Interpretation ID: 1985-02.42

TYPE: INTERPRETATION-NHTSA

DATE: 06/18/85

FROM: AUTHOR UNAVAILABLE; Jeffrey R. Miller; NHTSA

TO: Mr. H. Nakaya

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. H. Nakaya Branch Manager Mazda (North America), Inc. 24402 Sinacola Court Farmington Hills, Michigan 48018

Dear Mr. Nakaya:

Please forgive our delay in responding to your letter of May 30, 1984, asking for interpretations of Standard No. 108 as it applies to center high-mounted stoplamps.

In your letter you stated that the preamble to the final rule discussed the definition of "window opening" and concluded that the rear window opening shall be the perimeter of the rear glazing that is unobstructed and free of opaqueness. You have presented two rear window designs in which (1) ceramic opaque dots descend in increasing size to the bottom of the glazing and in which (2) shaded material becomes progressively darker as it descends, though the material is translucent, not opaque. You also show a design with an interior-mounted windshield wiper, including motor and cover, placed on the rear vertical centerline above the bottom of the glazing. In each instance you have asked at what point would the National Highway Traffic Safety Administration (NHTSA) consider an "obstruction" exists for purposes of defining the bottom of the window.

The phrase "window opening" does not appear in Standard No. 108. The preamble discussion appears to be irrelevant with respect to the final rule, and was intended as a clarification of proposed location requirements which, in fact, were not adopted. The notice of proposed rulemaking of January 8, 1981, proposed a definition of "daylight opening" as "the maximum unobstructed opening through the glazing surface...," relating to three alternative locations proposed for the lamp in which the term "daylight opening" was used as a locational reference. For instance, in Alternative 1, proposed paragraph S4.3.1.9(a) would have placed "the center of the lamp within 3 inches of the outside bottom edge of the rear window daylight opening." When the final rule was adopted in October 1983, none of the three alternatives was judged acceptable and a requirement allowing more design freedom was adopted omitting all reference to "daylight opening." Paragraph S4.3.1.8 simply specified that "no portion of the lens shall be higher than the top of the back window or lower than three inches below the bottom of the back window." The requirement was even further relaxed in the May 1984 response to petitions for reconsideration in which paragraph S4.3.1.8 was amended to allow mounting "at any position on the centerline" (note, no limitation on upper mounting height relative to the rear window) and if "mounted below the rear window, no portion of the lens shall be lower than 6 inches on convertibles, or 3 inches on other passenger cars" The preamble also clarified that, if the lamp were mounted on the interior, photometric compliance would be judged with the glazing in place.

Thus, whether glazing is opaque or obstructed is not the question a manufacturer must ask in determining the location of the lamp with respect to the lower edge of the window. If the lamp is mounted on the interior, it must meet photometric and visibility requirements with the glazing in place, taking into account any graduated dots on or opaqueness of that glazing, and any wiper motor. If the lamp is mounted on the outside, its upper permissible height is determined by the height of the car and not by the window. The question of opaqueness or obstruction is irrelevant to the lower permissible height of 3 inches below the window. The window is the perimeter of its glazing, and 3 inches is measured from the lower edge.

Sincerely,

Jeffrey R. Miller Chief Counsel

Mr. Frank Berndt Chief Counsel National Highway Traffic Safety Administration 400 7th Street, S.W. Washington D.C. 20590

Re: Interpretation of FMVSS 108; Lamps, Reflective devices and Associated Equipment - High Mounted Stoplamp

Dear Mr. Berndt:

The recent final rule amending Standard No. 108 addresses many issues raised by manufacturers, including the definition of "window opening". The preamble of the final rule discussed this definition and concluded that the rear window opening shall be the perimeter of the rear glazing that is unobstructed and free of opaqueness. Applying this definition to the bottom rear window opening boundry, certain aspects of the final rule establishing this boundry as the reference for the mounting location are still not clear. Our questions are as follows:

1. In Figure 1, two examples are shown (out of many possible designs) that are aimed at minimizing the visibility of objects in the passenger compartment by means of a graduated shade. Design A employees a series of ceramic, opaque dots forming an array that become progressively larger (and allow less light transmittance) as they descend toward the glazing/body interface. Also, Design B utilizes a material that becomes progressively darker (and allows less light transmittance) as it approaches the bottom of the rear window glazing. However, the material is translucent, not opaque. For purposes of defining the bottom of the rear window opening, please consider individually each graduated shade design and identify the point (A, B or C) at which the NHTSA would consider the bottom rear window opening obstructed (should reference point B be identified, please quantify).

2. Contained in Figure 2 is a depiction of a rear window wiper motor, cover and blade. The motor and motor cover are mounted inside the vehicle along the vehicle centerline for reasons of symmetry. Although a small obstruction is projected onto the rear glazing, the device does not contact the glazing and is limited to only a narrow portion of the bottom rear window opening. Again, for purposes of defining the bottom of the rear window opening, please consider this design and identify the point at which the NHTSA would consider the bottom window opening obstructed. Further, does availability of such a device as a factory option or as standard equipment have any bearing on this matter?

We would appreciate your interpretation of these aspects of FMVSS 108 at your earliest convenience.

Thank you.

Sincerely,

H. Nakaya Branch Manager

NH/mls

enclosures