Rear-end Collisions
Rear-end Collisions, in which one vehicle runs into the back of another, can be treated in the same way as head-on collisions, except that the closing speed is the difference between the two speeds, and, while the occupants of the striking car suffer a frontal impact similar to that experienced in head-on collisions and tend to travel forward with respect to the car, those in the struck car tend to travel backwards relative to the car and therefore apply forces to the back of the seat.
Impacts with Walls
In impacts of cars with walls, at all angles of approach( the angle between long axis of vehicle and wall) more than about 40°(see Fig.21.1), the impact is effectively a head-on collision, though less severe than impacts at angles approaching 90°, and the front-seat occupants move towards the windscreen.
The velocity of impact with the windscreen, steering assembly or instrument panel decreases as the angle of approach becomes smaller, but is greatly influenced by the coefficient of friction between the car and the wall; for example, when the coefficient changes from 0.25 to 0.5( approximately from a wooden surface to a concrete wall), the impact velocities of the occupants on the interior of the car are approximately doubled.
After impact the car may rotate towards or away from the wall-towards the wall if friction with the wall is low, and/or the angle of approach is small, and away from it when the friction is high, and/or the angle of approach is large.
4 Intersection Collisions
Almost all intersection car collisions involve a striking and a struck car. The striking car suffers mainly frontal impact, and the struck car a side impact. In most such accidents the paths of the two cars are at right angles, probably at a crossroads or Tjunction. The struck car is usually moving more slowly than the striking car. In one investigation about 50 per cent of the struck cars were judged to be travelling at less than 2omile/h(32km/h), and in about 60 percent the angles between colliding vehicles were about 90°。