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 Illinois 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 Illinois Commercial Driver's License Study Guide. 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 tractor-trailer equipped with ABS, you should:

Stop harder than you would otherwise.

Use extra braking force to ensure the ABS kicks in.

Brake as you normally would.

Brake using less pressure than you would otherwise use.

When driving a tractor-trailer combination equipped with an Anti-Lock Braking System (ABS), you should brake in the same manner that you would in a vehicle without ABS.

2. The emergency air line:

Is controlled by the foot brake.

Is connected to the relay valves.

Supplies air to the trailer air tanks.

Prevents skids.

The emergency air line (also known as the supply line) has two functions. The first is to supply air to the trailer air tanks on a combination vehicle, and the second is to control the emergency brakes.

3. Using the trailer hand brake while experiencing a trailer jackknife will:

Stop the skid.

Straighten the trailer.

Increase traction.

Continue the skid.

If you are experiencing a trailer jackknife, you can help your tires regain traction by releasing the brakes. Using a trailer hand brake while experiencing a skid will only cause the skid to continue.

4. Compared to other commercial motor vehicles, combination vehicles need more space on the road because they are longer and they:

Need more space to turn and stop.

Drive more slowly.

Are twice the width.

Swerve more often.

Combination vehicles need more space on the road than other commercial vehicles because they are longer and need more space to turn and stop. It is especially important to properly manage space when you are operating a combination vehicle.

5. A trailer will be most likely to swing around when:

It is full.

Traveling in a straight line.

It is empty.

The wheels are rotating.

An empty trailer will require a longer stopping distance than a loaded trailer. Additionally, a trailer is most likely to swing out and strike other vehicles when it is lightly loaded or empty.

6. Which of the following types of vehicles is most prone to the “crack-the-whip" effect?

An automobile

A three-axle tractor

A bobtail tractor

A triple combination

Double and triple combinations are the most vulnerable to turning over as a result of the "crack-the-whip" effect.

7. To test the trailer service brakes, you should:

Move the vehicle forward slowly and apply the brakes with the brake pedal.

Reverse the vehicle slowly and apply the brakes with the hand control.

Reverse the vehicle slowly and apply the brakes with the brake pedal.

Move the vehicle forward slowly and apply the brakes with the hand control.

To test the trailer service brakes, you should first ensure that the braking system has a normal air pressure level, then release the parking brake. You should then move the vehicle forward slowly and apply the brakes with the hand control. If the trailer service brakes are working properly, you will feel the brakes activate.

Grade This Section