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Drivers who want to drive combination vehicles must pass the combination vehicles test. The Oklahoma 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 Oklahoma CDL Manual. Take this practice test now to prepare for the actual OK CDL combination test!
1. When uncoupling a trailer, after shutting off the trailer air supply to lock the trailer brakes, you should:
pull the tractor forward until the fifth-wheel comes out from under the trailer.
back up gently to ease the pressure on the fifth-wheel locking jaws.
inspect the trailer supports.
2. As part of your vehicle inspection, you are checking that air flows to all trailers. After using the trailer handbrake to provide air to the service line, you go to the rear of the rig. When you open the emergency line shut-off valve at the rear of the last trailer, you should hear:
the service line valve close.
a mechanical vibration.
air escaping from the open valve.
3. If you must drive slowly, how should you alert following drivers?
Turn on your taillights
Flash your brake lights
Use your emergency flashers if it is legal
4. What is countersteering?
Turning the steering wheel quickly the other way after steering in an emergency situation.
Staying off the brake while steering to the right to avoid an accident.
Locking your wheels while turning in an emergency situation.
5. Most truck driver deaths in crashes result from:
truck rollovers.
driving side-by-side with another truck.
6. Most hydraulic brake failures occur for one of two reasons, one of which is:
loss of hydraulic pressure.
relying too much on the engine braking effect.
excessive downshifting.
7. While driving, you should use your mirrors to:
check where the rear of your vehicle is while you make turns.
know where other vehicles are around you.
All of the above.
8. Dollies with ABS are required to have a malfunction lamp:
on the left side.
on the rear.
on the right side.
9. The proper following distance for a 60-foot vehicle traveling at 50 mph is:
6 seconds
7 seconds
4 seconds
10. Weight that is loaded so there is a high center of gravity:
makes a vehicle easier to handle.
reduces the chance that the load will shift to the side or fall off.
causes greater chance of rollover.
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OK CDL Combination Test

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