Iowa CDL Practice Test: General Knowledge (IA) 6

5 out of 5 (39 votes)
80% Passing score
50 Questions
10 Mistakes allowed
As an Iowan preparing for your CDL general knowledge test, you know the importance of thorough preparation. Our sixth Iowa CDL practice test is a crucial step in your study regimen, designed to mirror the actual test you'll face at the DMV in 2026. This practice test offers 50 questions covering a wide range of topics crucial for every aspiring commercial driver. You'll be tested on vital subjects including vehicle equipment, handling emergencies, accident procedures, pre-trip inspections, and basic knowledge about hazardous materials. This is essential learning, even if you're not pursuing a HazMat endorsement right now. Understanding that every question counts, our CDL general knowledge test requires a minimum of 40 correct answers to pass, reflecting the real test's rigor. What makes our Iowa CDL practice test stand out is its unwavering relevance to the current year, 2026, ensuring you're studying up-to-date material. Our DMV practice test format is not just a simple quiz. It's a tool that molds to your study needs. Struggle with specific topics? Focus your practice on those areas. Need multiple attempts to solidify your knowledge? Retake the online practice test as many times as necessary. And the beauty of online practice tests is their flexibility - study anytime and anywhere, fitting preparation into your busy schedule. We've designed this test to give you the confidence and knowledge needed to ace the Iowa DMV written test. With permit test questions closely resembling those you'll face, you're not just practicing - you're getting a taste of the actual test environment. So, dive into the test, focus on your weak spots, and keep retaking it until you're consistently hitting that pass mark or better. Your path to obtaining your Iowa CDL in 2026 starts here, with diligent practice and a commitment to mastering the essential knowledge every commercial driver needs.
FREE CDL Practice Test App
Pass your Iowa CDL General Knowledge test with the NextDoorDriving app. Real questions and answers—100% free and ad-free.
Download on the App Store

Sample Iowa CDL Test Questions - General Knowledge

Question 1

What should you do before entering a curve in a commercial vehicle?

  1. A Reduce speed and select the proper lower gear before the curve
  2. B Shift to a higher gear and accelerate before turning
  3. C Stop at the entrance to every curve

Correct answer: A – Reduce speed and select the proper lower gear before the curve

Slow to a safe speed and select the proper gear before entering the curve. This allows the driver to apply slight power through the curve, helping maintain vehicle stability and control. Braking or attempting a difficult gear change after entering the curve can increase the risk of skidding or losing control.

Source: Iowa Commercial Driver’s License Manual — § 2.3.1, “Manual Transmissions—Before Entering a Curve”

Question 2

After using the right shoulder to avoid a collision, what is the preferred way to return to the roadway when the shoulder is clear?

  1. A Remain on the shoulder until stopped, then signal and check mirrors before returning
  2. B Brake hard and steer sharply onto the pavement
  3. C Turn sharply onto the pavement and then brake hard
  4. D Maintain speed and gradually edge back onto the pavement

Correct answer: A – Remain on the shoulder until stopped, then signal and check mirrors before returning

The Iowa CDL manual advises staying on a clear shoulder until the vehicle has stopped. Brake gently as speed decreases because loose shoulder material can cause a skid. Before reentering the roadway, signal and check the mirrors. A special steer-counter-steer procedure is used only if circumstances force the driver back onto the pavement before stopping.

Source: Iowa Commercial Driver’s License Manual — § 2.17.1, “Steering to Avoid a Crash—Leaving the Road; Returning to the Road”

Question 3

How should you normally brake a commercial vehicle equipped with antilock brakes?

  1. A Use less pedal pressure than the stop requires
  2. B Brake normally, using only the force needed to stop safely
  3. C Push the pedal as hard as possible during every stop
  4. D Release the accelerator and let ABS apply the brakes

Correct answer: B – Brake normally, using only the force needed to stop safely

With ABS, apply the brakes as you normally would and use only the braking force necessary to stop safely while maintaining control. ABS activates when wheels are about to lock, but it does not automatically brake when the accelerator is released. A straight truck or combination with working ABS on every axle may receive full brake application during an emergency stop.

Source: Iowa Commercial Driver’s License Manual — § 2.18.6, “Braking with ABS”

Question 4

What is the most immediate danger presented by a damaged or leaking exhaust system?

  1. A Normal exhaust noise may damage the driver’s hearing
  2. B Poisonous fumes may enter the cab or sleeper berth
  3. C Visible smoke may discolor the roadway
  4. D Exhaust may damage vehicles traveling behind the truck

Correct answer: B – Poisonous fumes may enter the cab or sleeper berth

A broken exhaust system can allow poisonous fumes to enter the cab or sleeper berth. Exhaust leaks are especially dangerous when ventilation is limited, because carbon monoxide can cause sleepiness and may be fatal in sufficient amounts. Inspect for leaks and for loose, broken, or missing pipes, stacks, brackets, clamps, bolts, and nuts.

Source: Iowa Commercial Driver’s License Manual — § 2.1.3, “What to Look For—Exhaust System Defects”, Iowa Commercial Driver’s License Manual — § 2.13.1, “Vehicle Checks—Exhaust System”

Question 5

Which statement about downshifting for a curve is correct?

  1. A Select the proper lower gear before entering the curve
  2. B Wait until the vehicle begins descending after the curve
  3. C Downshift while traveling through the sharpest part of the curve
  4. D Complete the downshift only after leaving the curve

Correct answer: A – Select the proper lower gear before entering the curve

The driver should reduce speed and downshift to the proper gear before entering a curve. Being in the correct gear permits slight acceleration through the turn and helps maintain stability. Waiting until the vehicle is already in the curve divides the driver’s attention and may leave the vehicle traveling too fast or in an unsuitable gear.

Source: Iowa Commercial Driver’s License Manual — § 2.3.1, “Manual Transmissions—Before Entering a Curve”

Question 6

At 55 mph, what minimum following interval is recommended for a 30-foot commercial vehicle under good conditions?

  1. A 3 seconds
  2. B 4 seconds
  3. C 5 seconds
  4. D 6 seconds

Correct answer: B – 4 seconds

The Iowa CDL manual recommends at least one second of following distance for every 10 feet of vehicle length at speeds below 40 mph. A 30-foot vehicle requires three seconds under that formula. Because 55 mph is above 40 mph, one additional second is needed, making the minimum recommended interval four seconds under good conditions.

Source: Iowa Commercial Driver’s License Manual — § 2.7.1, “Space Ahead—How Much Space?”

More Iowa CDL Practice Tests
Other CDL Endorsements