Home / Experts/Tech / Why Flashing Brake Lights Are The Cheap Safety Feature You Never Knew You Needed, And Why They’re Banned From The U.S.

Why Flashing Brake Lights Are The Cheap Safety Feature You Never Knew You Needed, And Why They’re Banned From The U.S.


In the beginning, there was the brake lamp, and it did a decent job. Granted, it wasn’t perfect. Trucks, elephants, and people on penny farthings couldn’t really see low-mounted brake lamps, nor was there an extra method of redundancy should low-mounted brake light bulbs burn out. That’s why the National Highway Traffic Safety Administration mandated high-mount stop lamps on cars in 1986 and on light trucks and vans in 1994. There were a few missteps at first, notably the Chevrolet Lumina APV minivan’s center brake light mounted below the main brake lights, but eventually everyone sorted their shit out and the center high-mount stop light was properly implemented on America’s roadways.

But what about different brake lights for different purposes, say a standard illumination for when you’re slowing down and a super bright illumination for when you’re doing a panic stop and don’t want to become a Cadillac DeVille’s new hood ornament? Depending on what you drive, you may already have this rather wonderful feature.

As with many other safety solutions from the three-point seat belt to the crumple zone, emergency stop signals are originally a European phenomenon. The first stability control-dependent emergency stop signals were fairly crude. Heavy braking would get picked up by the stability control, which would send a signal to the lighting control module and illuminate extra bulbs in the tail lamps on Y2K-era BMW E39 5-Series executive cars equipped with the LCM3 lighting module, E46 3-Series compact executive cars, and X5 midsize luxury SUVs. Since then, emergency stop signals have spread to Volvos like the second-generation S80 sedan and Mercedes-Benzes like the mid-2000s S-Class executive barge. I’ll admit, emergency stop signals are one of the little touches I really appreciate on my 3-Series. Call me a spoiled prat, but I don’t see why other cars don’t have this wonderful feature. Here’s a quick visual of how emergency stop signals, or Dynamic Brake Force Display in BMW-speak, work on an E90 3-Series.

E90 emergency stop signal
Photo credit: BMW

Kinda brilliant, right? As with most pieces of technology, emergency stop signals have grown to be much more impressive than they were in the era of Backstreet Boys and American Pie. Mercedes-Benz was the first to market with brake lights that would flash at 3-5 Hz under emergency braking from speeds above 31 mph (50 km/h), a system that has since been mandated across the European Union. While a few aftermarket companies offer flashing brake light modules, specific control parameters that only flash the lights under emergency braking are really where it’s at. Here’s a brief video on the Mercedes system in action.

However, such advancements come with caveats. Because of outdated North American lighting standards, Americans can’t actually have these fancy flashing brake lights. See, FMVSS 108 is the governing document for vehicle lighting in America and section 5.5.10 states that all lamps that aren’t headlamps, turn signals, hazard warning lamps, side marker lamps or school bus warning lamps “shall be wired to be steady-burning.”

In 2005, Mercedes-Benz petitioned the NHTSA to allow up to 5,000 cars with flashing emergency stop signals on American roads, and was firmly denied. It’s rather infuriating to see, considering the evidence in support of flashing emergency stop signals.

One 2014 study found that flashing brake lights reduced the reaction times of participants by 10 to 21 percent given a following distance of two seconds or greater and reduced collisions by 90.9 percent over standard brake lights. Yes, this means that some simple flashing lights could be more effective than automatic emergency braking and wouldn’t require a radar sensor in the grille or cameras in the windscreen. With such an improvement to offer for the low, low price of $free.99, its genuinely maddening that flashing emergency stop signals aren’t allowed in North America.

[Editor’s Note: Part of the issue with flashing brake lights in the US market is that America remains the lone global holdout for allowing red rear turn indicators. The issue with flashing brake lamps is that in the US, they could be mistaken for turn indicators or hazard lamps, a problem that doesn’t exist in the rest of the world where indicators are amber. Sure, we Americans came up with the transistor and the Hot Pocket, but we can be idiots, too. – JT]

Fortunately, intrepid owners of certain late-model cars who value the safety of flashing emergency stop signals over legality aren’t completely out of luck. It’s entirely possible to code flashing emergency stop signals into a late-model Audi, BMW, Volkswagen or Mercedes-Benz, with a variety of forum posts detailing the coding for each model. Yeehaw, fuck the law, am I right? Hopefully the tortoises behind American tail lamp legislation can eventually right this wrong and bring the wonderful lighting innovation to the masses. One can only dream.

