Cdl Combination Vehicle Test Your Knowledge

Front 1

1. What two things are important to prevent rollover?

Back 1

Keep the cargo as close to the ground as possible, and drive slowly around turns.

Front 2

2. When you turn suddenly while pulling doubles, which trailer is most likely to turn over?

Back 2

The rear trailer is twice as likely to turn over as the tractor.

Front 3

3. Why should you not use the trailer hand brake to straighten out a jackknifing trailer?

Back 3

This is the wrong thing to do since the brakes on the trailer wheels caused the skid in the first place.

Front 4

4. What is off tracking?

Back 4

When a vehicle goes around a corner, the rear wheels follow a different path than the front wheels. This is called off tracking or “cheating.

Front 5

5. When you back a trailer, you should position your vehicle so you can back in a curved path to the driver’s side. True or False?

Back 5

True.

Front 6

6. What type of trailers can get stuck on railroad highway crossings?

Back 6

Low slung units (lowboy, car carrier, moving van, possum-belly livestock trailer). Single-axle tractor pulling a long trailer with its landing gear set to accommodate a tandem axle tractor.

Front 7

1. Why should you not use the trailer hand valve while driving?

Back 7

Do not use it in driving because of the danger of making the trailer skid.

Front 8

2. Describe what the trailer air supply control does.

Back 8

The trailer air supply control on newer vehicles is a red eight-sided knob, which you use to control the tractor protection valve.

Front 9

3. Describe what the service line is for.

Back 9

The service line (also called the control line or signal line) carries air, which is controlled by the foot brake or the trailer hand brake.

Front 10

4. What is the emergency air line for?

Back 10

The emergency line (also called the supply line) has two purposes. First, it supplies air to the trailer air tanks. Second, the emergency line controls the emergency brakes on combination vehicles.

Front 11

5. Why should you use chocks when parking a trailer without spring brakes?

Back 11

If the trailer does not have spring brakes, use wheel chocks to keep the trailer from moving.

Front 12

6. Where are shut-off valves?

Back 12

Shut-off valves are used in the service and supply air lines at the back of trailers used to tow other trailers.

Front 13

1. What might happen if the trailer is too high when you try to couple?

Back 13

If the trailer is too high, it may not couple correctly.

Front 14

2. After coupling, how much space should be between the upper and lower fifth wheel?

Back 14

Make sure there is no space between upper and lower fifth wheel.

Front 15

3. You should look into the back of the fifth wheel to see if it is locked onto the kingpin. True or False?

Back 15

True.

Front 16

4. To drive you need to raise the landing gear only until it just lifts off the pavement. True or False?

Back 16

True.

Front 17

5. How do you know if your trailer is equipped with antilock brakes?

Back 17

Trailers will have yellow ABS malfunction lamps on the left side, either on the front or rear corner.

Front 18

1. Which shut-off valves should be open and which closed?

Back 18

The front trailers shut-off valves open and the rear closed.

Front 19

2. How can you test that air flows to all trailers?

Back 19

Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers (this test assumes that the trailer handbrake or the service brake pedal is on), then close the valve. If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly(s) are in the OPEN position.

Front 20

3. How can you test the tractor protection valve?

Back 20

Charge the trailer air brake system and push the air supply knob in. Shut the engine off. Step on and off the brake pedal several times to reduce the air pressure in the tanks. The trailer air supply control should pop out when the air pressure falls into the pressure range specified by the manufacturer.

Front 21

4. How can you test the trailer emergency brakes?

Back 21

Charge the trailer air brake system and check that the trailer rolls freely. Then stop and pull out the trailer air supply control valve. Pull gently on the trailer with the tractor to check that the trailer emergency brakes are on.

Front 22

5. How can you test the trailer service brakes?

Back 22

Check for normal air pressure, release the parking brakes, move the vehicle forward slowly, and apply trailer brake with the hand control trolley valve, if so equipped.