CDL Air Brakes Test (2024) - FREE District of Columbia CDL Practice Test

1. If stopped on a hill, how can you start moving without rolling back?

Release the parking brake before you have applied enough engine power to keep from rolling back.
Partly engage the clutch before you take your right foot off the brake, put on the parking brake if necessary.
Press on the gas pedal, even if you have to roll back a little.
None of the above.

2. Which of the following is a reason why air tanks must be drained?

Your transmission fluid may drain out.
Your brakes may fail due to the water freezing.
The governor may stop the compressor from pumping air.
Your battery fluid may drain out.

3. If you must make an emergency stop, you should:

apply the brakes as hard as you can to lock them.
brake in a way that will keep your vehicle in a straight line.
use the hand brake before the brake pedal.
None of the above.

4. Passive railroad crossings:

have at least one traffic control device.
should never be crossed using a CMV.
do not have traffic control devices.
usually have a person directing traffic.

5. Perception Distance + Reaction Distance + Brake Lag Distance + Braking Distance = ?

Partial Stopping Distance
Stopping Distance - (minus) Brake Fade Distance
Total Air Pressure
Total Stopping Distance

6. The posted speed limit:

is only a suggestion.
may only be exceeded when driving in rural areas.
should never be exceeded.
should only be exceeded when passing other vehicles.

7. If a vehicle is equipped with ABS, when you start the engine:

the wheels will lock up.
the spring brakes will come on.
the trailer emergency brakes will come on.
the ABS indicator light on the dash should come on and then turn off.

8. The braking power of the spring brakes:

is not affected by the condition of the service brakes.
is not affected by the air pressure level.
depends on the brakes being in adjustment.
All of the above.

9. Trailers built on or after March 1, 1998 are required to be equipped with anti-lock brakes. These trailers will have:

yellow malfunction lamps on the left side.
yellow malfunction lamps on the right side.
blue malfunction lamps on the right side.
red malfunction lamps on the left side.

10. The use of brakes on a steep downgrade is:

the main braking factor.
dangerous, and should be avoided at all costs.
much more effective than the engine braking effect.
a supplement to the braking effect of the engine.

DISTRICT OF COLUMBIA CDL AIR BRAKES PRACTICE TEST