An anti-lock braking system (ABS) is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding. It is an automated system that uses the principles of threshold braking and cadence braking, which skillful drivers with previous-generation braking systems practiced. It does this much faster and with better control than a driver could manage.
ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces; however, on loose gravel or snow-covered surfaces, ABS can significantly increase braking distance, although still improving vehicle control. Since its widespread use in production cars, anti-lock braking systems have improved considerably.
Recent versions prevent wheel lock under braking and electronically control the front-to-rear brake bias. Depending on its specific capabilities and implementation, this function is known as electronic brakeforce distribution (EBD), traction control system, emergency brake assist, or electronic stability control (ESC).