Car collisions from a representative; sample of.urban and rural accidents in Great Britain have been analyzed. sA damage severity index scale has been developed which involves comparing the damage to a case vehicle with damage to a similar make and model vehicle which has been in an experimental impact. Damage severity is then correlated with injury severity for four crash configurations: head on, front corner, side, and rear end. The benefits from lap/diagonal seat belts show an increase in at least 12 mph in equivalent barrier speeds for the same injury level in head-on and front-corner impacts, but in side impacts there is no significant benefit to the occupants remaining in the cars.Penetration of the passenger compartment in side impacts and rollover is shown to be closely related to injury severity. When better experimental data are available, this method should allow different makes and models of cars to be assessed in terms of injury prevention.