GMC 2011 Acadia Owner's Manual page 73

Why Safety Belts Work
When you ride in or on anything,
you go as fast as it goes.
Take the simplest vehicle. Suppose
it is just a seat on wheels.
Put someone on it.
I n f o r ma t i o n P r o v i d e d b y :
Seats and Restraints
Get it up to speed. Then stop the
vehicle. The rider does not stop.
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