South Dakota General Knowledge CDL Practice Test

This is a free 20-question practice test for the General Knowledge portion of the South Dakota Commercial Driver's License knowledge exam. Questions are pulled from a pool of 97 drawn from the AAMVA CDL Manual, which is the source document the South Dakota Driver Licensing Program uses to write its actual exam.

How it works: Click an answer. The correct choice highlights in green, and you'll see a short explanation. Aim for 85% or better before you sit for the real test in South Dakota.

Question 1 of 20

You are driving on a two-lane road. An oncoming driver drifts into your lane. You should:

Steer right onto the shoulder
Flash your high beams
Honk your horn
Brake hard and stop in your lane

Correct. When an oncoming driver drifts into your lane, the safer escape is right onto the shoulder. Steering left risks a head-on if the other driver corrects.

Question 2 of 20

A safe practice when entering a freeway is to:

Stop at the end of the on-ramp and wait
Use the entire on-ramp to accelerate to traffic speed and merge into a gap
Slow to 25 mph regardless of traffic
Force traffic to make space

Correct. Use the on-ramp to match traffic speed before merging. Stopping at the end of an on-ramp is dangerous.

Question 3 of 20

When driving in heavy fog, you should:

Drive faster to get out of it
Use high-beam headlights
Pull off the road if visibility is too low to drive safely
Follow another vehicle's tail lights closely

Correct. If visibility is so poor that you cannot drive safely, pull completely off the road, turn on four-way flashers, and wait for conditions to improve.

Question 4 of 20

Speed control on long downgrades is best maintained by:

Riding the brakes
Selecting a low gear before the descent and using the engine plus intermittent firm brake applications
Coasting in neutral
Braking only at the bottom

Correct. Pre-select a low gear, use engine braking, and apply brakes in firm intermittent pulses. This prevents brake fade.

Question 5 of 20

When should you place reflective triangles on a divided highway after stopping due to a breakdown?

10, 50, and 100 feet behind the vehicle
10 feet to the rear, 100 feet to the rear, and 200 feet to the rear
10, 100, and 200 feet to the rear, on the traffic side
100, 200, and 500 feet to the rear

Correct. On a divided highway with traffic from one direction, place triangles 10, 100, and 200 feet behind the vehicle, on the shoulder or in the lane you stopped in.

Question 6 of 20

Which of these is NOT a hazard you should look out for ahead?

Pedestrians
A vehicle stopped on the shoulder
Roadway construction
A clear, dry road

Correct. Hazards are conditions that could lead to a crash: pedestrians, stopped vehicles, work zones, debris. A clear, dry road is the absence of a hazard.

Question 7 of 20

Driver fatigue is most often caused by:

Inadequate sleep, long work hours, and night driving
Hot weather
Heavy traffic
Cold meals

Correct. Sleep deprivation, long hours, and circadian-low night-driving hours are the leading causes of fatigue. Sleep before driving; pull over when drowsy.

Question 8 of 20

Which of these is true about driving in fog?

Use high beams to see further
Use low beams; high beams reflect back and reduce visibility
Drive at the posted speed limit
Use the four-way flashers only when stopped

Correct. In fog, high beams reflect off water particles and impair vision. Use low beams. Many drivers also use four-way flashers when moving slowly to alert traffic.

Question 9 of 20

You should back from the driver's side rather than the passenger's side when possible because:

You can see better out of the driver's window
It is required by law
Trailers track that direction
Mirrors only work on that side

Correct. Driver-side ("sight side") backing gives the driver direct visual feedback through the open window in addition to mirror checks.

Question 10 of 20

Which of these is a sign of tire failure?

Heavy thumping or vibration
A loud bang
The vehicle pulling to one side
All of the above

Correct. Vibration, a loud bang from a blowout, and pulling to one side are all classic signs of tire failure.

