FMVSS 108: Lamps, Reflective Devices and Equipment explained.

What FMVSS 108 says it is for

The eCFR heads this section "Standard No. 108; Lamps, reflective devices, and associated equipment." Under 49 CFR part 571, the Federal Motor Vehicle Safety Standards are the numbered standards that set safety performance requirements for motor vehicles and equipment. The text below is quoted from 571.108 as current through October 29, 2026.

This standard specifies requirements for original and replacement lamps, reflective devices, and associated equipment.

The purpose of this standard is to reduce traffic accidents and deaths and injuries resulting from traffic accidents, by providing adequate illumination of the roadway, and by enhancing the conspicuity of motor vehicles on the public roads so that their presence is perceived and their signals understood, both in daylight and in darkness or other conditions of reduced visibility.

What it applies to

The application section of the standard says:

This standard applies to: S3.1 Passenger cars, multipurpose passenger vehicles, trucks, buses, trailers (except pole trailers and trailer converter dollies), and motorcycles;

Applicability is decided by the text of the standard as written, including any exclusions it lists, and by the date-specific rules in it. This page does not decide whether a particular vehicle or item is covered.

How the standard is organized

The eCFR text of 571.108 has these top-level sections:

• S1: Scope
• S2: Purpose
• S3: Application
• S4: Definitions
• S5: References to SAE publications
• S6: Vehicle requirements
• S7: Signal lamp requirements
• S8: Reflective device requirements
• S9: Associated equipment requirements
• S10: Headlighting system requirements
• S11: Replaceable light source requirements
• S12: Headlamp concealment device requirements
• S13: Replaceable headlamp lens requirements
• S14: Physical and photometry test procedures and performance requirements

In all, the text has 753 numbered headings. Use the finder above to search them; for example, a search for "test" lists the headings that mention tests.

Second-level headings at a glance

These are the numbered sub-sections one level below the top, in order (first 40 of 60):

• S3.2 Retroreflective sheeting and reflex reflectors manufactured to conform to S8.2 of this standard; and
• S6.1 Required lamps, reflective devices, and associated equipment by vehicle type
• S6.2 Impairment
• S6.3 Equipment combinations
• S6.4 Lens area, visibility and school bus signal lamp aiming
• S6.5 Marking
• S6.6 Associated equipment
• S6.7 Replacement equipment
• S7.1 Turn signal lamps
• S7.2 Taillamps
• S7.3 Stop lamps
• S7.4 Side marker lamps
• S7.5 Clearance and identification lamps
• S7.6 Backup lamps
• S7.7 License plate lamps
• S7.8 Parking lamps
• S7.9 High-mounted stop lamps
• S7.10 Daytime running lamps (DRLs)
• S7.11 School bus signal lamps
• S8.1 Reflex reflectors
• S8.2 Conspicuity systems
• S9.1 Turn signal operating unit
• S9.2 Turn signal flasher
• S9.3 Turn signal pilot indicator
• S9.4 Headlamp beam switching device
• S9.5 Upper beam headlamp indicator
• S9.6 Vehicular hazard warning signal operating unit
• S9.7 Vehicular hazard warning signal flasher
• S9.8 Vehicular hazard warning signal pilot indicator
• S10.1 Vehicle headlighting systems
• S10.3 Number. See Tables I-a and I-c
• S10.4 Color of light
• S10.5 Mounting location
• S10.6 Mounting height
• S10.7 Activation
• S10.8 Effective projected luminous lens area
• S10.9 Visibility
• S10.10 Indicator
• S10.11 Markings
• S10.12 Spacing to other lamps

Key requirements, quoted from the text

These are excerpts from the requirements sections of 571.108, in the order the standard presents them. Long paragraphs are shortened where marked with [...]; the eCFR has the complete text, tables and figures, which this page omits.

