Interpretation ID: aiam2190
611 Bouldin Avenue
Austin
TX
78704;
Dear Mr. McNiel: This is in reply to your petition of November 7, 1975, 'for th correction of subsection S4.5.4 and S4.6(b) as set forth by existing Federal Motor Vehicle Safety Standard No. 108.'; It is your opinion that S4.5.4, which requires activation of stop lamp upon application of the service brakes, is design restrictive, and 'leaves no opportunity for innovation by the private sector for other solutions for the activation of a motor vehicle's stoplamps' (sic). You have suggested that S4.5.4 be amended to include at its end 'or by other beneficial means which will not impair the lighting system or the mechanical functioning of the vehicle'.; Any performance standard is design restrictive to some extent, it mus restrict manufacturers to designs that meet the desired performance requirements. Its validity as a performance standard depends on whether the restrictions of the standard are only as narrow as reasonably necessary to achieve the desired safety performance. In this case we have found that the requirement meets this test. A signal to other drivers that the service brakes are being applied is precisely the performance being sought in S4.5.4. A signal based on some other condition (e.g., vehicle deceleration) might not be as timely, or might fail altogether to operate at the critical moment (as where it is based on lifting the accelerator pedal). Since the requirement is limited to the desired safety performance, we find it valid, and your petition in this area is denied.; You also ask for an amendment of S4.6(b) to include 'rear lamps' amon those that may be flashed for signalling purposes, since you believe that conventional wiring circuits presently allow these lamps to be flashed when headlamps are flashed. When the headlamps are flashed by means of the on-off switch, it is true that rear lamps will flash. But that type of flashing is in no way restricted by the standard. The flashing intended to be regulated by S4.6(b) is by automatic means (see S3 definitions) and, except for rear turn signal lamps, these automatic devices would not be connected to rear lamp circuits. Thus, there appears to be no need for the amendment you suggest and your petition is accordingly denied.; We appreciate your continuing efforts on behalf of traffic safety. Sincerely, Robert L. Carter, Associate Administrator, Motor Vehicl Programs;