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 Idaho 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 Idaho 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 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. The emergency air line supplies air to the:

Relay valves.

Trailer air tanks.

Signal line.

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

2. Before beginning a trip, you should:

Leave the service line valve open.

Remove the relay valves.

Close the emergency line valve.

Before a trip, you should ensure that air reaches all air brakes on all trailers by opening up the rear emergency line and service line shut-off valves and listening for escaping air. Close both shut-off valves before beginning to drive.

3. When backing up while coupling a trailer, the tractor should be positioned:

Directly in front of the trailer.

Directly next to the trailer.

Parallel with the trailer.

When backing up to couple a trailer, you should position the tractor directly in front of the trailer. Trying to couple while backing at an angle could cause the trailer to move and the landing gear to break.

4. During a trip, landing gear should be:

Completely raised.

Completely lowered.

Skimming the pavement.

Landing gear, or trailer supports, should always be completely raised before a vehicle is driven. Landing gear that is not entirely raised could catch on railroad tracks or other hazards on the roadway.

5. 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.

6. What does an Anti-Lock Braking System (ABS) do?

It allows a vehicle's wheels to lock up.

It prevents a vehicle's wheels from locking up.

It makes turning a vehicle easier.

An Anti-Lock Braking System (ABS) helps prevent wheel lockup during hard braking. If ABS detects impending lockup, it reduces braking pressure to a safe level.

7. If unsure if a trailer has an Anti-Lock Braking System (ABS), you can:

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

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

Assume it does have ABS.

If you do not know whether or not a trailer is equipped with ABS, look under the vehicle for the electronic control unit and wheel speed sensor wires coming from the back of the brakes.

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