S6.1.1 Quantity. Except as provided in succeeding paragraphs of this S6.1.1 each vehicle must be equipped with at least the number of lamps, reflective devices, and items of associated equipment specified for that vehicle type and size in Table I and Section 6.6, designed to conform to the requirements of this standard. Multiple license plate lamps and backup lamps may be used to fulfill photometric requirements for those functions.

S6.1.1.1 Conspicuity systems. Each trailer of 2032 mm or more in overall width, and with a GVWR over 10,000 lbs., except a trailer designed exclusively for living or office use, and each truck tractor must be equipped with retroreflective sheeting, reflex reflectors, or a combination of retroreflective sheeting and reflex reflectors as specified in S8.2.

S6.1.1.2 High-mounted stop lamps. Each multipurpose passenger vehicle, truck, and bus required by this standard to be equipped with a high-mounted stop lamp, whose vertical centerline, when the vehicle is viewed from the rear, is not located on a fixed body panel but separates one or two moveable body sections, such as doors, which lacks sufficient space to install a single high-mounted stop lamp on the centerline above such body sections, must have two high-mounted stop lamps identical in size and shape. S6.1.1.2.1 The two lamps must be located at the same height, with one vertical edge of each lamp on the vertical edge of the body section nearest the vehicle centerline.

S6.1.1.3 Truck tractor rear turn signal lamps. A truck tractor need not be equipped with turn signal lamps mounted on the rear if the turn signal lamps installed at or near the front are of double face construction and are located such that they meet the photometric requirements for double faced turn signal lamps specified in Footnote 6 of Table VII. S6.1.1.3.1 The flashing signal from a double faced signal lamp must not be obliterated when subjected to external light rays from either in front or behind, at any and all angles.

S6.1.1.4 Daytime running lamps. Any pair of lamps on the front of a passenger car, multipurpose passenger vehicle, truck, or bus, whether or not required by this standard, other than parking lamps or fog lamps, may be wired to be automatically activated, as determined by the manufacturer of the vehicle, in a steady burning state as daytime running lamps (DRLs) in accordance with S7.10.5.

S7.1.1.10 Spacing to other lamps. S7.1.1.10.1 Each front turn signal lamp must also be designed to comply with any additional photometry requirements based on its installed spacing to other lamps as specified by this section. Where more than one spacing relationship exists for a turn signal lamp the requirement must be the one that specifies the highest luminous intensity multiplier of Tables VI-a and VI-b.

S7.1.1.10.2 Spacing measurement for non-reflector lamps. For any front turn signal lamp that does not employ a reflector to meet photometric requirements, the spacing must be measured from the light source of the turn signal lamp to the lighted edge of any lower beam headlamp, or any lamp such as an auxiliary lower beam headlamp or fog lamp used to supplement the lower beam headlamp.

S7.1.1.10.3 Spacing measurement for lamps with reflectors. For any front turn signal lamp which employs a reflector, such as a parabolic reflector, to meet photometric requirements, the spacing must be measured from the geometric centroid of the turn signal lamp effective projected luminous lens area to the lighted edge of any lower beam headlamp, or any lamp such as an auxiliary lower beam headlamp or fog lamp used to supplement the lower beam headlamp.

S7.1.1.10.4 Spacing based photometric multipliers. (a) where the spacing measurement of S7.1.1.10.2 or S7.1.1.10.3 between a turn signal lamp and the lighted edge of any lower beam headlamp is less than 100 mm the photometric multiplier must be 2.5. (b) where the spacing measurement of S7.1.1.10.2 or S7.1.1.10.3 between a turn signal lamp and the lighted edge of any lamp such as an auxiliary lower beam headlamp or fog lamp used to supplement the lower beam headlamp is at least 75 mm but less than 100 mm the photometric multiplier of Table VI must be 1.5. [...]

