North Carolina CDL Air Brakes Practice Test

A truck or bus equipped with air brakes traveling at 55 mph would typically require a stopping distance of more than 300 feet under ideal conditions. This figure accounts for several factors that contribute to stopping distance, including the perception time, reaction time, and the actual braking distance.

When a driver notices the need to stop, there is a slight delay (perception and reaction time) before braking begins. Once the brakes are applied, the vehicle still continues to travel forward until the brakes take full effect, which determines the braking distance. Due to the weight and size of trucks and buses, their braking systems—including air brakes—require a longer distance to stop effectively compared to lighter vehicles.

In general, the stopping distance for larger vehicles traveling at higher speeds significantly increases due to their momentum, requiring them to have longer stopping distances. This is why recognizing that stopping distance exceeds 300 feet is critical for safety—ensuring that drivers are aware of the limitations of air brake systems in larger vehicles.