GMC 2003 Sonoma Owner's Manual page 39

I -
Never do this.
Here two children are wearing the same belt.
The belt can't properly spread the impact
forces. In a crash, the two children can be
crushed together and seriously injured. A belt
must be used by only one person at a time.
Q:
What if a child is wearing a lap-shoulder belt,
but the child is so small that the shoulder belt
is very close to the child's face or neck?
A:
Move the child toward the center of the vehicle, but
be sure that the shoulder belt still is on the child's
shoulder, so that in a crash the child's upper
body would have the restraint that belts provide. If
the child is so small that the shoulder belt is
still very close to the child's face or neck, you might
want to place the child in a seat that has a lap
belt, if your vehicle has one.
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