GMC 2006 Savana Owner's Manual page 39

CAUTION:
{
Never do this.
Here two children are wearing the same belt.
The belt can not 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:
If the child is seated in a rear outside seat position,
move the child toward the center of the vehicle. Also
see Rear Safety Belt Comfort Guides on page 1-28.
If the child is sitting in the second row center seat
position, move the child toward the safety belt
buckle. In either case, 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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