Investigations in New South Wales of passenger car crashes involving the death of wearers of lap/sash belts have led to the conclusion that head impact with a rigid part (usually in the side) of the occupied car is responsible for more deaths than any other impact.

The experimental work reported in this paper consists of crash simulations to map the space swept by the head of a lap/sash belted occupant, in head-on and in a range of side impacts in which no invasion or loss of head space occurs. The simulations employed an Ogle-MIRA dummy which has a very compliant thorax, modified with the stacked ball joint neck from a Sierra 1050 dummy, this combination having been shown to closely reproduce head motion of human volunteers in frontal crashes reported in the literature. The work includes validation of the dummy and an investigation of the influence on head space of the angle of crash, of inertia reels in the sash straps, and of seat springing, in contrast to the hard seats used for the volunteer crashes. The results provide evidence of the value of increasing head space so as to reduce the likelihood of head impact of otherwise well restrained occupants of passenger cars.

Three current model cars are tested for availability of head space which is found to be inadequate, especially in front corner impacts on the occupant's side of the car, involving about 22° impact yaw