Interpretation ID: 18795.ztv

Mr. Tadashi Suzuki
Manager, Automotive Equipment
Legal & Homologation Sect.
Stanley Electric Co., Ltd.
2-9-13, Nakameguro, Meguro-ku
Tokyo 153-8636
Japan

Re: Motorcycle Headlamp

Dear Mr. Suzuki:

This is in reply to your letter of September 10, 1998, asking for an interpretation of Federal Motor Vehicle Safety Standard No. 108 as it applies to a motorcycle headlamp design that your company is considering.

You have asked whether the design depicted in your letter is permitted by the amendment to motorcycle headlamp specifications published in the Federal Register on August 10, 1998 (63 FR 42582). As you have explained it:

"This headlamp system consists of two headlamps disposed symmetrically about the vertical centerline of the motor-cycle. Each headlamp has two single filament bulbs. The lower beam is provided by the inner light sources, on the other hand the upper beam is provided by both of the light sources. In other words, the vehicle provides the lower beam by two light sources, and provides the upper beam by four light sources. The distance of the effective projected luminous lens area of the two headlamps is not greater than 200mm."

You believe that this design complies with new paragraph S7.9.6.2(b) which states:

"If the system consists of two headlamps, each of which provides both an upper and lower beam, the headlamps shall be mounted either at the same height and symmetrically disposed about the vertical centerline or mounted on the vertical centerline. If the headlamps are horizontally disposed about the vertical centerline, the distance between the closest edges of their effective projected luminous lens areas shall not be greater than 200mm (8 in.)."

We confirm that your headlamp system complies with the requirements of S7.9.6.2(b).

We would like to take this opportunity to clarify this new paragraph. S7.9.6.2 covers three types of headlighting systems. Subparagraph (a) applies to a single-headlamp system. Subparagraph (b) applies to a system of two headlamps, each of which provides both an upper and lower beam. Subparagraph (c) applies to a system of two headlamps, one of which provides an upper beam and one of which provides a lower beam. In the systems covered by subparagraphs (a) and (c), the upper beam is not permitted to be higher than the lower beam. But subparagraph (b) is silent as to beam location. The preamble to the August 10 amendment makes clear our intent to prohibit the upper beam from being higher than the lower beam on all motor vehicle headlighting systems, because the higher mounting height gives longer seeing distance to the lower beam, providing a safety advantage to drivers. However, when both beams are provided within a single motorcycle headlamp, there is no discernable safety benefit in requiring that the lower beam be uppermost. Thus, Stanley's design in which the upper beam is provided by both higher and lower light sources is permitted by subparagraph(b).

We also want to clarify that each of the three types of headlamp systems are intended to provide the same safety performance, namely a single complying beam pattern. Regardless of whether a two-headlamp or a one-headlamp system is used, and regardless of whether the upper and lower beam functions of a two-headlamp system are segregated or distributed, the light output and distribution of the system must conform to the requirements of S7.9.1. A system of the type described in subparagraph (b) of S7.9.6.2 is not intended to have twice the light output of systems described in S7.9.6.2(a) or S7.9.6.2(c).

You have also asked for confirmation of your interpretation that "when a headlamp has a single lens, it should be regarded [as] a single headlamp irrespective of the number of the light sources and reflectors within the lamp body." The example you depict shows two light sources and their respective reflectors in a single housing consisting of a single chamber, covered by a single lens. We confirm your interpretation that this is a single headlamp, but not because it has a single lens. The fact that the lamp has a single lens is not the determinant. It is possible to design a headlamp with a single lens but with separate housings and chambers; this type of design would effectively create two headlamps.

Sincerely,
Frank Seales, Jr.
Chief Counsel
ref:108
d.2/22/99