Energy Analysis of Vehicle-to-Cable Barrier Impacts
Jennifer Schmidt, Curt Meyer, Karla Lechtenberg, Ronald Faller, Bob Bielenberg, Cody Stolle, Dean Sicking, John Reid
An accident reconstruction technique was developed for estimating the energy absorbed during an impact with a cable barrier system as well as the initial impact velocity. The kinetic energy absorbed during a cable barrier system impact is comprised of several components: (1) plastic deformation/rotation of posts in a rigid foundation or soil foundation; (2) vehicle-ground interaction; (3) internal cable energy; and (4) frictional losses during vehicle-barrier interaction. The energy absorbed by deforming the J-bolt clips was analyzed and determined to be negligible for this study. Charts were developed that estimate the energy absorbed by deforming S3x5.7 (S76x8.5) cable line posts based on the soil condition, deformed post orientation, and deformed post height above the ground. Charts were also developed relating the cable tension to the cable energy absorbed versus the lateral deflection of the vehicle and the frictional energy versus the vehicle's distance traveled for both a straight cable system and an exterior-curved cable system. However, without additional crash testing to verify the relationships, these charts are only applicable to the cable barrier systems for which the full-scale crash tests were conducted. In the straight system impact, the vehicle's estimated initial velocity using the reconstruction technique was 55.1 mph ± 3.0 mph (88.7 km/h ± 4.9 km/h), and the actual velocity of the vehicle was 61.6 mph (99.1 km/h). In one curved system impact, the vehicle's estimated initial velocity was 61.0 mph ± 0.3 mph (98.1 km/h ± 0.4 km/h), and the actual velocity of the vehicle was 61.6 mph (99.1 km/h). In another curved system impact, the vehicle's estimated initial velocity was 63.2 mph ± 2.4 mph (101.6 km/h ± 3.7 km/h), and the actual velocity of the vehicle was 63.1 mph (101.6 km/h). Future improvements for the cable barrier system accident reconstruction procedure are discussed.
Highway Safety, Crash Test, Roadside Appurtenances, Accident Reconstruction, Energy Analysis, Cable Barrier System, and Speed Determination