Interpretation ID: nht68-4.2

DATE: 08/20/68

FROM: AUTHOR UNAVAILABLE; Charles A. Baker; NHTSA

TITLE: FMVSS INTERPRETATION

TEXT: Thank you for your letter of July 24, 1968, to Mr. George C. Nield, concerning the method of operating school bus signal lamps as required by Motor Vehicle Safety Standard No. 108.

Paragraph S3.1.3.2(b)(2) of Standard No. 108 requires that the system of red and amber signal lamps shall be wired so that the red signal lamps are automatically energized, and the amber signal lamps are automatically de-energized, when the bus entrance door is opened. Paragraph S3.1.2 of the standard does not permit the installation of an additional lamp, reflective device or associated equipment if it impairs the effectiveness of the required equipment.

Therefore, the criteria for determining the compliance of an additional manual switch for controlling operation of the signal lamps is whether or not the manual switch would impair the effectiveness of the required automatic entrance door switch. A manual switch which overrides the entrance door switch only while the entrance door is closed does not appear to impair the effectiveness of the required automatic switch. However, a manual switch which controls operation of the signal lamps while the entrance door is open would definitely impair the effectiveness of the automatic switch.

With respect to the requirements of Standard No. 108, I must point out that this Bureau does not issue approvals on items of lighting equipment or on vehicle designs incorporating this equipment. Therefore, the above comments are for your information only and in no way relieve the vehicle manufacturer from his responsibility for certifying that the assembled vehicle meets the requirements of the standard.

Thank you for writing.