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South Dakota CDL practice test

Getting a commercial driver's licence in South Dakota starts with the CDL knowledge tests. The content is federal: every state, South Dakota included, writes its tests from the FMCSA CDL manual, so the general knowledge test has 50 questions, the endorsement tests have 20 to 30, and the passing score is 80% on each. The South Dakota driver licensing agency administers the test; the rules behind it are published by the FMCSA. Try the free South Dakota CDL practice questions below, then pick a full test.

Free South Dakota CDL practice questions

Five questions from the general knowledge, air brakes and combination vehicles banks, the three tests most South Dakota Class A applicants take first. Show the answer to read the explanation.

  1. Allowing for brake lag, the total stopping distance for an air-brake vehicle at 55 mph on dry pavement with good brakes is:

    • About 100 feet
    • About 216 feet
    • About 300 feet
    • Over 450 feet
    Show answer
    Answer: D. Over 450 feet

    Perception, reaction, and braking distance add up to about 419 feet, and air brake lag adds roughly 32 feet more. That is more than one and a half football fields.

    Source: FMCSA CDL Manual, Section 5.4.3 (Stopping Distance)

  2. Brake lag in an air system (the delay between pressing the pedal and the brakes working) is about:

    • One-half second or more
    • One-tenth of a second
    • Two seconds
    • It is instant, with no delay
    Show answer
    Answer: A. One-half second or more

    Air has to flow through the lines to the brake chambers before anything happens. Unlike hydraulic brakes, which act almost instantly, air brakes need half a second or more, which adds distance at speed.

    Source: FMCSA CDL Manual, Section 5.4.3 (Brake Lag Distance)

  3. If the low air pressure warning comes on while you are driving, you should:

    • Drive to the nearest repair shop no matter how far
    • Stop and safely park as soon as possible, because the spring brakes may apply on their own
    • Pump the brakes to rebuild pressure
    • Turn off the engine while moving to save air
    Show answer
    Answer: B. Stop and safely park as soon as possible, because the spring brakes may apply on their own

    Low air means the brakes may soon stop working or the spring brakes may lock on suddenly. Use the remaining air to get safely off the road while you still have control.

    Source: FMCSA CDL Manual, Section 5.4.4 (Low Air Pressure)

  4. Your brakes are very hot after a long downgrade and you need to park. Instead of setting the parking brake, you should:

    • Leave the vehicle in neutral with no brakes
    • Pour water on the drums before parking
    • Use wheel chocks to hold the vehicle until the brakes cool
    • Set the trailer hand valve
    Show answer
    Answer: C. Use wheel chocks to hold the vehicle until the brakes cool

    Setting spring brakes on very hot drums can damage them as they cool. Chock the wheels and let the brakes cool first. Chocks are also the answer in freezing wet weather when brakes could freeze locked.

    Source: FMCSA CDL Manual, Section 5.4.5 (Parking Brakes)

  5. Why is repeatedly pressing and releasing (fanning) the brake pedal a problem in an air-brake vehicle?

    • It wears out the brake pedal spring
    • It overheats the compressor and melts the belt
    • It cancels the ABS
    • Each application uses stored air, and the compressor may not keep up, leaving too little pressure to stop
    Show answer
    Answer: D. Each application uses stored air, and the compressor may not keep up, leaving too little pressure to stop

    Every time you apply the brakes some air is let out. If you use air faster than the compressor replaces it, pressure drops until the brakes cannot stop you or the spring brakes lock on.

    Source: FMCSA CDL Manual, Section 5.1.7 and 5.4.2 (The Brake Pedal; Braking on Downgrades)

Every CDL test for South Dakota drivers

Each page has ten free sample questions, the real question count, the 80% pass mark and what the test covers.

How the South Dakota CDL knowledge test works

You take the general knowledge test first; it is required for every CDL class. Class A drivers add the combination vehicles test. Almost everyone takes the air brakes test, because skipping it puts an air brake restriction on the licence. Endorsements (hazmat, tanker, doubles/triples, passenger, school bus) each have their own knowledge test. Pass the tests and you hold a commercial learner's permit; the skills test in a truck comes later.

Fees, appointment rules and test centre locations are set by South Dakota and change over time, so check the state driver licensing agency before you go. What does not change is the content, and that is what PassRig drills.

South Dakota CDL test questions

How many questions are on the South Dakota CDL test?

The South Dakota CDL general knowledge test follows the federal model: 50 questions, 40 correct to pass. Endorsement tests are shorter: air brakes 25, hazmat 30, and combination vehicles, tanker, doubles/triples, passenger and school bus 20 each.

What is the passing score on the South Dakota CDL permit test?

80% on every knowledge test, the same pass mark used across the United States.

Where do I take the CDL knowledge test in South Dakota?

At the South Dakota state driver licensing agency (the DMV, DOT or equivalent). Check its website for locations, appointments and current fees; the test content itself comes from the FMCSA CDL manual.

Does PassRig have South Dakota CDL practice questions?

Yes. Pick South Dakota in the app and you get practice sets and mock exams built from the knowledge test content your state uses, with the real counts and the 80% line.

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