Why do we analyze collisions?

Topics related to collision & Trajectory analysis formerly on our 'Registrants only' area however which we get asked about frequently so believe shoud be in the open forum too
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brian
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Joined: Tue Jul 14, 2009 10:52 am

Why do we analyze collisions?

Post by brian » Wed Apr 21, 2010 10:46 am

Q: April 21, 2010: In the world, there are lots of softwares used in collision analysis. And the aim is to find delta V and energy losses, right? But why do we need to find delta V and energy losses? Maybe this question seems weird to you but ? wonder the main aim. Actually my question is ' why do we analyze collisions? (rcd via email)
A: Collisions are analyzed for a wide range of reasons:
  • Law enforcement has a need to determine speeds of vehicles in order to ascertain the circumstances of a collision; Who is to blame for the collision? Were any laws broken? Was the accident avoidable? They are mainly looking for the speeds, not the impact speed change.

    Insurance and litigation driven investigations all have a need to determine speeds of vehicles in order to ascertain the circumstances of a collision to find out who’s responsible for damages? There is a need for speed AND impact speed change to determine responsibility AND to determine whether the injury or death from the accident ‘would be expected’ or is unique. Part of the determination of ‘what levels of deltaV do people die or get seriously injured’ comes from the statistical studies performed by the 3rd group of people who analyze collisions:

    Federal, state and private researchers (NHTSA, AASHTO, etc.) all have a need to get a basic overview of the circumstances surrounding groups of accidents in order to determine where and how occupants of vehicles are getting killed and injured. Is it due to driver behavior? Vehicle design? Roadway design? Or some combination of each? Here the DeltaV plays an important role in determining trends. This helps determine possible safety measures to propose to help reduce fatalities and injuries.
The accuracy needs of researchers who look at groups of collisions vary; obviously for some you may want an efficient and economical technique. For example, in statistical studies, since you are looking at large groups of accidents, you may not require great accuracy as you are basically looking for trends. This is why NHTSA as part of the NASS studies simply use damage analysis (first CRASH and now SMASH/WinSMASH (internal 'damage option only' NHTSA version of CRASH). For damage analysis you simply measure the amount of crush and through the stiffness coefficients approximate the energy dissipated in crushing the vehicle and come up with a DeltaV or impact speed change.
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