A steady cyan lamp that switches on when a vehicle is driving itself would become explicitly permitted equipment under the federal lighting standard in a rule NHTSA proposed on October 26, and no manufacturer would have to install one.
NHTSA wrote that it “is not proposing to mandate ADS marker lamps on all vehicles equipped with ADS,” only that any lamp a carmaker chooses to fit must meet the new specification.
Comments on the proposal close November 25, 2026.
The same notice would test integral-beam headlamps at the voltage marked on the lamp, with the specification written in watts rather than fixed at 12.8 volts, drop a rule that places the lower beam above the upper beam in stacked headlamps, confine the requirements for hand-operated turn signal, hazard and beam-switch controls, and their telltales, to vehicles with manually operated driving controls, and replace the word “indicator” with “telltale” where appropriate.
Among those five changes the lamp is the one addition. NHTSA anticipates the package will count as a deregulatory action under Executive Order 14192 if it is finalized, and it has put no dollar figure on costs or benefits.
Two of the control paragraphs it would narrow, S9.1.1 and S9.4, are the FMVSS 108 provisions NHTSA waived for Zoox in July, 11 months after Zoox filed its exemption petition, and S9.1.1 is one NHTSA’s audit of the Tesla Cybercab asked the company to account for.
Key Takeaways
- The cyan lamp is permitted, with no mandate. NHTSA’s October 26 notice sets a specification for any ADS marker lamp a manufacturer installs and says the agency lacks sufficient information to conclude there is a safety need to require one.
- The trigger is a condition, with no SAE level named. The lamp indicates a vehicle “operating without the expectation that an occupant is monitoring the roadway.”
- Four to eight lamps, capped at 125 candela in front. One or two each at the front, each side and rear; side and rear lamps are held to 90 cd with the headlamps off and 18 cd with them on.
- Steady burn, automatic shutoff, no optical combining with another lamp. The lamp may come on automatically when the vehicle enters that mode, must go off automatically when it leaves it, and cannot be optically combined with any other lamp, a stricter line than SAE J3134 or the UNECE draft.
- California’s statute would yield where the specs differ. Vehicle Code sections 25950 and 38750 adopt J3134; NHTSA’s tentative view is that a final rule preempts them on photometry, location, optical combining and the color boundaries, among other points.
- Mercedes-Benz received permits in December 2023. California approved freeway testing of turquoise lights for an initial two years and Nevada approved them on Model Year 2026 EQS and S-Class DRIVE PILOT cars.
- Comments are due November 25, 2026 in docket NHTSA-2026-1519 at regulations.gov.
What the Lamp Would Have to Do
NHTSA’s proposed definition ties the lamp to a circumstance rather than a technology: a lamp “used to indicate when a vehicle is operating without the expectation that an occupant is monitoring the roadway.”
The rule text mentions no SAE level. A Mercedes-Benz with DRIVE PILOT engaged on a freeway and a robotaxi with no driver’s seat both meet that condition.
Any lamp installed must burn steadily. It may come on automatically when the vehicle enters that mode, must go off automatically when a person is again expected to watch the road, and every marker lamp on the car must change state together. NHTSA left out J3134’s ban on a manual switch and asks whether one should be prohibited.
NHTSA asks whether a flashing mode should be allowed for signaling pedestrians and says it has found no research supporting one.
Vehicles without an automated driving system could not carry the lamp at all.
| Position | Lamps | Maximum, headlamps off | Maximum, headlamps on |
|---|---|---|---|
| Front | 1 or 2 | 125 cd | 125 cd |
| Each side | 1 or 2 | 90 cd | 18 cd |
| Rear | 1 or 2 | 90 cd | 18 cd |
Cyan, the blue-green that SAE J578 defines, was chosen because amber, red and white already carry meanings in the standard.
NHTSA says the color “is distinct from the blue hue used by law enforcement” and that the allowed intensities are “substantially less intense than law enforcement lighting,” and the lamp cannot flash, which is why the agency expects no conflict with state laws that reserve blue for police and tow trucks.
