Texas CDL — Air Brakes practice
Texas CDL — Air Brakes: Safe Driving Practices practice test
Following distance, scanning, blind spots, using your lights, and the habits that prevent crashes and keep you in control.
Content reviewed against official driver handbooks · August 12, 2026
20 questions · pass with 16 correct. You get instant feedback and an explanation after every answer.
Choose your level
Up to 20 questions on this topic, with feedback after every answer.
Study offline
Texas Practice Test Pack — 2026 Printable Edition
$4.99 · One-time purchase. Instant download.
Our own printable edition — nobody paid us to show it to you, and everything in it is free to read here too.
Study questions with answers
12 sample Safe Driving Practices questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
Show all 12 questions with answers
1. For the applied-pressure leakage test on a combination vehicle, you shut off the engine with air built up to governor cutoff and hold the foot brake fully applied. How much pressure loss in one minute is too much?
Correct answer: More than 4 psi
With the brake pedal held down, the leakage rate should be no more than 3 psi per minute for single vehicles and no more than 4 psi per minute for combination vehicles. More than that means an air leak that must be fixed before driving.
2. You are performing the static leakage test on a single vehicle: engine off, fully charged system, foot off the brake, parking brake released, and you time the pressure drop. What is the most the pressure may fall?
Correct answer: 2 psi in one minute
With the brakes released, air loss should be less than 2 psi in one minute for a single vehicle and less than 3 psi in one minute for a combination vehicle.
3. During inspection you check push rod travel on an s-cam brake with a manual slack adjuster. When you pull hard on the push rod, about how much movement means the brake needs adjustment?
Correct answer: More than one inch
With the parking brakes released, pull hard on each slack adjuster you can reach. If a push rod moves more than about one inch where it attaches to the slack adjuster, the brake needs adjustment.
4. The governor stops the compressor from pumping once tank pressure climbs to roughly what level?
Correct answer: 125 psi
The governor "cuts out" the compressor at around 125 psi. When pressure drops to about 100 psi, it cuts the compressor back in to rebuild pressure.
5. Why should you drain the air storage tanks on a vehicle with manually operated drain valves at the end of each day of driving?
Correct answer: To remove water and oil that could freeze and cause brake failure
Compressed air carries water and a little compressor oil into the tanks. If not drained daily, the water can freeze in cold weather and cause brake failure.
6. What job does an alcohol evaporator perform in some air brake systems?
Correct answer: It reduces the chance of ice forming in air brake valves in cold weather
The alcohol evaporator introduces alcohol into the air system to help keep ice from forming in valves and other parts during cold weather. Its container should be checked and filled daily in cold weather.
7. Which type of foundation brake is found most often on commercial vehicles with air brakes?
Correct answer: S-cam drum brakes
The s-cam drum brake is the most common foundation brake. The s-shaped camshaft twists to push the brake shoes against the inside of the drum.
8. You are braking hard in a tractor-trailer where only the tractor has antilock brakes. What should you watch for?
Correct answer: The trailer swinging out; ease off the brakes if it does and you safely can
With ABS on the tractor alone, you should keep steering control, and a jackknife becomes less likely. The trailer does not have that protection, so keep an eye on it in your mirrors and, when it is safe, let up on the brakes if it starts to swing out.
9. Some air tanks with automatic drain valves also have electric heating devices. What are the heaters for?
Correct answer: They keep the automatic drain from freezing up in cold weather
Automatic drains push water and oil out of the tank on their own. In cold weather that drain could freeze, so some are fitted with electric heaters to keep it working.
10. Your air compressor has its own oil supply instead of using engine oil. What should you do before driving?
Correct answer: Check the compressor's oil level
Some compressors are lubricated by engine oil, while others carry a separate supply. When the compressor has its own oil, checking that oil level is part of getting ready to drive.
11. An air brake setup actually combines three separate braking systems. Which set names all three?
Correct answer: Service, parking, and emergency brakes
The handbook describes air brakes as three systems in one: the service brakes you work with the pedal, the parking brakes you set with the parking control, and the emergency brakes, which borrow parts of the other two to stop the vehicle if the system fails.
12. As part of the seven-step air brake check, how do you test that the low pressure warning signal works?
Correct answer: Shut the engine off, turn the key on, and fan the pedal until the warning activates
With the engine off but the key in the on position, fan the brake pedal to reduce tank pressure. The warning light or buzzer must come on before pressure drops below 55 psi.
More CDL — Air Brakes topics
Practice Safe Driving Practices in another state
Every Texas question is written from the official Texas 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
Study offline
Texas Practice Test Pack — 2026 Printable Edition
$4.99 · One-time purchase. Instant download.
Our own printable edition — nobody paid us to show it to you, and everything in it is free to read here too.