Timeline of a Car Crash

In designing the Falcon XT, Ford engineers set out to discover the anatomy of a car crash and found that the accident is typically over before we’re even consciously aware of it happening.

This is a reconstruction of a crash involving a stationary Ford Falcon XT sedan being struck in the driver’s door by another vehicle travelling at 50 km/h [30 mph].

0 milliseconds – An external object touches the driver’s door.

1 ms – The car’s door pressure sensor detects a pressure wave.

2 ms – An acceleration sensor in the C-pillar behind the rear door also detects a crash event.

2.5 ms – A sensor in the car’s centre detects crash vibrations.

5 ms – Car’s crash computer checks for insignificant crash events, such as a shopping trolley impact or incidental contact. It is still working out the severity of the crash. Door intrusion structure begins to absorb energy.

6.5 ms – Door pressure sensor registers peak pressures.

7 ms – Crash computer confirms a serious crash and calculates its actions.

8 ms – Computer sends a “fire” signal to side airbag. Meanwhile, B-pillar begins to crumple inwards and energy begins to transfer into cross-car load path beneath the occupant.

8.5 ms – Side airbag system fires.

15 ms – Roof begins to absorb part of the impact. Airbag bursts through seat foam and begins to fill.

17 ms – Cross-car load path and structure under rear seat reach maximum load.
Airbag covers occupant’s chest and begins to push the shoulder away from impact zone.

20 ms – Door and B-pillar begin to push on front seat. Airbag begins to push occupant’s chest away from the impact.

27 ms – Impact velocity has halved from 50 km/h to 23.5 km/h. A “pusher block” in the seat moves occupant’s pelvis away from impact zone. Airbag starts controlled deflation.

30 ms – The Falcon has absorbed all crash energy. Airbag remains in place. For a brief moment, occupant experiences maximum force equal to 12 times the force of gravity.

45 ms – Occupant and airbag move together with deforming side structure.

50 ms – Crash computer unlocks car’s doors. Passenger safety cell begins to rebound, pushing doors away from occupant.

70 ms – Airbag continues to deflate. Occupant moves back towards middle of car.
Engineers classify crash as “complete”.

150-300 ms – Occupant becomes aware of collision.

Mind Hacks corroborates these conclusions, stating that the start of concious awareness is typically found to be around 200-300 ms.

55 thoughts on “Timeline of a Car Crash

  1. TheJonas

    Unfortunately for the engineers the vast majority of airbag deployed accidents are multi-impact.

    I’ve walked away from more than a few. Only one with a vehicle that had airbags, though.

    I can honestly say that despite the multi-impact caveat, I am a true believer in the airbag.

  2. Dude, bricks.

    What I never understood about the crash saftey accident experiments in US.. was why the hell the vast majority take place at 30-35MPH, the car or the object is always stationary, and they were *emphasis* on SINGLE impact events.

    In my world of experience, the driver is usually aware of the impending collision some milliseconds BEFORE the collision occurs, and quite rarely is this long enough to deploy the breaks to slow to within 30MPH and hit a stationary object with no debris to impact the driver through the windscreen. Then again I’m one of the few people whose lack of wearing a seat belt and late deployment of the airbag saved their life during a high speed crash.

    It’s nice to know the crash computer can at least do the same thing as the human brain; it is limited to just about the same response – a crash event is occurring, close eyes to prevent maximum bodily injury. My only problem with the data is the non-real life speed. Change 35 to 60, add a second event, and slice the milliseconds in half. That’s a real crash.

  3. Dude, bricks.

    Sorry, i omitted an important detail, 30mph is supposed to represent a 60mph combined crash speed. God forbid you get hit head on 40, or 60, or hit in the side while traveling that fast by a 30mph car.

  4. Andreas

    Wow thats heavy.
    In one of our german car forum is a link to a self made flash video wish shows (with text and scary music) the other side of a crash. It tells you what happed to your body in ex. with how much g-force your heart will slings against your thorax.

    Its realy scary :-(

  5. UXO

    @TheJonas
    “Unfortunately for the engineers the vast majority of airbag deployed accidents are multi-impact.”

    Err… no. I’ve investigated several thousand car crashes (no exaggeration). In my experience, higher-severity, air bag deployment collisions are predominantly single impact events, and in cases for which there are additional collisions, they tend to be of lower severity (although not always). This is why some of the better, newer-generation air bag systems can independently deploy individual air bags – you might get benefit from a driver’s frontal air bag some time after deploying a side air bag, or a curtain might be useful a couple of seconds after a passenger’s frontal air bag deploys.

    By the way, the answer to the comment by @Dude, bricks is simple: it’s too expensive to design for such energetic collisions, whether in terms of engineering, construction, or operating the TANK you’d need. Energy dissipated in a collision goes up with the square of the speed change, so designing for a 60 event instead of a 30 event would require approximately 4 times the strength. In addition to which, just because the vehicle structure survives, doesn’t mean YOU will – I’ve seen cases in which the person wasn’t struck by anything inside the vehicle (other than the seat belt), but died because the inertia of the blood in the aorta tore through the artery wall, causing them to bleed internally. So, in addition to a ridiculously overdesigned shell, you’d need several feet of foam, air bags, or whatever, to slow you down without killing you.

