This is a fascinating run down of an ‘anatomy of a crash’ from Australian car magazine Drive suggesting that the accident can be 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.
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.
The video of the crash test, from which is the above is taken, is also available online.
As you can see, it’s a lab-based crash test and so doesn’t capture the messiness of many real world impacts.
I checked out their figure for conscious awareness kicking in at 150-300ms and it seems to be accurate and mostly taken from the work of neuroscientist Benjamin Libet.
There’s a good 2004 review article from the Archives of Neurology that actually cites 300ms as the start of conscious awareness, some other reviews cite 200ms as a ‘rule of thumb’ figure.
Link to Drive on ‘Anatomy of a Crash’ (<a href="http://www.sentientdevelopments.com/2009/02/will-you-perceive-event-that-kills-you.html
“>via Sentient Developments).
Link to paper on ‘Neuronal Mechanisms of Conscious Awareness’.
Mind Hacks 
True, but surely this is trivial. We sense events 150-300ms late *all the time*. This means that, while the accident has already happened, it makes no difference to any observer of that event. What the article and your post suggests, probably unintentionally, is that in a high speed crash we are not aware of anything happening until it’s “too late”. But of course our “rate of experience” varies little in relation to the speed at which events unfold. Doesn’t it?
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