Georgia CDL — Air Brakes practice
Georgia CDL — Air Brakes: Speed & Space Management practice test
Choosing a safe speed, keeping a space cushion, adjusting for weather and traffic, and understanding stopping distance.
Content reviewed against official driver handbooks · August 12, 2026
8 questions · pass with 6 correct. You get instant feedback and an explanation after every answer.
Study questions with answers
8 sample Speed & Space Management questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
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1. Unlike hydraulic brakes, air brakes do not act the instant you press the pedal. How long does the air take to travel through the lines and apply the brakes?
Correct answer: One half second or more
This delay is called brake lag. Hydraulic brakes respond instantly, but in an air system it takes one half second or more for air to reach the brakes, so brake lag distance adds to your total stopping distance.
2. For a normal stop in an air-braked vehicle, the manual says to press the brake pedal so that:
Correct answer: The vehicle comes to a smooth, safe stop
For a normal stop, push the pedal down and control the pressure so the vehicle comes to a smooth, safe stop. With a manual transmission, do not push the clutch in until engine rpm nears idle.
3. Which distance is unique to air-braked vehicles when figuring total stopping distance?
Correct answer: Brake lag distance
All drivers face perception, reaction, and braking distance. Air-braked vehicles add a fourth element — brake lag distance — because air must flow through the lines before the brakes act.
4. During stab braking in an emergency, when do you release the brake pedal — and when do you press it again?
Correct answer: Release when the wheels lock up; reapply fully once the wheels start rolling again
In stab braking you apply the brakes fully, release when the wheels lock up, and apply fully again as soon as the wheels start rolling. It can take up to a second for wheels to start rolling after you release.
5. Add together perception distance, reaction distance, brake lag distance, and braking distance for an air-braked vehicle at 55 mph on good pavement. The total is:
Correct answer: Over 450 feet
At 55 mph under good conditions, the total stopping distance for a vehicle with air brakes is over 450 feet — perception, reaction, and brake lag all add distance before effective braking even begins.
6. At 55 mph, roughly how much extra distance does brake lag alone add to your stop compared to a vehicle with instant brakes?
Correct answer: About 32 feet
At 55 mph on dry pavement, the roughly 0.4-second brake lag adds about 32 feet of travel before the brakes even begin to slow the vehicle.
7. Controlled braking means:
Correct answer: Applying the brakes as hard as possible without locking the wheels
With controlled (squeeze) braking you apply the brakes as hard as you can without locking the wheels, keeping steering movements small. If the wheels lock, ease off, then reapply.
8. How does a heavier load change the braking job your air brakes have to do?
Correct answer: The brakes must absorb more energy, so more braking effort and distance are needed
The brakes must absorb the vehicle's energy of motion, and a heavier vehicle carries more energy at the same speed. Heavily loaded vehicles need more braking effort and distance — although a very lightly loaded truck with stiff suspension can also be harder to stop smoothly because of wheel lockup.
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Every Georgia question is written from the official Georgia driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free