Air Brake Test Stopping Distance & Brake Performance

Question 1

What are the three main components that make up total stopping distance for a vehicle with air brakes?

Accepted Answer

Perception distance, reaction distance, and braking distance

Answer

Total stopping distance is the sum of perception distance (time to see a hazard), reaction distance (foot moving to brake), and braking distance (vehicle coming to a stop).

Question 2

Approximately how long is the brake lag time for air brakes compared to hydraulic brakes?

Accepted Answer

Air brakes lag about 0.4 seconds vs. 0.1 seconds for hydraulic brakes

Answer

Air brakes have a lag of approximately 0.4 seconds because air must travel through the lines to activate the brakes, while hydraulic brakes respond almost instantly at about 0.1 seconds.

Question 3

At 55 mph on dry pavement, approximately how many feet of additional stopping distance does air brake lag add compared to the moment you press the brake pedal?

Accepted Answer

About 32 feet

Answer

At 55 mph, a vehicle travels roughly 80 feet per second, so 0.4 seconds of brake lag adds approximately 32 feet before braking even begins.

Question 4

A fully loaded truck traveling at 55 mph on dry pavement requires approximately how many feet to come to a complete stop?

Accepted Answer

About 335 feet

Answer

At 55 mph, a fully loaded truck needs roughly 335 feet to stop when accounting for perception, reaction, brake lag, and braking distance on dry pavement.

Question 5

How does vehicle weight affect stopping distance for air-braked vehicles?

Accepted Answer

Empty trucks often take longer to stop than fully loaded trucks due to reduced traction

Answer

Empty trucks can require up to 40% more stopping distance than loaded trucks because lighter vehicles have less weight pressing the tires onto the pavement, reducing traction.

Air Brake Practice Test Practice Test

Air Brake Practice Test Practice Test

Air Brake Test Stopping Distance & Brake Performance