GMC Yukon XL Denali Owner's Manual page 97

According to accident statistics,
children and infants are safer when
properly restrained in a child
restraint system or infant restraint
system secured in a rear seating
position.
In a crash, children who are not
buckled up can strike other people
who are buckled up, or can be
thrown out of the vehicle. Older
children need to use safety belts
properly.
WARNING
Never allow more than one child
to wear the same safety belt. The
safety belt cannot properly spread
the impact forces. In a crash, they
can be crushed together and
seriously injured. A safety belt
must be used by only one person
at a time.
WARNING
Never allow a child to wear the
safety belt with the shoulder belt
behind their back. A child can be
seriously injured by not wearing
the lap-shoulder belt properly. In a
crash, the child would not be
restrained by the shoulder belt.
The child could move too far
forward increasing the chance of
head and neck injury. The child
might also slide under the lap
(Continued)
Seats and Restraints
WARNING (Continued)
belt. The belt force would then be
applied right on the abdomen.
That could cause serious or fatal
injuries. The shoulder belt should
go over the shoulder and across
the chest.
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