Interpretation ID: aiam2513
Dry Launch
1113 Greenville
Livermore
CA 94550;
Dear Mr. Moore: This is in reply to your letter of December 27, 1976, asking severa questions about Federal Motor Vehicle Safety Standard No. 108. You referenced my letter of October 7, 1976 to Wesbar Corporation, and my views about the prohibition against the optical combination of lamps (S4.4.1).; It is evident from your letter and others that our previou interpretations of the term 'optical combination' have been found to be ambiguous and lacking in the objective criteria that a Federal motor vehicle safety standard must provide. We have reviewed the matter, and now wish to modify our previous interpretation. In our view a lamp is 'optically combined' when the same light source (i.e. bulb) and the same lens area fulfill two or more functions (*e.g.* taillamp and stop lamp, clearance lamp and turn signal lamp). A dual filament bulb would be regarded as the 'same light source'. In determining conformance, the photometric requirements for clearance and taillamp functions, where two bulbs are located in a single compartment, must be met with only the bulb energized that is designed to perform the specific function. But the 15 candlepower maximum under Standard No. 108, however, would be determined with both the taillamp and clearance lamp bulb energized. Further, the lamp must be located to meet requirements for both clearance and taillamps. our re- interpretation means that the issue of light spill-over from one area of the lamp to another is irrelevant to conformance.; You have also asked whether the November 1975 amendments (S4.3.1.1.1 'permit clearance lights that are designed *for OEM application only* be allowed to have lower or no photometrics in this area but still be considered a combination clearance and sidemarker lamp' as the lamp otherwise complies with Standard No. 108.; The amendment in question was intended to cover clearance lamps only If a lamp is intended as a combination clearance and side marker lamp and does not meet the requirements for a clearance lamp because of the exemption provided by S4.3.1.1.1, it must nevertheless meet the requirements for side marker lamps. If it doesn't, a separate conforming side marker lamp must be provided.; Yours truly, Frank Berndt, Acting Chief Counsel