CDL AIR BRAKES PRACTICE TEST - DISTRICT OF COLUMBIA

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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 District of Columbia CDL knowledge test. The DC 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 District of Columbia CDL Manual. Take this DC CDL practice test now to prepare for the actual air brakes test!
1. It is not safe to drive a vehicle that has brake drums with cracks that are longer than ___ the width of the friction area.
1/2
1/4
9/10
3/5
2. Vehicles with air brakes require more stopping distance than vehicles with hydraulic brakes. Why?
Air brakes use different brake drums.
When driving vehicles with air brakes, the average perception distance increases from 400 feet to 2200 feet.
It takes one half second or more for the air to flow through the lines to the brakes.
Stopping distance for vehicles with air brakes is made up of six different factors.
3. Empty trucks have the best braking. True or False?
False.
True.
It depends on the truck.
It depends on the cargo.
4. If you must stop on a one-way or divided highway, you should place warning devices _______ toward the approaching traffic.
5, 25 and 50 feet
10, 100 and 200 feet
5, 50 and 500 feet
3, 15 and 45 feet
5. Air tanks usually hold enough compressed air to allow the brakes to be used _________ even if the compressor stops working.
for 3 days
for one day
several times
for one stop
6. If your trucks has a high center of gravity, which of the following is true for curves?
You should slow down, as your truck can roll over at the posted speed limit for the curve.
You should travel at the posted speed limit.
Reduce your speed to a crawl.
None of the above.
7. If your brakes fail while you are driving on a downgrade, you should:
use an escape ramp if it's available.
immediately start looking outside your vehicle for something to stop it.
take the least hazardous escape route you can.
All of the above.
8. You should drain the air tanks completely. If water and oil collect in the air tanks:
your brakes could become hard to press.
your brakes could fail.
your brakes could heat up.
None of the above.
9. If the low pressure warning signal doesn t work
you could lose air pressure and you would know it.
in dual systems the stopping distance will be decreased.
this could cause sudden emergency braking in a single-circuit air system.
None of the above.
10. In vehicles with air brakes, the brake pedal:
let the air out of the spring brakes.
controls the air pressure applied to the brakes.
tells you how much pressure is in the air tanks.
pumps air into the air storage tanks.
 
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Frequently Asked Questions

To obtain a driver's license in the District of Columbia, teens between 16 to 20 are enrolled in the Gradual Rearing of Adult Drivers (GRAD) Program:

  • If you are at least 16 years old, you can obtain a learner permit.
  • If you are 16 ½ and have held a learner permit for at least 6 months without traffic violations, you are ready for the provisional driver license.
  • If you are 17 years old and have held a provisional driver license for at least 6 months, you can obtain a full license with conditions (until you turn 18).

At 21 years old, you are released from the GRAD program, and you may immediately schedule a road test.

To schedule and take the DMV written test in the District of Columbia, you have three options:

  1. Select a DC DMV Service Center and schedule an appointment in person at takemydrivingtest.com/dc. Choose a location, date, and time for your exam.
  2. Select a Test Proctoring Center.
  3. If you are between 16 and 20 years old you can choose to take the exam online at home. Upon completing the virtual knowledge test, you'll promptly receive your test results. If you pass, simply visit any DC DMV Office within 14 business days to obtain your learner permit.

DC DMV requires you to bring specific documents to verify your eligibility for a class D driver's license: 

  • Proof of identity and age.
  • Proof of lawful presence.
  • Proof of Social Security Number.
  • Two proofs of district residency.
  • Parental Consent Form (if you are under 18 years old).
  • Medical/Eye Form (If you have a particular condition or if you're above 70 years).

Refer to the official DC Document Verification Guide for the complete list of acceptable documents.

The DMV written test in the District of Columbia is available in multiple languages, including English, Amharic, Arabic, Cantonese, French, German, Japanese, Korean, Mandarin, Portuguese, Russian, Spanish, Tagalog, Thai, and Vietnamese. Additionally, audio-assisted tests are provided for individuals who require assistance with reading.

To prepare for the DMV written test, you can refer to the official DC Driver's Handbook. The manual covers various information about road rules, traffic signs, and safe driving practices. Study carefully the different sections and test your knowledge with our free practice tests!

Learner permit:
  • Driving only with an instructor aged 21 or older (no passengers allowed).
  • Specific driving hour restrictions (from 6 am to 9 pm).
  • All occupants must wear seat belts.
  • Mobile phones cannot be used while driving.

Provisional license (16 ½ - 20 years old):
  • Driving alone with a maximum of one passenger aged 21 or older in the front seat, or with siblings/child.
  • Specific time restrictions:
- September to June (Sunday to Thursday from 6 am to 10:59 pm; Friday and Saturday from 6 am to 11:59 pm)
- July and August (from 6 am to 11:59 pm).
  • No driving for compensation (if under 18).
  • All occupants must wear seat belts.

Full license with conditions (under 18):
  • Same restrictions as the provisional license if you are a minor, but you are allowed to transport two passengers under 21.

Driving hour restrictions don't apply if you are accompanied by a holder of a valid driver's license aged 21 or older or for job, school, religious, or sport activities.


The DC instruction permit is valid for a period of two years for U.S. citizens and cannot be renewed. After its expiration, you will need to retake and pass the knowledge test again. During this period, practice to enhance your driving skills before the road test.

If you don't pass the DMV written test, you must wait 72 hours for a second try. If you fail six consecutive attempts, you will have to wait twelve months from the date of your initial test before retaking it. Sign up for DMV Premium and practice with extra tests to maximize the chance of passing!

DC CDL Air Brakes Test

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