Interpretation ID: aiam3520
Ph.D.
Executive Secretary
United Sidecar Association
Inc.
1621 Palomino Lane
Kingwood
TX 77339;
Dear Dr. Kendall: This is in reply to your letter of September 9, 1981, asking severa questions about Federal Motor Vehicle Safety Standard No. 108.; You have asked for a clarification of our position on pulsatin headlamps and stoplamps, commenting that several States have expressed a concern 'that a light of variable intensity may be confused by the citizen as an emergency vehicle which is allowed to have flashing headlights.'; As you have indicated, paragraph S4.6(a) of Standard No. 108 require turn signal lamps, hazard warning signal lamps, and school bus warning lamps to flash when activated, while S4.6(b) requires all other lamps to be steady burning. By 'steady burning,' the standard means a light that is essentially unvarying in intensity. There is, however, an exception in S4.6(b) to the 'steady burning' requirement. Means may be provided 'to flash headlamps and side marker lamps for signalling purposes.' Paragraph S3 of the standard defines 'flash' as meaning 'a cycle of activation and deactivation of a lamp by automatic means....' In our view, a lamp whose intensity varies from a higher output to a lower output would not be 'steady burning' or 'flash' within the meaning of those terms and hence would be prohibited. But if complete deactivation occurs, then the lamp 'flashes.' Installation of flashing lamps under the S4.6(b) exception is not restricted to emergency vehicles. It is permissible under the standard for a motorcycle to have a device which gives the motorcyclist the option of causing a motorcycle headlamp to operate automatically through cycles of activation and deactivation instead of burning steadily.; On the other hand, stop lamps that either flash or are of variabl intensity are not allowed by S4.6(b) of Standard No. 108 since they are not steady-burning while in use.; I hope this answers your questions. Sincerely, Frank Berndt, Chief Counsel