All deaths from road accidents in certain areas and periods were studied. Analysis of 224 deaths to car occupants from collisions between cars and lorries showed that such accidents were the commonest cause of death for car occupants on motorways and link roads. The impacts were such that relatively poor protection could be given by occupant restraint systems. Collisions of cars into the rear of lorries caused the most severe injuries; most of these accidents occurred at night. The traffic characteristics of cars and lorries are largely incompatible and increase the likelihood of collisions and of extremely severe injuries to car occupants. Some reduction in deaths may be expected from making lorries more conspicuous and eliminating the rear overhang. More fundamental measures are segregation of lorries from cars and return of traffic to railways.