Instructions

Combination

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Commercial.. Read More

All applicants who are applying for a Class A CDL should be prepared to take the Combination test. This test covers information found in Section 6 of the Commercial Driver's License Manual. Section 6 provides the information needed to safely operate tractor-trailers, doubles, triples, and straight trucks with trailers. The test is made up of 20 multiple-choice questions, and applicants will have two minutes per question to correctly answer a minimum of 16 questions. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question 20

Passing Score 16

15. When driving a bobtail tractor, you should be aware that:

Bobtails stop very easily.

Bobtails cannot drive as fast as tractors with semitrailers.

Bobtails are more difficult to stop than tractors with semitrailers.

Bobtails are illegal in most states.

Bobtail tractors are tractors that are not attached to any semitrailers. When operating a bobtail, you should be aware that stopping can be difficult and that it will take a longer distance to bring the bobtail to a complete stop than it would a tractor attached to a loaded semitrailer.

16. If unsure if a trailer is equipped with ABS, you can:

Check under the trailer for wheel speed sensors coming from the back of the brakes.

Try driving on a slippery surface and see if ABS kicks in.

Assume it does have ABS.

Remove a tire and look for the ABS sensor on the axle.

Trailers and converter dollies built on or after March 1, 1998 are required to have Anti-Lock Braking Systems (ABS). This will be indicated by the presence of a yellow malfunction lamp. You can determine if older trailers have ABS by checking under the trailers for ECU and wheel speed sensor wires coming from the back of the brakes.

17. To prevent a trailer from rolling over, you should:

Speed up when nearing a corner.

Make sudden steering moves.

Take on-ramps faster than the posted speed limit.

Drive slowly around corners.

To reduce the risk of a rollover when driving a combination vehicle, you should keep the weight of the cargo as low to the ground as possible and drive slowly around turns.

18. If colors are being used to distinguish glad hands, which color is used for service lines?

Orange

Yellow

Green

Blue

When trailer air lines are color-coded, the service lines are generally blue and the emergency lines are generally red.

19. What is another name for the service line?

The signal line

The cable line

The surplus line

The power line

The trailer service air line is also referred to as the control line or signal line.

20. What can the “crack-the-whip” effect do?

Turn over trailers.

Make loud noises.

Make trucks accelerate.

Make trucks decelerate.

The "crack-the-whip" effect can cause a trailer to turn over during a lane change. To avoid this phenomenon, drivers should make lane changes at slow, safe speeds.

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