Emergency brakes are a secondary braking system installed in motor vehicles. Also known as e-brakes, hand brakes and parking brakes, emergency brakes are not powered by hydraulics and are independent of the service brakes used to slow and stop vehicles. There are state and federal laws requiring emergency brakes for motor vehicles [source: NHTSA].
There are four types of emergency brakes:
- Stick lever, which is generally found under the instrument panel (found in older-model vehicles)
- Center lever, which is found in between separated front seats
- Pedal, which is found to the left of the floor pedals
- Electric or push button, which are found amongst the other console controls
Using only levers and cables, each type of emergency brake is completely mechanical and bypasses the normal brake system. This ensures that a vehicle can be brought to a complete stop if there’s a failure of the brake system [source: Ofria].
When you set the emergency brake, the brake cable passes through an intermediate lever, which increases the force of your pull, and then passes through an equalizer. At the U-shaped equalizer, the cable is split in two. The equalizer divides the force and sends it evenly across the two cables connected to the rear wheels.
Motor vehicles use either drum brakes or disc brakes. Drum brakes are common in the rear wheels, while disc brakes are most common on the front wheels (or all four wheels). In a rear drum situation, the emergency brake cable runs directly to the brake shoes, bypassing the hydraulic brake system. In this simple, mechanical bypass, the emergency brake system requires no extra parts to control the brakes.
Cars with rear disc brakes have a more complicated emergency brake system, sometimes requiring an entire drum brake system to be mounted inside of the rear rotor, called an exclusive parking brake or auxiliary drum brake [source: Owen].