Illinois CDL Class B Practice Test (IL) 3

4.8 out of 5 (585 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Preparing for your Illinois CDL Class B exam is a significant step towards a successful career in commercial driving. Our third CDL practice test is designed to help you gain the confidence and knowledge required to pass the actual written permit test in 2026. This DMV practice test consists of 20 carefully crafted questions that mirror the format and content of the real exam. To pass, you'll need to correctly answer at least 16 questions. One of the unique features of our practice test is the immediate feedback provided for each Illinois permit test question. Not only will you know whether your answer is correct or incorrect, but you'll also receive detailed explanations. This feature is crucial in helping you understand the material deeply, rather than just memorizing answers. It's an effective learning tool that addresses your specific areas of weakness and reinforces your strengths. Our DMV CDL practice test is specifically tailored for Class B CDL applicants in Illinois. It covers a broad range of subjects essential for every aspiring commercial driver. Topics include pre-trip vehicle inspection, basic vehicle control, gear shifting strategies, handling hills and steep downgrades, effective communication with other road users, speed control, and awareness of drug and alcohol regulations. These subjects are critical for both the DMV written permit test and your future responsibilities on the road. To ensure you're studying the most current material, we regularly update our Illinois CDL class B practice test to reflect the latest driving laws and regulations. The 2026 version includes the newest guidelines, providing you with the most relevant and accurate preparation material. Additionally, we incorporate visual learning aids like images of road signs and traffic scenarios. These aids are especially helpful for visual learners, making complex concepts easier to grasp. Overall, our Illinois CDL general knowledge practice test offers a comprehensive, up-to-date, and effective way to prepare for your CDL Class B exam in 2026!
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Sample Illinois CDL Test Questions - General Knowledge

Question 1

What causes most serious commercial-vehicle skids?

  1. A Driving too fast for the road conditions
  2. B Improper brake adjustment alone
  3. C Excessive weight on the steering axle
  4. D Tire wear alone

Correct answer: A – Driving too fast for the road conditions

Most serious skids result from traveling too fast for road conditions. Excessive speed can force a driver to brake too hard, steer too sharply, or apply too much power to the drive wheels. Adjusting speed for traction, visibility, curves, and other conditions reduces the need for sudden control inputs that can start a skid.

Source: Illinois CDL Study Guide — § 2.19, “Skid Control and Recovery”

Question 2

When is it acceptable to drive a tank vehicle with a valve or manhole cover open?

  1. A Never
  2. B Only during daylight
  3. C Only on local streets
  4. D Only when the tank is traveling on a highway

Correct answer: A – Never

The Illinois CDL study guide states that a tank vehicle must never be driven with open valves or manhole covers. Before movement, valves must be in the correct position and manhole covers must close properly with suitable gaskets. These checks help prevent leaks or the loss of the tank's contents during transportation.

Source: Illinois CDL Study Guide — § 8.1.1, “Leaks”; § 8.1.2, “Check Special Purpose Equipment”

Question 3

A commercial vehicle is stopped on a straight, level, two-lane road. Where should its three warning triangles be placed?

  1. A One about 100 feet ahead, one 10 feet behind, and one about 100 feet behind
  2. B One 10 feet behind, one 100 feet behind, and one 200 feet behind
  3. C One 50 feet behind, one 100 feet behind, and one 10 feet ahead
  4. D One 10 feet ahead and two 10 feet behind

Correct answer: A – One about 100 feet ahead, one 10 feet behind, and one about 100 feet behind

Federal warning-device rules require protection in both directions on a two-way or undivided roadway. The Illinois CDL guide describes the placement as one device about 100 feet in front, one 10 feet behind to mark the vehicle's location, and one about 100 feet behind. The devices should be placed on the shoulder or in the occupied lane as appropriate.

Source: Illinois CDL Study Guide — § 2.5.2, “Communicating Your Presence”, 49 CFR § 392.22(b)(1) – Emergency Signals; Stopped Commercial Motor Vehicles

Question 4

What roadway condition is indicated by a BUMP warning sign?

This sign warns drivers to _____________.
  1. A A depression or dip in the roadway
  2. B A sharp rise or bump in the roadway profile
  3. C The end of the travel lane
  4. D A steep downhill grade

Correct answer: B – A sharp rise or bump in the roadway profile

On Illinois roads, the BUMP warning sign identifies a sharp rise or bump in the roadway profile ahead. The separate DIP sign is used for a depression. Warning signs alert drivers to conditions that may require a speed reduction or another safety-related response, particularly when operating a large or heavily loaded vehicle.

Source: 625 ILCS 5/11-301 – Department to Adopt Sign Manual, Manual on Uniform Traffic Control Devices, 11th Edition with Revision 1 — § 2C.26, “BUMP and DIP Signs (W8-1 and W8-2)”

Question 5

In a manual-transmission CMV stopped on a hill, what should you do before taking your right foot off the service brake?

  1. A Shift into neutral
  2. B Release the brake before engaging the clutch
  3. C Partly engage the clutch
  4. D Keep the clutch fully depressed until the vehicle begins rolling

Correct answer: C – Partly engage the clutch

Partly engaging the clutch before removing your right foot from the service brake helps prevent the vehicle from rolling backward. The parking brake may also be used when necessary and should not be released until enough engine power is applied to hold the vehicle. A trailer hand valve may be used for this purpose on an appropriately equipped tractor-trailer.

Source: Illinois CDL Study Guide — § 2.2.1, “Accelerating”

Question 6

A retarder prevents the drive wheels from skidding on a slippery roadway.

  1. A True
  2. B False

Correct answer: B – False

A retarder does not prevent skids. When the drive wheels have poor traction, retarder braking can cause those wheels to lose their grip and slide. The retarder should be turned off whenever the roadway is wet, icy, or covered with snow.

Source: Illinois CDL Study Guide — § 2.3.4, “Retarders”

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