    Side impacts, as described above, are particularly bad, because there’s so little distance before you hit something hard and unpleasant. You tend to fare better in frontal impacts, which take a fair bit longer, roughly 80-120 milliseconds, and give you a lot more distance between you and the hard bits.

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  7. Daniel A

    Interesting. I was in one single impact collision. The driver pulled off from a side street without warning and I hit the side of his vehicle. I was doing about 30 mph. It’s amazing what happened. It very rare that one notices how slowly awareness takes place. I was driving, and then I registered that my vision was blocked, and then I was sitting in my car, windshield broken, airbag deployed and deflated…and then It took me a second or two to figure out that something had happened. My brain may have registered that there was a car, but not in time for me to have any hope of stopping or altering my course. It’s a very surreal moment.

  8. Bill Sagazoid

    I find interesting that there is no mention of seat belts. I find that there is only one logical reason for safety belts in a vehicle is to simply the identification of the occupants remains. I refer to then as cadaver keepers.

  9. Laurent

    Nice described. Lots of events in just a third of a second. Humans can’t perceive all the events that are occuring so fast. The eye itself has a latency of a tenth o a second. That’s why movies frame rate is more than 25.

  10. ROBOT

    Speed has never killed.
    It is the rate of accelaration or dedeceleration that does the job.

  11. Chuck Norris

    I was aware of the car crash before impact since I saw it coming. Not that it mattered, because I didn’t budge, I’m Chuck Norris, Bitch.

  12. Lloyd Morgan Post author

    @Bill Sagazoid I’m unsure whether you’re being facetious or serious? Nevertheless, seat belts are extremely effective devices and have a well-proven track record.

    In one study focusing on 6237 patients admitted to North Carolina trauma centres, it was found that the use of seat belts reduced the rate of mortality by more than 50%. Not only that, but “patients wearing seat belts also had significantly shorter hospital stays, fewer days in the intensive care unit, and fewer days on the ventilator”.

    Of course, as with everything, there are caveats: seat belts are less effective in lateral impacts than frontal collisions, seat belts can cause injuries and deaths by themselves (‘seat belt syndrome’—lumbar vertebrae separation and paralysis), and of course there’s good old moral hazard (protecting motorists from the consequences of bad driving encourages bad driving). However, the positives still outweigh these negatives, as this quote from a UK study looking at seat belts six years after they became compulsory shows:

    There has been a marked reduction in brain and facial injuries, intra-abdominal solid organ injuries and long bone fractures. On the debit side there has been in increase in the incidence of whiplash neck injuries, thoracic injuries, and intra-abdominal hollow viscus injuries.

  13. Rick Day

    Of course, this means when it comes to a bullet to the head, suicide is painless. You would be dead before you could become aware of it.

  14. Lewis

    You left out the step where the airbag asks Chuck Norris for permission to inflate and then Chuck Norris inflating the airbag with his own lungs. Everywhere. All teh time..

  15. G1

    Been there done that but the bullet did not do the job. Went straight through the head now I got an even bigger hole in my brain. I am now looking for an air-bagless car. Will post the script – hopefully from the afterlife x

  16. Parker

    They don’t show it at any higher speed than 30 MPH because you typically won’t survive a head-on at more than 30 because if 2 cars are going 30mph, the combined crash is 60 and thats considered a high speed crash.

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  18. kk

    > if 2 cars are going 30mph, the combined crash is 60 and thats considered a high speed crash.

    No. Common misconception. Review your basic phyics. Two identical cars hitting each other head on at 30 mph is the same as one car hitting a wall at 30 mph.

    OP, classy post. Thanks for finding the specific numbers and not a bunch of sensationalist pictures.

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  20. me

    @kk >>No. Common misconception. Review your basic phyics. Two identical cars hitting each other head on at 30 mph is the same as one car hitting a wall at 30 mph.

    Err.. NO! That’s like saying a baseball hitting a stationary bat has the same impact as a hitting a swinging bat. I think it’s you who should dig out the physics books.

  21. Trebant

    It sound more like a comercial as to how fast their computers & sensors are then some real study!

  22. Rick

    @KK That is incorrect. The cars are approaching each other at a relative speed of about 60 mph, if both are going 30mph toward each other.

    So both cars’ initial collision experience will be about 60 mph.

  23. Emtucifor

    You guys are thinking about the 2 cars going 30 mph toward each other incorrectly. Stop trying to add speed and think about force.

    What deceleration does a 30mph car undergo when it hits a solid unmovable wall? It decelerates to 0mph in effectively 0 space (yes, it crumples, but the point is that the front bumper stops nearly instantly and then the rest of the car crushes and comes to rest behind it). The force it experiences directly correlates to its speed and nothing else.

