The relation between crash severity and lower leg responses are studied using mathematical models, not only with the 50th percentile Hybrid III dummy, but also using biofidelic feet model and a female dummy model. A number of countermeasures, including toepan padding and foot airbag, were evaluated in a broad spectrum of crash situations, occupant sizes and foot positions.

The simulations showed that an airbag in the foot area optimized for the most severe crash reduced forces higher than 3.5 kN in the right tibia in most crash situations. However, tibial axial forces were higher in 50% of the simulations with a foot bag optimized for a severe crash than without foot air bag in various crash conditions. The biofidelic foot and ankle model rotated less than the Hybrid III foot. The difference in tibia load was relatively small between the dummy model and the human foot model.

The study shows that an implementation of a countermeasure in cars has to be preceded by an investigation of dummy responses in several crash situations to avoid sub-optimization of the car safety performance.