Injuries to the lower leg are still a frequent occurrence in frontal crashes and the most serious injuries have been found to be associated with the ankle region (pilon, calcaneal and talar neck fractures). These injuries are not only of a high severity, they are also associated with long term impairment, which contributes significantly to the societal cost associated with road traffic accidents. In order to reduce these injuries, the ability to determine the potential injury risk in legislative crash tests as well as the capability to assess the performance of proposed enhanced safety measures in the vehicle footwell region is essential. If this is to be achieved a biofidelic assessment tool with appropriate injury criteria is required.

In Europe, the protection afforded against injury in frontal impacts is currently assessed by the Hybrid III dummy in an offset deformable barrier test. For the lower leg the tibia index injury criterion is used, however this relates primarily to the risk of tibia fracture and is not appropriate for the determination of the risk of injury to the ankle.

This paper reports an overview of the biofidelity of existing dummy legs and the results of a series of PMHS tests which have recreated in the laboratory the more serious ankle injuries seen in real world crashes. The limitations of this work in terms of its application to an ankle injury criterion using peak tibia force for the Hybrid III are discussed and proposals for future work using a different approach are made in order to obtain these important criteria.

The results show the significantly enhanced biofidelity of the THORLx lower leg compared to the Hybrid III leg. The paper concludes that the early introduction of a more biofidelic leg such as the THORLx lower extremity is essential if additional and reliable lower leg criteria are to be usefully implemented.