A 2023 UNECE draft would let the front lamp share optics with the daytime running lamp, and SAE J3134 lets a marker lamp go dark while it is optically combined with a signal lamp such as a turn signal. NHTSA would allow neither, because a shared optic would shift the perceived color.
A Survey of More Than 4,400 Drivers and Five Mercedes Test Cars
SAE J3134 was first issued in May 2019 for front lamps only, and its December 2025 revision added rear and side lamps, which the American Association of Motor Vehicle Administrators recommends so police can tell whether a person or the software is driving.
NHTSA cites a survey led by Japan’s National Traffic Safety and Environment Laboratory and presented to the UNECE lighting working party in April 2025. It covered more than 4,400 drivers in the United Kingdom, Japan, the United States and Germany.
Upwards of 80 percent of the American and British respondents said automated vehicles should carry a marker lamp, and around 70 percent in each of the four countries said a car’s operating mode should be visible from outside.
Mercedes-Benz presented its recommendations to NHTSA and to the UNECE task force, argued for a 360-degree view of the lamps, and ran a two-year validation in California from 2023 to 2025 with five vehicles to log how other road users reacted.
Mercedes received permits in December 2023: a California permit, limited at first to two years, to test turquoise lights on freeways with the lamps built into the front and rear lamps and both outside mirrors, and a Nevada permit covering Model Year 2026 EQS and S-Class DRIVE PILOT production cars.
California’s Statute Would Yield Where the Specs Differ
NHTSA found at least one state, California, that explicitly permits the lamp, through Vehicle Code sections 25950 and 38750, which point to J3134 and J578.
Because the federal spec departs from J3134 on photometry and headlamp state, lamp location, multiple-lamp arrangements and optical combining, manual activation, spacing from identification lamps, the color boundaries and incidental light from a backup lamp, NHTSA’s tentative view is that a final rule would preempt the California sections there and leave them standing on the rest.
State laws that cap lamp colors, such as Maryland’s, would be preempted only as far as they block a compliant lamp.
NHTSA knows of no state that requires or bans the lamp, believes any future state ban would likely be preempted, and wants comment on whether it should also stop states from requiring one.
If adopted, the rule would take effect immediately.
How to comment. The proposal is docket NHTSA-2026-1519, published at 91 FR 67243. Comments go to regulations.gov, by fax to (202) 493-2251, or by mail to Docket Management, U.S. Department of Transportation, 1200 New Jersey Avenue SE, West Building, Suite W58-213, Washington, DC 20590, and must arrive by November 25, 2026.
What a Cyan Light Would Mean in the Next Lane
Once a final rule lands, a steady cyan glow on the car beside you means its software is driving and nobody inside is expected to be watching the road. Red, amber, white and police blue keep the meanings they have now, and the lamp’s 125-candela front limit matches a parking lamp rather than a light bar.
Whether you ever see one is the automakers’ call. One of them received state permits in December 2023, and the survey NHTSA cites found about four in five American respondents saying self-driving cars should carry a marker lamp. The deregulatory half of the package reaches further, because it removes the rulebook’s assumption that every vehicle has a hand on a turn-signal stalk.
Frequently Asked Questions
What is an ADS marker lamp?
An ADS marker lamp is an exterior light that tells other road users a vehicle is operating “without the expectation that an occupant is monitoring the roadway,” the definition NHTSA proposed on October 26, 2026. ADS stands for automated driving system. The lamp burns steadily in cyan, may come on automatically when the vehicle enters that mode and must go off automatically when it leaves it.
Is NHTSA requiring cyan lights on self-driving cars?
NHTSA is proposing to permit the lamp, with a specification any installed lamp must meet. The agency wrote that it “is not proposing to mandate ADS marker lamps on all vehicles equipped with ADS” and that it “lacks sufficient information to conclude that there is a safety need” to require one. A manufacturer that skips the lamp faces no new obligation.
