GMC 2009 Savana - Manual (Page 206)

Braking
See Brake System Warning Light on page 3-31.
Braking action involves perception time and reaction
time. Deciding to push the brake pedal is perception
time. Actually doing it is reaction time.
Average reaction time is about three-fourths of
a second. But that is 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 three-fourths of a second, a vehicle
moving at 60 mph (100 km/h) travels 66 feet (20 m).
That could be a lot of distance in an emergency,
so keeping enough space between the vehicle and
others is important.
And, of course, actual stopping distances vary greatly
with the surface of the road, whether it is pavement
or gravel; the condition of the road, whether it is
wet, dry, or icy; tire tread; the condition of the brakes;
the weight of the vehicle; and the amount of brake force
applied.
Avoid needless heavy braking. Some people drive in
spurts — heavy acceleration followed by heavy
braking — rather than keeping pace with traffic. This is a
mistake. The brakes might not have time to cool between
hard stops. The brakes will wear out much faster with a
lot of heavy braking. Keeping pace with the traffic and
allowing realistic following distances eliminates a lot of
unnecessary braking. That means better braking and
longer brake life.
If the engine ever stops while the vehicle is being driven,
brake normally but do not pump the brakes. If the brakes
are pumped, the pedal could get harder to push down.
If the engine stops, there will still be some power brake
assist but it will be used when the brake is applied. Once
the power assist is used up, it can take longer to stop and
the brake pedal will be harder to push.
Adding non-dealer/non-retailer accessories can affect
vehicle performance. See Accessories and Modifications
on page 5-3.
4-4