Crash reconstruction technique for longitudinal barriers

A procedure for reconstructing run-off-road accidents into longitudinal W-beam guardrail systems was developed by estimating energy dissipation during an impact. Correlations were developed between the vehicle's departure angle, velocity, type of vehicle, and the energy dissipated. Energy losses are due to (1) barrier-vehicle friction; (2) post/soil deformations; (3) guardrail beam deformations, and (4) vehicle energy losses attributed to the vehicle (this is composed of actual vehicle damage and tire-ground friction, with vehicle damage being predominate). Barrier-vehicle friction losses were found to range from about 5 to 36%, depending upon speed and impact angle. The energy to cause permanent deflection of the guardrail posts in a system was found to be roughly equivalent to the amount of energy dissipated by the rail deformation of that system. Comparisons with full-scale crash test results showed that the developed iterative reconstruction procedure accurately estimated impact velocities within 3%.