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 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 need to correctly answer a minimum of 16 questions to pass. The Combination test is not a replacement for the Double/Triple endorsement test.

Number of Question 20

Passing Score 16

1. What does the trailer air supply control look like?

It is a square blue knob.

It is a triangular yellow knob.

It is an eight-sided red knob.

It is a circular orange knob.

On newer vehicles, the trailer air supply control is an eight-sided red knob. It's used to control the tractor protection valve.

2. In a vehicle equipped with an automatic tractor protection valve, the valve will pop out when:

Air pressure drops to a level between 20 and 45 psi.

You are experiencing a trailer jackknife.

Wheels have regained traction after a skid.

Air pressure is above 45 psi.

In vehicles equipped with an automatic tractor protection valve, the valve will pop out if air pressure drops to a level between 20 and 45 psi. When the valve pops out, the protection valve will close, stopping the flow of air.

3. When coupling a trailer:

Make sure to couple matching glad hands.

Any glad hand can be connected to any other glad hand.

It is best to leave one glad hand unattached.

Only one set of glad hands should be connected.

When coupling, make sure you couple matching glad hands. They are often color-coded to help drivers avoid mistakes. Typically, blue is used for service lines and red is used for emergency lines.

4. 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.

5. When a combination vehicle goes around a corner:

The turn should be made as tightly as possible.

The front and rear wheels move in different paths.

The rear wheels should run over the curb.

It is acceptable for street signs to be knocked over if they are too close to the road.

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is called off-tracking. This effect is especially pronounced on vehicles with trailers.

6. When connecting a converter dolly to a second or third trailer, the trailer height should be:

Slightly higher than the center of the fifth wheel.

Level with the center of the fifth wheel.

Slightly lower than the center of the fifth wheel.

Next to the center of the fifth wheel.

When connecting a converter dolly to a second or third trailer, the trailer height should be correct. It should be slightly lower than the center of the fifth wheel.

7. If a trailer is too high:

It will not make a difference when coupling.

It may not couple correctly.

Coupling will be more secure.

Coupling will be easier.

Before coupling together a tractor and a trailer, you should make sure the trailer is at the proper height. If the trailer is too low, the trailer nose may be damaged. If the trailer is too high, it may not be able to couple correctly.

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