GMC 1996 Sierra Owner's Manual page 159

Control of a Vehicle Braking
You have three systems that make your vehicle
go
where
you want
it to
go.
They are the brakes, the steering and
the accelerator. All three systems have
to
do their work
at the places where the tires meet the road.
Sometimes, as when you're driving on snow or ice, it's
easy
to
ask more of those control systems than the tires
and road can provide. That means you can lose control
of
your vehicle.
Braking action involves perception time and
reaction time.
First, you have to decide to push on the brake pedal.
That's perception time. Then you have to bring up your
foot and do
it.
That's reaction rime.
Average reaction time is about 3/4 of a second. But
that's only an average. It might be less with one
driver and as long as two or three seconds or more with
another. Age, physical condition, alertness, coordination
and eyesight all play a part. So do alcohol, drugs and
frustration. But even in 3/4 of a second, a vehicle
noving at 60 mph (1 00 kmh) travels 66 feet (20 m).
That could be a lot of distance in an emergency, so
keeping enough space between your vehicle and others
is important.
And, of course, actual stopping distances vary greatly
with the surface of the road (whether it's pavement or
gravel); the condition of the road (wet, dry, icy); tire
tread; and the condition of your brakes.
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