CDL General Knowledge Practice Test 2026: Practice test 3

Practice test 3 of 6 for the CDL General Knowledge Practice Test: 25 more questions with answers and explanations.

Commercial vehicle
United States
150 questions
Checked October 10, 2026

Question 1 of 25
Is a radar detector allowed in a commercial motor vehicle?
- Yes, if it is turned off
- Yes, on interstate highways
- Only in states that allow them
- No
Show answer
Answer: D. No
A driver may not use a radar detector in a CMV or drive a CMV that has one in it.
Question 2 of 25
In the seven-step inspection method, what is the first step?
- Vehicle overview
- Check the signal lights
- Check the brakes
- Check the engine compartment
Show answer
Answer: A. Vehicle overview
Step 1 is the vehicle overview: general condition, leaning, leaks, hazards nearby and the last inspection report.
Question 3 of 25
Before you check the engine compartment, what should you do?
- Turn on the high beams and flashers
- Start the engine and let it warm up
- Set the parking brake or chock the wheels
- Release the parking brake fully
Show answer
Answer: C. Set the parking brake or chock the wheels
Step 2 starts by making sure the vehicle cannot move: set the parking brake and/or chock the wheels.
Question 4 of 25
In which step of the seven-step inspection do you check tires, wheels, suspension and brakes on each side of the vehicle?
- Step 6, the signal lights
- Step 1, the overview
- Step 3, inside the cab
- Step 5, the walkaround
Show answer
Answer: D. Step 5, the walkaround
The walkaround in step 5 covers lights, tires, wheels, suspension, brakes, cargo securement and fuel tanks on every side.
Question 5 of 25
What is the last step of the seven-step inspection?
- Read the last inspection report
- Check the engine oil
- Walk around the vehicle
- Start the engine and check the brakes
Show answer
Answer: D. Start the engine and check the brakes
Step 7 is to start the engine and check the brake system, including the parking brake and service brake tests.
Question 6 of 25
What is the minimum tread depth for the front (steering) tires?
- 4/32 inch in every major groove
- 1/32 inch in every major groove
- 6/32 inch in every major groove
- 2/32 inch in every major groove
Show answer
Answer: A. 4/32 inch in every major groove
Front tires need at least 4/32 inch of tread in every major groove.
Question 7 of 25
What is the minimum tread depth for tires that are not on the front axle?
- 4/32 inch
- 6/32 inch
- 2/32 inch
- 1/32 inch
Show answer
Answer: C. 2/32 inch
Tires other than the front tires need at least 2/32 inch of tread in every major groove.
Question 8 of 25
How much play in the steering wheel can make the vehicle hard to steer?
- More than 45 degrees (about 8 inches on the rim)
- Any play at all, even less than a quarter inch
- More than 2 degrees (about half an inch on the rim)
- More than 10 degrees (about 2 inches on a 20-inch wheel)
Show answer
Answer: D. More than 10 degrees (about 2 inches on a 20-inch wheel)
Steering wheel play of more than 10 degrees can make it hard to steer.
Question 9 of 25
How do you check hydraulic brakes during the inspection?
- Drive at 30 mph and brake hard; the truck should stop straight
- Pump three times, then hold for five seconds; the pedal should not move
- Hold the pedal for one minute with the engine off; it should sink
- Press the pedal once quickly; it should spring back up right away
Show answer
Answer: B. Pump three times, then hold for five seconds; the pedal should not move
With hydraulic brakes, pump three times and hold for five seconds. The pedal should stay firm.
Question 10 of 25
How do you test the service brakes at the end of the inspection?
- Move forward at about 5 mph and brake firmly
- Apply the parking brake while moving
- Pump the pedal several times while parked
- Drive at highway speed and brake hard
Show answer
Answer: A. Move forward at about 5 mph and brake firmly
Go forward slowly, about 5 mph, then brake firmly. Note any pulling or delay.
Question 11 of 25
How do you check that the parking brake will hold?
- Push against the truck by hand from behind
- Set it and gently pull against it in a low gear
- Release it at highway speed and feel the pull
- Park on a steep hill and walk away to see
Show answer
Answer: B. Set it and gently pull against it in a low gear
With the parking brake on, try to pull forward gently in a low gear. The vehicle should not move.
Question 12 of 25
Which emergency equipment must a truck carry?
- A spare tire, a tow strap and jumper cables
- A fire extinguisher, warning devices and spare fuses
- Snow chains, a jack and a tire iron
- A first aid kit, a shovel and a flashlight
Show answer
