In road vehicles, the parking brake, also known as a handbrake or emergency brake (e-brake), is a mechanism used to keep the vehicle securely motionless when parked. Parking brakes often consist of a pulling mechanism attached to a cable which is connected to two wheel brakes. In most vehicles, the parking brake operates only on the rear wheels, which have reduced traction while braking. The mechanism may be a hand-operated lever, a straight pull handle located near the steering column, or a foot-operated pedal located with the other pedals.
Overview
While most automatic transmission vehicles have parking brakes, it is often not engaged by American drivers when parking. However, it is recommended to use it, as the parking pawl in the gearbox could fail due to stress or another vehicle striking the car, causing the car to roll. In manual transmission vehicles, the parking brake can be engaged to help keep the vehicle stationary. When parking on an uphill gradient, it is recommended that the front wheels face away from the curb. This would prevent the car from rolling into the roadway by using the curb to block the front passenger tire in the event of a parking brake failure. Similarly, on a downhill gradient, the front wheels should face the curb for the same reason, and the wheels should face to the side of the road on which vehicles are driven on an uncurbed road regardless of orientation. In a manual transmission, leaving the car in first gear (or in reverse if pointing downhill) is also advised, as the engine will prevent the car from rolling if the parking brake fails.
The parking brake in most vehicles is still completely mechanical. Traditionally engaged by pulling a lever, the cables manually engage part of the car's braking system, usually the rear disk or drum brakes. The mechanical nature allows the driver to apply the brake even if the main hydraulic brake system fails.
Pictograph symbols and/or lights may be used to indicate the location of a parking brake, its application or release.
Other uses
In manual and automatic transmission vehicles, the parking brake can also be used for various driving situations which require the vehicle to be momentarily stopped. For example, the brake can be engaged when moving off an uphill slope, as this allows the driver to hold the accelerator and clutch pedals steady without the vehicle rolling backwards. Other common situations is when the vehicle is stopped at a traffic light, a pedestrian crossing, or simply waiting to turn in front of oncoming traffic. The parking brake would ensure the car is secure, should another vehicle come into physical contact from behind, causing the car to jolt forward. It is not recommended to use the parking brake when the vehicle is in-motion, unless there is a problem with the main brakes, as this can lock the back wheels and cause a skid. This is known as a handbrake turn, which is often performed in street racing and off-road rally racing to initiate rear wheel drift.
In the event of hydraulic brake failure, the parking brake can be used to slow a vehicle. In such cases, the lever should be slowly engaged to prevent locking up the wheels.
Parking brake variations
The position of the parking brake differs between vehicle models and manufacturers. However, a universal feature is either one or two of the warning lights which appear on the dashboard when the parking brake is engaged.
Center or stick lever
The most common placement of the parking brake is in the center console of the vehicle, in between the driver and front passenger seats. Operating the brake is performed by pulling the lever up (which is connected to a ratchet) until there is tension. To disengage the brake, the button is held while simultaneously pulling the lever up to disengage the ratchet and then pushed all the way down with the button still held. In older vehicle models, a stick lever may be used instead which is located under the instrument panel.
Pedal or pull handle
Some vehicles have the parking brake operated by a small foot pedal, located by the other pedals. Depressing the foot pedal would engage the brake and pressing it again will release it. A pull handle variation also exists; by pulling or releasing the handle, this engages and releases the parking brake, respectively. Many vehicles have a combination of the two; a pedal to engage the brake and a handle to release it.