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Drivers who want to drive combination vehicles must pass the combination vehicles test. The District of Columbia CDL combination test consists of 20 questions, and you'll need at least 16 correct answers to pass (80%). The test covers the combination vehicles section of the District of Columbia CDL Manual. Take this practice test now to prepare for the actual DC CDL combination test!
1. On front tires, tread should be at least:
4/32 inch
4/16 inch
2/32 inch
1/16 inch
2. When checking the air and electric lines to the trailer, be sure that the air lines are properly connected to the gland hands, and are:
secured with enough air leaks for turns.
secured with enough slack for turns.
properly greased.
None of the above.
3. _________ can make vehicle handling unsafe.
Poor ventilation
Dry roads
Poor weight balance
4. When the wheels of a trailer lock up, the trailer will tend to swing around. This is more likely to happen when:
the trailer is fully loaded.
the trailer is overloaded.
the trailer is empty or lightly loaded.
None of the above.
5. If the spring brakes do not release when you push the trailer air supply control, you should:
check the air line connections.
pump the brakes.
rev or lug the engine.
check the electrical cables.
6. If you try to couple when the trailer is too low:
the tractor could roll away.
it might not couple correctly.
the tractor may strike and damage the trailer nose.
All of the above.
7. As you approach off ramps and on ramps, remember:
that the posted speed limit may not be safe for larger vehicles.
to always brake and turn at the same time.
that downgrades make it easier to reduce speed.
to maintain your highway speed.
8. Most heavy-duty vehicles use:
air brakes.
solid brakes.
pressure brakes.
hydraulic brakes.
9. To prevent rollover, you should:
drive slowly around corners.
drive on the shoulder of the road when possible.
turn the engine off while turning.
drive in the left lane.
10. It's very important to distribute the cargo so it is:
piled up.
in the centre of the load.
as low as possible.
as high up as possible.
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DC CDL Combination Test

Number of questions: 20
Correct answers to pass:16
Passing score:80%
Number of questions: 20
Correct answers to pass:16
Passing score:80%
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