Missouri CDL Combination Vehicles Practice Test

The Missouri CDL Combination Vehicles test is a multiple-choice knowledge test you take for your commercial learner's permit. Missouri Department of Revenue (licenses) and Missouri State Highway Patrol (testing) says you need 80% to pass (source).

Last updated Oct 7, 2026. FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC.

By Scott Wilder, Editor

Last reviewed against the Missouri CDL manual on October 7, 2026

Scott Wilder on X | scottwilderhq.com

FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC. It offers free exam-style practice tests built from the official CDL manual. FirstTry CDL is not affiliated with any DMV, FMCSA or government agency. Practice questions are exam-style questions built from the official CDL manual, not actual test questions.

Missouri CDL permit facts

What	What Missouri says	Source
Combination Vehicles pass mark	80%	Official page
Combination Vehicles test questions	20	Official page
CLP fee	$44, which is a $25 written test fee, a $10 permit fee and a $9 office fee. Pay by card, check or cash	Official page
Duplicate CLP fee	$14	Official page
CLP validity	360 days. It cannot be renewed. When it ends you must pass all the knowledge tests again for a new CLP	Official page
CLP holding period	Hold the CLP at least 14 days before the CDL skills test. The test paper alone is not a permit	Official page
Knowledge test retest rule	You may retake a failed test right away, but the examiner can make you come back on a later day	Official page
Test languages	Commercial knowledge tests are English only, and no translators are allowed (RSMo 302.720).	Official page

20 question Combination Vehicles practice test

1. What can happen if you do not lock the pintle hook latch correctly?
1. A. Only a small noise
2. B. The trailer and vehicle can separate
3. C. The brake lights stay on
4. D. The tires wear faster
Show answer
Answer: B. The trailer and vehicle can separate
The trailer and vehicle can separate, which can cause death or serious injury.
From the official CDL manual, section 6.4.3.
2. How can you tell if an older trailer has ABS?
1. A. Check the tire sidewalls for an ABS mark
2. B. Look for an ABS plate on the kingpin
3. C. Look under it for the ECU and wheel speed sensor wires from the back of the brakes
4. D. Check the build date on the landing gear
Show answer
Answer: C. Look under it for the ECU and wheel speed sensor wires from the back of the brakes
These parts show that the trailer has ABS.
From the official CDL manual, section 6.3.1.
3. The manual says to avoid quick lane changes, especially in what condition?
1. A. When the rig is fully loaded
2. B. When the rig is empty
3. C. When the road is dry
Show answer
Answer: A. When the rig is fully loaded
Quick lane changes are most risky when the rig is fully loaded.
From the official CDL manual, section 6.1.1.
4. You push in the trailer air supply control, but the spring brakes stay on. What should you check?
1. A. The ABS lamp bulb
2. B. The air-line connections
3. C. The fifth wheel grease
4. D. The trailer tires for proper inflation
Show answer
Answer: B. The air-line connections
The manual says to check the air-line connections if the spring brakes will not release.
From the official CDL manual, section 6.2.5.
5. To test the tractor protection valve, you shut off the engine and lower the air pressure. When should the air supply control pop out?
1. A. Within the manufacturer's range, usually 20 to 45 psi
2. B. Above 100 psi
3. C. At 60 to 80 psi
4. D. It should not pop out at all
Show answer
Answer: A. Within the manufacturer's range, usually 20 to 45 psi
The knob should pop out as pressure falls into this range.
From the official CDL manual, section 6.5.2.
6. Turning right at a corner, why should the rear of your rig stay close to the curb?
1. A. It gives the trailer more room to off-track
2. B. It keeps the trailer wheels from skidding
3. C. It keeps the trailer lights visible to drivers behind
4. D. It stops other drivers from passing you on the right
Show answer
Answer: D. It stops other drivers from passing you on the right
Keeping the rear close to the curb keeps other drivers from squeezing past on the right.
From the official CDL manual, section 6.1.6.
7. Besides colors, what can help you join the correct glad hands?
1. A. Hoses of different lengths
2. B. Different rubber seal shapes
3. C. Metal tags stamped "service" and "emergency"
Show answer
Answer: C. Metal tags stamped "service" and "emergency"
Metal tags marked service and emergency help you avoid mixing up the lines.
From the official CDL manual, section 6.2.5.
8. Where is the yellow ABS malfunction lamp found on a trailer?
1. A. On the right side, near the landing gear
2. B. On the nose of the trailer, near the glad hands
3. C. Inside the tractor cab only
4. D. On the left side, at the front or rear corner
Show answer
Answer: D. On the left side, at the front or rear corner
The manual places the lamp on the left side of the trailer, front or rear corner.
From the official CDL manual, section 6.3.1.
9. Which setup can get hung up on a raised railroad crossing?
1. A. A tandem-axle tractor pulling a short trailer
2. B. A single-axle tractor pulling a long trailer with landing gear set for a tandem-axle tractor
3. C. A straight truck with a single rear axle
4. D. A tractor pulling a trailer with the landing gear fully raised
Show answer
Answer: B. A single-axle tractor pulling a long trailer with landing gear set for a tandem-axle tractor
The landing gear is set low for a tandem tractor, so it can catch on a raised crossing.
From the official CDL manual, section 6.1.4.
10. What happens when you pull out the trailer air supply control?
1. A. Air is supplied to the trailer
2. B. The trailer service brakes release
3. C. The tractor parking brakes lock
4. D. The air is shut off and the trailer emergency brakes come on
Show answer
Answer: D. The air is shut off and the trailer emergency brakes come on
Pulling the knob out shuts off the trailer air supply and applies the emergency brakes.
From the official CDL manual, section 6.2.3.
11. When you couple a gooseneck hitch, what do you remember about safety chains?
1. A. They are optional for short trips
2. B. They are needed only for loaded trailers
3. C. All trailers are required by law to have them
4. D. They replace the clamp latch
Show answer
Answer: C. All trailers are required by law to have them
The manual says all trailers are required by law to have safety chains.
From the official CDL manual, section 6.4.7.
12. Your trailer air tanks have automatic drains. What should you still do?
1. A. Nothing, they never need a check
2. B. Open the drains to make sure the moisture is out
3. C. Close all the shut-off valves
Show answer
Answer: B. Open the drains to make sure the moisture is out
Automatic drains keep out most moisture, but you should still open the drains to check.
From the official CDL manual, section 6.2.6.
13. What do relay valves do for the trailer brakes?
1. A. They let the trailer brakes apply more quickly
2. B. They lock the trailer brakes for parking
3. C. They fill the trailer tanks
4. D. They close the air-lines
Show answer
Answer: A. They let the trailer brakes apply more quickly
Relay valves on the service line let the trailer brakes apply faster.
From the official CDL manual, section 6.2.4.
14. You pile more cargo on a truck. What happens to its center of gravity?
1. A. It moves higher, which makes the truck steadier
2. B. It moves lower because of the extra weight
3. C. It moves higher, so the truck turns over more easily
4. D. It stays the same if the cargo is tied down
Show answer
Answer: C. It moves higher, so the truck turns over more easily
A higher center of gravity makes the truck easier to turn over.
From the official CDL manual, section 6.1.1.
15. With the tractor partly clear, what should you check about the trailer supports?
1. A. That the ground supports the trailer and the landing gear is not damaged
2. B. That the kingpin is greased
3. C. That the tires are new
4. D. That the glad hands are open
Show answer
Answer: A. That the ground supports the trailer and the landing gear is not damaged
You make sure the ground is supporting the trailer and the landing gear is not damaged.
From the official CDL manual, section 6.4.2.
16. Engine off, you test the tractor protection valve. How do you lower the air pressure in the tanks?
1. A. Open the drain valves on the trailer
2. B. Step on and off the brake pedal several times
3. C. Pull the trailer hand valve once
Show answer
Answer: B. Step on and off the brake pedal several times
With the engine off, step on and off the brake pedal several times to reduce the air pressure.
From the official CDL manual, section 6.5.2.
17. You must back a trailer along a curved path. Which way should you curve?
1. A. To the passenger's side
2. B. To the driver's side
3. C. Either side; it makes no difference
4. D. Away from the nearest wall, no matter which side it is on
Show answer
Answer: B. To the driver's side
Backing toward the driver's side lets you see the path.
From the official CDL manual, section 6.1.7.
18. A bobtail tractor is compared with a tractor-semitrailer at maximum gross weight. Which stops in less distance?
1. A. The bobtail, because it weighs less
2. B. They stop in the same distance
3. C. It depends only on tire tread depth
4. D. The loaded tractor-semitrailer
Show answer
Answer: D. The loaded tractor-semitrailer
Bobtails take longer to stop than a tractor-semitrailer loaded to maximum gross weight.
From the official CDL manual, section 6.1.3.
19. Cargo is loaded toward one side and makes the trailer lean. What is the result?
1. A. The trailer tracks better in turns
2. B. A rollover is more likely
3. C. Braking distance gets shorter
4. D. Nothing, if the weight is within legal limits
Show answer
Answer: B. A rollover is more likely
A load off to one side makes the trailer lean, which makes a rollover more likely.
From the official CDL manual, section 6.1.1.
20. When should you slow down for a turn in a tractor-trailer?
1. A. Halfway through the turn
2. B. Before you go into the turn
3. C. After the turn is finished
4. D. Only if the road is wet
Show answer
Answer: B. Before you go into the turn
You must slow to a safe speed before you enter the turn.
From the official CDL manual, section 6.1.2.

