Interpretation ID: nht87-2.62

TYPE: INTERPRETATION-NHTSA

DATE: 08/03/87

FROM: ERIKA Z. JONES -- CHIEF COUNSEL NHTSA

TO: DOUGLAS H. BOSCO -- HOUSE OF REPRESENTATIVES

TITLE: NONE

ATTACHMT: ATTACHED TO LETTER DATED 08/19/88 TO DOUGLAS H BOSCO, FROM ERIKA Z JONES, REDBOOK A32 (2) STANDARD 108; LETTER DATED 06/16/88, TO ERIKA Z. JONES, FROM DOUGLAS H. BOSCO; LETTER DATED 06/09/88 TO JERRY K YOST FROM L.F ROLLIN; LETTER DATED 03/28/8 8 TO C-MORE-LITE JERRYS SERVICE FROM DON O. HORNING RE TEST REPORT NO 92606; 1988 LETTER TO ERIKA JONES FROM JERRY'S SERVICE

TEXT: Dear Mr. Bosco:

This is in reply to your recent letter on behalf of your constituent, Jerry Yost. Mr. Yost would like to know of the permissibility under Federal regulations of a headlamp relay which would allow a headlamp's lower beam to remain in operation when the u pper beam is activated. You enclosed some diagrams from Mr. Yost and asked for confirmation of his assessment that they would demonstrate that "the candela criterion in the existing regulations for high-beam" would be met "when low and high-beam are com bined."

Federal Motor Vehicle Safety Standard No. 108, Lamps, Reflective Devices, and Associated Equipment, is the regulation governing the permissibility of relays allowing simultaneous operation of upper and lower beams on motor vehicle headlamps. The standar d specifies requirements for two generic types of headlamps, sealed beam (an indivisible unit encompassing the reflector, lens, and light source), and replaceable bulb (the replaceable in the event of burn out). Eight different types of sealed beam head lamps are permitted (denominated Types A through H), and three types of replaceable bulbs (He1, HB3, and HB4). However, in only one of the sealed beam systems is simultaneous operation of upper and lower beam specifically permitted, the Type F system (pa ragraph S4.5.12). Simultaneous beam operation is also permitted in replaceable bulb headlighting systems comprising four headlamps designed to conform to Type F photometry (S4.5.8, with Type F photometrics at Figure 15). Simultaneous operation of both beams is not a required feature of any of these systems but an option available to vehicle manufacturers. Thus, Mr. Yost's relay is permissible in any of these systems employing the simultaneous activation option.

However, simultaneous activation of both beams is explicitly prohibited in headlighting systems consisting of four replaceable bulb lamps designed to meet photometrics other than those of Type F (S4.5.8), and implicitly prohibited under the agency's inte rpretations of materials of the Society of Automotive Engineers relating to means of switching beams that are incorporated by reference into Standard No. 108. These materials refer to operation of separate beams with no reference to joint operation. As I discussed with your Administrative Assistant, Mitch Stogner, the agency's principal historic concern with simultaneous

2 activation of lower and upper headlamp beams is that the maximum candlepower limitations established by the Federal vehicle lighting standard could be exceeded. These limitations are set forth in SAE Standard J579c, the photometric requirements applic able to all headlighting systems except those designed to meet Type F photometry. These photometrics were intentionally adopted to allow simultaneous activation without exceeding the overall candlepower limit deemed desirable for motor vehicle safety. Based upon its research, the agency has concluded that frontal lighting on motor vehicles should not exceed 150,000 candela when the lamps are activated. In addition, the Type F. photometrics establish maximum values for two lower beam test points in o rder to reduce the possibility of excessive foreground light and glare resulting from simultaneous use. The diagrams that Mr. Yost provided describe the installation and operation of the relay, measurement of 7" circular headlamps (Type D under Standard No. 108) with a mechanical aimer, and how various types of headlighting systems look on the front of cars. While we appreciate having the benefit of this information, only that pertaining to the design of the relay is relevant to permissibility of use with systems designed to meet Type F photometrics.

As Standard No. 108 does not specify the design of relay switches, Mr. Yost should be encouraged to contact motor vehicle manufacturers who may be interested in using headlighting systems designed to meet Type F photometrics with the option of simultaneo us activation of both beams. The agency has no present plan to modify Standard No. 108 to allow simultaneous use with any system employing photometrics other than Type F and, as indicated earlier, considers this a prohibited practice with other systems.

I hope that this information is useful to you.

Sincerely,