Interpretation ID: 77-1.40
TYPE: INTERPRETATION-NHTSA
DATE: 03/04/77
FROM: AUTHOR UNAVAILABLE; F. Berndt; NHTSA
TO: Dry Launch
TITLE: FMVSS INTERPRETATION
TEXT: This is in reply to your letter of December 27, 1976, asking several 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 previous 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,
DRY LAUNCH
December 27, 1976
Frank A. Berndt Acting Chief Counsel U.S. Department of Transportation National Highway Traffic Safety Administration In a recent discussion with an Engineer at the California Highway Petrol's Certification Office in Sacramento, we discussed combining of lighting functions. He had a copy of a letter from you to Mr. B. A. Weber of Wesber Corporation dated October 7, 1976. As a result of reading this, the following two questions come to mind - the third question I have been intending to write you about.
1. Question and Answer to No. 2 was the following:
"Can a clearance lamp and tail lamp be combined in a single compartment with no opaque barrier wall existing between the clearance lamp bulb and the tail lamp bulb?
The answer is no because the same luminous area of the lens would be lighted when both lamps are in use, and the lamps would be "combined optically."
I ask if no barrier existed between the two functions and both photometric tests simultaneously, (that is, neither were over maximums or under minimums) and both passed their tests when the other one was extinquished (that is, not over maximums or not under minimums), why must the opaque wall exist at all? In view of public safety, it would appear to enhance it as well as save money and weight by omitting the opaque wall.
2. If an opaque wall must exist between clearance light and tail light, there is bound to be a certain amount of "spill over" of one compartment's light into the next. In this case what limit of "spill over" might exist realistically?
3. Recently, an amendment to Federal 108 allowed the covering of the 45 degrees sector of a clearance light that was inboard (S4.3.1.1.1). Does this 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 long as all other rules of Federal 108 are met and they are properly mounted?
I would appreciate a prompt reply as your answers affect two decisions for new lights that we are working on.
Dennis G. Moore