Connecticut CDL — Air Brakes practice
Connecticut 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
13 questions · pass with 10 correct. You get instant feedback and an explanation after every answer.
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12 sample Handling Emergencies 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. What does an antilock braking system do during hard braking?
Correct answer: It keeps the wheels from locking so you can steer and stay in control
ABS senses impending lockup and eases pressure to keep the wheels turning; it may not stop you sooner, but it lets you steer around obstacles and avoid skids.
Source: Connecticut CDL Manual, Section 5.4.2 (Braking with Antilock Brakes)
2. What is a modulating control valve on the dash used for?
Correct answer: It lets the driver bring the spring brakes on gradually when the service brakes fail
The handle is spring-loaded so the driver feels the braking; the farther it is moved, the harder the spring brakes grab, giving you a way to slow down if the service brakes quit.
Source: Connecticut CDL Manual, Section 5.1.15 (Parking Brake Controls)
3. If the low air pressure warning comes on while you are driving, what should you do?
Correct answer: Stop and safely park the vehicle as soon as possible
A low-air warning may mean a leak; controlled braking only works while air remains, so stop and park safely right away before the spring brakes engage on their own.
Source: Connecticut CDL Manual, Section 5.4.7 (Low Air Pressure)
4. When may you fully apply the brakes in an emergency stop?
Correct answer: When you routinely drive a straight truck or a combination that has working ABS on all its axles
The one exception to braking as usual is that a vehicle with functioning ABS on all axles can be brought to an emergency stop with the brakes fully applied.
Source: Connecticut CDL Manual, Section 5.4.2 (Braking with Antilock Brakes)
5. How is stab braking performed?
Correct answer: Fully apply the brakes, release when the wheels lock, then reapply once they roll again
Stab braking presses the brakes all the way, releases when wheels lock, and reapplies fully once they start rolling; it can take up to a second for wheels to roll again after releasing.
Source: Connecticut CDL Manual, Section 5.4.3 (Emergency Stops)
6. The yellow ABS malfunction lamp stays lit after the start-up bulb check. What should you conclude?
Correct answer: Your usual brakes still work, so drive normally and get the system fixed soon
A lamp that stays on means antilock control may be missing at one or more wheels, yet the ordinary braking system is untouched, so drive as you normally would and book the repair promptly.
Source: Connecticut CDL Manual, Section 5.4.2 (Braking with Antilock Brakes)
7. Which two braking methods are recommended for an emergency stop?
Correct answer: Controlled braking and stab braking
In an emergency you can use controlled braking or stab braking; both aim to keep the vehicle straight while allowing you to steer if needed.
Source: Connecticut CDL Manual, Section 5.4.3 (Emergency Stops)
8. You brake hard on a slick road in a truck with no ABS. What happens if the steering axle wheels lock?
Correct answer: You can no longer steer the vehicle
Front wheels that are sliding cannot turn the truck, so the steering wheel does nothing; wheels locking elsewhere invite a skid, a jackknife, or a spin.
Source: Connecticut CDL Manual, Section 5.4.2 (Braking with Antilock Brakes)
9. What describes the controlled braking method?
Correct answer: Braking as hard as possible without locking the wheels, keeping steering movements small
Controlled braking means applying maximum pressure short of locking the wheels; if you must steer more or the wheels lock, release and reapply as soon as you can.
Source: Connecticut CDL Manual, Section 5.4.3 (Emergency Stops)
10. Why may a heavily loaded truck need a very long distance to stop once the spring brakes apply by themselves?
Correct answer: Spring brakes are not fitted to every axle, so braking force is limited
Because some axles have no spring brakes at all, a loaded vehicle keeps far less braking than usual, which is why you should park while the tanks still hold enough air to work the foot brake.
Source: Connecticut CDL Manual, Section 5.4.7 (Low Air Pressure)
11. As overheated brake drums expand, what happens to braking performance?
Correct answer: The shoes must travel farther to reach the drum, and contact force drops
Heat expands the drums so the shoes and linings have to move farther to touch them, and the force of that contact is weaker, so braking suffers.
Source: Connecticut CDL Manual, Section 5.4.5 (Brake Fading or Failure)
12. Some buses carry a second parking control fed by its own small air tank. Why does that help in an emergency?
Correct answer: Its reserve air can free the spring brakes long enough to move the bus a few times
Holding that spring-loaded control in sends reserve air to the spring brakes so the bus can be moved clear of danger, but the small tank empties after a few tries, so plan where you are going first.
Source: Connecticut CDL Manual, Section 5.1.15 (Parking Brake Controls)
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