM: STEPHEN P. WOOD -- NHTSA ACTING CHIEF COUNSEL

TO: SAMUEL KIMMELMAN -- PRODUCT ENGINEERING MANAGER IDEAL DIVISION PARKER HANNAFIN CORPORATION

TITLE: NONE

ATTACHMT: LETTER DATED 03/22/89 FROM SAMUEL KIMMELMAN -- PARKER HANNIFIN TO TAYLOR VINSON -- NHTSA; OCC 3309

TEXT: Dear Mr. Kimmelman:

This is in reply to your letter to Taylor Vinson of this office. I regret the delay in responding. You express your understanding that Standard No. 108 "allows vehicles with combined function rear stop and turn signal/hazard lamps to operate in either of two modes when both the hazard switch and brake switch have been actuated." You have expressed these two modes as follows:

"1. The hazard switch is the major control for operation of the combined rear stop and turn signal/hazard lamps.

a. Actuating the hazard switch some period of time after actuation of the brake switch will cause the rear lamps to change from steady on, stop signal, to flashing, hazard signal.

b. Actuating the brake switch some period of time after actuation of the hazard switch will not change the flashing lamps, hazard signal, to steady on, stop signal.

2. The brake switch is the major control for operation of the combined rear stop and turn signal/hazard lamps.

a. Actuating the brake switch some period of time after actuation of the hazard switch will cause the rear lamps to change from flashing, hazard signal, to steady on, stop signal.

The front flashing hazard lamps will also become steady on.

b. Actuating the hazard switch some period of time after actuation of the brake switch will not change the rear steady on lamps, stop signal, to flashing, hazard, while the front hazard lamps go from off to steady on."

You ask for confirmation of your understanding, and if it is correct, whether NHTSA is presently considering rulemaking "to specify a specific signal from the combined function rear stop and turn signal/hazard lamps when both the hazard and brake switche s are actuated."

Neither of these modes are correct, for the reasons discussed below. Initially we note that systems with combined-function lamps are those that use red lenses for the rear turn signals lamps, and not the amber lenses that Standard No.

108 allows. The second point we wish to make is that you may have confused hazard warning lamps with turn signal lamps. The basic Federal requirements for stop lamps are those of SAE Standard J586c Stop Lamps, August 1970, which is incorporated by refe rence in Standard No. 108. Paragraph 4.2 of J586c states "When a stop signal is optically combined with the turn signal, the circuit shall be such that the stop signal cannot be turned on in the turn signal which is flashing." The identical provision is found in paragraph 4.4 of SAE Standard J588e Turn Signal Lamps, September 1970, which is also incorporated by reference in Standard No. 108. This clearly means that a turn signal cannot be overriden by a stop lamp. In addition, you should note that re gulations of the Federal Highway Administration's Bureau of Motor Carrier Safety forbid the optical combination of a stop lamp with a turn signal lamp unless the stop lamp function is deactivated when the turn signal lamp is activated (49 CFR 393.22(b)(2 ).

Assuming, however, that you meant hazard warning system lamps, there is no provision in Standard No. 108 for hazard warning system operation (those of SAE Recommended Practice J945 Vehicular Hazard Warning Signal Flasher, February 1968, incorporated by r eference in Standard No. 108) specifying priority of operation with respect to the stop lamp system. Because paragraph S5.5.4 of Standard No. 108 requires the stop lamps to be activated upon application of the service brakes, we interpret this as allowi ng the stop lamp system to override the hazard warning system. This opinion, of course, relates only to the rear lamps. The hazard warning system at the front of a vehicle must operate at any time the system is actuated.

In response to your question about the possibility of rulemaking, please note that the agency does not plan any rulemaking on this subject.

Sincerely,