No matter how terrible and split-second an accident, in their aftermath many vehicles have their hazard-warning lights flashing.

Is this a feature of modern vehicle management systems: to automatically activate hazard lights on detecting a collision?

I'm curious because the alternative, that people in accidents have the foresight to activate hazard lights in such circumstances, would tell me something unexpected about human nature.

  • 1
    What are you using as your litmus for hazard-warning lights being on after an accident? IOW: What makes you think hazard lights are being used at all in any accident? What is the percentage of accidents where the warning lights are used? As far as I am aware, there's no automatic feature to turn warning lights on in an accident, but I might have missed something somewhere. Jun 26, 2018 at 23:43
  • News footage, primarily. Here are two collisions from today's news in Europe. The former instantly killed the driver and mangled the driving area, but the hazards were clearly on. The latter you can see them come on as the attacker rams the building. Both, very different circumstances seem unlikely situations to turn to a hazard switch on a dash. bbc.co.uk/news/uk-england-cambridgeshire-44612842 bbc.co.uk/news/av/world-europe-44619097/…
    – user31414
    Jun 26, 2018 at 23:54
  • I've seen a few videos on the YouTube in which a crashed vehicle has instant flashers. It appears almost exclusively non-USA video footage, however.
    – fred_dot_u
    Jun 27, 2018 at 0:13
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    Yes. It was a feature of BMWs for many years; probably still is. The SRS "airbag" computer triggers this based on impact sensors.
    – SteveRacer
    Jun 27, 2018 at 1:36
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    @Solar Mike: AFAIK most modern vehicles unlock the doors upon detected accident (at least those that automatically lock when you drive). Also most modern vehicles will turn on warning lights upon impact or even emergency-braking. Cutting the power would disable warning lights, unlock feature, emergency call and the ability to move the vehicle from a dangerous place, if it´s still moving.
    – Daniel
    Jun 27, 2018 at 8:17

1 Answer 1


Yes, modern vehicles do this. They can also activate the hazard lights in an emergency braking situation, so even before/no impact.

I experienced this firsthand when attending a driving seminar where we practiced emergency braking, skidding etc. - where another attendee had a newer Mercedes, which kept blinking away at those exercises.

In the future EU-Vehicles will most certainly be required to automatically call emergency services in an accident too, and some cars already have this feature.

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