GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 23

CAUTION:
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It is extremely dangerous to ride in a cargo area,
inside or outside of a vehicle. In a collision, people
riding in these areas are more likely to be seriously
injured or killed. Do not allow people to ride in any
area of your vehicle that is not equipped with seats
and safety belts. Be sure everyone in your vehicle is
in a seat and using a safety belt properly.
Your vehicle has indicators as a reminder to buckle your
safety belts. See Safety Belt Reminders on page 3-36.
In most states and in all Canadian provinces, the
law requires wearing safety belts. Here is why:
You never know if you will be in a crash. If you do have
a crash, you do not know if it will be a serious one.
A few crashes are mild, and some crashes can be so
serious that even buckled up, a person would not
survive. But most crashes are in between. In many of
them, people who buckle up can survive and sometimes
walk away. Without belts they could have been badly
hurt or killed.
After more than 40 years of safety belts in vehicles, the
facts are clear. In most crashes buckling up does
matter... a lot!
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