Questions and Answers Regarding
ANTILOCK BRAKE SYSTEMS (ABS)
|When used properly,
an antilock brake system (ABS) is a safe and effective braking system. ABS allows
the driver to maintain directional stability,control over steering, and in some
situations, to reduce stopping distances during emergency braking situation,
particularly on wet and slippery road surface. To gain this safety advantage,
drivers must learn how to operate their ABS correctly.
What is ABS?
An antilock braking system works with the regular or foundation brakes on
your vehicle. ABS simply keeps your base brakes from locking up. In vehicles
not equipped with ABS, the driver can manually pump the brakes to prevent
wheel lockup. In vehicles equipped with ABS, the driver's foot remains firmly
on the brake pedal, allowing the system to automatically pump the brakes.
Why is that important?
When your brakes lock up on wet and slippery roads or during a panic stop,
you lose steering control and your vehicle can spin. Rear wheel ABS prevents
wheel lockup so that your car stays in a straight line. If your car has ABS control
on all four wheels, you also keep steering control. If you have steering control,
it is possible to avoid a crash by steering around hazards if a complete stop
cannot be accomplished in time.
How do I know whether my vehicle has ABS?
Most newer car models offer ABS as either standard or optional equipment.
There are different ways to find out whether your car has an antilock brake system:
* Read your owner's manual
* Check your instrument panel for an amber ABS indicator light after you turn on
* When you buy, lease or rent, ask your dealer or rental car company.
Will I notice anything when the ABS is working?
In many vehicles, drivers may experience a rapid pulsation
of the brake pedal--almost as if the brakes are pushing back at you. Sometimes
the pedal could suddenly drop. Also, the valves in the ABS controller may make a
noise that sounds like grinding or buzzing. In some cars you may feel a slight
vibration--this means the ABS is working. It is important NOT to take your foot
off the brake pedal when you hear noise or feel pulsations, but instead continue to
apply firm pressure.
Does ABS change the way I should use the brakes?
You should not pump your brakes if you have ABS. Just hold your foot
firmly on the brakes pedal and remember that you can still steer.
How does ABS work?
What ABS does is similar to a person pumping the brakes. It automatically
changes the pressure in your car's brake lines to maintain maximum brake performance
just short of locking up the wheels. ABS does this very rapidly with electronics.
Do cars with ABS stop more quickly than cars without?
ABS is designed to help the driver maintain control of the vehicle
during emergency braking situations, not make the car stop more quickly. ABS may shorten stopping
distances on wet or slippery roads and many systems will shorten stopping distances on dry roads.
On very soft surfaces, such as loose gravel or unpacked snow, an ABS system may actually
lengthen stopping distances. In wet or slippery conditions, you should still make sure
you drive carefully, always keep a safe distance behind the vehicle in front of you, and maintain a speed
consistent with the road conditions.
Are all antilock systems the same?
They are all very similar in the way they control brake pressure, but some sytems
are designed to prevent only the rear wheels from locking up. These rear-wheel-only systems are
found on pickups and sport-utility vehicles. Rear-wheel ABS keeps your vehicle from spinning
out of control, but you will not have steering control if the front wheels lock up. All other
ABS systems-including those for cars and minivans--are designed to keep all four wheels from locking up.
If you own a pickup or sport-utility vehicle, you can check your owner's manual to see what
type of ABS you have.
How can I familiarize myself with ABS?
Read your owner's manual for more details on the complete operation and benefits
of ABS. The antilock brake system is speed sensitive, and will not activate at very slow
speeds. One way to familiarize yourself with the operation of ABS is to test drive the
vehicle at a speed above which the ABS activates (usually above 10 mph) in
an unobstructed parking lot and apply the brakes firmly. It is easier to activate the ABS on a wet and slippery
road surface. The antilock system should prevent the wheels from skidding. Pulsation may be felt
in the brake pedal and you may hear a clicking sound. Avoid pumping the brake, even if the
pedal is pulsating.
Where Can I get more information about ABS?
Call the NHTSA Auto Safety Hotline on 1-888-327-4236, 1-888-DASH-2-DOT.