What do ABS, traction control and ESC actually do?
They are three related systems built on the same hardware, addressing three different loss-of-control situations. Understanding what each does explains why the car sometimes seems to interfere.
ABS — anti-lock braking system. Prevents wheels locking under heavy braking.
Why locking is bad. A locked wheel is sliding, and a sliding tyre provides less grip than a rotating one — and, critically, provides no steering. A car with locked front wheels travels in a straight line regardless of the steering wheel.
ABS uses wheel speed sensors to detect a wheel decelerating far faster than the others and rapidly modulates brake pressure — many times per second — to keep it just short of locking.
What it does and does not do. It preserves steering under emergency braking, which is its main benefit. It does not reliably shorten stopping distances, and on loose surfaces such as gravel or fresh snow it can lengthen them, because a locked wheel builds a wedge of material ahead of it.
In use: press hard and keep pressing. The pedal will pulse and grind loudly, which is normal and frequently causes drivers to lift off — the single most common mistake.
Traction control (TCS). Prevents wheels spinning under acceleration. Detecting a driven wheel turning faster than the others, it reduces engine torque or brakes that wheel to restore grip. Useful pulling away in the wet or on ice.
ESC — electronic stability control. The most consequential of the three, and it addresses loss of directional control rather than braking or acceleration.
ESC compares where the driver is steering against where the car is actually going, using a yaw sensor and steering angle sensor. Detecting a skid, it brakes individual wheels to generate a corrective turning moment — braking the outer front wheel to counter oversteer, or an inner rear wheel to counter understeer.
It is among the most effective safety technologies ever mandated, with studies attributing very substantial reductions in single-vehicle and rollover fatalities. Mandatory on new cars in the EU since 2014.