Cadillac CTS-V 2009 Owner's Manual page 18

CAUTION:
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Sitting in a reclined position when your vehicle is in
motion can be dangerous. Even if you buckle up,
your safety belts cannot do their job when you are
reclined like this.
The shoulder belt cannot do its job. 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 your safety belt properly.
1-12
Do not have a seatback reclined if the vehicle is
moving.