Mr. Dennis G. Moore


Sierra Products Inc.

1113 Greenville Road

Livermore, CA  94550


Dear Mr. Moore:


This responds to your letter requesting interpretation of Federal Motor Vehicle Safety Standard (FMVSS) No. 108, Lamps, Reflective Devices, and Associated Equipment.  Specifically, you asked several questions relating to the standard’s requirements for effective projected luminous lens area, including the permissibility of using light-emitting diodes (LEDs) to meet those requirements.  Our responses to those questions are set forth below.  We note that your letter also raised concerns regarding the agency’s enforcement of these requirements of Standard No. 108.  We are referring the enforcement-related aspects of your letter to our Office of Vehicle Safety Compliance, which will respond to those questions in a separate letter.


By way of background, the National Highway Traffic Safety Administration is authorized to issue FMVSSs that set performance requirements for new motor vehicles and items of motor vehicle equipment (see 49 U.S.C. Chapter 301).  This agency does not provide approvals of motor vehicles or motor vehicle equipment, nor do we endorse any commercial products.  Instead, manufacturers are required to certify that their vehicles and equipment meet applicable standards.  Also, it is unlawful for dealers to sell motor vehicles or motor vehicle equipment that do not meet applicable standards. 


Your first question seeks clarification of the legal definition of “Effective Projected Luminous Lens Area” or “Effective Light Emitting Surface” including whether there have been any recent amendments or interpretations to that aspect of the standard.  Both terms are defined in 49 CFR 571.108 S4. 


Effective light-emitting surface” means that portion of a lamp that directs light to the photometric test pattern, and does not include transparent lenses, mounting hole bosses, reflex reflector area, beads or rims that may glow or produce small areas of increased intensity as a result of uncontrolled light from an area of ½ degree radius around a test point.


Effective projected luminous lens area” (EPLLA) means the area of the orthogonal projection or the effective light-emitting surface of a lamp on a plane perpendicular to a defined direction relative to the axis of reference.  Unless otherwise specified, the direction is coincident with the axis of reference.


These definitions were most recently updated in a final rule published in the Federal Register (69 FR 48805) on August 11, 2004.  That rule amended the standard for turn signal lamps, stop lamps, taillamps, and parking lamps to increase compatibility with the requirements of the Economic Commission for Europe (ECE) and to improve the visibility of these lamps.  In that rulemaking, the definition for “effective light-emitting surface” was added to the standard, and the definition of “effective projected luminous lens area” was modified to its current state (69 FR 48814).


In your letter, you also asked if the EPLLA requirements for “stop” or turn signal lamps are 7¾ inches (50 cm/sq) for vehicles less than 80 inches wide and 11 5/8 inches (75 cm/sq) for vehicles over 80 inches wide.  The answer to this question is that these are the minimum requirements. 


In relevant part, S5.1.1.26 of the standard provides:


On a motor vehicle whose overall width is less than 80 inches:

(a)            The effective projected luminous lens area of a single compartment stop lamp, and a single compartment rear turn signal lamp, shall be not less than 50 square centimeters (7¾ square inches).

(b)            If a multiple compartment lamp or multiple lamps are used to meet the photometric requirements for stop lamps and rear turn signal lamps, the effective projected luminous lens are of each compartment or lamp shall be at least 22 square centimeters, provided the combined area is at least 50 square centimeters (7¾ square inches).


With regard to vehicles over 80 inches wide, S5.1.1 of FMVSS No. 108 refers to Table I of the standard (Required Motor Vehicle Lighting Equipment Other Than Headlamps), which in turn refers to SAE J1395 (rev. April 1985) (Turn Signal Lamps for Use on Motor Vehicles 2032 mm or More in Overall Width).  Paragraph S5.3.2 of SAE J1395 states that “the functional lighted lens area of a single lamp… shall be at least 75 cm sq.”


You also asked whether there are EPLLA requirements for taillamps, side marker lamps, clearance lamps, and identification lamps.  Specifically, you asked whether a manufacturer could use “one or two Red Dots of LED light to fulfill FMVSS #108 requirements.”  The answer is that there is no minimum EPLLA for these lamps.  We note, however, that under S5.3 of the standard, these lamps must meet the visibility requirements specified in paragraph S5.3.2, which includes meeting the area requirements listed in Figure 19 or the candela requirements listed in Figure 20.  Alternatively, paragraph S5.3.2.4 permits lamps to be located such that they meet the visibility requirements specified in any applicable SAE Standard.  The applicable SAE Standards are listed in FMVSS No. 108 in Tables I and III.  These tables incorporate by reference SAE J585e (rev. Sept. 1972) with regard to tail lamps, and SAE J592e (rev. July 1977) with regard to side marker, clearance, and identification lamps.  Paragraph S3.6 of SAE J585e (rev. Sept. 1977) specifies the photometric requirements for tail lamps, and paragraph S3.4 of SAE J592e (rev. July 1977) specifies the photometric requirements for the other lights.  If the photometric requirements of the respective SAE standards incorporated by reference are met by one or more LEDs, then such a lamp would meet the relevant requirements of FMVSS No. 108.


If you have any additional questions, please feel free to contact Ari Scott of my staff at (202) 366-2992.






Anthony M. Cooke

Chief Counsel