Idaho CDL Combination Test (ID) 2026

5 out of 5 (43 votes)
80% Passing score
20 Questions
4 Mistakes allowed
As an Idahoan, you know that driving a combination vehicle in our state comes with its own set of unique challenges and responsibilities. That's why our Idaho CDL combination practice test is designed to help you master the skills and knowledge needed to earn your endorsement with confidence. Our comprehensive practice driving test is tailored specifically for Idaho, ensuring you're studying the most relevant information and road regulations. Our Idaho CDL combination practice test includes a variety of multiple-choice questions that cover all the critical areas you need to know. From coupling and uncoupling procedures to pre-trip inspections, driving techniques, backing and maneuvering, and air brake systems, we've got you covered. With 20 questions in each test and a requirement to get at least 16 correct answers to pass, you'll be well-prepared for the real test. Understanding the increased stopping distances required for combination vehicles due to their greater weight is essential for maintaining safety on Idaho roads. Our Idaho practice drivers test will help you grasp these concepts, ensuring you can handle the unique challenges of these larger, heavier vehicles. The DMV practice test is available online, making it easily accessible whether you're using a mobile device, desktop computer, or our mobile app. This accessibility means you can study anytime, anywhere, fitting your preparation into your busy schedule. Plus, our Idaho combination CDL test is regularly updated to reflect the most current driving laws and regulations, so you're always studying the most up-to-date information. Whether you're new to driving combination vehicles or looking to refresh your knowledge, our Idaho CDL combination practice test is an invaluable tool. By tailoring the test to Idaho's specific rules, regulations, and road signs, we ensure that you're getting the most relevant practice possible. Start preparing today with our reliable, accessible, and up-to-date Idaho drivers test practice.
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Sample Idaho Combination Test Questions

Question 1

What should you do if the low-air-pressure warning activates while driving a combination vehicle?

  1. A Increase speed to raise compressor output
  2. B Stop and safely park as soon as possible
  3. C Make a sharp turn to test vehicle control
  4. D Use only the trailer hand valve

Correct answer: B – Stop and safely park as soon as possible

The Idaho CDL manual directs the driver to stop and safely park as soon as possible when the low-air warning activates. Controlled braking is available only while sufficient air remains in the tanks. Waiting until the spring brakes apply can cause a long stopping distance or a skid, depending on the vehicle’s load and road conditions.

Source: Idaho Commercial Driver’s License Manual — § 5.4.7, “Low Air Pressure”

Question 2

What should be verified when inspecting glad hands before connecting the trailer air lines?

  1. A The couplers have been lubricated with engine oil
  2. B Both couplers are attached to the same air line
  3. C The service and supply seals have been removed
  4. D The couplers and rubber seals are clean and able to seal

Correct answer: D – The couplers and rubber seals are clean and able to seal

Glad hands connect the tractor’s service and emergency air lines to the trailer. Their rubber seals prevent air from escaping, so the couplers and seals should be cleaned and checked before connection. The service and emergency glad hands must also be matched correctly.

Source: Idaho Commercial Driver’s License Manual — § 6.2.5, “Hose Couplers (Glad Hands)”

Question 3

After connecting the trailer air lines, what pressure condition must be reached before checking the trailer brakes and backing fully under the trailer?

  1. A Between 60 and 80 psi
  2. B One-half of normal system pressure
  3. C Normal operating pressure
  4. D No pressure in the trailer tanks

Correct answer: C – Normal operating pressure

After supplying air to the trailer, wait until system pressure reaches normal. Check for crossed lines, listen for the trailer brakes to apply and release, and look for major air loss. Once the brakes are verified and pressure is normal, lock the trailer brakes before backing under the trailer to engage the kingpin.

Source: Idaho Commercial Driver’s License Manual — § 6.4.1, “Coupling Tractor-Semitrailers”

Question 4

Before driving, the trailer landing gear only needs to be raised a few inches above the pavement. True or false?

  1. A True
  2. B False

Correct answer: B – False

Raise the landing gear completely before driving and secure the crank handle. Landing gear left partly down can catch on railroad tracks or other objects. After it is raised, also verify adequate clearance between the landing gear and tractor frame and between the tractor tires and trailer nose.

Source: Idaho Commercial Driver’s License Manual — § 6.4.1, “Coupling Tractor-Semitrailers,” Step 15, “Raise Front Trailer Supports (Landing Gear)”

Question 5

Where are the service- and supply-line shut-off valves located on a trailer used to tow another trailer?

  1. A Inside the tractor cab
  2. B At the rear of the tractor
  3. C At the front of the trailer
  4. D At the rear of the trailer

Correct answer: D – At the rear of the trailer

The Idaho CDL manual places these shut-off valves at the rear of trailers designed to tow other trailers. Valves between connected units must be open so air can reach the following trailer. The valves at the rear of the last trailer must be closed.

Source: Idaho Commercial Driver’s License Manual — § 6.2.7, “Shut-off Valves”

Question 6

Which procedure correctly tests a trailer’s emergency brakes?

  1. A Charge the trailer system, pull out the trailer air-supply control, and gently pull against the trailer
  2. B Apply only the trailer hand valve while traveling at highway speed
  3. C Press the foot brake repeatedly until the compressor stops
  4. D Disconnect the service line and listen for air at the tractor

Correct answer: A – Charge the trailer system, pull out the trailer air-supply control, and gently pull against the trailer

First charge the trailer air-brake system and confirm that the trailer rolls freely. Stop, pull out the trailer air-supply control or move it to the emergency position, and gently pull with the tractor. Resistance verifies that the trailer emergency brakes have applied. Applying the hand valve while moving slowly is instead used to test trailer service brakes.

Source: Idaho Commercial Driver’s License Manual — § 6.5.2, “Combination Vehicle Brake Check,” “Test Trailer Emergency Brakes”

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