S7.1.1.11 Multiple compartment lamps and multiple. lamps. S7.1.1.11.1 A multiple compartment lamp or multiple lamps may be used to meet the photometric requirements of a front turn signal lamp provided the requirements of S6.1.3.2 are met. S7.1.1.11.2 If a multiple compartment lamp or multiple lamps are used on a passenger car or on a multipurpose passenger vehicle, truck, bus, or trailer of less than 2032 mm in overall width, and the distance between adjacent light sources does not exceed 560 mm for two compartment or lamp arrangements and does not exceed 410 mm for three compartments or lamp arrangements, then the combination of the compartments or lamps must be used to meet the photometric requirements for the corresponding number of lighted sections specified in Tables VI-a or VI-b. [...]

S8.1.11 Photometry. Each reflex reflector must be designed to conform to the photometry requirements of Table XVI-a when tested according to the procedure of S14.2.3 for the reflex reflector color as specified by this section.

S8.1.12 Physical tests. Each reflex reflector must be designed to conform to the performance requirements of the vibration test, moisture test, dust test, and corrosion test of S14.5, and the color test and plastic optical material test of S14.4. S8.1.1P3 Alternative side reflex reflector material. Reflective material conforming to GSA Federal Specification L-S-300 (incorporated by reference, see § 571.5), may be used for side reflex reflectors if this material as used on the vehicle, meets the performance requirements of Table XVI-a.

S8.2 Conspicuity systems. The requirement for conspicuity systems may be met with retroreflective sheeting, conspicuity reflex reflectors, or a combination of retroreflective sheeting and conspicuity reflex reflectors.

S8.2.1 Retroreflective sheeting. S8.2.1.1 Retroreflective sheeting must consist of a smooth, flat, transparent exterior film with retroreflective elements embedded or suspended beneath the film so as to form a non-exposed retroreflective optical system.

S8.2.1.2 Retroreflective sheeting material. Retroreflective sheeting must meet the requirements, except photometry, of ASTM D 4956-90 (incorporated by reference, see § 571.5) for Type V Sheeting. Sheeting of Grade DOT-C2 of no less than 50 mm wide, Grade DOT-C3 of no less than 75 mm wide, or Grade DOT-C4 of no less than 100 mm wide may be used.

S9.1 Turn signal operating unit. S9.1.1 The turn signal operating unit installed on passenger cars, multipurpose passenger vehicles, trucks, and buses less than 2032 mm in overall width must be self-canceling by steering wheel rotation and capable of cancellation by a manually operated control.

S9.1.2 Physical tests. Each turn signal operating unit must be designed to conform to all applicable performance requirements of S14.9.

S9.2 Turn signal flasher. S9.2.1 The means of producing the turn signal pilot indicator signal may be incorporated in the flasher. A means of producing an audible signal may be incorporated in the flasher.

S9.2.2 Physical tests. Each turn signal flasher must be designed to conform to all applicable performance requirements of S14.9.

S9.3 Turn signal pilot indicator. S9.3.1 Each vehicle equipped with a turn signal operating unit where any turn signal lamp is not visible to the driver must also have an illuminated pilot indicator to provide a clear and unmistakable indication that the turn signal system is activated.

S10.1 Vehicle headlighting systems. S10.1.1 Each passenger car, multipurpose passenger vehicle, truck and bus must be equipped with a headlighting system conforming to the requirements of Table II and this standard.

S10.7 Activation. See Tables I-a and I-c, Table II, and S6.1.5.

S10.13 Sealed beam headlighting systems. All sealed beam headlighting systems must be of a type designated in Table II-a. Each sealed beam headlamp must be designed to conform to the specifications furnished with respect to it pursuant to appendix C of part 564 of this chapter and Table II-a of this standard. The dimensions applicable to the design of a specific type are those identified with an “I” for interchangeability specified on the applicable drawing(s) filed in Docket No. NHTSA 98-3397.

S10.13.1 Installation. A sealed beam headlighting system must consist of the correct number of designated headlamp units as specified for the applicable system in Table II-a. The units must have their beams activated as specified in Table II-a. A system must provide in total not more than two upper beams and two lower beams.

