Numerical simulation plays a key role in design for crashworthiness. Analysis of vehicle structure performance, occupant motion and restraint systems, and occupant/structure interaction are currently tackled by different methods in design offices, using different software and, often, different analysts. However, this paper demonstrates that it is now feasible to adopt a single unified approach. The argument is developed with particular reference to occupant modelling and is supported by quantitative correlations between sled tests and simulation.