Washington CDL Combination Vehicles Practice Test

The Washington CDL Combination Vehicles test is a multiple-choice knowledge test you take for your commercial learner's permit. Washington State Department of Licensing (DOL) 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 Washington 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.

Washington CDL permit facts

What	What Washington says	Source
Combination Vehicles pass mark	80%	Official page
Combination Vehicles test questions	20	Official page
CLP fee	$40	Official page
CLP validity	180 days. Renew once within 30 days of expiring for 180 more days. Doubles/triples and hazmat tests do not renew with the CLP	Official page
CLP holding period	Wait 14 calendar days after your original or upgraded CLP before the skills test	Official page
Test languages	The CDL knowledge test comes in English, Spanish, Russian and Serbian-Croatian. Language interpreters are not allowed. The study guide is English only.	Official page

20 question Combination Vehicles practice test

1. Which trailers are not required to have spring brakes?
1. A. Trailers built before 1998
2. B. All trailers shorter than 40 feet
3. C. Only trailers carrying hazardous materials
4. D. Converter dollies and trailers built before 1975
Show answer
Answer: D. Converter dollies and trailers built before 1975
The manual says these are not required to have spring brakes.
From the official CDL manual, section 6.2.8.
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. In Step 9 of coupling, what do you do to lock the trailer brakes?
1. A. Push in the "air supply" knob
2. B. Pull out the "air supply" knob
3. C. Put the transmission in neutral
4. D. Raise the landing gear
Show answer
Answer: B. Pull out the "air supply" knob
Pulling out the "air supply" knob locks the trailer brakes.
From the official CDL manual, section 6.4.1.
4. Before you couple, what should you check about the trailer kingpin?
1. A. That it is painted
2. B. That it is longer than the jaws
3. C. That it is wet with oil
4. D. That it is not bent or broken
Show answer
Answer: D. That it is not bent or broken
The manual says to make sure the trailer kingpin is not bent or broken.
From the official CDL manual, section 6.4.1.
5. Why check the clearance between the rear of the tractor frame and the landing gear?
1. A. To see if the trailer is level
2. B. So the tractor does not hit the landing gear in a sharp turn
3. C. To measure the kingpin
4. D. To check tire wear
Show answer
Answer: B. So the tractor does not hit the landing gear in a sharp turn
When the tractor turns sharply, it must not hit the landing gear.
From the official CDL manual, section 6.4.1.
6. Why should you back a trailer slowly?
1. A. You can make corrections before you get far off course
2. B. The tractor brakes cool faster
3. C. The mirrors work better at low speed
4. D. The air tanks fill faster
Show answer
Answer: A. You can make corrections before you get far off course
Slow backing leaves time to correct before you are far off course.
From the official CDL manual, section 6.1.7.
7. Why should you take the key with you when you go under the trailer to inspect the coupling?
1. A. So no one else can move the truck while you are under it
2. B. To keep the battery from draining
3. C. So the trailer lights stay on
4. D. To keep the engine from idling
Show answer
Answer: A. So no one else can move the truck while you are under it
Leaving the key invites someone to move the truck while you are exposed.
From the official CDL manual, section 6.4.1.
8. Triples have a rearward amplification of 3.5. How easily can the last trailer roll, compared with a five-axle tractor?
1. A. 1.5 times as easily
2. B. 3.5 times as easily
3. C. 2 times as easily
4. D. 10 times as easily
Show answer
Answer: B. 3.5 times as easily
The manual says the last trailer of triples can roll 3.5 times as easily as a five-axle tractor.
From the official CDL manual, section 6.1.2.
9. What does the rubber seal in a glad hand do?
1. A. It locks the two couplers together
2. B. It shows which line is service
3. C. It filters dirt from the air
4. D. It prevents air from escaping
Show answer
Answer: D. It prevents air from escaping
The rubber seal keeps air from escaping at the connection.
From the official CDL manual, section 6.2.5.
10. 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.
11. When the ABS computer senses a wheel is about to lock up, what does it do?
1. A. It raises the braking pressure
2. B. It turns off the brakes on that axle for good
3. C. It reduces the braking pressure to a safe level
Show answer
Answer: C. It reduces the braking pressure to a safe level
The computer reduces the braking pressure to a safe level so you keep control.
From the official CDL manual, section 6.3.2.
12. 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.
13. How should the trailer height compare with the fifth wheel when you back under?
1. A. High enough that the tractor does not touch it
2. B. Level with the fifth wheel plate
3. C. As high as the landing gear will go
4. D. Low enough that the tractor raises it slightly
Show answer
Answer: D. Low enough that the tractor raises it slightly
The trailer should be raised slightly by the tractor as you back under.
From the official CDL manual, section 6.4.1.
14. How do you test the trailer service brakes?
1. A. Pull out the air supply knob and stay parked
2. B. Open the trailer shut-off valve at the rear
3. C. Move forward slowly and apply the trailer hand control
4. D. Park and apply the hand valve for ten minutes
Show answer
Answer: C. Move forward slowly and apply the trailer hand control
You should feel the trailer brakes come on.
From the official CDL manual, section 6.5.2.
15. 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.
16. What have tests shown about stopping a bobtail tractor?
1. A. It stops more smoothly than a loaded rig
2. B. It can be very hard to stop smoothly
3. C. It is easy to stop on any road
Show answer
Answer: B. It can be very hard to stop smoothly
Tests show bobtails can be very hard to stop smoothly, so drive them with care.
From the official CDL manual, section 6.1.3.
17. 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.
18. A 60-foot rig is going 45 mph. What is the shortest following time the manual allows?
1. A. 7 seconds
2. B. 6 seconds
3. C. 5 seconds
4. D. 8 seconds
Show answer
Answer: A. 7 seconds
60 feet gives 6 seconds, and going over 40 mph adds 1 more second.
From the official CDL manual, section 6.1.2.
19. 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.
20. 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.

Washington CDL Combination Vehicles questions

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

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

Is the Washington 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. Washington uses its own handbook: https://dol.wa.gov/media/pdf/42/cdlguidepdf

How much does a CDL permit cost in Washington?

CLP fee: $40.

What languages is the Washington CDL knowledge test offered in?

The CDL knowledge test comes in English, Spanish, Russian and Serbian-Croatian. Language interpreters are not allowed. The study guide is English only.

Sources

https://dol.wa.gov/driver-licenses-and-permits/commercial-driver-licenses-cdl/cdl-training-and-testing/cdl-knowledge-test
https://dol.wa.gov/driver-licenses-and-permits/commercial-driver-licenses-cdl/cdl-training-and-testing/commercial-learners-permit-clp
https://dol.wa.gov/driver-licenses-and-permits/commercial-driver-licenses-cdl/cdl-training-and-testing/cdl-skills-test
https://dol.wa.gov/media/pdf/42/cdlguidepdf
Manual sections used in this test: 6.1.2; 6.1.3; 6.1.7; 6.2.4; 6.2.5; 6.2.6; 6.2.8; 6.3.1; 6.3.2; 6.4.1; 6.4.2; 6.4.3; 6.5.2

Combination Vehicles practice test in nearby states