PRIORITIES FOR EU MOTOR VEHICLE SAFETY DESIGN

much to learn about side impact compatibility, there is general agreement about certain
aspects.
With the struck side occupant being intimately involved in the impact, the initial intruding
velocity of the car side has much more relevance than the final velocity change of the whole
car. The most serious and relevant injuries are determined well before the car has reached
its final velocity. The consequence of this is that the impact velocity of the bullet vehicle is
the most appropriate indicator of impact severity, rather than the target car’s velocity change.
During the period when the injuries occur, the overall change in velocity of either vehicle is
small and this explains why vehicle mass has little influence.
Similarly, the stiffness of the bullet car’s front also has little influence. In general, frontal
stiffnesses are very much greater than those of the car’s side and there is usually little
deformation of the bullet vehicle’s main structure.
As for frontal impact, the quality of the structural interaction between the cars has a major
effect. High fronted bullet vehicles impact above the sill of the target car loading the door
and the occupant directly. Bullet vehicles, which interact with the sill and door pillars, put
reduced loads through the door. In a perpendicular impact, homogeneously stiff fronts can
spread their load across the side of the car picking up on the pillars and sill. Weaker
structures can be deformed by the pillar and sill allowing the car’s front to pass between
them, deform the door and load the occupant. Because of this, weaker fronts can be more
aggressive.
The intrusion profile of the car side has been long recognised as influencing injury risk.
Clearly, by their shape and stiffness, the front of the bullet car has the potential help to
promote more uniform intrusion profiles.
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