Oregon CDL: Combination Vehicles Practice Test

Not quite. The answer is If the trailer has no spring brakes, you will be able to drive away but you won't have trailer brakes.

Trailers built before 1975 are not required to have spring brakes. If you cross the air lines when coupling such a trailer, you may have no air pressure to supply the trailer brakes. You'll be able to drive, but you won't be able to brake the trailer. Always test the trailer air brakes before you start to drive.

Not quite. The answer is The shank

Don't drive the vehicle until you're sure that the coupling is correct. Check to make sure of the following: There is no space between the upper and lower fifth wheel, the fifth wheel jaws have closed around the shank of the kingpin, the locking lever is in the "lock" position, and the safety latch is in position over the locking lever. If anything isn't right, don't drive the vehicle until you've found and corrected the problem. If you drive it anyway, your trailer could come loose while you're driving.

Not quite. The answer is Apply and release the trailer service brakes while you listen for sounds.

If you cross the air lines, supply air will be sent to the service line instead of the supply line and the trailer air tanks. Without a supply of air, the trailer service brakes won't work. Therefore, to make sure that the air lines aren't crossed, send air to the trailer brakes by pushing in the trailer air supply control (red knob). Let the pressure normalize. Then turn off the engine and try the trailer brakes. You should see and hear the brakes in action and then see the air pressure normalize again.

Not quite. The answer is the trailer's emergency brakes to come on.

The trailer air supply valve (which is manually controlled by the red dashboard knob) senses air pressure in the supply (emergency) line. If air pressure in the supply line is lost, the trailer air supply valve will close automatically, and the resulting loss of air pressure in the tractor protection valve will cause it to close as well. And loss of pressure in the supply line will cause the trailer emergency (spring) brakes to come on.

Not quite. The answer is a yellow malfunction lamp on the left side.

A trailer with ABS has a yellow malfunction lamp on either the left front corner or the left rear corner. Make sure you know where to look for it.

Not quite. The answer is the trailer emergency glad hand.

During the coupling process, after you've backed the tractor till it's touching the trailer and you've parked the tractor, it's time to connect the air lines. Connect the tractor emergency air line to the trailer emergency glad hand. Connect the tractor service air line to the trailer service glad hand.

Not quite. The answer is trailer emergency brakes to come on.

If air pressure in the emergency air line drops too low (say because of a bad leak in the service line), the trailer emergency brakes will come on. Also, the tractor protection valve will close to keep air from escaping from the tractor.

Not quite. The answer is at normal pressure.

Before backing under a trailer during the coupling process, make sure that the air pressure is at normal levels so you'll be able to brake safely.

Not quite. The answer is On the left front or left rear corner

On a trailer, the yellow ABS malfunction lamp is located on the left front or left rear corner. Make sure you know where to look for it.

Not quite. The answer is It will keep dirt and water out of the lines.

Some vehicles are equipped with "dead-end" or dummy couplers. When the air lines are not connected to a trailer, connect the glad hands to the dummy couplers to keep water and dirt out of the glad hands and air lines. If your vehicle doesn't have dummy couplers, you may be able to connect the glad hands to each other.

Not quite. The answer is glad hands

As part of your vehicle inspection test, if your vehicle is equipped with air brakes and has a trailer, you will inspect the air connections between the truck or tractor and the trailer. These connections are made with hose couplers (commonly called "glad hands" because they vaguely resemble shaking hands). These glad hands have rubber seals to form a tight connection and prevent air from escaping. Make sure that the glad hands are locked in place and free of damage or air leaks.

Not quite. The answer is makes firm contact with the ground.

When uncoupling a loaded trailer, lower the landing gear until it makes firm contact with the ground. Then crank the landing gear in low gear for a few more turns – just enough to lift some weight off the tractor, but not so much that you lift the trailer off the fifth wheel. This will make it easier to unlatch the fifth wheel now and couple next time.

Not quite. The answer is the tractor protection valve to close.

The tractor protection valve keeps air in the tractor if the trailer breaks away or develops a bad leak. If air pressure drops too low in the service line, the tractor protection valve will close. This stops air from escaping from the tractor and lets air out of the trailer emergency line, causing the trailer emergency brakes to come on.

Not quite. The answer is of the danger of making the trailer skid.

The trailer hand valve (also known as a trolley valve or Johnson bar) controls only the trailer brakes, not the tractor brakes. If you apply it while you're driving, you'll brake the trailers but not the tractor. This can cause a skid or even a jackknife. Instead, use the foot brake, which sends air to the tractor brakes as well as the trailer brakes.

Not quite. The answer is the brakes will fail if the air supply leaks away.

If the trailer lacks spring brakes, make sure you chock the wheels whenever you park. If air pressure leaks away, the trailer's brakes will fail. Without chocks, the trailer could roll away.

Not quite. The answer is (a) The tractor is on level ground.

When coupling a trailer to a tractor, it's a good idea to make sure that you're on a level surface free of dips or potholes. If you back the tractor over a large bump, dip, or pothole, you might damage something as you attempt to push the tractor underneath the trailer. On the other hand, the trailer itself need not be perfectly level. You want it to be aligned so that it will be raised slightly when the tractor is backed underneath it.

Not quite. The answer is trailer emergency brakes to come on.

With the loss of air pressure, the tractor protection valve will close and the trailer emergency brakes will come on.

Not quite. The answer is Turn wide as you complete the turn.

If you swing wide to the left before you turn right, another driver may try to pass you on your right, which can lead to a collision. Instead, start the right turn with the rear of your vehicle as close to the curb as possible and then turn wide as you complete the turn. This will deny drivers room on the right to try to pass you.

Not quite. The answer is B.

If you swing wide to the left before you turn right, another vehicle may try to pass you on your right while you are turning. Instead, as shown in path B, make the right turn with the rear of your vehicle as close to the curb as possible and turn wide as you complete the turn. This will deny other vehicles enough room on the right to try to pass you.

Not quite. The answer is It controls the emergency brakes on combination vehicles.

The emergency air line is often colored red. It supplies air to the trailer air tanks and controls the emergency brakes on combination vehicles.