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Anonymous Poster

Accident Reconstruction

04/12/2009 6:44 AM

How to calculate the impact speeds of two vehicles colliding? What factors are involved in determining the collision speed? If we can estimate collision speed of two colliding vehicles, how to calculate the initial speeds before application of breaks.
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edignan
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Engineering Fields - Systems Engineering - New Member Popular Science - Weaponology - New Member

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#1

Re: Accident Reconstruction

04/12/2009 1:40 PM

NOT MY FIELD DISCLAIMER

But I understand later model cars they just strip the ABS computer, most of which have a tattletale.

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mayt2u
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#2
In reply to #1

Re: Accident Reconstruction

04/12/2009 4:16 PM

I think they have an actual 'black box' located under the center floor boards. This box has to be cut out using metal cutters. The boxes have 6-10 parameters in them. They stop recording if the air bag is deployed. The parameters range from engine speed, throttle/brake position, g-forces 3 way etc..

If your looking to do this stuff yourself, any High School Physics books have it in the first few chapters. Good luck.

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Jaguar
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#3

Re: Accident Reconstruction

04/13/2009 2:13 AM

It was roughly explained to me a long time ago. It's all basically energy in, energy out and friction.

The knowns:

  • direction of travel of both vehicles before impact
  • mass of both vehicles before impact
  • point of impact
  • direction and distance of travel of vehicles after impact
  • mass and direction and distance of travel of parts separated from the vehicles
  • road surface type and coating due to weather conditions if any (rain, snow, ice, fog, condensation, oil (at intersections especially))
  • tire type and size
  • length of all skid marks

With that information and applying common equations for mass, friction, energy and vectoring, the total energy of each vehicles at the time of impact can be determined. Working back from there determines the speed of each vehicle.

Lawyers often call upon recognized experts in this field when putting together major cases.

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