Interpretation ID: aiam3753
Manager
Safety & Emission Control Engineering
BMW of North America
Inc.
Montvale
NJ 07645;
Dear Mr. Ziwicka: This is in reply to your letter of August 15, 1983, asking for a interpretation of Federal Motor Vehicle Safety Standard No. 108 with respect to spacing of turn signal lamps on motorcycles.; As you have noted, SAE Standard J588e is the basic Federal requiremen for turn signal lamps referenced by Tables I and III of Standard No. 108 for all motor vehicles. One of the requirements of J588e is that the front turn signal must be separated from the low beam headlamp by at least 4 inches measured from the filament center of the turn signal to the inside diameter of the retaining ring of the low beam headlamp. But, as you further point out, paragraph S4.3.1.7 of Standard No. 108 relieves this restriction under certain circumstances. However, because Table IV of Standard No. 108 specifically requires a minimum edge to edge separation distance of 4 inches between the turn signal lamp and the headlamp on a motorcycle, you believe that it is unclear whether S4.3.1.7 relieves this restriction also, and have asked us for an interpretation that it does.; We are unable to provide the interpretation that you seek. True, SA J588e does incorporate a spacing restriction which is relieved by S4.3.1.7 under certain circumstances. However, although the requirements of J588e generally do apply to motorcycle turn signal lamps, the spacing restriction does not apply, having been superseded by the specific language in Table IV addressed to motorcycles. We believe that it is important to maintain a minimum edge to edge distance on motorcycles that exceeds the minimum allowable on other motor vehicles, in order to assure that the conspicuity of the turn signal will not be masked by the headlamp beam. Because the motorcycle headlamp beam is not fixed in relation to the road as an automobile headlamp is, its vertical and horizontal aim will change with the lean angle and the steering angle of the machine. The higher intensity portions of the beam will rise above the horizontal, thus producing more glare and reducing the conspicuity of the turn signal. Further, given the almost universal daytime use of headlamps, the lesser conspicuity of the turn signal on motorcycles during daylight hours must not be compromised.; I hope that this answers your question. Sincerely, Frank Berndt, Chief Counsel