Oklahoma CDL Combination Test (OK) 2026

5 out of 5 (53 votes)
80% Passing score
20 Questions
4 Mistakes allowed
If you're getting ready to hit the road with a Commercial Driver's License in Oklahoma, you've come to the right place. Our Oklahoma CDL combination test is designed to prepare you thoroughly for your combination vehicle endorsement. This Oklahoma CDL combination practice test covers everything you need to know, from coupling and uncoupling procedures to mastering pre-trip inspections. With our carefully crafted multiple-choice questions, you'll dive into crucial topics such as safe driving techniques, backing and maneuvering, and understanding the complex air brake systems that are vital for operating larger vehicles safely. Our Oklahoma written driving test practice draws from a large pool of questions to give you a broad and deep understanding of what to expect on the actual test. Each session includes 20 questions, and you'll need to get at least 16 correct to pass. This ensures you are well-equipped to handle the increased stopping distances and other challenges unique to combination vehicles. The practice is not just about answering questions; it's about learning the logic behind each one. Each question provides immediate feedback and detailed explanations, helping you understand why an answer is correct or incorrect, reinforcing your learning every step of the way. In addition to the Oklahoma DMV practice test, we recommend complementing your study with additional resources like the Oklahoma driver's handbook, a state-certified driver's ed course, and flashcards for road signs. This combination of materials will help you target all areas covered in the DMV permit test, giving you a comprehensive understanding of both the practical and theoretical aspects of driving combination vehicles. Prepare with confidence knowing that our CDL combination practice test is designed to build your skills and knowledge, helping you become a safe and competent driver on Oklahoma's roads. The more you practice, the better prepared you'll be to handle real-world driving situations with ease and safety.
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Sample Oklahoma Combination Test Questions

Question 1

What are the two functions of a trailer’s emergency air line?

  1. A Operating the stop lamps and improving fuel economy
  2. B Inflating the tires and controlling the service brakes
  3. C Supplying the trailer air tanks and controlling the emergency brakes
  4. D Releasing the fifth wheel and raising the landing gear

Correct answer: C – Supplying the trailer air tanks and controlling the emergency brakes

The emergency or supply line delivers air to the trailer air tanks and controls the trailer emergency brakes. A loss of pressure in this line causes the trailer emergency brakes to apply. The pressure loss also causes the tractor protection valve to close, protecting the tractor’s air supply.

Source: Oklahoma Commercial Driver’s License Manual — § 6.2.4, “Trailer Air-lines”

Question 2

During normal operation of a multiple-trailer combination, how should the air-line shut-off valves be positioned?

  1. A Emergency valves open and service valves closed throughout the combination
  2. B Emergency valves closed and service valves open throughout the combination
  3. C Valves on earlier trailers open and both valves at the rear of the last trailer closed
  4. D Valves on earlier trailers closed and both valves at the rear of the last trailer open

Correct answer: C – Valves on earlier trailers open and both valves at the rear of the last trailer closed

The service and emergency shut-off valves on trailers and dollies ahead of the last trailer must remain open so air reaches the entire combination. Both shut-off valves at the rear of the last trailer must be closed during normal operation. They may be opened temporarily when checking airflow and then closed again.

Source: Oklahoma Commercial Driver’s License Manual — § 6.2.7, “Shut-off Valves”; § 6.5.2, “Combination Vehicle Brake Check”

Question 3

Along with slowing for turns, which cargo-loading practice helps prevent a combination vehicle from rolling over?

  1. A Placing most cargo near the trailer doors
  2. B Applying the trailer hand valve before the foot brake
  3. C Concentrating the load on one side of the trailer
  4. D Keeping the cargo as low as possible

Correct answer: D – Keeping the cargo as low as possible

Keeping cargo low reduces the vehicle’s center of gravity and its tendency to roll over. The Oklahoma manual pairs this practice with driving slowly around turns, ramps, and corners. Cargo should also be centered and distributed across the vehicle rather than placed heavily on one side.

Source: Oklahoma Commercial Driver’s License Manual — § 6.1.1, “Rollover Risks”

Question 4

What may happen when the brakes are applied after a major leak develops in the trailer service air line?

  1. A The trailer air tanks will refill more quickly
  2. B Only the tractor’s parking brakes will release
  3. C The trailer service brakes will remain applied without losing air
  4. D Air pressure may fall quickly enough to apply the trailer emergency brakes

Correct answer: D – Air pressure may fall quickly enough to apply the trailer emergency brakes

A major service-line leak may not be obvious until the driver applies the brakes. Brake application can allow air to escape rapidly, lowering tank pressure. If pressure falls far enough, the trailer emergency brakes will apply; a low-air warning requires the driver to bring the vehicle to a safe stop and have the system repaired.

Source: Oklahoma Commercial Driver’s License Manual — § 6.2.8, “Trailer Service, Parking and Emergency Brakes”; § 5.2, “Dual Air Brake”

Question 5

Should the trailer hand valve be applied before the brake pedal to prevent skids during normal driving?

  1. A No, the hand valve should not be used that way
  2. B Yes, because it applies every brake equally
  3. C Yes, but only during straight-line braking
  4. D Yes, but only while turning

Correct answer: A – No, the hand valve should not be used that way

Do not use the trailer hand valve for routine braking because applying only the trailer brakes can cause a trailer skid. The foot brake applies the service brakes throughout the combination and presents less danger of a skid or jackknife. The hand valve should be reserved for testing the trailer brakes.

Source: Oklahoma Commercial Driver’s License Manual — § 6.2.1, “Trailer Hand Valve”

Question 6

Which combination of actions helps reduce rollover risk?

  1. A Load cargo toward the front and accelerate through turns
  2. B Keep cargo low and drive slowly around turns
  3. C Load cargo toward the rear and maintain the posted limit in every turn
  4. D Raise the cargo’s center of gravity and brake inside turns

Correct answer: B – Keep cargo low and drive slowly around turns

The Oklahoma manual identifies two key rollover precautions: keep cargo as close to the ground as possible and drive slowly around turns. A high center of gravity makes a loaded vehicle easier to overturn. The load should also be centered and spread out because an off-center load can make the trailer lean.

Source: Oklahoma Commercial Driver’s License Manual — § 6.1.1, “Rollover Risks”

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