Arizona Air Brakes CDL Practice Test

What is considered a factor that makes the total stopping distance for air brakes longer than hydraulic brakes?

1. Brake lag distance.

2. Action distance.

3. Perception distance.

4. Effective braking distance.

The correct answer is: Brake lag distance.

The total stopping distance for air brakes is longer than for hydraulic brakes primarily due to brake lag distance. When using air brakes, there is an inherent delay, known as brake lag, that occurs between the time the driver applies the brake and when the brakes actually engage. This delay is caused by the time it takes for air to travel through the brake lines, which directly impacts how quickly the vehicle will begin to slow down. Brake lag distance adds to the overall stopping distance because it accounts for the additional time and distance the vehicle will continue to travel after the driver has applied the brakes. This is particularly significant for larger vehicles that utilize air brakes, as they can take longer distances to start decelerating compared to vehicles with hydraulic systems, which have a more immediate response due to liquid being used to transmit force directly. Understanding this concept is essential for drivers operating vehicles with air brakes, emphasizing the need for increased stopping distances and cautious driving practices to ensure safety on the road.