Cyan Marker Lamps Proposed by NHTSA for Self-Driving Vehicles

A new color for the road

The main U.S. vehicle safety regulator wants to give driverless cars a color of their own. On Friday, October 23, the National Highway Traffic Safety Administration proposed changes to Federal Motor Vehicle Safety Standard No. 108, the federal rule that governs vehicle lighting. The changes would add optional cyan "ADS marker lamps" that tell police and other road users when an automated driving system is driving the vehicle.2427 The notice appeared in the Federal Register on October 26 under docket NHTSA-2026-1519. That opened a 30-day comment period that ends November 25.27

The lamps themselves are only part of the package. NHTSA presented the proposal as a broader update of its lighting rules for automated vehicles. It would also change how manual turn-signal, hazard and beam-switching controls are handled, update headlamp testing for LED systems, and drop outdated rules on where headlamps must sit vertically.28 Administrator Jonathan Morrison said the changes deal with "unnecessary regulatory burdens" for vehicles built without traditional manual controls, while also setting clear performance standards for the marker lamps.27

What the rule would actually require

One point is consistent across the coverage: the lamps are optional. Any manufacturer that installs them would have to meet the federal specification. A driverless car without them would still be legal under the draft.2226 One local outlet summarized the proposal as something that "would require" cyan lamps, but the same article goes on to say the lights would not be mandatory. The more careful reporting, and NHTSA's own wording, make clear this is a permission backed by a standard, not a mandate.28

The technical rules are detailed. The lamps would burn steadily rather than flash, and all of them would switch on and off together. They could only be lit while the automated system handles the whole driving task and nobody inside is expected to watch the road. They would go dark as soon as a person needs to pay attention again.2227 A vehicle could carry one or two lamps on the front, on each side and on the rear, so between four and eight in total. Each would be mounted at least 15 inches off the ground. Maximum brightness would be 125 candela for front lamps. Side and rear lamps could reach 90 candela with the headlamps off, but only 18 candela with them on.13 Cyan could not be built into another lamp, such as a daytime running light, and makers could not add cyan lighting beyond the specified layout.1322

The activation rule matters more than it first seems. Because the lamps may only shine when no human is expected to monitor the road, the Level 2 driver-assistance systems sold on most new cars would not qualify.11 Some early coverage guessed that hands-off systems like Tesla's Full Self-Driving could be included.25 The activation language in the proposal points the other way, and that reading looks like a misunderstanding of the draft.

Why cyan, and where it came from

NHTSA did not invent the idea. The color comes from SAE J3134, an industry recommended practice first issued in May 2019 and revised in December 2025 to add side and rear lamps.13 Red, amber and white already have fixed meanings on a vehicle. The agency argues that the blue-green defined in SAE's standards is different enough from police blue, and much dimmer.11 NHTSA's specification largely follows J3134 but departs from it on brightness limits, mounting locations, combined lamps and the exact color boundaries.1316

Mercedes-Benz did much of the groundwork. The company ran a two-year road test in California from 2023 to 2025 with five vehicles fitted with marker lamps. It also told NHTSA that lamps visible from every direction would help law enforcement without causing distraction or confusion.17 NHTSA also pointed to a survey of more than 4,400 drivers in the U.S., U.K., Japan and Germany. More than 80 percent of the American and British respondents said automated vehicles should carry such a lamp.1113

The gaps in an optional signal

The agency openly admits it cannot measure the benefit. NHTSA says it cannot estimate the safety gains or how many vehicles the rule would affect, given how early the market is.25 It also says it lacks the evidence to justify requiring the lamps on every automated vehicle.11

That is the proposal's weak point. If the signal is optional, a dark vehicle tells you nothing. EVXL points to cars that can be driven either way, where a person may or may not be in charge. In those vehicles an unlit car could have a human driving or an eyes-off system from a maker that skipped the lamps.13 NHTSA is also asking whether states should be barred from requiring the lamps. If finalized, the rule would override parts of California's vehicle code wherever the federal version differs from J3134.13 EVXL says these two positions pull against each other: the agency says the evidence for a mandate isn't there yet, while also considering stopping states from gathering that evidence themselves.13 That criticism seems fair. A lamp is most useful to a police officer when it can be relied on, and an optional lamp cannot be.

An older concern applies too. A Stanford legal scholar warned that if any vehicle shows turquoise when no automated system is engaged, the color loses its meaning for officers and pedestrians.14 China shows how that can happen. Unofficial "little blue lights" spread across driver-assistance models there, and regulators told automakers to stop fitting them.11 By mid-2026, more than 755,000 Chinese-built vehicles reportedly had such lamps, and most of them use Level 2+ systems rather than true automation.18 On October 20, China's industry ministry opened comments on a draft standard that keeps turquoise lamps for Level 3 and above and bans them on everything else.13 The U.S. proposal also keeps the lamp for genuine automation. It does this through the activation rule, not a ban by name.

The lamps also say nothing about what the car is about to do. NHTSA will not let them flash as a signal to pedestrians and says it knows of no research supporting that use.11

The robotaxi context

The timing reflects how fast robotaxi services are spreading. In the same week as the lighting proposal, Waymo said it would add nearly 250 square miles of driverless coverage over about a week across Los Angeles, Nashville, Orlando, San Diego and the San Francisco Bay Area.15 In Orlando alone, Waymo is adding 53 square miles, nearly doubling its service area to 120 square miles.9 In San Diego, which opened to the public only on September 1, the service map is pushing north to La Jolla, UC San Diego and UTC.18

Waymo now serves 15 U.S. metros. On October 14 it opened San Antonio, San Diego and Tampa to anyone with its app, while Denver and Las Vegas still admit riders gradually.7 One industry press release, citing trade reports, puts Waymo's fleet at more than 4,000 vehicles and over 500,000 paid rides a week.10 Waymo, Tesla and Zoox have not been found to publicly support or oppose the cyan proposal.24

The lamps may matter less to Waymo than the other half of the proposal. Under the draft, vehicles without manual driving controls would no longer need a hand-operated turn-signal stalk, hazard switch or beam switch. They would only need some non-manual way to run those lights.27 The agency notes that an automated system "cannot forget that the turn signals are active."16 Several outlets name Tesla's Cybercab, which has no steering wheel or pedals, as the clearest beneficiary. NHTSA's review of how the Cybercab was certified remains open.2226 Tesla has run the Cybercab in limited areas of Austin since September 4.7 Electrek warns that changing rules after the fact for a vehicle that already broke them sets a bad precedent.20

The broader direction of federal policy

The direction of federal policy is clear. Throughout 2026, NHTSA has been removing assumptions about human drivers from its standards. It earlier dropped the manual brake pedal requirement for vehicles driven only by an automated system, and it is drafting its first safety standard for automated driving systems.2227 Most coverage treats the cyan lamp as the friendly public face of a deregulatory package.2327 That framing seems right. Cyan gets the headlines, but the control-requirement changes are what make purpose-built robotaxis easier to certify.

Cyan itself has critics. Writing at The Autopian, Jason Torchinsky argued that blue-green is too easy to confuse with a green "go" signal and suggested purple instead.19 Abroad, the UN's automated-vehicle working party declined in 2022 to recommend mandatory lamps, citing the need for more research.13

NHTSA's proposal sets a common design that the U.S., China and SAE broadly agree on. That should save automakers and suppliers from each inventing their own version. But as long as the lamp stays optional and states may be blocked from requiring it, a missing cyan light will tell people on the street very little.