ASE School Bus Certification - Body Systems and Special Equipment (S1) Practice Test

The Anti-lock Braking System (ABS) utilizes speed sensors and control modules to prevent wheel lock-up during braking. Speed sensors are critical components that monitor the rotational speed of each wheel. If a wheel begins to slow down significantly compared to the others—indicating potential lock-up—the system's control module activates. This module processes data from the speed sensors and adjusts brake pressure accordingly, modulating the brakes to prevent skidding.

The relationship between the speed sensors and control modules allows the ABS to respond in real-time to varying wheel speeds, ensuring that the vehicle maintains steering control and stability during hard braking situations. This functionality greatly enhances safety by reducing the likelihood of loss of control, particularly on slippery or uneven surfaces.

In contrast, other options involve components that do not play a direct role in the function of ABS. For instance, while hydraulic pumps may be involved in some braking systems, they do not specifically prevent wheel lock-up. Similarly, brake light switches and electrical relays serve different functions in the braking system and do not directly connect to the ABS's goal of wheel speed regulation. Lastly, wheel bearings and drive shafts are crucial for supporting the wheel assembly and transferring power but are not involved in the ABS system’s operation.