Chevrolet 2007 Express 2007 Express Owner's Manual page 36

The lap part of the belt should be worn low
and snug on the hips, just touching the thighs.
In a crash, this applies force to the strong pelvic
bones. And you would be less likely to slide
under the lap belt. If you slid under it, the belt
would apply force at your abdomen. This
could cause serious or even fatal injuries.
36
The shoulder belt should go over the shoulder
and across the chest. These parts of the body
are best able to take belt restraining forces.
The safety belt locks if there is a sudden stop or
a crash.
CAUTION:
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You can be seriously hurt if your shoulder
belt is too loose. In a crash, you would
move forward too much, which could
increase injury. The shoulder belt should
fit against your body.