NHTSA Wants Robotaxis to Glow Cyan: Federal Proposal Sets AV Light Standard

By Grace Kim

Robotaxis and other self-driving cars could soon carry standardized cyan-colored lights to signal when a robot, not a human, is doing the driving. The U.S. Department of Transportation's National Highway Traffic Safety Administration announced the proposal on Oct. 23, alongside other proposed federal requirements for automated vehicles.

The bright blue-green lamps would function as automated driving system marker lights. NHTSA said the color would let motorists and law enforcement know when an automated system is operating a vehicle. The agency picked cyan for two reasons: nothing else on the road uses it, and the industry already backs it.

Who chose the color, and why?

SAE International, the aerospace and automotive professional association, recommended cyan for AVs. Its reasoning: a unique color carries a clear meaning, unlike standard light colors such as amber, red, or white. The group arrived at blue-green after consulting manufacturers, suppliers, research organizations, and experts on several potential color options.

NHTSA added that the cyan specifications it proposes differ enough from the blue lights some states reserve for law enforcement or towing vehicles. That distinction matters — a marker lamp that could be confused with a police light would defeat its own purpose.

The takeaway: one color, one meaning, and a shade legally distinct from emergency blue.

What happens next?

The proposal now enters a 30-day public comment period. NHTSA Administrator Jonathan Morrison said in a statement that the rule establishes "clear performance standards for automated vehicle marker lamps" and paves the way for "safe innovation and setting clear rules of the road for automated vehicles."

That language signals the agency wants a uniform national standard rather than a patchwork of state rules — a meaningful step for AV operators scaling across multiple markets.

Mercedes already ran the experiment

Mercedes-Benz introduced turquoise lights in 2023 on its EQS sedan and S-class, permitted that year in California and Nevada. The lights indicate when those vehicles run in the automaker's "Drive Pilot" mode. Mercedes said it worked with engineers, compliance managers, data protection officers, and ethics experts to select the color. The automaker's tests showed teal was clearly distinguishable from both traffic and emergency lighting.

So NHTSA isn't inventing the concept from scratch. It's codifying a practice one major automaker has already road-tested in two states.

Does the color actually communicate anything?

Cyan has one more advantage, and it's cultural rather than technical: it reads as futuristic. The color shows up across science fiction, including Disney's 2010 film Tron: Legacy. Turquoise lights on a Mercedes's exterior mirrors and front and rear lamps, or cyan lamps on a robotaxi, instantly signal "technology" to anyone watching.

Motorists in cities where AVs are already being road tested will likely grasp that the color marks a vehicle as autonomous, electric, or otherwise high tech. Mercedes has suggested educational measures before and during market launch to teach the public what the color means. But even without a campaign, the association with science fiction and the future does much of the communication work on its own.

In plain terms: the color sells the message before anyone writes a brochure.

If the comment period closes without major objections, the U.S. would gain its first federal visual standard for marking automated vehicles — giving Mercedes's turquoise experiment, and every robotaxi operator that follows, a single nationwide color code.