The Relationship Between Car Size and Occupant Injury in Traffic Accidents in Japan

The relationship between car size and occupant injury is examined using traffic accident data from all over Japan. For head-on collisions, the occupant injury rate is formulated based on the approximation of occupant injury by delta-V. The effects on occupant injury of the sizes of the striking and struck vehicles, as well as the effects of seat belt use and vehicle velocity, are examined in head-on, side-impact and single-car collisions.

As occupant injuries are also influenced by the other car or cars involved in a collision, the number and size distribution of vehicles is important. Sensitivity analysis shows that the effect of the number of lighter cars is greater in head-on collisions and that the effect of the number of heavier cars is greater in side-impact collisions, relative to the total number of fatalities.