The relationship of injury risk to accident severity in impacts with roadside barriers

Roadside barriers are homologated in Europe to EN1317, which includes tests for containment (resistance to penetration by an impacting vehicle), and accident severity, measured by acceleration severity index (ASI) and theoretical head impact velocity (THIV). Barriers are classed according to ASI measurement. There has been debate as to whether class C barriers (ASI 1.5 to 1.9) should be considered acceptable from an injury risk point of view, but the debate has been hampered by lack of quantitative correlation between accident severity level and injury risk. This study presents data from three physical crash tests and 50 computer simulations. A small car equipped with crash dummy was impacted into a barrier at a range of speeds and angles, and with variations to the vehicle conditions and occupant positions. Measurements from the crash dummy in the tests and simulations were compared with published injury limits derived from volunteer and cadaver tests and plotted against ASI and THIV. Results showed that, although ASI did show a correlation with injury risk, the level chosen for the boundary between class B and C barriers in EN1317 does not provide significant discrimination between higher and lower risk of injury. However, the EN1317 limit for THIV, which applies to all barrier classes, was found to be a reliable discriminator between acceptable and unacceptable injury risk.