Side impact regulations have been introduced in many countries to improve occupant protection in side collisions. As a result, car structures have been improved significantly. However, the number of fatalities and serious injuries in side collisions is still large. To understand the causes of these injuries and to identify their potential countermeasures, accident analyses of side collisions were newly conducted.

From the accident data analysis, it was shown that the contacts with the head and chest during side crashes are still a major cause of serious injuries and death. The impact vehicle type affected the injured body regions of the occupant in the struck vehicle, and the chest was frequently injured in the struck car when impacted by an 1BOX type vehicle. Occupant seating postures were surveyed in vehicles on the roads, and it was found that from a side view that the head location of 50% of the drivers was in line or overlapped with the vehicle’s B-pillar. This observation suggests that in side collisions head injuries may occur frequently due to contacts with the B-pillar.

A series of side impact tests were conducted to examine test procedures that would be beneficial for improving occupant protection. When the 1BOX was a striking vehicle, the chest deflection of the ES-2 dummy was large. The crash tests also included car-tocar crash tests in which either (1) both cars are moving or (2) one car is stationary, i.e., an ECE R95 test. The injury measures of the ES-2 dummy were substantially smaller if the struck car was moving.

The tests also were conducted for an occupant seating position where the head would make contact with the B-pillar. To investigate the effectiveness of curtain side airbags for head protection in car-to-car crashes, these test were conducted for struck cars with and without a curtain side airbag. It was demonstrated that the curtain side airbag was effective for reducing the number of head injuries in car-to-car crashes.