Interpretation ID: nht93-9.1

DATE: December 2, 1993

FROM: Harry C. Gough, P.E. -- Automotive Engineering Professional Specialist, State of Connecticut, Department of Motor Vehicles

TO: Chief Counsel, NHTSA

TITLE: None

ATTACHMT: Attached to letter dated 3/29/94 from John Womack to Harry C. Gough (A42; Std. 108)

TEXT:

I am writing on behalf of the State of Connecticut Department of Motor Vehicles. We are requesting a written opinion or interpretation regarding the meaning of the terms "flash alternately" or "alternately flashing" as they apply to school bus overhead signal lamps required under FMVSS #108. The terms are used in SAE Standard J887, which is incorporated by reference. The reason for the request is that a manufacturer of strobe (gaseous-discharge) lamps has supplied test documentation indicating that a system they offer complies with the mechanical, color, and intensity provisions of SAE J887 and thus comply with FMVSS #108. The system offered uses what is referred to as a quad-pulse strobe flash pattern. Effectively the lamp on one side flashes on and off four times in a 255 millisecond period and then stays off for 745 milliseconds, then the lamp on the opposite side of the bus repeats the aforementioned pattern. While the pattern is repeated alternately from side to side a question arises as to whether "alternately flashing" refers to the pattern heretofore described or do the four distinct on/off cycles on each side of the school bus defeat the intent of the term alternating.

While I realize your office is very busy with such interpretations, I would appreciate a response at your earliest convenience. If there are any additional questions or information required, please feel free to have your office call me at (203) 566-3754.

Thank you in advance for your attention to this matter.