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 Missouri 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

8. What is a bobtail tractor?

A tractor without a trailer

A tractor attached to two trailers

A tractor with a tank

Tractors without semi-trailers are referred to as bobtail tractors. Operating a bobtail tractor requires drivers to exercise caution.

9. A driver should test the tractor protection valve by:

Pulling the yellow, diamond-shaped knob.

Releasing air with the brake pedal.

Unlocking the trailer doors.

You should test the tractor protection valve by allowing the air supply to properly charge, turning off the engine, then releasing air from the system by pressing the brake pedal several times. The tractor protection valve should move into its emergency position when psi drops to an unsafe level.

10. If a parked trailer does not have spring brakes, you should keep the trailer from moving by:

Having the vehicle parked against a wall or other vehicle.

Using chock blocks.

Parking on a slight incline.

If a parked trailer does not have spring brakes, wheel chocks should be used to prevent it from moving.

11. When backing up your tractor while coupling it to a trailer, the trailer brakes should be:

Deactivated.

Locked.

Unlocked.

Correctly following the steps to couple and uncouple trailers is vital to safely operating a combination vehicle. Before backing your tractor under the trailer while coupling, make sure your trailer brakes are locked.

12. When a vehicle goes around a corner, the rear wheels:

Follow the same path as the front wheels.

Follow a different path than the front wheels.

Should not be a concern to the driver.

When any vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is called off-tracking. The degree of off-tracking will be greater on long vehicles than on short vehicles.

13. 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.

75 and 105 psi.

50 and 65 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.

14. If you cannot reverse your trailer in a straight path, you should:

Swerve back and forth while backing.

Back toward the driver's side.

Back toward the passenger's side.

If you need to back your trailer but cannot back up in a straight path, you should back on a curved path toward the driver's side of the vehicle. This will allow you the best possible visibility while backing.

Grade This Section

See the exact questions that will be on the 2024 Missouri DMV exam.

99.2% of people who use the cheat sheet pass the FIRST TIME

Click Here
Full Cheat Sheet Unlock Your Exclusive Cheat Sheet!