Question 11 of 20

You are driving on a steep downgrade and your brakes have failed. The best escape is to:

Pump the brakes furiously
Use a runaway escape ramp
Try to bail out of the cab
Sound the horn and continue

Correct. If a runaway escape ramp is available, use it. Modern arrester beds use loose gravel or sand to slow the vehicle without injury to the driver.

Question 12 of 20

When should you use four-way flashers?

Only when parked
When the vehicle is stopped or moving slowly enough to be a hazard to other traffic
Only at night
Whenever you want

Correct. Four-way emergency flashers warn other drivers when your vehicle is stopped or moving slowly relative to traffic.

Question 13 of 20

On a vehicle equipped with ABS, you should:

Pump the brakes during emergency stops
Apply the brakes the way you always have, with steady pressure
Use the parking brake instead
Never use the service brakes

Correct. With ABS, brake the way you always would. The system prevents wheel lockup automatically; pumping interrupts ABS function.

Question 14 of 20

Which of these statements about backing a heavy vehicle is true?

Backing is always safe if you go slow
Whenever possible, use a helper outside the vehicle to guide you
Always back from the right side because you can see better
Backing is the same as backing a car

Correct. Backing is always risky for heavy vehicles. Use a helper, communicate with hand signals agreed in advance, back slowly, and if alone, get out and look (G.O.A.L.).

Question 15 of 20

Wet brakes can cause:

Reduced braking power, brakes pulling to one side, or wheel lockup
Better braking
No effect on the brakes
Improved fuel economy

Correct. After driving through deep water, brakes may be wet — they can lose effectiveness, pull to one side, or grab. Apply the brakes lightly while driving slowly to dry them.

Question 16 of 20

If you are involved in an accident, you should:

Drive away if no one is hurt
Notify authorities, protect the scene with warning devices, and care for the injured
Move all vehicles immediately
Make no statements at all

Correct. Stop, protect the scene, notify authorities, care for injured persons, and exchange the required information. Failing to stop is a serious offense.

Question 17 of 20

Most drivers who fall asleep at the wheel:

Are aware they are tired and pull over
Do not realize they are about to fall asleep
Have been drinking
Have been on the road less than an hour

Correct. Most drivers who fall asleep do not realize how drowsy they are. The only fix is to stop and rest before fatigue reaches that point.

Question 18 of 20

The blood-alcohol concentration (BAC) at or above which a CDL driver is considered to be driving under the influence in a commercial motor vehicle is:

Correct. The federal BAC limit for CDL drivers operating a commercial vehicle is .04 — half the .08 limit for non-commercial drivers in most states.

Question 19 of 20

When should you use your high beams?

Whenever it is dark
When other drivers are within 500 feet ahead
When other drivers are not within 500 feet of you and you are not following another vehicle within 500 feet
In fog

Correct. Federal and state law requires you to dim high beams when within 500 feet of an oncoming vehicle, or when following within 500 feet of another vehicle.

Question 20 of 20

Which is the safest stopping technique for a non-ABS vehicle whose brakes have started to lock up?

Continue braking hard until you stop
Stab braking: brake hard, release, brake hard again
Pump the brakes lightly
Coast in neutral

Correct. On a non-ABS vehicle, stab braking — full brake application until wheels lock, release, repeat — keeps the vehicle straight while still slowing.

About the South Dakota General Knowledge exam

Most state DMVs administer 50 General Knowledge questions and require 80% (40 correct) to pass. Questions are pulled from a much larger pool, so two applicants taking the test on the same day will see different mixes. The questions on this site are drawn from the AAMVA CDL Manual chapters that every state's exam is built from.

The South Dakota Driver Licensing Program follows the federal CDL standards established by FMCSA. To earn the General Knowledge credential, you must answer at least 80% of the questions correctly. Many candidates score lower the first time because the test pulls from a large pool — refreshing this page will give you a different mix of questions, drawn from the same authoritative source.

Want more practice? Try the full General Knowledge question bank or browse all South Dakota CDL practice tests.