vehicle is in motion, both the moving vehicle
and its occupants gain “kinetic energy”
.
The higher the vehicle speed and the heavier
the weight of the vehicle, the greater the
amount of energy that will be released in the
event of an accident.
However, the most significant factor is the
speed of the vehicle. For example, if the
speed doubles from around 25 km/h to
around 50 km/h (around 15 mph to around
31 mph), the kinetic energy increases by
a factor of four.
The amount of kinetic energy depends on the
speed of the vehicle and the weight of the
vehicle and passengers. The higher the speed
and the heavier the weight, the greater the
amount of energy that will be released in the
event of an accident.
Passengers not wearing seat belts are not
“connected” to the vehicle. In the event of
a frontal collision, they will continue to move
forwards at the same speed at which the ve-
hicle was travelling before impact, until
something stops them. Because the passen-
gers in our example are not restrained by seat
belts, the entire amount of kinetic energy will
only be released at the point of impact
.
In the event of an accident at speeds be-
tween around 30 km/h (around 19 mph) and
around 50 km/h (around 31 mph), forces act
on the body which can easily exceed one
tonne (1,000 kg or around 2,200 lbs). These
forces are even greater at higher speeds.
This example applies not only to frontal colli-
sions, but to all accidents and collisions.
What happens to vehicle oc-
cupants who have not fas-
tened their seat belts
Please refer to at the start of the chap-
Fig. 23 An unbelted driver is thrown forwards.
Fig. 24 The unbelted rear passenger is thrown
forwards, hitting the belted driver.
Many people believe that they can brace their
weight with their hands in a minor collision.
This is not true.
Even at low speeds, the forces acting on the
body in a collision are so great that it is not
possible to brace oneself with arms and
hands. In a frontal collision, vehicle occu-
pants who have not fastened their seat belts
will be thrown forward and will make un-
checked contact with parts of the vehicle in-
Seat belts
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