Iowa CDL Combination Practice Test (IA) 2

4.9 out of 5 (46 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Prepare yourself thoroughly for the CDL combination test with this comprehensive Iowa CDL combination practice test. Designed specifically for Iowa drivers, this practice permit test features 20 multiple-choice questions that cover vital topics such as inspection procedures, safe driving practices, and air brake systems. To pass, you need to answer at least 16 questions correctly, ensuring you have a solid grasp of the material. This Iowa permit practice test not only familiarizes you with the types of questions you will encounter on the actual test but also helps you identify any gaps in your knowledge. Each time you complete the practice permit test, you'll receive a detailed summary of your performance. This includes highlighting the questions you answered incorrectly and providing the correct answers for those questions, aiding in your learning process. One of the unique aspects of the combination CDL practice test is its focus on real-world driving conditions specific to Iowa. Whether you're navigating the busy streets of Des Moines, dealing with the challenging weather conditions in the northern parts of the state, or handling the agricultural equipment on rural roads, this Iowa combination vehicle test prepares you for the diverse driving scenarios you might face. Understanding the risks of jackknifing, where the trailer swings out of alignment with the tractor, is critical. Through smooth braking and careful handling, you'll learn to avoid this dangerous situation, which is vital for safe driving. Moreover, the driving practice test can be taken as many times as needed, allowing you to practice until you are completely comfortable with the material. This repeated exposure not only boosts your confidence but also ensures that you are well-prepared for the actual CDL combination test. Whether you are a new driver or someone looking to refresh your knowledge, the Iowa DOT practice test is an invaluable tool in your preparation arsenal. By taking this practice test multiple times, you can steadily improve your score and be confident in your ability to pass the official test.
FREE CDL Practice Test App
Pass your Iowa CDL Combination Vehicles test with the NextDoorDriving app. Real questions and answers—100% free and ad-free.
Download on the App Store

Sample Iowa Combination Test Questions

Question 1

After the fifth wheel first touches the trailer, what should be connected before the tractor backs fully underneath?

  1. A Nothing until the kingpin is locked
  2. B Only the emergency air line
  3. C Only the service air line
  4. D Both the emergency and service air lines

Correct answer: D – Both the emergency and service air lines

Before backing completely under the trailer, inspect the glad-hand seals and connect both air lines. Join the tractor emergency line to the trailer emergency glad hand and the tractor service line to the service glad hand. Support the lines where they will not be crushed or caught as the tractor moves under the trailer.

Source: Commercial Driver’s License Manual—Modernized Testing System — § 6.4.1, Step 7, “Connect Air-lines to Trailer”

Question 2

Why is the trailer hand valve unsuitable for parking?

  1. A Air can leak away and release the brakes on trailers without spring brakes
  2. B It applies excessive force to the trailer tires
  3. C It permanently drains the tractor’s air tanks
  4. D It prevents the fifth wheel from unlocking

Correct answer: A – Air can leak away and release the brakes on trailers without spring brakes

Parking with the trailer hand valve can leave the vehicle dependent on air pressure remaining in the system. If the air leaks out, the trailer brakes may release when the trailer is not equipped with spring brakes. Use the parking brakes instead, and use wheel chocks when parking a trailer that has no spring brakes.

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

Question 3

After connecting the air lines and supplying air to the trailer, which check helps confirm that the trailer brakes apply and release?

  1. A Rev the engine while watching the tachometer
  2. B Apply and release the brakes while listening for brake movement and escaping air
  3. C Turn the steering wheel from lock to lock
  4. D Check only the trailer lights in the mirrors

Correct answer: B – Apply and release the brakes while listening for brake movement and escaping air

After air pressure reaches normal, Iowa’s CDL manual directs the driver to shut off the engine, apply and release the trailer brakes, and listen. The brakes should be heard moving when applied, followed by escaping air when released. The air-pressure gauge should also be checked for evidence of a major air loss.

Source: Commercial Driver’s License Manual—Modernized Testing System — § 6.4.1, Step 8, “Supply Air to Trailer”

Question 4

Which actions are proper when disconnecting trailer lines during uncoupling?

  1. A Hang the electrical cable with its plug pointing downward
  2. B Attach the glad hands to the tractor’s dummy couplers
  3. C Couple the glad hands together if dummy couplers are not used
  4. D All of the above

Correct answer: D – All of the above

The disconnected glad hands may be attached to dummy couplers at the rear of the cab or coupled together. The electrical cable should be hung with the plug pointing down to keep moisture from entering it. All air and electrical lines must also be supported so they cannot be damaged while the tractor is driven without the trailer.

Source: Commercial Driver’s License Manual—Modernized Testing System — § 6.4.2, Step 5, “Disconnect Air-lines and Electrical Cable”

Question 5

Why should you not apply the trailer hand valve to straighten a trailer that has begun to jackknife?

  1. A The hand valve cannot operate the trailer brakes
  2. B Additional trailer braking continues the condition that caused the wheels to skid
  3. C The hand valve works only while the vehicle is parked
  4. D The hand valve is the recommended way to straighten the trailer

Correct answer: B – Additional trailer braking continues the condition that caused the wheels to skid

A trailer jackknife commonly begins when the trailer wheels lock and lose traction. Applying the trailer hand valve continues braking those wheels rather than helping them regain their grip. Release the brakes to recover traction; once the trailer tires grip the road again, the trailer should begin following the tractor and straightening out.

Source: Commercial Driver’s License Manual—Modernized Testing System — § 6.1.5, “Prevent Trailer Skids”

Question 6

What damage may occur if a trailer is positioned too low during coupling?

  1. A The trailer brakes will release
  2. B The air lines will become too short
  3. C The tractor may strike and damage the trailer nose
  4. D The trailer will always rise without making contact

Correct answer: C – The tractor may strike and damage the trailer nose

The trailer should be low enough to rise slightly when the tractor backs beneath it, but it must not be excessively low. If it is too low, the tractor can strike and damage the trailer nose. Raise or lower the landing gear as necessary and verify that the kingpin and fifth wheel are properly aligned.

Source: Commercial Driver’s License Manual—Modernized Testing System — § 6.4.1, Step 6, “Check Trailer Height”

More Iowa CDL Practice Tests
Other CDL Endorsements