What is "parking brake"

n. A brake#Etymology 4 in a vehicle that can be set to avoid the vehicle rolling down a hill or being pushed away.

n. a brake operated by hand; usually operates by mechanical linkage [syn: hand brake, emergency, emergency brake]

In cars, the parking brake, also called hand brake, emergency brake, or e-brake, is a latching brake usually used to keep the vehicle stationary. It is sometimes also used to prevent a vehicle from rolling when the operator needs both feet to operate the clutch and throttle pedals. Automobile hand brakes usually consist of a cable directly connected to the brake mechanism on one end and to a lever or foot pedal at the driver's position. The mechanism is often a hand-operated lever (hence the hand brake name), on the floor on either side of the driver, or a pull handle located below and near the steering wheel column, or a (foot-operated) pedal located far apart from the other pedals.

Although sometimes known as an emergency brake, using it in any emergency where the footbrake is still operational is likely to badly upset the brake balance of the car and vastly increase the likelihood of loss of control of the vehicle, for example by initiating a rear-wheel skid. Additionally, the stopping force provided by using the handbrake is small and would not significantly aid in stopping the vehicle. The parking brake operates generally only on the rear wheels, which have reduced traction while braking but in some cases, parking brake operates on the front wheels, as done in most Citroens manufactured since the end of World War II. The hand brake is instead intended for use in case of mechanical failure where the regular footbrake is inoperable or compromised. Modern brake systems are typically very reliable and equipped with dual-circuit hydraulics and low-brake-fluid sensor systems, meaning the handbrake is rarely used to stop a moving vehicle.

The most common use for a parking brake is to keep the vehicle motionless when it is parked. Parking brakes have a ratchet locking mechanism that will keep them engaged until a release button is pressed. On vehicles with automatic transmissions, this is usually used in concert with a parking pawl in the transmission.

Hand brakes are also used to assist in hill starts on vehicles with manual transmissions. Use of the handbrake frees both feet for use on the accelerator and clutch pedals, allowing the car to move off without rolling back at all.

Handbrakes are never used to slow the vehicle when it is in motion, as doing so generally locks only the back wheels and sends the car into a handbrake turn. Handbrake turns are often used in street racing to initiate drifting, but such a maneuver is often seen as an error among regular road users, and is dangerous in many situations.