GMC 2010 Canyon Crew Cab Owner's Manual page 35

WARNING:
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Sitting in a reclined position when the vehicle is in
motion can be dangerous. Even when buckled up,
the safety belts cannot do their job when reclined
like this.
The shoulder belt cannot do its job because it will
not be against your body. Instead, it will be in front
of you. In a crash, you could go into it, receiving
neck or other injuries.
The lap belt cannot do its job either. In a crash,
the belt could go up over your abdomen. The belt
forces would be there, not at your pelvic bones.
This could cause serious internal injuries.
For proper protection when the vehicle is in
motion, have the seatback upright. Then sit well
back in the seat and wear the safety belt properly.
Do not have a seatback reclined if the vehicle is
moving.
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