South Dakota CDL — Air Brakes practice
South Dakota 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
14 questions · pass with 11 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. Air pressure has fallen far enough that the spring brakes come on in a heavily loaded truck. Why does the manual say the stop will take a long distance?
Correct answer: Spring brakes do not act on every axle
Spring brakes are not fitted on all axles, so a heavy vehicle has less braking than usual once they apply. That is why the manual calls it much safer to stop while the tanks still hold enough air for the foot brake.
Source: South Dakota Commercial Driver License Manual — Section 5.4.7, Low Air Pressure
2. At highway speed your low air warning light and buzzer come on. The gauge is still above the range where spring brakes apply, and the next exit is several miles ahead. What does the manual tell you to do?
Correct answer: Stop safely right away, while the brakes are still yours to control
The manual says not to wait for the spring brakes to apply by themselves. As soon as the light and buzzer appear, you make a safe stop at once, because the brakes still respond to you at that point and may not later.
Source: South Dakota Commercial Driver License Manual — Section 5.1.14, Spring Brakes
3. On a wet road in a truck without ABS, you brake hard and turn the steering wheel to miss a stalled car, but the truck keeps sliding straight ahead. What does the manual's explanation point to?
Correct answer: The steering wheels have locked up
When the steering wheels lock, they slide instead of rolling, and the manual says steering control is lost. Lockup at the other wheels shows up differently: the vehicle can skid, jackknife or spin. ABS is there to help you avoid wheel lockup.
Source: South Dakota Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
4. According to the manual, what should ABS let you do while you are braking hard?
Correct answer: Steer around an obstacle and avoid skids from over-braking
The manual says ABS may or may not shorten the stop. What it should give you is the ability to steer past an obstacle during braking and to avoid the skids that over-braking causes.
Source: South Dakota Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
5. You are using the controlled braking method in an emergency stop. How does the manual say to handle the steering wheel?
Correct answer: Make only very small steering movements
Controlled braking means braking as hard as possible without locking the wheels while steering only slightly. If a bigger steering correction is needed, or the wheels lock, you release the brakes and reapply them as soon as you can.
Source: South Dakota Commercial Driver License Manual — Section 5.4.3, Emergency Stops
6. Your trailer has ABS but your tractor does not. Under hard braking the tractor begins to jackknife. What does the manual tell you to do?
Correct answer: Ease off the brakes, if you safely can, until you regain control
ABS on the trailer alone makes a trailer swing less likely, but the tractor can still lose steering or start to jackknife. The manual's answer is to release brake pressure, when that can be done safely, until control comes back.
Source: South Dakota Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
7. Which pair of braking methods does the manual give for emergency stops in an air-braked vehicle?
Correct answer: Controlled braking and stab braking
For an emergency stop the manual offers two methods, controlled braking and stab braking. Either should keep the vehicle going straight and leave you able to turn if you must.
Source: South Dakota Commercial Driver License Manual — Section 5.4.3, Emergency Stops
8. Your air leakage test shows the system losing air faster than the manual allows. What does the manual say to do, and why?
Correct answer: Find and fix the leaks before driving, or you could lose your brakes on the road
A loss rate above the limit means air is escaping somewhere. The manual's instruction is to look for the leaks and repair them before the vehicle moves, because brakes that depend on that air could be lost while you are driving.
Source: South Dakota Commercial Driver License Manual — Section 5.3.3, Step 7 Final Air Brake Check
9. Section 11 explains why the air brake check matters. What does it say a loss of air pressure will cause?
Correct answer: The emergency brakes come on, stopping the vehicle abruptly and without control
The "Why Inspect" note says air brake safety devices vary, and the check confirms they work as pressure falls from normal to low air. Losing air pressure makes the emergency brakes activate, and the result is a sudden stop the driver does not control.
Source: South Dakota Commercial Driver License Manual — Section 11.1.2, Air Brake or Hydraulic Brake Check
10. What does the ABS computer do when it senses that a wheel is about to lock?
Correct answer: It lowers brake pressure to a level that is safe
ABS watches for impending lockup. When it detects it, the computer backs the brake pressure down far enough that the wheel keeps rolling, which lets you maintain control.
Source: South Dakota Commercial Driver License Manual — Section 5.4.2, Braking with Antilock Brakes
11. In stab braking, a driver puts the brakes fully back on before the locked wheels have started rolling again. What does the manual say happens?
Correct answer: The vehicle will not straighten out
Stab braking is full application, release when the wheels lock, then full application again once the wheels are rolling. Wheels can need up to a second to start rolling after the release, and braking again too soon keeps the vehicle from straightening.
Source: South Dakota Commercial Driver License Manual — Section 5.4.3, Emergency Stops
12. Your truck's low air warning is an automatic wig wag. What does it do once system pressure climbs back above 55 psi?
Correct answer: It rises out of your view on its own
A wig wag swings a mechanical arm in front of the driver when pressure falls under 55 psi. The automatic kind lifts back out of sight by itself as pressure recovers; only the manual reset type has to be repositioned by hand.
Source: South Dakota Commercial Driver License Manual — Section 5.1.11, Low Air Pressure Warning
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Every South Dakota question is written from the official South Dakota 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