    Now if you propel a ball at the wall at 30mph, it rebounds with a certain force. Now make the same throw but remove the wall and have a friend throw an identical ball #2 from the other direction so they exactly collide where the wall used to be. How fast would ball #2 have to be traveling to make ball #1 undergo the exact same rebound and force as with the wall? Obviously, it would have to be going exactly 30 mph.

    See, the wall resists a 30mph crash of a 4000-pound car with exactly the force applied to it: a 30 mph crash of a 4000-pound car. A heavier car traveling faster will hit with more force, but it will resist with that force.

    So I hope you can see now that the only speed an identical opposing car can be traveling to simulate crashing with a solid wall is: exactly the same speed.

    Another way to look at it: if you were in motionless in outer space and you threw a wrench, you would be propelled backwards (or spin yourself, but set that aside for now). If you turned exactly around and then caught a new wrench that was sailing toward you at the same speed you’d thrown the first wrench, you’d come exactly to a stop. Hitting an identical car coming toward you is a bit like “catching” it and coming to an exact stop. The force is exactly enough to make you stop. If it was a bigger car, you’d get pushed backward after impact, and if it was a larger car, you’d push it backward.

    In fact, it would probably be less deceleration forces on your body to hit a car instead of a wall: the cars could interpenetrate or slip to the side or above/below and thus decelerate over a greater distance, reducing the force on you.

  24. Emtucifor

    Er, “directly correlates to its speed and nothing else” >> I wasn’t ignoring force = mass x velocity here, but trying to say that the wall doesn’t have anything to do with the force the car experiences.

  25. Emtucifor

    >> and if it was a SMALLER car, you’d push it backward.

    Please read between the lines as I obviously can’t avoid silly mistakes. :)

  26. Orlandin

    The reason that most crashes are tested around 30 mph, is the fact that beyond that, your chances of survival diminish quickly. An airbag can only deploy so fast before it is considered a hazard instead of a saving point. The 30 to 35 mph rule also comes from the fact that most cities have a city wide 35 mph speed limit unless otherwise posted.

  27. x

    i am really speechless. the breakdown you presented is really scary and will certainly have it in mind when i am driving….. thanks for sharing it.

  28. Bob Sagazoid

    @Lloyd Morgan
    As long as people have the mentality that they will avert serious injury or death by simply wearing seat belts people will continue to disregard and ignore their responsibilities as drivers. I continue to tell judges when they ask me why I continue ignoring the consequences of being fined for not wearing a seat belt, I reply “Your honor, a seat belt ticket is an inconvenience; where as, my head sticking through the windshield is a consequence. This is a consequence I painstakingly try to avoid at all costs, and which a seat belt never plays an active role in.” Out of 17 tickets I’ve only paid the fine twice because the jurisdiction that wrote the ticket was only interested in the revenue the tickets generate.

    Now I will not say I have never been in an accident. I have been in three. The first was when myself and another driver backed into each other in a parking lot. The second accident a result of a punctured diesel fuel tank on a semi-truck during a rain storm causing the vehicle I was in to slide out of control into a river. Being the only one not wearing a seat belt I was the only one able to escape the vehicle after it submerged. My three friends drowned. A third accident involving a herd elk and a power pole let me watch another three friends die. After losing control and striking a power pole avoiding the herd of elk. Myself and one other person were the only ones to escaped prior to the live power lines falling on the vehicle igniting the fuel tank. The two of us were not wearing seat belts.

    These people were not able to undo their belts because the crash computer triggers a mechanism in the seat belt latch that prevents it from releasing, this mechanism does not dis-engage by design. To ensure this feature does not fail another design feature is that the latch is made from steel that is harder than the piece that is inserted into it. When the two pieces are strained the softer piece is deformed preventing it from unlatching. This design is still being used today.

    I have lost 37 friends and family members directly related to injuries caused by seat belts or they’re death was a result not being able to exit the vehicle. Six of those 37 have died when a rib underneath the seat belt breaks and punctures their heart. Four died when the pillar post behind their seat was struck pushing the post down and back causing the shoulder belt to crush their chest and/or break their neck. The remaining ones died in one of three ways of which were burning, drowning, or being struck by another vehicle while being trapped. On another ironic and sad note five emergency personnel were killed at different times while trying to rescue these people from their various accidents.

    So again I will again re-iterate that my description of seat belts as cadaver keepers seems fairly accurate. Seat belts merely simplify the process of recovering and identifying remains of the vehicle occupants. Been there, done this, FAR, FAR, FAR, too many times.

  29. Benjamin Koshkin

    Really cool. It’s hard to beleive that all this electronic equipment responds so quickly.

    Benjamin Koshkin

  30. GeekInput

    It takes 70 ms for this to happen and an idiot to take his eyes off the road to text message someone or pick up a phone call.

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