S10.13.2 Simultaneous aim. Type F sealed beam headlamps may be mounted on common or parallel seating and aiming planes to permit simultaneous aiming of both headlamps provided that there is no provision for adjustment between the common or parallel aiming and seating planes of the two lamps. When tested with any conforming Type UF and LF headlamps in accordance with S14.2.5, the assembly (consisting of the Type UF and LF headlamps, mounting rings, the aiming/seating rings, and aim adjustment mechanism) must be designed to conform to the applicable photometric requirements.

S11 Replaceable light source requirements. Each replaceable light source must be designed to conform to the dimensions and electrical specifications furnished with respect to it pursuant to part 564 of this chapter, on file in Docket No. NHTSA 98-3397, and must conform to the following requirements:

S11.1 Markings. If other than an HB Type, the light source must be marked with the bulb marking designation specified for it in compliance with appendix A or appendix B of part 564 of this chapter. The base of each HB Type must be marked with its HB Type designation. Each replaceable light source must also be marked with the symbol DOT and with a name or trademark in accordance with S6.5.

S11.2 Ballast markings. If a ballast is required for operation, each ballast must bear the following permanent markings: (a) Name or logo of ballast manufacturer; (b) Ballast part number or unique identification; (c) Part number or other unique identification of the light source for which the ballast is designed; (d) Rated laboratory life of the light source/ballast combination, if the information for the light source has been filed in appendix B of part 564 of this chapter; (e) A warning that ballast output voltage presents the potential for severe electrical shock that could lead to permanent injury or death; (f) Ballast output power in watts and output voltage in rms volts AC or DC; and (g) The symbol ‘DOT’.

S11.3 Gas discharge laboratory life. For light sources that use excited gas mixtures as a filament or discharge arc, the “rated laboratory life” is determined in accordance with sections 4.3 and 4.9 of SAE Recommended Practice J2009 FEB93, Forward Discharge Lighting Systems (incorporated by reference, see 571.108 S5.2 of this title).

S11.4 Physical tests. S11.4.1 Each replaceable light source must be designed to conform with the performance requirements of the deflection test and pressure test requirements of S14.7. S11.4.2 Replaceable light sources must be designed to conform with the requirements of section VII of appendix A of part 564 of this chapter, or section IV of appendix B of part 564 of this chapter, for maximum power and luminous flux when test by the procedure of S14.7.3.

S12 Headlamp concealment device requirements. S12.1 While the headlamp is illuminated, its fully opened headlamp concealment device must remain fully opened should any loss of power to or within the headlamp concealment device occur. S12.2 Whenever any malfunction occurs in a component that controls or conducts power for the actuation of the concealment device, each closed headlamp concealment device must be capable of being fully opened by a means not requiring the use of any tools. Thereafter, the headlamp concealment device must remain fully opened until intentionally closed. S12.3 Except for malfunctions covered by S12.2, each headlamp concealment device must be capable of being fully opened and the headlamps illuminated by actuation of a single switch, lever, or similar mechanism, including a mechanism that is automatically actuated by a change in ambient light conditions. S12.4 Each headlamp concealment device must be installed so that the headlamp may be mounted, aimed, and adjusted without removing any component of the device, other than components of the headlamp assembly. [...]

S12.7 Certification election. Manufacturers of vehicles with headlamps incorporating VHAD or visual/optical aiming must elect to certify to S12.1 through S12.5 or to S12.6 prior to, or at the time of certification of the vehicle, pursuant to 49 CFR Part 567. The selection is irrevocable.

S13 Replaceable headlamp lens requirements. S13.1 A replacement lens for a replaceable bulb headlamp or integral beam headlamp that is not required to have a bonded lens must be provided with a replacement seal in a package that includes instructions for the removal and replacement of the lens, the cleaning of the reflector, and the sealing of the replacement lens to the reflector assembly. S13.2 Each replacement headlamp lens with seal, when installed according to the lens manufacturer's instructions on an integral beam or replaceable bulb headlamp, must not cause the headlamp to fail to comply with any of the requirements of this standard.

