In a representative sample of tow-away side collisions from the UK Midlands, one third of front seat occupants were alone, on the struck side of the car. The other two thirds were either a non struck side occupant alone or two occupants sitting together. Occupant restraint, especially in perpendicular side impacts, was a notable factor in determining injury outcome for belted non struck side occupants. With both front seats occupied, there was a reduction in AIS 2+ injury to belted non struck side occupants due to a reduction in chest and lower limb injuries. Struck side occupants sustained increased injury rates to the extremities when accompanied by a belted non struck side occupant but no notable increases in moderate to serious injury to the head, chest, abdomen or pelvis.