Federal Motor Vehicle Safety Standards; Modernization of FMVSS No. 108 To Accommodate ADS-Equipped Vehicles

NHTSA has issued a notice of proposed rulemaking to amend Federal Motor Vehicle Safety Standards No. 108, "Lamps, reflective devices, and associated equipment," to remove requirements that assume a human driver and to standardise marker lamps on vehicles equipped with Automated Driving Systems (ADS). The NPRM was published in the Federal Register on 26 October 2026 (FR Doc. 2026-21794, RIN 2127-AM70, Docket No. NHTSA-2026-1519) and comments are due by 25 November 2026. If you build, import or certify lighting equipment for the US automotive market, this changes the compliance test conditions for integral beam headlamps and opens an optional ADS marker lamp specification.

FMVSS No. 108 was written around a human driver. In its Unified Agenda entry for RIN 2127-AM70, NHTSA states that the standard "includes requirements that assume a human driver and manual controls, references the location of a human driver, or specifies the operation of manual controls to effectuate testing for compliance with the standards."

That creates a certification problem rather than a safety problem. Where a compliance test procedure instructs a technician to operate a manual control — a beam selector, a turn signal lever — a vehicle without those controls cannot be tested as written, regardless of how its lighting performs on the road.

This NPRM is one item in a broader NHTSA programme. The agency's 23 October 2026 announcement records that it has already proposed modernising FMVSS for transmission shift display (No. 102), windshield defrosting and wiping (Nos. 103/104), tire placard location (No. 110) and braking system controls (No. 135), and has announced upcoming efforts on controls and displays (No. 101), mirrors and rearview display (No. 111), electronic stability control (No. 126) and sun visors and warning labels (Nos. 201/208). The FMVSS No. 135 NPRM was published on 26 June 2026 (FR Doc. 2026-12981).

The consistent principle across that programme, stated in the FMVSS No. 135 NPRM, is that vehicles retaining manual controls "must continue to meet all existing safety requirements associated with manual controls, regardless of whether the vehicle is equipped with an ADS." This is not a relaxation for conventional vehicles.

Four distinct changes are on the table, and only two of them are ADS-specific.

Test voltage for integral beam headlamps. The NPRM would amend the test voltage specification applicable to integral beam type headlamps. The specific voltage values are set out in the regulatory text in the docket.

Vertical headlamp arrangements. The proposal would remove requirements that apply to vertical headlamp arrangements. NHTSA frames both of these as removing unnecessary requirements and providing design flexibility without impact on vehicle safety.

Driver-centric requirements for vehicles without manual controls. Further proposed changes address vehicles equipped with ADS that do not have manually operated driving controls.

ADS marker lamps. NHTSA states in the Federal Register notice that it "is proposing to amend FMVSS No. 108 to incorporate standardized specifications for front, rear, and side ADS marker lamps if they are installed on a motor vehicle." The agency grounds this in its long-standing position that "highway traffic safety is enhanced by the familiarity of drivers and other road users" with standardised lighting signals. Its 23 October 2026 announcement describes the objective as standardising performance criteria for identifying marker lamps on ADS-equipped vehicles.

Note the conditional: if they are installed. On the face of the notice this is a permissive specification, not an installation mandate.

The instrument is a notice of proposed rulemaking amending 49 CFR Part 571, specifically § 571.108 (FMVSS No. 108). The Federal Register document number is 2026-21794, the RIN is 2127-AM70, the docket is NHTSA-2026-1519, and the notice begins at printed page 67253. The issuing authority is the National Highway Traffic Safety Administration, U.S. Department of Transportation.

Stage matters here. This is a proposal. Nothing in it is enforceable, and nothing in it is final until NHTSA issues a final rule with its own effective and compliance dates. Do not re-engineer a lamp against proposed text.

FMVSS No. 108 governs lamps, reflective devices and associated equipment across passenger cars, multipurpose passenger vehicles, trucks, buses, trailers and motorcycles. The ADS-specific amendments in this NPRM are directed at manufacturers of ADS-equipped vehicles that lack manually operated driving controls.

One detail circulating in secondary regulatory indexes — that the ADS marker lamp provisions would establish an optional cyan colour — is unverified secondary-source intelligence. It is not confirmed by the Federal Register text excerpts available at the time of writing. Read the colour and photometric specifications directly from the proposed regulatory text in the docket before briefing an optics team.

Three groups, with very different exposure levels.

Lighting suppliers and headlamp test houses. The integral beam test voltage amendment and the deletion of the vertical headlamp arrangement requirements affect every manufacturer certifying headlamps to FMVSS No. 108, not only ADS developers. A change in test voltage specification changes photometric test conditions, which means test reports and internal compliance documentation generated under the current specification will need to be reconciled against whatever the final rule adopts.

ADS developers building vehicles without manual controls. This is the group the rulemaking exists for. Removing requirements predicated on manual beam switching or manual turn signal cancellation removes a certification barrier that currently has no clean resolution other than an exemption route.

Conventional vehicle manufacturers. Largely unaffected on the ADS provisions. NHTSA's stated position across this modernisation programme is that vehicles with manual controls continue to meet the existing requirements tied to those controls.

One thing only: a comment, if you want influence. Comments on FR Doc. 2026-21794 are due by 25 November 2026, filed to Docket No. NHTSA-2026-1519.

There is no new compliance obligation. The sources available do not specify proposed lead time, effective date, or compliance date for the amended requirements, and I will not estimate them.

The comment period closes 25 November 2026. After that, NHTSA reviews comments and may issue a final rule. The sources give no date for a final rule and no indication of the agency's target.

Until a final rule is published, the current text of 49 CFR 571.108 applies in full, including the vertical headlamp arrangement requirements and the existing integral beam test voltage specification. Certification and enforcement proceed on the existing standard.

Pull the full NPRM from the docket and route the regulatory text — not the summary — to your lighting engineering lead and your photometric test house. The two non-ADS changes are the ones that will quietly affect existing programmes.

For the integral beam test voltage change, ask your test lab one question: if NHTSA adopts the proposed specification, does our existing photometric data remain valid, or does the lamp require retest? Get that answer in writing now, while there is no queue pressure. If retest is required across a headlamp portfolio, the lab booking decision belongs in your FY27 budget cycle, not in the week the final rule publishes.

For the vertical headlamp arrangement deletion, flag it to design and styling. A removed constraint is a design option, but only once it is final — do not release tooling against proposed text.

If you are developing an ADS-equipped vehicle without manual driving controls, map every FMVSS No. 108 requirement your vehicle currently cannot satisfy as written, and check whether the proposal resolves each one. Where it does not, say so in your comment, with the specific paragraph citation. A docket comment that identifies an unresolved test procedure gap is materially more useful to the agency than a general statement of support.

If you are considering ADS marker lamps, treat the proposed specification as the likely baseline but verify colour, photometry and mounting location directly from the proposed text before committing to an optical design.

Put 25 November 2026 in the calendar as the comment deadline for Docket No. NHTSA-2026-1519. After that, watch for NHTSA's next FMVSS modernisation NPRMs — the agency has announced forthcoming proposals on FMVSS No. 101 (controls and displays), No. 111 (mirrors and rearview display), No. 126 (electronic stability control) and Nos. 201/208 (sun visors and warning labels). No publication dates for those have been announced.