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71 Responses

  1. My 2012 Audi will automatically kick on the hazard lights if I panic-brake, though I don’t believe it is a factory option on North American cars. I have always had the habit of switching on my hazards when I see traffic ahead on the freeway or am braking harder than normal.

  2. I like this, if and when the braking is actually a panic or emergency stop, which _is_ what the Mercedes video demonstrated.

    Other taillight related irritations.

    1. The flashing cyclops (third brake light) operate on all brakes presses no matter what. Many new cars seems to have this. I hate it with the heat of a thousand suns! I could accept the flashing, like above, was a panic stop.

    2. Red turn signals, don’t need to explain on that one.

  3. I’ve added flashing brake lights to motorcycles. They’re a common add-on; they don’t replace the factory stop lamp but are mounted adjacent to it. They seem to catch drivers’ attention earlier than a standard brake light does, judging from what I’ve noticed in my mirrors.

    1. Same here. For a motorcyclist, being rear-ended while stopped at an intersection is a frequent cause of accidents (aside from a emergency stop). MSF training says to always check mirrors when stopped at a sign/light for this reason. If I see a vehicle approaching from the rear when I’m stopped, I release and then touch the brake lever and they flash four times and then stop (no recycling). Almost always, anecdotally the car behind stops further back than if I hadn’t (that happens too : -)

      I’ve heard this bit of wisdom about car-motorcycle accidents: “The car driver isn’t looking for a bike, they are only checking for the absence of a car.” e.g., a car isn’t in the space they plan to use when looking for a gap in oncoming traffic to make a turn, coming to a not-quite full stop, switching lanes…

    2. Honestly I’ve found these, along with the flashing/strobing headlight to be more distracting than helpful. I think since it’s not common people might mistake it for a bad light/bulb or something. I think if we did adopt the emergency blinking the public would better handle situation. Saying that, I do flash my brake lights at times coming to a stop to “grab attention” then just solid.

      Of course, none of this matters when people are looking at their phones.

    3. I’ve seen those but mostly on Harleys, and almost always wired to the main stop lamp. I find it very annoying, because mostly I notice it when I’m stuck behind a pack of middle aged suburbanites bumbling along at five under, wobbling a bit, and hitting the brakes all the time. All that flashing gets annoying really fast.

  4. Okay, this explains why I’ve been increasingly seeing er, poorly-done tuner cars with an aftermarket/black market version of this feature.

    They seem to flash at a constant rate no matter what kind of braking, which is actually super distracting in normal braking situations, at least to me.

    1. The aftermarket ones I’ve experienced flash a few times when brake is first applied (no matter how hard) then change to steady light. If the brake is lifted and re-applied within 10 seconds of the initial brake application, the brake light won’t flash and stays solid. It makes sense since my old tuner car is 1/6th the size and weight of anything Ashleigh-Marree-Lyn is driving with their eyes glued to their phones.

  5. After I learned in my 20’s (mid 90’s) that European drivers would hit the hazards when emergency braking, I made it a habit. Seems like a no-brainer, and dumb that it wasn’t taught in drivers ed here.

    1. You add the step of reaching for the hazards indicator to the process of emergency braking?
      Like you actually dedicate a hand and a thought process to reaching for the hazards when “OMG I need to brake NOW” happens?

      1. I do it if I’m on the highway, coming up on a sudden traffic jam, and there’s no-one in the lane behind me. My reasoning is that the next person to show up back there is going to be charging straight toward my ass at 75 mph, and I want them to have every possible chance of noticing me in my tiny old Miata before they shove my entire face under the bumper of whatever brodozer I am stuck behind. Once someone else has successfully come up behind me without totaling my beloved NA and/or causing my accidental beheading, I turn them back off.

