[Code of Federal Regulations]
[Title 49, Volume 4]
[Revised as of October 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 49CFR393.24]

[Page 1100]
 
                        TITLE 49--TRANSPORTATION
 
        CHAPTER III--FEDERAL MOTOR CARRIER SAFETY ADMINISTRATION,
                      DEPARTMENT OF TRANSPORTATION
 
PART 393--PARTS AND ACCESSORIES NECESSARY FOR SAFE OPERATION--Table of Contents
 
    Subpart B--Lighting Devices, Reflectors, and Electrical Equipment
 
Sec. 393.24  Requirements for head lamps and auxiliary road lighting lamps.

    (a) Mounting. Head lamps and auxiliary road lighting lamps shall be 
mounted so that the beams are readily adjustable, both vertically and 
horizontally, and the mounting shall be such that the aim is not readily 
disturbed by ordinary conditions of service.
    (b) Head lamps required. Every bus, truck, and truck tractor shall 
be equipped with a headlighting system composed of at least two head 
lamps, not including fog or other auxiliary lamps, with an equal number 
on each side of the vehicle. The headlighting system shall provide an 
upper and lower distribution of light, selectable at the driver's will.
    (c) Fog, adverse-weather, and auxiliary road-lighting lamps. For the 
purposes of this section, fog, adverse-weather, and auxiliary road 
lighting lamps, when installed, are considered to be a part of the 
headlighting system. Such lamps may be used in lieu of head lamps under 
conditions making their use advisable if there be at least one such lamp 
conforming to the appropriate SAE Standard \1\ for such lamps on each 
side of the vehicle.
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    \1\ Wherever reference is made in these regulations to SAE Standards 
or SAE Recommended Practices, they shall be:
    (a) As found in the 1985 edition of the SAE Handbook with respect to 
parts and accessories other than lighting devices and reflectors.
    (b) When reference is made in these regulations to SAE Standards or 
SAE Recommended Practices, they shall be as found in the 1985 edition of 
the SAE Handbook:
    (1) With respect to parts and accessories other than lighting 
devices and reflectors:
    (2) Lighting devices and reflectors on motor vehicles manufactured 
on and after March 7, 1990, shall conform to FMVSS 571.108 (49 CFR 
571.108) in effect at the time of manufacture of the vehicle. Should a 
conflict arise between FMVSS 571.108 and a SAE Standard, FMVSS 571.108 
will prevail.
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    (d) Aiming and intensity. Head lamps shall be constructed and 
installed so as to provide adequate and reliable illumination and shall 
conform to the appropriate specification set forth in the SAE Standards 
\1\ for ``Electric Head Lamps for Motor Vehicles'' or ``Sealed-Beam Head 
Lamp Units for Motor Vehicles.''

[33 FR 19735, Dec. 25, 1968, as amended at 41 FR 53031, Dec. 3, 1976; 53 
FR 49397, Dec. 7, 1988]