Cadillac 2007 STS Owner's Manual page 16

In most states and in all Canadian provinces,
the law says to wear safety belts. Here is
why: They work.
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
bad 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!
16
Why Safety Belts Work
When you ride in or on anything, you go as fast
as it goes.
Take the simplest vehicle. Suppose it is just a
seat on wheels.