Question: when would an anti-lock braking system start to work

title: Anti-lock braking system
text: Typically ABS includes a central electronic control unit ( ECU ) , four wheel speed sensors , and at least two hydraulic valves within the brake hydraulics . The ECU constantly monitors the rotational speed of each wheel ; if it detects the wheel rotating significantly slower than the speed of the vehicle , a condition indicative of impending wheel lock , it actuates the valves to reduce hydraulic pressure to the brake at the affected wheel , thus reducing the braking force on that wheel ; the wheel then turns faster . Conversely , if the ECU detects a wheel turning significantly faster than the others , brake hydraulic pressure to the wheel is increased so the braking force is reapplied , slowing down the wheel . This process is repeated continuously and can be detected by the driver via brake pedal pulsation . Some anti-lock systems can apply or release braking pressure 15 times per second . Because of this , the wheels of cars equipped with ABS are practically impossible to lock even during panic braking in extreme conditions . 

Answer: answer: When a wheel significantly rotates faster or slower compared to the vehicle speed, the anti-lock braking system includes a central electronic unit (ECU), the function of which is to control the braking force applied to the wheel, making it turn faster or slower. Some anti-lock systems can apply or release braking pressure 15 times per second .