Dear Mr. Yu:
This responds to your letters of February 1 and 12, 1996, asking for interpretations of Motor Vehicle Safety Standard No. 108 with respect to the rear lighting configuration depicted on a drawing that you enclosed with each letter.
In your letter of February 1, you are concerned with the four lamps designated "1", "2", "3", and "4". They are all amber, and activated when the brake pedal is applied. Lamps 1 and 2 flash alternatively with lamps 3 and 4. The lamps are extinguished when the brakes are released.
The drawing you enclosed show that these are not lamps that are required by Standard No. 108, but supplemental lighting equipment. Paragraph S5.5.10 of Standard No. 108 specifies the required lamps that may flash in use, and S5.5.10(d) clarifies that "all other lamps shall be steady burning." This means that supplemental lighting equipment added by the manufacturer or dealer before a vehicle's first sale must be steady burning. I would also like to call your attention to paragraph S5.1.3 of Standard No. 108; supplemental lighting equipment is permissible if it does not impair the effectiveness of lighting equipment required by the standard. Even if paragraph S5.5.10 permitted supplemental lighting equipment to flash, we believe that your system would impair the effectiveness of the stop lamps. The four lamps are activated simultaneously with the stop lamps, but are of a different color and flash in use. When confronted with an array of red steady burning lamps and amber flashing ones, there is a strong likelihood of at least momentary confusion in a driver following the bus.
In your letter of February 12, your drawing shows two amber lamps mounted approximately at the upper right and left corners of the vehicle. They, too, flash when the brake pedalis depressed. This appears to be a variation of the four-lamp system discussed above, and for the same reasons we consider this system also to be prohibited by S5.5.10(d).
This also responds to Gillig's telephone call of February 13 to Taylor Vinson in which it asked for NHTSA's views on systems of flashing red lamps instead of amber ones. Additional red lamps that are activated simultaneously with the stop lamps appear to serve as a supplemental stop lamp system. However, under S5.5.10(d), they, too, must be steady burning. If Gillig wishes to configure the systems described in this letter to be both red and steady burning, we would not view such a configuration as creating an impairment of the effectiveness of other rear lighting equipment within the meaning of paragraph S5.1.3.
If you have further questions, you may refer them to Taylor Vinson of this Office (phone: 202-366-5263).
Samuel J. Dubbin Chief Counsel ref:108 d:3/34/96