Federal regulators propose a special light for driverless cars

The federal government wants driverless cars to carry a special light. The National Highway Traffic Safety Administration (NHTSA) has proposed cyan marker lights, a blue-green color, to show when an automated driving system is operating a vehicle. The goal is to give police and other road users a clear, consistent signal.

What changed

NHTSA released proposed changes to Federal Motor Vehicle Safety Standard No. 108, the federal rule that covers vehicle lighting. The rewrite is aimed at autonomous vehicles. For years, people have debated how a driverless car should tell the world no one is at the wheel. Ideas included flashing text, audio alerts and custom lights. This proposal picks one answer: cyan.

Why cyan

Carmakers already use red, amber, white, and flashing blue or red lights for brakes, turn signals, headlights and emergency vehicles. Cyan is not used for any of those jobs, so it could fill a gap without confusing other drivers.

There is some precedent. Mercedes-Benz won state-level approval for turquoise lights on its Level 3 Drive Pilot cars. The company has since dropped that idea in favor of a Level 2++ system. NHTSA now wants one national standard that companies such as Waymo, Nuro, Zoox, GM and Mercedes could all use.

Optional, but with rules

Carmakers would not be required to add the cyan lights. But NHTSA would set federal standards for their color, brightness and location. Any company that chooses to use them would have to follow the same legal setup, instead of a mix of different colors and signals.

Other rule changes

The proposal also trims rules written with a human driver in mind. NHTSA wants to remove these requirements:

• Physical hazard switches inside the vehicle
• Manual beam shifters
• Turn levers

The agency would also update a 12.8-volt testing standard so automakers can build around modern LED lighting more easily. NHTSA is also considering dropping rules on whether high-beam lights sit above or below low-beam lights.

The bigger picture

This fits a wider Department of Transportation push to speed up deployment of self-driving vehicles. That includes making it easier to build cars without a steering wheel or pedals. Regulators are still enforcing current rules, though. Last month, NHTSA opened an audit query into the Tesla Cybercab. It is examining how Tesla certified the vehicle, which lacks sideview mirrors, pedals and a steering wheel that federal standards currently require.

What is not known yet

This is a proposal, not a final rule. The report does not say when it could take effect or whether the details will change. It also does not say which companies plan to add the cyan lights, since they would be optional.