GMC 1996 Sierra Owner's Manual page 44

Children
Everyone in a vehicle needs protection! That includes
infants and all children smaller than adult size.
I n
fact,
the law in every state in the United States and in every
Canadian province says children up to some age must be
restrained while in a vehicle.
Smaller
Children
and
Babies
A
CAUTION:
Smaller children and babies should always be
restrained
in a
child or infant restraint. The
instructions for the restraint will say whether it is
the right type and size for your child. A very
young child's hip bones are so small that a
regular belt might not stay low on the hips, as it
should. Instead, the belt will likely be'over the
child's abdomen. In a crash, the belt would apply
force right on the child's abdomen, which could
cause serious or fatal injuries. So, be sure that
any child small enough for one is always properly
restrained in a child or infant restraint.