Answer: B. A fire extinguisher, warning devices and spare fuses
Required emergency equipment is a charged, rated fire extinguisher, warning devices such as three reflective triangles, and spare fuses unless the vehicle has circuit breakers.
Question 13 of 25
Your oil pressure gauge shows low or falling pressure while you drive. What should you do?
- Speed up to raise the pressure
- Turn off the gauge
- Keep driving and check it at your next stop
- Stop as soon as it is safe
Show answer
Answer: D. Stop as soon as it is safe
Low or changing oil pressure can mean engine damage. Stop right away when it is safe.
Question 14 of 25
You find defects listed on the previous driver's inspection report. When should you sign the report?
- Only if the defects were repaired or certified as not needing repair
- Only at the end of your own trip, after you drive the vehicle
- Always, before you start the engine, whatever the report says
- Never; only a mechanic may sign an inspection report
Show answer
Answer: A. Only if the defects were repaired or certified as not needing repair
Review the last report and sign it only when the defects listed were certified as repaired or not needing repair.
Question 15 of 25
When you must back up, which way should you back if you have a choice?
- Into traffic
- Uphill
- Toward the driver's side
- Toward the right side
Show answer
Answer: C. Toward the driver's side
Backing toward the driver's side lets you see better.
Question 16 of 25
What does G.O.A.L. mean when backing?
- Get Out And Look
- Gear Options Are Limited
- Go Only At Low speed
- Give Others A Lane
Show answer
Answer: A. Get Out And Look
Before and while backing, get out and look at your path if you are not sure what is behind you.
Question 17 of 25
How should you back a large vehicle?
- Quickly, to finish the move
- In the highest reverse gear
- Slowly, in the lowest reverse gear
- In neutral, letting it roll
Show answer
Answer: C. Slowly, in the lowest reverse gear
Back slowly in the lowest reverse gear so you can correct steering errors and stop quickly.
Question 18 of 25
You are backing a trailer and want the trailer to go to the left. Which way do you turn the steering wheel?
- Hold it straight
- Turn it left, then quickly right
- To the left
- To the right
Show answer
Answer: D. To the right
When backing a trailer, turn the steering wheel in the opposite direction from where you want the trailer to go.
Question 19 of 25
Which kind of manual transmission usually needs double clutching?
- An unsynchronized transmission
- An automatic transmission
- A synchronized transmission
- Any transmission in top gear
Show answer
Answer: A. An unsynchronized transmission
Unsynchronized manual transmissions usually need double clutching. Synchronized ones do not.
Question 20 of 25
When should you downshift?
- After speed builds on a downgrade
- In the middle of a curve
- Before a downgrade and before a curve
- Only when the engine stalls
Show answer
Answer: C. Before a downgrade and before a curve
Shift down before a downgrade and before a curve so you stay in control.
Question 21 of 25
What should you do with a retarder on wet, icy or snowy roads?
- Set it to the highest level
- Use it instead of the brakes
- Turn it off
- Use it only in curves
Show answer
Answer: C. Turn it off
Retarders can make the drive wheels skid on slippery roads, so turn them off.
Question 22 of 25
Your drive wheels start to spin as you pull away. What should you do?
- Apply the trailer brakes
- Take your foot off the accelerator
- Shift into a higher gear quickly
- Press harder on the accelerator
Show answer
Answer: B. Take your foot off the accelerator
If the drive wheels spin, ease off the accelerator to regain traction.
Question 23 of 25
How far ahead do most good drivers look?
- 30 to 40 seconds
- 12 to 15 seconds
- 3 to 5 seconds
- 1 to 2 seconds
Show answer
Answer: B. 12 to 15 seconds
Looking 12 to 15 seconds ahead gives you time to spot hazards and plan.
Question 24 of 25
At highway speed, looking 12 to 15 seconds ahead means looking about how far?
- About 2 miles
- About 100 feet
- About one city block
- About a quarter of a mile
Show answer
Answer: D. About a quarter of a mile
At lower speeds 12 to 15 seconds is about one block. At highway speeds it is about a quarter of a mile.
Question 25 of 25
How do convex (curved) mirrors make objects look?
- Smaller and farther away than they really are
- Closer but the right size
- Larger and closer than they really are
- Exactly as they are
Show answer
Answer: A. Smaller and farther away than they really are
Convex mirrors show a wider area, but things look smaller and farther away.

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