Missouri CDL Combination Vehicles questions

What score do you need to pass the Missouri CDL Combination Vehicles test?

Missouri says you need 80% to pass the Combination Vehicles test.

Is the Missouri CDL Combination Vehicles test the same as other states?

The Combination Vehicles test is built on the same federal knowledge standards in every state, so the topics match the CDL manual. Missouri uses its own handbook: https://dor.mo.gov/forms/Commerical_Driver_License.pdf

How much does a CDL permit cost in Missouri?

CLP fee: $44, which is a $25 written test fee, a $10 permit fee and a $9 office fee. Pay by card, check or cash.

What languages is the Missouri CDL knowledge test offered in?

Commercial knowledge tests are English only, and no translators are allowed (RSMo 302.720).

Sources

https://dor.mo.gov/resources/official-final-rules/documents/12_CSR_10-24_300_CDL_Written_Examinations_Final.pdf
https://dor.mo.gov/driver-license/issuance/commercial/
https://dor.mo.gov/driver-license/documents/feechart.pdf
https://dor.mo.gov/driver-license/issuance/commercial/cdl-permit.html
https://dor.mo.gov/faq/driver-license/cdl-clp.html
https://dor.mo.gov/forms/Commerical_Driver_License.pdf
Manual sections used in this test: 6.1.1; 6.1.2; 6.1.3; 6.1.4; 6.1.6; 6.1.7; 6.2.3; 6.2.4; 6.2.5; 6.2.6; 6.3.1; 6.4.2; 6.4.3; 6.4.7; 6.5.2

Combination Vehicles practice test in nearby states