        1. I just ordered one to splice into the brake light on my 2010 Miata. This one blinks 3 times upon initial press then stays steady. If you release and reapply brakes within 10 seconds, it doesn’t start blinking. Lights have to stay off for more than 10 seconds before the pulse cycle starts. Seems like a low cost way to avoid getting it in the rear end (as that’s just not the way I roll 🙂 )


      2. I learned about the OODA loop in my 20s too.
        many things happen when I need to emergency brake:
        observe: how much time do I have? What are alternatives? (change lanes, put it in the ditch, etc)
        orient: prioritization of alternatives. what is going on behind me?
        decide: pick the best option
        act (assuming an emergency stop is the right choice): one hand on the steering wheel to stop. one hand hits the flashers and then goes to the wheel (if slippy) or to the gearshift. One foot on clutch (if I don’t have time to take it out of gear), one foot on the brake. modulate brakes, focus on car control. be prepared to change tactics. back to the top of the loop

      3. In truly emergency braking, it’s difficult to have added the muscle memory to go for the flashers, but in most situations (for me) just shy of full-on emergencies, I usually have the presence of mind (and enough muscle memory at this point) to smack the hazard button. Luckily for me, the hazard button is by itself and right on top the center dash, so there’s little need for accuracy.

          1. Unlike those of us with questionably designed older domestics.

            My Fords have them on the steering column near the gauge cluster. An ’80s Chevy I used to have had it on the *underside* of the column no less. No quick emergency use there!

      4. It’s useful when you’re on a motorway (highway) when you can see the traffic ahead of you is stopped rather than just slowing down. In situations like that, as long as you’re paying attention and not tailgating the car in front, you should have several seconds to start braking, reach out and put the hazards on, and put your hand back on the wheel.

    2. The reason this isn’t taught is that if you are in a car with red turn signals that are shared with the brake lights (ie. lots of cheap domestic cars), by doing this you may actually be disabling 2 of your 3 brake lights. Ask anyone from the rust belt about people driving with hazards on at highway speed in blizzard conditions. It’s absolutely dangerous on cars equipped like this.

      1. Agreed, in the Midwest driving during thunderstorms I use the tail lights around me to help ensure I am on the road and maintaining my lane. Hazzard flashers give that brief second of doubt/confusion that could be dangerous.

      2. In bad enough conditions, the hazards are the only way the car behind you is going to know you’re there. Regular taillights aren’t bright enough. I had to do it last year, and its terrifying having semis appear next to you going at least 20mph faster.

    3. Turning your hazards on when you’re not a disabled vehicle is next-level stupid.

      Nobody around you is going to understand what you’re trying to convey because you’re doing something differently than how everybody expects it to be done.

      Also, there’s a good chance your hazards and brake lights are the same lights.

      Also, you should have been focused on controlling your vehicle.

      “Seems like a no-brainer”…. yeah. That’s for sure.

      1. So if you come upon a sudden stop in a highway where there is poor visibility due to rain/snow/fog you’re not going to turn on your hazards? There’s a reason they’re called hazard lights, not disabled vehicle lights.

        Definitely disagree 100%. I have hit, and have seen others hit, hazards during emergency braking once the brakes are on and the car is under control. Anything to get the driver behind’s attention away from their cellphone, makeup, etc.

      2. Turning on your “hazards” when traffic is approaching a “hazard” (such as unexpected stopped traffic) seems entirely appropriate to me.

        People who can’t eventually understand why you’re doing it seem exceptionally dim.

        For drivers whose cars use the brake lights as four ways, an option is to repeatedly stab the brake pedal, even after you’ve slowed down most of the way.

  6. The problem with this is that it’s an arms race.

    Been to a construction site or factory lately?

    We used to put reverse beepers on heavy equipment. Then we started putting them on anything that moves. Then on anything that moves in any direction. Now there’s just constant high pitched beeping from all directions at all times and none of it gets your attention.

    The same will be true for brake strobes. They get your attention now because their _unusual_. But once everybody has them you’ll have to do something even more obnoxious to stand out.

  7. I coded these into both my wife’s and my Minis. The nice thing is when coding it, there’s different levels to engage the flash. @ 5kg, 7kg, 9kg of force on the pedal. I have mine set to the middle setting. Sad part is, I have no idea if it works/what it looks like! Same reason people barely ever know if they have a brake light out.

  8. Anecdotal, but my fiancées 2018 Mazda3 has brake lights that flash a couple times when braking. Not sure if there’s a speed at which that cuts off, but I’ve definitely seen the center brake light flashing during normal braking. I guess there’s some concession for it somewhere as I’ve seen flashing brake lights on other late model vehicles and I’m seeing comments to that effect as well.