S14.1 General test procedures and performance requirements. S14.1.1 Each lamp, reflective device, item of conspicuity treatment, and item of associated equipment required or permitted by this standard must be designed to conform to all applicable physical test performance requirements specified for it.

S14.1.2 Plastic optical materials. All plastic materials used for optical parts such as lenses and reflectors on lamps or reflective devices required or allowed by this standard must conform to the material test requirements of S14.4.2. S14.1.3 All coatings used on optical materials must have added to their formulations an optical brightener, whose presence is detectable by ultraviolet light, to aid in testing for their presence. Other equivalent industry accepted methods may be used as an alternative.

S14.1.4 Samples. S14.1.4.1 Samples submitted for laboratory test must be new, unused, manufactured from production tooling and assembled by production processes, and representative of the devices as regularly manufactured and marketed. S14.1.4.2 Each test sample must include not only the device but also accessory equipment necessary to operate in its intended manner. Where necessary a mounting bracket shall be provided so that the device may be rigidly bolted in its operating position on the various test equipment. S14.1.4.3 Dust and photometric tests may be made on a second set of mounted samples, if desired, to expedite completion of the tests.

S14.1.5 Laboratory facilities. The laboratory must be equipped to test the sample in accordance with the requirements of the specific device.

Defined terms

The standard defines 76 terms in its definitions section; the first 12 are quoted here from the eCFR.

• Adaptive driving beam means a long-range light beam for forward visibility, which automatically modifies portions of the projected light to reduce glare to traffic participants on an ongoing, dynamic basis.
• Aiming plane means a plane defined by the surface of the three aiming pads on the lens.
• Aiming reference plane means a plane which is perpendicular to the longitudinal axis of the vehicle and tangent to the forwardmost aiming pad on the headlamp.
• Aiming screws are the horizontal and vertical adjusting screws with self-locking features used to aim and retain a headlamp unit in the proper position.
• Axis of reference means the characteristic axis of the lamp for use as the direction of reference (H = 0°, V = 0°) for angles of field for photometric measurements and for installing the lamp on the vehicle.
• Backup lamp means a lamp or lamps which illuminate the road to the rear of a vehicle and provide a warning signal to pedestrians and other drivers when the vehicle is backing up or is about to back up.
• Beam contributor means an indivisible optical assembly including a lens, reflector, and light source, that is part of an integral beam headlighting system and contributes only a portion of a headlamp beam.
• Cargo lamp is a lamp that is mounted on a multipurpose passenger vehicle, truck, or bus for the purpose of providing illumination to load or unload cargo.
• Clearance lamps are lamps which show to the front or rear of the vehicle, mounted on the permanent structure of the vehicle as near as practicable to the upper left and right extreme edges to indicate the overall width and height of the vehicle.
• Coated materials means a material which has a coating applied to the surface of the finished sample to impart some protective properties. Coating identification means a mark of the manufacturer's name, formulation designation number, and recommendations for application.
• Color Fundamental definitions of color are expressed by Chromaticity Coordinates according to the CIE 1931 Standard Colorimetric System, as described in the CIE 1931 Chromaticity Diagram (incorporated by reference, see § 571.5).
• Color bleeding means the migration of color out of a plastic part onto the surrounding surface.

Limits of this page

This page quotes the text of 49 CFR 571.108 as published in the eCFR, current through October 29, 2026. It omits tables, figures, cross-referenced test procedures in other parts, and the preambles and rulemaking history that explain the rule. It does not tell you whether a given vehicle, part or product complies, how to run a test, or what a manufacturer must certify. Compliance questions go to the manufacturer's engineers, qualified counsel or NHTSA. The eCFR is an editorial compilation, not the official legal edition of the Federal Register.

Sources

Sources opened and read November 2, 2026.

• eCFR: 49 CFR 571.108, Standard No. 108; Lamps, reflective devices, and associated equipment. (current through October 29, 2026) (read November 2, 2026)
• eCFR: 49 CFR part 571, Federal Motor Vehicle Safety Standards (current through October 29, 2026) (read November 2, 2026)