Michigan CDL - Air Brakes Practice Exam

What does the ABS system help prevent during hard braking?

1. Engine stall

2. Wheel lock-up

3. Loss of steering control

4. Brake wear

The correct answer is: Wheel lock-up

The Anti-lock Braking System (ABS) is specifically designed to prevent wheel lock-up during hard braking situations. When a driver applies the brakes forcefully, especially in slippery conditions, the wheels can stop turning altogether, causing the vehicle to skid. This is dangerous as it can lead to loss of control and longer stopping distances. The ABS system uses sensors to monitor the speed of each wheel. If it detects that a wheel is about to lock up, it automatically modulates the brake pressure to that wheel, allowing it to continue rotating. This helps maintain traction with the road surface, enabling the driver to steer the vehicle even while braking hard. As a result, the main function of ABS is to enhance safety by preventing wheel lock-up and allowing for better vehicle control during emergency braking situations.