United States Department of TransportationInterpretation ID: aiam4642
MO 63303;
Dear Mr. Egley: This is in reply to your letters with respect to th Sudden Stop Flasher (SSF), your invention, now registered with the U.S. Patent Office. Your first letter is a 'Request for Evaluation/Interpretation' of your invention, your second is 'An Appeal for Variant Interpretation.' I regret the delay in responding. You have explained that the SSF operates as follows: when a vehicle reaches a certain high rate of deceleration, the SSF automatically flashes all three of the stop lamps on passenger cars at a rapid rate. If the vehicle has crashed, the SSF continues to flash until the ignition switch is recycled. You recognize that Federal Motor Vehicle Safety Standard No. 108, Lamps, Reflective Devices, and Associated Equipment, requires stop lamps to be steady burning. You nevertheless ask for a favorable interpretation because the SSF will be actuated only rarely, and 'the concept of flashing tail lights to get the attention of drivers has already been approved in the hazard warning system.' Because of the expense of developing the SSF, you state that you are not willing to undertake it 'unless NHTSA would indicate at least tentative acceptance, subject to demonstration and testing of a working model.' You are correct that Standard No. 108 requires stop lamps to be steady burning, and hazard warning signal lamps to flash (generally through the turn signal lamps). The primary reason for the distinction is that stop lamps are intended to be operated while the vehicle is in motion, while the hazard warning lamps are intended to indicate that the vehicle is stopped. Each lamp is intended to convey a single, easily recognizable signal. If a lamp which is ordinarily steady burning begins to flash, the agency is concerned that the signal will prove confusing to motorists, thereby diluting its effectiveness. Even if we did not have this reservation about the SSF, we could not change the steady burning requirement through interpretation. A change could be made through rulemaking only. We do not currently have information indicating that a flashing signal would be superior to a steady burning one. The SSF is based upon the concept that a flashing lamp increases vehicle conspicuity, and hence should shorten the reaction time of following drivers. As you noted, 'whether the SSF could significantly improve safety is the primary consideration.' In research sponsored by this agency that led to the adoption of the center high-mounted stop lamp, a field study was conducted using 600 taxicabs in San Diego and Sacramento. The cabs were equipped with one of three kinds of center lamps, a steady-burning one, or one that flashed at 2.5 Hz, or one that flashed at either l.5, 2.5, 4.5, or 7.0 Hz depending on the degree of deceleration. The test fleet accumulated 4l million miles. The study found that there was no statistically significant differences among the lamps (Mortimer, R.G., Field test evaluation of rear lighting deceleration signals: II - Field test. Final Report, DOT-HS-806-125, 198l). The agency would be unlikely to issue grants or fund research for the SSF, a proprietary device. Most of its vehicle safety research is devoted to obtaining data to support the development of standards that are more performance-oriented. I am sorry that we cannot be more positive in our response, but we do appreciate your interest in reducing traffic accidents, and deaths and injuries associated with them. Sincerely, Stephen P. Wood Acting Chief Counsel;