Vermont CDL — Air Brakes practice
Vermont CDL — Air Brakes: Handling Emergencies practice test
What to do when things go wrong — brake failure, tire blowouts, skids, and stalling on railroad tracks.
Content reviewed against official driver handbooks · August 12, 2026
11 questions · pass with 9 correct. You get instant feedback and an explanation after every answer.
Study questions with answers
11 sample Handling Emergencies questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.
Show all 11 questions with answers
1. For a vehicle to be controlled safely, each brake has to carry its part of the load. Which brakes does the manual say drop out of that effort first?
Correct answer: The ones that are out of adjustment
Brakes that are out of adjustment quit doing their share before the properly adjusted ones do. That shifts the work to the remaining brakes, which can then overheat and fade.
Source: Vermont Commercial Driver's Manual — Section 5.4.5, Brake Fading or Failure
2. The manual explains how too much heat produces brake fade. Which of these is NOT part of that explanation?
Correct answer: The air tanks lose pressure as the drums heat up
Fade comes from heat changing the lining chemically, which lowers friction, and from the drums expanding so the shoes have farther to go and make weaker contact. Tank pressure is not part of the manual's account.
Source: Vermont Commercial Driver's Manual — Section 5.4.5, Brake Fading or Failure
3. What is a 'wig wag' on an air-braked vehicle?
Correct answer: A low air warning that drops a mechanical arm into the driver's view
The wig wag is one kind of low air pressure warning. Its arm falls into sight when system pressure goes under 55 psi. An automatic one lifts back out of view once pressure recovers, while a manual-reset one has to be put back by hand.
Source: Vermont Commercial Driver's Manual — Section 5.1.11, Low Air Pressure Warning
4. Your tractor has ABS and your trailer does not. Which two benefits does the manual say you should still get under braking?
Correct answer: Steering control and less chance of a jackknife
With ABS on the tractor alone you should keep steering control and be less likely to jackknife. The trailer can still swing, so the manual has you watch it and ease off the brakes, if that is safe, should it start to come around.
Source: Vermont Commercial Driver's Manual — Section 5.4.2, Braking with Antilock Brakes
5. Which sequence matches the manual's stab braking method?
Correct answer: Apply the brakes fully, release when the wheels lock, then apply fully again once the wheels start rolling
Stab braking is full application, release at lockup, and full application again when the wheels are turning. The wheels can need up to a second to start rolling, and braking again too soon keeps the vehicle from straightening out.
Source: Vermont Commercial Driver's Manual — Section 5.4.3, Emergency Stops
6. The manual says not to wait for the spring brakes to come on by themselves after a low air warning. What reason does it give for stopping as soon as the light and buzzer start?
Correct answer: At that point you can still control the brakes
At the first warning there is still enough air to brake under your own control. Waiting lets pressure fall toward the 20 to 45 psi range, where the spring brakes on tractors and straight trucks come fully on whether you are ready or not.
Source: Vermont Commercial Driver's Manual — Section 5.1.14, Spring Brakes
7. How hard do you apply the brakes when you use the controlled braking method in an emergency stop?
Correct answer: As hard as you can short of locking the wheels
Controlled braking means braking as hard as possible while the wheels keep turning, with only very small steering movements.
Source: Vermont Commercial Driver's Manual — Section 5.4.3, Emergency Stops
8. After a low air warning, what does the manual say about how long controlled braking stays possible?
Correct answer: Only for as long as the tanks still hold enough air
Braking under your own control depends on air left in the tanks. Once pressure falls into the 20 to 45 psi range the spring brakes apply on their own, which is why the manual calls it much safer to stop while the foot brakes still have air.
Source: Vermont Commercial Driver's Manual — Section 5.4.7, Low Air Pressure
9. You hear the safety relief valve on an air tank let go. Besides recognizing that something is wrong, what does the manual tell you to do about it?
Correct answer: Get a mechanic to fix the fault
The valve guards the first tank and everything downstream against excess pressure, and it usually opens at 150 psi. If it releases air, something has failed, and the manual sends the problem to a mechanic.
Source: Vermont Commercial Driver's Manual — Section 5.1.6, Safety Valve
10. In a hard freeze, ice forms inside the valves of an air brake system that has no alcohol evaporator. What does the manual warn that ice in the system can do?
Correct answer: Make the brakes stop working
An alcohol evaporator feeds alcohol into the air system to cut the risk of ice in the valves and other parts in cold weather. The manual warns that ice in the system can leave you without working brakes.
Source: Vermont Commercial Driver's Manual — Section 5.1.5, Alcohol Evaporator
11. On a dual air system, the low air warning light and buzzer are on as pressure builds after start-up. When should they shut off?
Correct answer: When pressure in both systems has risen to the value the manufacturer set
The warning should go off only when both the primary and the secondary system have climbed to the manufacturer's value, which has to be above 55 psi.
Source: Vermont Commercial Driver's Manual — Section 5.2, Dual Air Brake
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