    Using the VCDS diagnostic/coding tool, I checked a box that will make the lights in my Jetta Sportwagen flash, but only on hard, emergency braking.

  9. I’ve got an aftermarket option on my motorcycle. It’s not based on braking force, but rather the time since I last triggered the brake light. If I’m in stop and go traffic, it acts like a normal brake light. If it’s been a few minutes since I last braked, it’ll flash a couple times. If I tap the brakes and then hold, it’ll flash it’s brains out. It’s configurable and I think it’s worthwhile, though I was never rear ended before using it, it haven’t been rear ended since I got it ~5 years ago.


  10. Frankly, what I needed when I lived in Ontario was a brake light that came on whenever I stoped accelerating. The number of times I was nearly rearended when I disengaged the clutch to shift into second while pulling away from a stop light was truly frightening.
    That and a brake light for when you downshift. I’ve had drivers tell me that my brake lights weren’t working when the reason they didn’t come on is that I wasn’t using the brakes.

  11. I agree that a brake light that flashes on a hard stop is likely useful, especially once the majority of drivers become aware of the feature and understand what they’re seeing when it happens. However, the aftermarket kits that flash the brake lights at the slightest touch are annoying and potentially dangerous.

  12. I don’t know about other parts of the country, but I see these all the time in Chicagoland. I’ve never considered them particularly useful, it seems like they’re only on the most annoying vehicles on the road

  13. Re: BMW E90 3-Series brake light behavior — “. . . as long as the rear fog light is not switched on.”
    Er . . . “rear fog light”? Wha?!?!
    (I need to get out more often!)

    1. Mostly a European thing – cars will have an extra set of the taillamps that don’t normally illuminate, but can be switched on manually when driving in adverse conditions. On my Audi, they are in the middle of the light and come on at full brake light brightness.

  14. As others have said, these are popular aftermarket add-ons at some car dealers (particularly popular in Las Vegas for some reason), and being behind plenty of cars with flashing brake lights every time they apply the brake pedal has ruined the concept of this for me. Yes, I realize the OE style ones would only flash under hard braking, but the train has already left the station with aftermarket ones on the market and they’d diminish the effectiveness of the OE configuration.

    1. Yep, this has been ruined in the US by those stupid things.

      I really wish they would ticket people for illegal lighting modifications to their cars. I suppose some would be hard to prove, but a flashing CHMSL is a pretty easy slam dunk.

  15. A co-worker at my previous job entered an internal design contest submitting a brake light with our new at the time accelerometer to control the rate of flashing. Light braking flashed the light slowly and the flashing increased with the rate of deceleration. He won an HDTV with the idea, back when HDTVs were still relatively new. Of course, being that we were a semiconductor mfgr., not an auto parts mfgr., nothing ever came of the idea.

  16. Been driving in Europe the last week – and even in a modest little ’22 Opel Corsa I am impressed by the amount of safety tech they get in standard autos. It’s got lane assist, street sign recognition, driver alertness monitoring, hill assist and great lighting all around.

  17. When I was in Malaysia a decade or so back, many cars and buses had a red gumball light in the rear window that came on with the brake lights. That was distracting since it stayed on with the brake lights.

    The flash three times on hard braking is useful.

  18. I agree with everybody’s criticism of those aftermarket brake lights that flash no matter what. Very annoying. But the panic stop flashing is a great safety feature.

    My previous Audi A6 (C6 pre-facelift) had the option to program “brake light amplification”. It had an LED strip at the top of the rear lights that was the standard brake light (and turn signal in NAR vehicles) and below it it had three dual filament bulbs that would only act as tail lights, but with the feature activated would come on as additional brake lights with the brighter filaments when breaking hard, more than doubling the brake light surface area.

    Another feature that many premium European cars had, is that they used dual filament bulbs even for locations where the default is a single function (usually tail light). They are then activated when another important bulb fails, turning the tail light into a combination tail/stop/turn light until the separate defective break light/turn signal bulb has been replaced.

  19. I have aftermarket flashing brake lamps on both my motorcycle and my tiny Mazda. Where I live I’m surrounded by meth heads in lifted pickups, so I’m taking no chances. Yes, they’re annoying but that’s the point.

