Accidents with heavy goods vehicles result in a disproportionate number of car occupant fatalities. This analysis describes the nature of these collisions with the intention of providing a representative accident background against which under-run guard development can be considered. The nature of passenger compartment intrusion is described, as are the injuries suffered by the car occupants who died. The problem of under-run is also observed when cars strike buses or coaches. Estimates are given of the benefits available from providing under-run protection on the front and rear of heavy goods vehicles. Case histories illustrate typical accident experiences in various types of car to lorry impact.