Interpretation ID: aiam3497
6400 Goldbranch Road
Columbia
SC 29206;
Dear Mr. Moyer: This is in reply to your letter of September 22, 1981, about you 'alert device which automatically turns on the stop lamps of the vehicle when the accelerator is released.' You wish our permission to install the device for experimentation and testing on other vehicles, as well as an interpretation of Federal Motor Vehicle Safety Standard No. 108 whether your device is allowable.; As you know, the agency has devoted considerable effort to improve rea braking signals, culminating in its proposal that passenger cars be equipped with a single high- mounted stop lamp on the centerline of the vehicle. The concept of a pre-brake application signal is a familiar one to us, but the agency has conducted no formal research with respect to it, and in view of its stop-lamp proposal, is unlikely to do so. The technical issues that we consider relevant to your concept are (1) whether most rear-end accidents are preceded by a 'panic' stop by the struck vehicle, (2) whether panic stops involve unique driver behavior that can be reliably discriminated from non-panic stop behavior and used to trigger a pre-braking signal, and (3) whether the resulting signal will automatically result in a decrease in the reaction time of following drivers that is equal to the early warning time it provides. We know of no scientifically acceptable data that support these critical assumptions. We are especially concerned that a high rate of 'false alarms' may lead to a decrease in the overall warning value of the stop lamp signal itself, i.e., the 'cry wolf' phenomenon. This could lead to a significant reduction in the effectiveness of any proposed system.; Paragraph 2.1 of SAE Standard J586d, *Stop Lamps*, September 1977 incorporated by reference in Standard No. 108, defines a stop lamp as one whose operation indicates 'the intention of the operator of a vehicle to stop or diminish speed by braking.'; Your device would activate the stop lamp under a condition indicatin an intent other than the above, which could impair the effectiveness of the stop lamps. We view any use of required lighting equipment for a purpose other than as defined, as an 'impairment' within the prohibition of paragraph S4.1.3 of Standard No. 108 if the device is installed as original equipment. If the device is sold in the aftermarket, our laws preclude modifications that 'render ineffective in whole or in part' required lighting equipment, if the modifications are performed by a person other than the vehicle owner. We would consider your system prohibited by this provision as well.; Noting your comment that the device may be used for testing on schoo buses, this means that there is no prohibition under the laws that we administer which would forbid a school district from installing your device on its fleet. Such a modification would be subject to laws of the jurisdiction in which the school bus is registered and operates.; Sincerely, Frank Berndt, Chief Counsel