Antilock brake system or ABS means a portion of a service brake system that automatically controls the degree of rotational wheel slip during braking by: (1) Sensing the rate of angular rotation of the wheels; (2) Transmitting signals regarding the rate of wheel angular rotation to one or more controlling devices which interpret those signals and generate responsive controlling output signals; and (3) Transmitting those controlling signals to one or more modulators which adjust brake actuating forces in response to those signals.Checked 2026-08-12
Anti-lock Braking System (ABS)
The part of the brake system that controls wheel slip during braking so the wheels do not lock.
Also called: ABS · anti-lock brakes
What it means
Definition
The federal standard defines an antilock brake system as a portion of a service brake system that automatically controls the degree of rotational wheel slip during braking. It does so in three steps the standard sets out: sensing the rate of angular rotation of the wheels, transmitting those signals to controlling devices that interpret them and generate output signals, and transmitting those signals to modulators that adjust brake actuating forces. Steering remains possible because the wheels keep turning.
Why a buyer cares
What it changes
The base hydraulic brakes work whether or not ABS does, so an ABS lamp that stays lit points at a wheel-speed sensor or the module — and stability control, which is built on the same sensors, usually goes down with it.
In practice
Where you meet it
The ABS telltale on the cluster, and brake invoices naming a wheel-speed sensor or ABS module.
Two things that look alike
Not the same as
Pads, rotors and calipers are the base brakes; ABS is the control layer above them.
Read next
Related terms
Where this comes from
Sources
A second source was dropped in review: the Bendix manual on static.nhtsa.gov covers air-braked commercial trucks and trailers, not passenger cars.