Crash reconstruction technique for cable barrier systems

Cable barrier systems consisting of steel cables mounted on widely spaced weak posts are one of the most commonly used guardrail systems to protect errant vehicles from roadside hazards. When a vehicle impacts cable barriers, the cables are stretched, producing tension forces that safely redirect the impacting vehicle. The estimation of the energy absorbed during a vehicle barrier crash can aid in accident reconstructions, as it relates to estimation of the initial impact velocity, crash severity, and other accident features such as the occupant injuries during the accident. This article details an accident reconstruction technique developed for estimating the energy absorbed during a cable barrier impact. This absorbed energy comprises several components: (1) plastic deformation and rotation of posts in soil or a rigid foundation, (2) tire-ground interaction, (3) internal cable energy, and (4) frictional losses during vehicle-barrier interaction. Charts were developed to estimate the energy absorbed by deforming S3 × 5.7 posts. Three full-scale crash tests, conducted on straight and curved, three-cable barrier systems were used to validate the proposed methods. For both systems, the vehicles' estimated initial velocities using the reconstruction technique were within 1% and 10% of the actual velocities of the vehicle, respectively.