# Free District of Columbia CDL Air Brakes Practice Test 2023

Do you need an Air Brakes endorsement or an L endorsement for your commercial driving license? The District of Columbia CDL Air Brake has some differences from other endorsements because your license will receive a mark of restriction if you fail the test. So having good preparation before exam day is very necessary. To ensure that our DC CDL practice test questions are relevant, all of them are based on the DC CDL Manual. Each question has a detailed explanation for you to thoroughly learn the format and the topic. Don't be afraid of having a restriction on your license. Let’s try with our CDL practice test to get ready to pass the District of Columbia CDL Air Brake Test now.

Our CDL practice tests:
Based on 2021 DC commercial driver's license manual
Full answers + detailed explanations
Perfect for first-time, renewal applicants
DC CDL Air Brakes Test format:
25 questions
20 correct answers to pass
80% passing score
List of questions
1.
In case of emergency when driving a vehicle equipped with dual parking control valves, you should:
2.
The driver must be able to see a low air pressure warning which comes on before pressure in the service air tanks fall below ____ psi.
3.
All air brake equipped vehicles have:
4.
At 55 mph on dry pavement, the air brake lag distance is how many feet?
5.
On a long or steep downgrade, the foot brakes should be used:
6.
The spring brakes used on the chambers in a straight truck will bring you to a stop when air pressure drops below ___ psi.
7.
The application pressure gauge shows how much air pressure you:
8.
When should the spring brakes activate?
9.
What should a driver do when the low air pressure warning signal comes on?
10.
The safety valve reduces pressure at ___ psi.
11.
If you are driving down a steep downgrade and have reached your safe speed of 40 mph, you would apply the service brake until your speed dropped to ____ mph.
12.
Average stopping distance under normal conditions at 55 mph is:
13.
If your vehicle has an alcohol evaporator, every day during cold weather you should:
14.
To stop the vehicle, the brake shoes and linings are pushed against:
15.
In case of air pressure loss, a mechanical means of preventing the vehicle from moving is called:
16.
To test the parking brake, stop the vehicle, put the parking brake on, and:
17.
The service brake system ________.
18.
On newer vehicles what color is the parking brake knob?
19.
Some vehicles are equipped with a separate air tank used specifically to release the spring brakes in an emergency, called a:
20.
Brake drums or discs _______.
21.
How often should alcohol containers be checked during cold weather?
22.
What is used to put alcohol into the system and reduce ice risk?
23.
What is the purpose of a supply pressure gauge?
24.
In a dual air brake system, one system will typically control the rear brakes, and the other:
25.
What is an alternative name for a brake pedal?