Interpretation ID: 571.108--Convertible CHMSL Beam Angle--Magna
April 3, 2023
Doris C. Schaller
Homologation
Magna Steyr Engineering AG & Co KG
Liebenauer Hauptstrasse 317
8041 Graz Austria
Dear Ms. Schaller:
This responds to your request for an interpretation regarding the permissibility, under Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, reflective devices, and associated equipment, of two proposed variants for mounting the center high-mounted stop lamp (CHMSL) on a soft top convertible. Based on the information you provided in your letter, as explained in more detail below, we have concluded that mounting the CHMSL on the “service lid” is permissible under FMVSS No. 108, whereas mounting the CHMSL on the “soft top cover” is not.
Background
The National Highway Traffic Safety Administration (NHTSA) is authorized to issue Federal motor vehicle safety standards that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301). NHTSA does not provide approval of motor vehicles or motor vehicle equipment, and NHTSA does not determine compliance of a vehicle or item of motor vehicle equipment outside the context of an actual enforcement proceeding. Instead, manufacturers are required to self-certify that their products conform to all applicable safety standards that are in effect on the date of manufacture. The following represents NHTSA’s opinion regarding the applicability FMVSS No. 108 requirements to your CHMSL designs based on the information you have provided.
FMVSS No. 108 specifies requirements for original and replacement lamps, reflective devices, and associated equipment. Paragraph S6.1.3.1 of FMVSS No. 108 contains requirements for the mounting location of all required lamps, including CHMSLs, and states specifically that:
Each lamp, reflective device, and item of associated equipment must be securely mounted on a rigid part of the vehicle, other than glazing, that is not designed to be
removed except for repair, within the mounting location and height limits as specified in Table 1, and in a location where it complies with all applicable photometric requirements, effective projected luminous lens area requirements, and visibility requirements with all obstructions considered.
You ask how S6.1.3.1 applies to two possible lighting design variations. Although you ask that certain information in your interpretation request be treated as confidential, we do not need to reveal or reference the information other than in general descriptive terms in order to answer your questions. What follows is our interpretation based on our understanding of the facts you provided.
Variant 1: CHMSL mounted on the “service lid”
The first variant you describe places the CHMSL on the vehicle’s “service lid,” which we understand to be an access panel that is fixed in place during normal vehicle operation and that can be opened only with a specialized tool by technicians at certified repair shops. From the illustrations provided with your request, it appears that the service lid is located between the trunk and the passenger cabin at the rear of the vehicle.
You state that you believe that a configuration in which the CHMSL is located on the vehicle’s service lid complies with the mounting location requirement in S6.1.3.1 of FMVSS No. 108. We agree. As noted above, S6.1.3.1 of FMVSS No. 108 states that required lamps “must be securely mounted on a rigid part of the vehicle, other than glazing, that is not designed to be removed except for repair.” NHTSA believes that the service lid is “a rigid part of the vehicle,” based on the information that you have provided, which suggests that the service lid is similar (albeit adjacent) to a trunk lid. NHTSA has previously interpreted a vehicle’s “deck lid” (i.e., trunk lid) as a rigid part of the vehicle,[1] and while the service lid you describe is not a trunk lid, we believe that interpretation covers other similar lids on a vehicle, such as the service lid, that are solid and cannot be easily removed. Additionally, you expressly describe the service lid as “only [able to] be moved with special tools in qualified garages,” which is consistent with the “not designed to be removed except for repair” requirement. Therefore, so long as the CHMSL meets all photometric and other requirements, NHTSA believes that it would be permissible under FMVSS No. 108 to mount the CHMSL on the vehicle’s service lid.
Variant 2: CHMSL mounted on the “soft top cover”
The second variant you describe places the CHMSL on the “soft top cover,” which we understand to be the lid that covers the compartment at the rear of the vehicle in which the convertible soft top is stored while it is open (i.e., retracted). In this variant, the CHMSL would comply with all applicable photometric requirements while the soft top cover is fully open or closed. However, for the approximately 20-second duration of the soft top opening or closing process, the soft top cover tips backward, causing the CHMSL to be temporarily out of compliance with photometric requirements. The driver can initiate the opening or closing process when the vehicle is traveling at speeds of up to 50 kilometers per hour. From your description, there is no auxiliary CHMSL in operation while the soft top cover is in the process of opening or closing.
Based on the information you have provided, this second variant is not permissible. As noted above, S6.1.3.1 of FMVSS No. 108 states that a required lamp must be mounted “in a location where it complies with all applicable photometric requirements, effective projected luminous lens area requirements, and visibility requirements with all obstructions considered.” If there are obstructions that would cause the lamp to fail to meet photometric and visibility requirements, S6.2.2 of FMVSS No. 108 requires that “the vehicle must be equipped with an additional lamp or device of the same type which meet[s] all applicable requirements of this standard, including photometry and visibility.”
In a past interpretation request, a vehicle manufacturer sought to install a CHMSL on a movable rear spoiler, such that it would occasionally not comply with the photometric requirements for CHMSLs. The manufacturer stated that it would employ an additional CHMSL that met the requirements when the “primary” CHMSL on the movable spoiler did not. NHTSA responded[2] that this approach to compliance would be permissible under what is now S6.2.23 of FMVSS No. 108, which states that “If any required lamp…is obstructed by motor vehicle equipment…, and cannot meet the applicable photometry and visibility requirements, the vehicle must be equipped with an additional lamp … which meet[s] all applicable requirements of the standard, including photometry and visibility.”4 The situation you describe, where the CHMSL on the soft top will occasionally not comply with FMVSS No. 108, is similar to the one described above, except that it does not appear that your vehicle is equipped with an auxiliary CHMSL. Accordingly, it is our conclusion that the “soft top cover” CHMSL mounting variant is not permissible under FMVSS No. 108.
If you have further questions, you may refer them to Eli Wachtel of my staff at (202) 366-2992.
Sincerely,
Ann Carlson
Chief Counsel
Dated: 4/3/23
Ref: FMVSS No. 108
[1] See letter to M. Iwase (Sept. 15, 1988), available at https://www.nhtsa.gov/interpretations/2954o
[2] Letter to Michael Love (July 7, 1992), available at https://www.nhtsa.gov/interpretations/nht92-528. 3 The original reference was to S5.3.1.1.