Traffic accident analysis and reconstruction are the processes of scientifically analyzing available evidence to determine what happened in a traffic collision. The results of the reconstruction are used to explain how and why the accident happened (causation & liability issues) or how it could have been prevented. Typical reconstruction results include time, speed, and position histories for the involved vehicles at relevant points in the collision sequence, in addition to collision severity assessment. The reconstruction forms the foundational basis for other technical analyses, including human factors, biomechanics, injury causation, restraint system performance, and product liability.