In vehicles with automatic transmissions, the parking brake was originally intended for emergency stopping (for instance, if the foot brake completely failed due to a loss of hydraulic pressure or other malfunction).[4] As safety regulations became more stringent in the 1980s, and modern brake systems became more reliable (using dual-circuit hydraulics and low-brake-fluid sensors),[5] the likelihood of brake failure reduced; in most cases this failure might be indicated through a brake warning light appearing on the dashboard.[6][7] In the event of brake failure, the parking brake lever should be slowly engaged to prevent locking up the wheels and reduce speed.[8]
While most automatic transmission vehicles have parking brakes, it is often not engaged by drivers when parking.[9] 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.[10][11] Also, regular use of the parking brake reduces the chance of corrosion by keeping the cables in-motion.[12] In manual transmission vehicles, the parking brake can be engaged to help keep the vehicle stationary.