Why cyan instead of blue or green?
Amber, red and white already carry assigned meanings in FMVSS 108, and NHTSA chose the blue-green that SAE J578 defines as cyan in part because it is distinct from the blue many states reserve for police and tow trucks. The agency expects no conflict with those state laws because the lamp is held to far lower intensities and must burn steadily rather than flash. The proposed cyan boundaries match SAE’s blue-green boundaries, while FMVSS 108 keeps its existing green and blue boundaries, one of the points where the proposal departs from J3134.
How many lamps would a car carry and how bright would they be?
Four to eight: one or two at the front, one or two on each side and one or two at the rear, all mounted at least 15 inches off the ground. The front lamp is capped at 125 candela, the same as a parking lamp. Side and rear lamps are capped at 90 candela with the headlamps off and 18 candela with them on.
When would the lamp switch on?
The lamp may come on automatically when the vehicle begins operating without the expectation that an occupant is watching the road, and it must go off automatically when that expectation returns. All of the car’s marker lamps must switch together. The proposal omits SAE J3134’s ban on a manual switch and asks commenters whether one should be prohibited.
Could the lamp flash to signal pedestrians?
The proposal requires a steady burn. NHTSA asks for comment on a flashing mode that would communicate a vehicle’s intended movement to pedestrians, and says it is aware of no research supporting that use.
Would a hands-free driver-assistance system get the lamp?
The rule text names no system and no SAE level. It ties the lamp to a single condition, operation without the expectation that an occupant is monitoring the roadway, so a system that still requires the driver to watch the road does not fit the definition, and the rule bars the lamp from any vehicle without an automated driving system.
Which cars already have turquoise self-driving lights?
Mercedes-Benz received a California permit in December 2023 to test turquoise marker lights on freeways for an initial two years, with the lamps built into the front and rear lamps and both outside mirrors, and a Nevada permit covering Model Year 2026 EQS and S-Class DRIVE PILOT production vehicles. Mercedes also ran a two-year, five-vehicle validation in California from 2023 to 2025, which NHTSA cites in the proposal.
What happens to California’s turquoise light law?
California Vehicle Code sections 25950 and 38750 permit ADS marker lamps built to SAE J3134 and J578. NHTSA’s tentative conclusion is that a final rule would preempt those sections wherever the federal specification departs from J3134, including photometry, lamp location, optical combining and the color boundaries, and leave them intact elsewhere.
When would the rule take effect, and how do I comment?
NHTSA proposes immediate effectiveness if the rule is adopted. Comments are due November 25, 2026, in docket NHTSA-2026-1519 at regulations.gov, by fax to (202) 493-2251, or by mail to Docket Management, U.S. Department of Transportation, 1200 New Jersey Avenue SE, West Building, Suite W58-213, Washington, DC 20590.
What else is in the FMVSS 108 proposal?
Four changes that remove or narrow requirements: integral-beam headlamps tested at the voltage marked on the lamp with the specification in watts rather than at 12.8 volts, removal of the rule that places the lower beam above the upper beam in vertically stacked headlamps, limiting the manual turn signal, hazard and beam-switch control requirements and their telltales to vehicles with manually operated driving controls, and replacing “indicator” with “telltale” where appropriate. NHTSA expects the package to qualify as a deregulatory action under Executive Order 14192 if finalized and has not quantified costs or benefits.
Michael Kahn
Michael Kahn is the writer, photographer, and publisher behind The Weekly Driver. He cares about how cars drive and what they're like to own. He covers automobile industry news, car shows and events, and new car reviews. The reviews come from behind the wheel: day trips that favor back routes, treating a good meal as half the reason to go. He directs and produces the visual media, matching each car to a setting and mood that fit it. When he's not reviewing new cars, Michael races paddleboards, camels, and ostriches, along with the occasional exotic car on the racetrack, and has driven in every state and country visited.
https://theweeklydriver.com
