Blinking Brake Lights

Q: I’ve seen a few vehicles where their brake lights flash a few times when they first come on. It certainly gets my attention. Is that something available in new cars, or is it an aftermarket product? And if so, is it legal?

A: Assuming you’re not sending me this question from somewhere in Europe, it’s probably illegal. And when I say probably, I’m 99.9 percent sure it’s illegal. The Federal Motor Vehicle Safety Standards (FMVSS) section on vehicle lighting is about as long as George Orwell’s novel Animal Farm, and way less interesting, so I didn’t read all of it, but from what I did, flashing brake lights are not allowed on vehicles in the US (mostly).

I should point out that you asked if it is legal; not if it’s a good idea. One doesn’t necessarily correlate with the other. In Europe, some new cars come equipped with flashing emergency stop signals. Those kinds of things don’t get added to vehicle safety laws without consideration; driving simulation studies show that a driver’s braking reaction is faster when the car in front has flashing brake lights. In the US, our FMVSS laws still require that brake lights “shall be wired to be steady-burning.” The people who oversee the FMVSS must think less of human ability than their European counterparts; they’re concerned that flashing brake lights would confuse people.

Also, there is a difference between what’s allowed in Europe and what you probably saw on your drive. The flashing emergency stop signals you might find in the EU are set to only come on during rapid deceleration. In normal use, the brake lights would be steady-burning, but if you slam on your brakes in an emergency, they’d flash to hopefully draw the attention of any following drivers. Mercedes, which makes these lights available on some of their European models, estimates that the blinking lights activate about 23 times out of 10,000 brake applications. The infrequent activation contributes to the effectiveness when you really want someone’s attention and avoids “optical pollution.” The aftermarket systems I’ve seen available here blink every time you apply your brakes, which might get your attention, but provide no information on the intensity of the braking.

The FMVSS regulates vehicle manufacturers, dealers, and repair shops, so none of them will install blinking brake lights for you. But what about installing them yourself? The National Highway Traffic Safety Administration (the organization that oversees the FMVSS) has stated that they have no authority over what an individual does to their own vehicle. That doesn’t make self-installed flashing brake lights legal though. It just shifts the legal oversight from the federal government to the states. Washington (like other states) has adopted the FMVSS as state law. The Washington Administrative Code prohibits adding anything that would “impair the effectiveness of lighting equipment” required by FMVSS. You might not think it’s an impairment, but the current rules disagree.

I get why someone would want blinking brake lights. You can be a responsible and focused driver, but that doesn’t have any influence over how attentive the driver behind you is. If you want the blinking lights legally, the only way to do it, as far as I can tell, is to buy a 2006-2008 Mercedes S-class. Mercedes petitioned NHTSA to allow blinking emergency stop lights, and NHTSA granted a temporary exemption (to evaluate effectiveness) allowing the company to sell up to 5000 cars so equipped. That works out to about .00002 percent of all cars on the road, so the odds are high that if you see blinking brake lights, they’re not legal.