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.
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’.