handbrake
The mechanism, particularly the locking hand-operated lever or foot-operated toggle lever in a motorcar or the hand-operated crank on a railcar, which is used to set and release such a brake.
handbrake: a mechanical brake you control by hand or foot
A handbrake is a friction brake operated directly by the driver or operator, independent of the main hydraulic or pneumatic brake system. In motor vehicles, it typically consists of a lever (mounted on the transmission tunnel or integrated into the center console) or a foot-operated toggle that mechanically applies brake force to the rear wheels through steel cables or hydraulic lines. On rail vehicles, it is a hand-cranked wheel or lever that tightens brake shoes against the wheels of a single car or locomotive.
The automobile handbrake serves two distinct purposes: holding the vehicle stationary on a slope when parked, and providing emergency braking if the primary brake system fails. Modern cars increasingly use electromechanical handbrakes, where an electric motor drives the brake actuator, but the mechanical principle remains identical. Cable-operated handbrakes on older vehicles typically route through pulleys and equalizers to balance braking force between the two rear wheels; poorly adjusted cables cause uneven application and reduced holding power.
Function and failure modes
On railway stock, the handbrake (often called the side-rod or tender brake) engages wedges or force-multiplying linkages that press brake shoes against the wheels. A single handbrake on a freight wagon may require sustained manual effort to hold the car on a grade; operators must understand the mechanical advantage of the crank handle and the stopping distance needed for the mass involved. Corrosion of cables, wear in pivots, and glazed brake shoes that have lost friction are common causes of handbrake failure.
The term reflects its physical operation: you apply braking force by hand (or foot), as opposed to the automatic or continuous action of a main service brake. In older technical literature, the handbrake is sometimes called the "parking brake," "emergency brake," or "secondary brake," although modern usage reserves "emergency brake" for systems that engage automatically in a loss-of-pressure event. Proper maintenance involves regular cable tension checks, shoe replacement when friction material falls below manufacturer thickness, and functional testing on slopes to verify holding power.