  20. I’ve mentioned this to Mr. Torchinsky before on the tweeter. But my idea for this issue was to have the third brake light grow in size (or width) sequentially with deceleration.

    In other words, the third brake light would be very small (or illuminate only one or two LED bulbs at its center) for a light tap of breaks; but in an emergency braking situation, the full width of the third brake light would illuminate. A very wide third brake light, therefore, would be able to display with more precision the varying degrees of deceleration between a light tap and an emergency braking maneuver. The third brake light could also function as a rearward indicator of speed or mostly lack thereof – with a stationary vehicle at 0 mph illuminating the full width of the third brake light.

    This would function best if it were federally mandated, and all new vehicles spoke the same third brake light language. That way everybody on the road would know what that brake light ahead is trying to say to them.

    No annoying flashing lights. Still communicates how urgently the vehicle behind you needs to stop. Problem solved. I’ll take my check now. Thanks.

    1. To me, the biggest missed opportunity in the history of brake lights has always been that it’s not orange for car on/in motion but no brakes applied, red for brakes applied.

      I get the why, but still makes me wonder from time to time.

      And by now, we’d be getting to single lamps that did a color gradient as you braked harder, just like your idea.

  21. A lot of police cruisers around here have brake lights that will give three bright flashes before coming on steady, regardless of how the brakes are being used. Apparently that’s illegal? I mean, I’m sure there’s an exception for cops because of all the other crazy flashers they need to have, but what’s good for the goose is good for the gander, right?

  22. I’ve seen the bumper-mounted lights on XC60s light up before. It was an ‘oh-shit’ braking event and as a Volvo-guy having those lights come on unexpectedly was definitely an attention-grabber, though I do wonder if it would have the same effect for a regular motorist who isn’t familiar with the XC60’s brake light pattern.

  23. I really don’t like the idea of blinking break lights. I have been behind them on the road, mostly Wranglers and Rams, and in normal driving conditions it is distracting. I understand the point is to get my attention, but on my normal commute to work in normal conditions where I should be able to softly break, the blink makes me think I should hit my breaks hard since they are having an emergency. Dangerous for the people behind me, but I’ll be the one getting hit and not that Wrangler, so if that’s the goal it works.

    Btw, I also hate when LED daytime running lights turn off on one side when that turn signal is on. Just another thing to distract me from simple driving.

        1. There is still another one to do that. And the purpose of a turn signal is to signal your turn. Car makers feel that having a nearby DRL on near it may obscure the turn signal, which would defeat the purpose of the turn signal.

  24. My Nissan Pao’s concessions to safety are as follows: seat belts. That’s it. Maybe it has crumple zones, perhaps there’s a collapsing steering column but I’m not sure about either. As I’ve had two cars destroyed by rear end accidents, I now run these strobing brake LED bulbs. They flash 8x for one second then are continuously lit. An absolutely great upgrade for me and an illegal one too as any kind of flashing is verboten in the USA. Oh well, I don’t care, I’m using them anyway.

    1. These are actually very reasonable as a retrofit in my opinion. Your taillights are small and your car is positively tiny by today’s standards. There is obviously no way to make them flash under emergency braking only, so this is great. It’s a way better than the terrible 3x slow flashing LED brake lights I have seen that appear to actually delay the illumination of the brake lights. Those ones need to go!

    2. I think you are more likely to have someone run into the back of your car now that you have flashing brake lights.

      The only time I have seen flashing brake lights was in India. My reaction though was “WTF?”. Had I been driving, that would have increased the time before I applied the brakes. Anything that doesn’t fit into our expected patterns needs processing (which takes time), instead of an instinctive response.

      1. Nope. My video doesn’t do them sufficient justice, they grab your attention in a way that other brake lights can’t. There’s a set of these on our B2300 and following my wife in traffic I can assure you they stand out.

        Even if you’re not using strobing LED brake lights, it’s worth upgrading to LEDs because they fully illuminate instantaneously rather than the half second it takes an incandescent bulb. Sometimes that’s the difference between driving your Triumph TR6 home after a light tap on the bumper and having the bumper shoved two feet into the trunk. Ask me how I know.

        1. Whether they stand out or not is not the issue.

          It’s an issue of whether the driver of the car behind you instinctively reacts; by having something different from normal brake lights, he may not have an instinctive reaction to deal with your different lights.

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