Sa f e t y belts
passenge rs, a lways correct ly wear safety
belts when the vehicle is moving.
- Failure to pay attention to the warning light
that comes on could lead to personal injury.
Why use safety belts?
Frontal collisions and the law of physics
Frontal crashes create very strong forces for peo-
ple riding in vehicles.
Fig. 223 Unbe lted occupants in a vehicle heading for a wall
Fig. 224 The vehicle crashes into the wall
The physical princip les are simple . Both the vehi-
cle and the passengers possess energy which var-
ies with vehicle speed and body we ight . Engi-
neers call this energy "kinet ic energy."
The higher the speed of the vehicle and the
greater the vehicle's weight, the more energy
that has to be "absorbed" in the crash.
Vehicle speed is the most signific ant fac t or .
If
the speed doubles from 15 to 30 mph (25 t o 50
km/h), the energy increases 4 t imes!
Because the passengers of th is veh icle are not us-
ing safety belt s
¢fig. 223, they will keep mov ing
at the same speed the vehicle was moving just
262
before the crash, until something stops them -
here, the wall ¢
fig. 224 .
The same principles apply to people sitting in a
vehicle that is involved in a fronta l collision . Even
at city speeds of 20 to 30 mph (30 to 50 km/h),
the forces acting on the body can reach one ton
(2,000 lbs . or 1,000 kg) o r more . At g reater
speeds, these forces are even higher.
People who do not use safety belts are also not
attached to their vehicle . In a frontal collision
they will also keep moving forward at the speed
their vehicle was travelling just before the crash.
Of course, the laws of physics don't just apply to
frontal collisions, they determine what happens
in all kinds of accide nts and collisions .
What happens to occupants not wearing
safety belts?
In crashes unbelted occupants cannot stop
themselves from flying forward and being in-
jured or killed. Always wear your safety belts!
Fig. 225 A drive r not wearing a safety belt is violently
thrown forward
Fig. 22 6 A rear passe ng er not wea ring a safety be lt will fly
forwa rd and strike the driver
Unbelted occupants a re not ab le t o res ist the tre-
mendous forces of impac t by holdi ng tight or
llll-
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