Alaska CDL — Air Brakes practice
Alaska 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.
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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.
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1. Checking slack adjusters on s-cam brakes means releasing the parking brakes so the adjusters can move. What does the manual have you do first so the vehicle stays put?
Correct answer: Chock the wheels after parking on a level spot
With the parking brakes off, nothing holds the vehicle, so the manual has you park on a level surface and put chocks at the wheels before you pull on the slack adjusters.
Source: Alaska Commercial Driver License Manual — Section 5.3.2, During Step 5 Walk-around Inspection
2. The manual gives two other names for the brake pedal in an air brake system. What are they?
Correct answer: Foot valve or treadle valve
The manual notes that the brake pedal also goes by foot valve or treadle valve. Pushing it down harder applies more air pressure to the brakes.
Source: Alaska Commercial Driver License Manual — Section 5.1.7, The Brake Pedal
3. Besides brake fade, the manual lists other things that can make you need more application pressure than usual. Which of these is NOT on its list?
Correct answer: A burned-out warning light
The manual says the need for more pressure can also come from out-of-adjustment brakes, air leaks or mechanical problems. A dead warning light is a hazard of its own, but it does not change how much pressure a stop takes.
Source: Alaska Commercial Driver License Manual — Section 5.1.10, Application Pressure Gauge
4. Parked with the engine running, you watch the air gauge rise to roughly 125 psi and stop. After several brake applications it sinks to about 100 psi and begins rising again. Which part is controlling this?
Correct answer: The air compressor governor
The governor decides when the compressor pumps. It stops the compressor at the cut-out level, around 125 psi, and lets it pump again once the tanks are down to the cut-in level, around 100 psi.
Source: Alaska Commercial Driver License Manual — Section 5.1.2, Air Compressor Governor
5. You are making a normal stop in an air-braked truck with a manual transmission. When does the manual say to push the clutch in?
Correct answer: Once engine rpm has come down close to idle
For a normal stop you press the pedal and control the pressure so the stop is smooth and safe. With a manual transmission, the manual says to wait on the clutch until rpm is near idle, then pick a starting gear once you are stopped.
Source: Alaska Commercial Driver License Manual — Section 5.4.1, Normal Stops
6. According to the manual, what determines how much heat a brake drum can take without damage?
Correct answer: How hard the brakes are applied and for how long
Pushing the shoes and linings against the drum creates friction, and friction creates heat. The manual ties a drum's heat tolerance to how hard and how long you brake, and overheated brakes can quit working.
Source: Alaska Commercial Driver License Manual — Section 5.1.8, Foundation Brakes
7. Some automatic air tank drains can be had with electric heating devices. What are the heaters for?
Correct answer: Keeping the automatic drain from freezing in cold weather
Automatic drains expel water and oil on their own, but the drain itself can freeze. The manual says electric heating devices are available to help keep that from happening when it is cold.
Source: Alaska Commercial Driver License Manual — Section 5.1.4, Air Tank Drains
8. On a long hill, your application pressure gauge shows you need more and more pressure just to hold the same speed. What does the manual tell you to do?
Correct answer: Reduce speed and shift to a lower gear, because the brakes are fading
Needing rising application pressure to keep the same speed is a sign of brake fade. The manual's answer is to reduce speed and drop to a lower gear.
Source: Alaska Commercial Driver License Manual — Section 5.1.10, Application Pressure Gauge
9. In slow traffic, a driver keeps pressing and releasing the brake pedal when there is no need to. What risk does the manual point to?
Correct answer: Air can be used faster than the compressor restores it, leaving too little pressure to brake
Every release of the brakes lets some compressed air out of the system, and the compressor has to make it up. Needless pedal work can drain air quicker than it is replaced, and brakes without enough pressure will not work.
Source: Alaska Commercial Driver License Manual — Section 5.1.7, The Brake Pedal
10. Two tractor-trailers brake hard. One has ABS only on the tractor, and the other has ABS only on the trailer. In which one is the trailer less likely to swing out?
Correct answer: The one with ABS on the trailer
With ABS on the trailer alone, the manual says trailer swing becomes less likely. With ABS on the tractor alone, you should keep steering control and lower the jackknife risk, but you still have to watch the trailer.
Source: Alaska Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
11. For single air systems, found on vehicles from before 1975, what air pressure buildup does the manual give as a typical requirement?
Correct answer: From 50 psi to 90 psi in 3 minutes or less with the engine idling at 600 to 900 rpm
The 85-to-100 figure applies to dual air systems. For the older single systems, the manual's typical requirement is a climb from 50 psi to 90 psi inside 3 minutes at an idle of 600 to 900 rpm. If pressure builds too slowly, don't drive until it is fixed.
Source: Alaska Commercial Driver License Manual — Section 5.3.3, Step 7 Final Air Brake Check
12. Your truck has an alcohol evaporator, but its air tanks are the manually drained type. During a cold week, does the evaporator let you skip draining the tanks each day?
Correct answer: No. The tanks still have to be drained daily to clear out water and oil
The evaporator only lowers the risk of ice in the valves and other parts. The manual says the tanks must still be drained every day to remove water and oil. The only exception is a system fitted with automatic drains.
Source: Alaska Commercial Driver License Manual — Section 5.1.5, Alcohol Evaporator
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