Interpretation ID: 19843.ztv

Mr. Masao Muraoka
Deputy General Manager
Technical Administration ept.
Koito Mfg. Co., Ltd.
Shizuoka Works
500, Kitawaki
Shimizu-Shi, Shizuoka-ken
Japan

Re: Motorcycle Headlamp Photometry

Dear Mr. Muraoka:

This is in reply to your letter of April 6, 1999, pointing out an inconsistency between our letter to Stanley Electric Co. of February 22, 1999, and preamble language to a 1996 amendment of Federal Motor Vehicle Safety Standard No. 108.

The issue is the measurement of photometrics in two-lamp motorcycle headlamp systems: whether the photometric performance of Figure 32 is applied to each headlamp, or to the combined maxima of both headlamps. Our first interpretation on this subject was provided to M. Iwase of your company, who asked us about the measurement of photometrics in a two-lamp motorcycle headlamp system. We informed Mr. Iwase on November 29, 1985, that:

The fact that the combined maximum value of your system exceeds 75,000 candlepower [for upper beam] is permissible as long as the individual lamps themselves do not exceed 75,000 candlepower.

We confirmed this interpretation in the preamble of the 1996 amendment to Standard No. 108 adopting a new photometric standard for motorcycle headlamps (61 FR 45359). There we said that:

When a motorcycle is equipped with a two-lamp headlamp system, there is no summing of test point values in determining compliance. Each headlamp for use on a motorcycle must comply with specified photometrics for a single lamp, and not as a system of two headlamps.

Thus, the maximum values apply to a single headlamp, and not the system of two headlamps as [Koito and Suzuki] appear to believe" (at 45360).

However, our letter of February 22 informed Stanley Electric that "a [motorcycle headlamp] system of the type described in subparagraph (b) of S7.9.6.2 [a two-lamp system] is not intended to have twice the light output of systems described in S7.9.6.2(a) or S7.9.6.2(c)," which you interpret as contrary to our previous interpretations. You ask that we seek public comment if it is our intent to adopt "one photometric performance for each motorcycle."

We appreciate your calling this matter to our attention. We agree that our interpretation is incorrect and withdraw that portion of our letter of February 22 that is inconsistent with prior interpretations. A conflict appears to arise in the context of a motorcycle headlamp system permitted by S7.9.6.2(b), a two-lamp system in which each lamp contains an upper beam light source, or each lamp contains a lower beam light source. This system could produce total beam photometrics of twice the light output of a single beam system (S7.9.6.2(a)or S7.9.6.2(c)). The edges of luminous lens areas of headlamps meeting S7.9.6.2(b) must be no more than 8 inches apart when they are mounted horizontally, and our remarks in our letter of February 22 reflected our concern that this may be an insufficient distance to prevent glare arising from two beams, especially from the lower beam when other drivers are in close proximity. If you intend to produce a two-headlamp system with two full-intensity upper or lower beams, please keep in mind our safety concerns about glare.

We intend to study this question in the coming months as part of a petition from the Japanese Automotive Parts Industry Association, and would appreciate any data you may have on this subject.

Sincerely,
Frank Seales, Jr.
Chief Counsel
ref:108
d.9/29/99