Interpretation ID: 17323.ztv

Mr. Tadashi Suzuki
Manager
Automotive Equipment
Legal & Homologation Sect.
Stanley Electric Co.
2-9-13, Nakameguro-ku
Tokyo 153, Japan

Re: Headlamp light source arrangement

Dear Mr. Suzuki:

This is in reply to your letter of January 29, 1998, asking about the relationship of a planned replaceable light source headlamp system to Federal Motor Vehicle Safety Standard No. 108.

Paragraph S7.5(e)(2)(i)(A) specifies that the lower beam in a headlighting system may be provided "by the outboard light source (or the uppermost if arranged vertically) . . . ." In the system of interest to Stanley, the lower beam light source is placed above the upper beam light source but is also closer to the vehicle centerline than the upper beam light source. You have asked, in essence, whether this arrangement would comply with paragraph S7.5(e)(2)(i)(A).

This requirement originated with four-lamp headlamp sealed beam lighting systems in which headlamps were initially located side by side, with an identical horizontal centerline. Thus, the outboard specification was the one that was initially deemed most critical in drafting an amendment to Standard No. 108. However, when it was brought to the attention of the drafters that manufacturers intended to adopt four-lamp systems in which one lamp was mounted over the other, with an identical vertical centerline, the specification was proposed that the lower beam be provided by the upper lamp. The specification was applied to headlamp systems with replaceable light sources when these systems became permissible under Standard No. 108.

In Stanley's design, the two light sources do not have a common horizontal or vertical centerline. The horizontal centerline of the lower beam light source is 110 mm above that of the upper beam light source. Thus, the lower beam is clearly provided by the upper light source, in accordance with Standard No. 108. However, the vertical centerline of the lower beam light source is 20 mm inboard of that of the upper beam light source. That does not comport with the original intent of Standard No. 108 that the lower beam be provided by either the outermost lamp or by one with an identical vertical centerline to the upper beam lamp. In short, the lower beam light source must not only be the uppermost of the two light sources but, also, its vertical centerline must not be inboard of the vertical centerline of the upper beam light source. This means that Stanley's design does not comply with Standard No. 108.

Sincerely,
John Womack
Acting Chief Counsel
Ref:108
d.3/25/98