This paper proposes an idealisation for the manner in which the fronts of cars deform in the course of an impact. This idealisation has a number of features, firstly that the car fronts deform in a geometric manner which depends on the type of impact under consideration, secondly that all the crushable elements of the car front absorb energy by the extent they deform rearwards, thirdly that the energy absorption properties are uniform across the width of the car front, fourthly that the energy absorption behaviour of the individual car type in the full width rigid barrier test represents the energy absorption to average crush depth characteristic for all frontal crush configurations and finally that the geometry of the crush gives a unique relationship between the instantaneous displacement of the centre of gravity of the car and the instantaneous average crush depth for the impact under consideration.

The model is compared with the dynamic responses of 8 car types in 45% overlap rigid barrier tests at 50 kph and in 30 degree angled barrier tests at 56 kph. The calculated responses have a high degree of correspondence with the actual test behaviour of the cars.