Herr P. Binder
ITT Automotive Europe
Dear Herr Binder:
This replies to your FAX of September 3, 1996, asking for the regulations to be met by a new design for a center highmounted stop lamp (CHMSL).
As you describe it, in the intended design a passenger car will have two CHMSLs, one mounted in the car body and other mounted in the rear spoiler. The car body CHMSL will function until the rear spoiler extends at speed, and at the point "at which the spoiler will shade the CHMSL" the second CHMSL operates when the brake pedal is applied.
We assume that the second CHMSL is provided because as the spoiler extends it will mask to some extent the first CHMSL and may create a failure of the first CHMSL to comply with photometric and visibility requirements. This situation is addressed by paragraph S184.108.40.206 of Standard No. 108. This paragraph first specifies that lamps shall be located so that they meet visibility requirements specified in any applicable SAE Standard or Recommended Practice. In addition, this paragraph specifies that no part of a vehicle shall prevent any lamp from meeting the photometric output at any test point specified in any applicable SAE Standard or Recommended Practice. However, if motor vehicle equipment such as a spoiler prevents compliance by a lamp, an auxiliary lamp meeting the visibility and photometric specifications required for the original lamp shall be provided. We assume that the second CHMSL in the spoiler will meet these requirements.
Your letter does not say whether the first CHMSL is extinguished when the second CHMSL operates, or whether they would both operate together. Either method is acceptable to us and would not cause a noncompliance with Standard No. 108.
If you have any questions, you may refer them to Taylor Vinson of this Office.
Acting Chief Counsel