← CDL General Knowledge: Braking & Stopping

Free CDL General Knowledge: Braking & Stopping Practice Test (2026)

50 questions · 60 min · 80% to pass

50 Questions · 60 Minutes · 80% to Pass

Question 1 of 5

Sample Questions

Question 1

What is 'perception distance' in the context of stopping distance?

Answer: Perception distance is the distance your vehicle travels from the moment your eyes see a hazard until your brain recognizes it. The average perception time is 1.75 seconds.

Question 2

What is 'brake lag distance' and how long does it typically take for air brakes to respond?

Answer: Brake lag distance is the distance traveled between the time you apply the brake pedal and when the brakes actually engage. Air brakes have a lag time of about one-half second.

Question 3

What are the three factors that make up total stopping distance for a commercial vehicle?

Answer: Perception distance, reaction distance, and braking distance. All three must be added together to find the total stopping distance.

Question 4

At 55 mph on dry pavement, approximately how many feet does it take a fully loaded truck to stop?

Answer: Approximately 335 feet — significantly longer than a passenger car under the same conditions.

Question 5

How does doubling your speed affect the braking distance of a commercial vehicle?

Answer: Doubling your speed quadruples your braking distance. This is because braking distance increases with the square of the speed.