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 Driver License.. 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 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 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. 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.

2. If oil and water build up in your vehicle's air tanks, the brakes:

May not work correctly.

May feel squishy.

Will squeal loudly when used.

Will be extremely sensitive.

Air tanks should be drained daily to remove water and oil buildup. An excess of oil and water in the air tanks can interfere with proper brake function.

3. If you are operating a vehicle built before 1998 and are unsure if the trailer has an Anti-Lock Braking System (ABS), you can:

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

Look for a red light on the front right corner of the converter dolly.

Pump the air brakes to activate the ABS.

Assume the vehicle has ABS.

If you are operating a vehicle built before 1998 and are unsure if the trailer has an Anti-Lock Braking System (ABS), you can check under the trailer for wheel speed sensors coming from the back of the brakes.

4. A tractor protection valve is:

A device that keeps air in the tractor or truck brake system, should the trailer break away or develop a bad leak.

A device that prevents theft.

A device that controls fuel levels.

A device that allows the battery to recharge efficiently.

On combination vehicles with air brakes, the tractor protection valve keeps air in the tractor or truck brake system, should the trailer develop a bad leak or break away from the tractor.

5. Using the trailer hand valve while driving:

Will help you turn safely.

Will stop your trailer safely.

Can cause a skid.

Is impossible.

Never use the trailer hand valve while operating your vehicle. Using the trailer hand valve while driving can cause your trailer to skid.

6. What is another name for the service line?

Control line

Exchange line

Surplus line

Parallel line

The service line, also called the control line or signal line, carries air to the trailer brakes and is controlled by the foot brake or trailer hand brake.

7. Which type of vehicle is most prone to the “crack-the-whip” effect?

A five-axle tractor semi-trailer

A three-axle tractor semi-trailer

A bobtail tractor

A triple trailer

Triple combination trailers are most vulnerable to the "crack-the-whip" effect.

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