An emergency brake is a backup braking system designed to function even when there is total brake failure. It works through purely mechanical means, and is independent of the hydraulic system which controls the brakes normally. In addition to being used in emergency situations, this brake is also used as a parking brake, to prevent the car from rolling away, should it slip into gear. Like all parts of the braking system, it should be checked regularly to ensure that it is in good working order.
To activate the emergency brake, the driver typically pulls up a lever or pushes a pedal in the front of the vehicle. Steel cables attached to the brake run to the rear brakes of the car, which are typically drum brakes. When the cables are tightened, they pull the brake shoes into contact with the drum of the brake, bringing the car to a stop. In the case of disc brakes, the brake cables are attached to a small screw mechanism that pushes a piston into contact with the brake pads, forcing them to grip the brake rotor. Typically the brake has a self-locking system, meaning that the driver must lower the lever or move the pedal to take the brake off.
In a situation where a driver experiences total brake failure, the emergency brake can be used to bring the car safely to a stop. In this situation, the brake should be set slowly, rather than yanked, to prevent fishtailing or spinning out. Some drivers use an emergency brake deliberately for this purpose, but this sort of driving should only be undertaken by drivers who have been well trained, as it can be highly dangerous.
In a car with a manual transmission, the emergency brake is used as a parking brake on a regular basis, and some drivers may also use it at stop signs. Because of the frequent use, the brake is kept in good working order, although the cables may need to be periodically tightened. In cars with automatic transmissions, however, some drivers do not set the emergency brake as a parking brake. In addition to being unsafe, this also can lead to buildup of rust and corrosion in the brake cable, which could result in cable failure in an emergency.
Drivers should set the parking brake whenever they park, and they should also periodically inspect their emergency braking system or have it inspected. During an inspection, the condition of the cables should be checked, and they should be moved or tightened if necessary. In addition, the wear on the brake pads can be inspected at this time, to ensure that they do not need to be replaced.