Seat belts 169
the greater the amount of energy which has to be absorbed in the event of an acci-
The physical principle of a frontal collision
dent.
The speed of the vehicle is, nevertheless, the most important factor. Doubling the
speed of the vehicle from 25 km/h up to 50 km/hour increases the kinetic energy
four times.
The common opinion that it is possible to support your body in a minor accident
with your hands, is incorrect. Even in a collision at only a low speed, the forces
acting on the body are such that it is no longer possible to support your body.
Even if you only drive at a speed within the range from 30 km/hour to 50 km/hour,
the forces which are produced on your body in the event of an accident can easily
exceed 10.000 N (Newton). This equals a weight of one tonne (1 000 kg).
In the event of a frontal collision, occupants of the car not wearing a seat belt, are
thrown forward and strike in an uncontrolled way parts of the interior of the car,
such as steering wheel, dash panel, windscreen,⇒ fig. 170. The occupants of a
vehicle who have not fastened their seat belts may even be thrown out of the
vehicle. This can result in fatal injuries.
Fig. 170 The driver is thrown
forward if not wearing a belt
It is also important that rear seat occupants fasten their seat belts as they will other-
wise be thrown through the vehicle in an uncontrolled manner in the event of an
accident A rear seat passenger who has not fastened the seat belt is a danger not
only to himself but also for those seated at the front ⇒ fig. 171.
Important safety information regarding the use of
seat belts
The correct use of the seat belts considerably reduces the risk of
injury!
Fig. 171 The rear seat occu-
pant is thrown forward if not
wearing a belt
WARNING
The physical principle of a frontal accident can be explained quite simply:
•
The belt webbing must not be jammed in-between at any point or
twisted, or chafe against any sharp edges.
It is important that the belt webbing is properly routed if the seat belts
are to offer their maximum protection ⇒ page 170.
Motion energy, so-called kinetic energy, is produced as soon as the vehicle is
moving, both for the vehicle and its occupants. The magnitude of this kinetic energy
depends essentially on the speed at which the vehicle is travelling and on the
weight of the vehicle and the occupants. The greater the speed and weight increase,
•
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