CDL AIR BRAKES PRACTICE TEST - ILLINOIS

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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Illinois CDL knowledge test. The IL CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Illinois CDL Manual. Take this IL CDL practice test now to prepare for the actual air brakes test!
1. If air pressure does not build up fast enough:
the pressure may drop too low during driving.
you should put the parking brake on and gently pull against it in a low gear.
you may be forced to turn off the engine and release the parking brake.
you should turn the electrical power on and step on and off the brake pedal.
2. The supply pressure gauges tell you how much air pressure:
is in the air brakes.
is in the air tanks.
you are applying to the brakes.
is going to the brake chambers.
3. If the low air pressure warning light comes on, you should:
stop immediately.
set the parking brake.
continue to drive normally.
call for help.
4. Which of the following is not a braking system on a truck?
Service brake
Steering brake
Emergency brake
Parking brake
5. Hydroplaning is more likely if:
the road is wet.
tire pressure is low.
tire tread is worn.
All of the above.
6. The trailer hand valve should:
be used in driving.
never be used for parking.
never be used to test the trailer brakes.
All of the above.
7. Before driving a vehicle with a dual air system, the air compressor should build up a minimum of _____ pressure in both the primary and secondary systems.
10 psi
50 psi
100 psi
75 psi
8. When is it safe to leave your vehicle unattended without applying the parking brakes or chocking the wheels?
When the tank pressure falls to the "cut-in" pressure.
Only while you are taking a rest break.
Never.
When you are conducting your pre-trip inspection.
9. Under a pressurized system, the radiator cap:
should never be hot.
should never be removed until the system has cooled.
should be removed when the coolant is hot.
should always be cool.
10. Parking brakes are:
required on all vehicles.
not required on trailers.
not required on commercial vehicles with air brakes.
not required on buses.
 
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Frequently Asked Questions

To obtain a class D driver's license in Illinois, teens must follow the three steps of the Graduated Driver License (GDL) system. Here are the age requirements:

  • For a learner's permit, you must be at least 15.
  • For an initial license, you must be between 16-17.
  • For a full license, you must be between 18-20.

For applicants between 18 and 20 years old, a six-hour adult driver education course is required before getting a driver’s license.

Visit the Illinois Secretary of State’s office website to book your written test. You can choose dates and times based on your preferences and the available options at various Illinois DMV locations. 

You must present the following documents:

  • Proof of written signature (credit cards, mortgage documents, passport, etc).
  • Proof of date of birth with your full name.
  • Proof of Social Security Number.
  • Proof of residency (e.g., bank statement, insurance policy, or utility bill). For a REAL ID-compliant driver’s license, you have to bring two proofs.

Use this checklist to prepare for your visit and ensure you have all the necessary documents.

The DMV written test in Illinois is available in English. If you don't speak English well or experience any reading difficulties, you can request an oral examination in person at any Secretary of State driver’s license office.

The DMV written test is based on the Illinois Driver's Manual. Focus on road signs, safe driving practices and road rules. Take our free practice tests to prepare for the permit test, or sign up for DMV Premium to unlock more resources and prepare for your exam faster!

The Illinois DMV written test consists of 35 questions. Among them, 15 focus on traffic sign identification, and the remaining 20 are multiple-choice or true-false questions. These questions are based on the official manual, so it's important to study it well to maximize your chances of passing the exam.

Illinois imposes specific restrictions on new drivers according to their age.

Permit phase:
  • Driving is prohibited from 10 p.m. to 6 a.m. (Saturday-Thursday) and from 11 p.m. to 6 a.m. (Friday-Saturday).
  • The maximum number of passengers is one in the front seat, and the number of passengers in the back seat is limited to the available safety belts.
  • Drivers and passengers must wear safety belts.
  • Using a cell phone, including a hands-free device, is prohibited (except for emergencies).

Initial licensing phase:
  • Driving is prohibited from 10 p.m. to 6 a.m. (Saturday-Thursday) and from 11 p.m. to 6 a.m. (Friday-Saturday).
  • Drivers and passengers must wear safety belts.
  • During the first 12 months or until the driver turns 18, only one passenger under the age of 20 is allowed (except for family members). After this period, only one person is allowed in the front seat, and the number of passengers in the back seat is limited to the available safety belts.
  • Using a cell phone, including a hands-free device, is prohibited (except for emergencies).

Full licensing phase:
  • Drivers under 18 cannot operate for-hire vehicles transporting property or require a commercial driver’s license, and until 21, they are not allowed to use any for-hire vehicles transporting people.
  • Using a cell phone, including a hands-free device, is forbidden for drivers under 19 (except for emergencies).
If you are under 18, the learner’s permit is valid for two years, with a requirement to hold it for a minimum of nine months before qualifying for a driver's license. For applicants over 18,  the permit is valid for one year. If it expires, a renewal fee is applicable. 


If you fail the DMV written test, you can take a second attempt on the same day. However, if you fail because you were caught cheating, you will have to wait 30 days before retaking it. Generally, you have three attempts to pass the permit test within one year after the application.

IL CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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