Hawaii CDL: Combination Vehicles Practice Test

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 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 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 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.

Not quite. The answer is get away from your vehicle and call 911 or the posted emergency number.

A train traveling at 60 mph can take more than a mile to come to a complete stop. If your vehicle gets stuck on a railroad track, don't spend any time trying to free your vehicle. Get out of your vehicle and walk quickly at about a 45-degree angle to the tracks in the direction from which you expect trains to approach. That way, if your vehicle is hit, you won't be struck by flying debris. Call 911 or the telephone number on the railroad crossing sign for assistance.

Not quite. The answer is Push in the trailer air supply valve control.

The control for the trailer air supply valve is an eight-sided red knob on the dashboard. You push the knob in to supply compressed air to the trailer air brake system. You pull the knob out to evacuate air from the trailer air brake system (which will set the trailer brakes).

Not quite. The answer is supply air to the trailer system and then pull out the air supply knob.

Before you back under the trailer, you must lock the trailer brakes. First, supply air to the trailer air brake system and make sure that the system is working properly. Then set the trailer air supply control to lock the trailer brakes. To do this, pull out the red air supply knob (on newer vehicles) or move the tractor protection valve control to the emergency setting.

Not quite. The answer is the trailer brakes are locked.

During coupling, before backing under the trailer, set the trailer air supply control to shut off the air and lock the trailer brakes. On newer vehicles, this control is an eight-sided red knob. You pull it out to shut off the air.

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 the coupling surface of the trailer is just below the middle of the tractor fifth wheel.

The tractor fifth wheel should tilt downward toward the trailer. As you start to back the tractor under the trailer, the coupling surface of the trailer should be just below the middle of the tractor fifth wheel.

Not quite. The answer is the emergency and service air lines.

Before backing under the trailer, you must lock the trailer brakes – which means that you first have to make sure that the trailer brakes are working. Connect the emergency and service air lines and test the trailer brakes.

Not quite. The answer is A 5-axle tractor towing a 52-foot trailer

When any vehicle turns, its rear wheels will follow a shorter path than its front wheels. This is called off-tracking or "cheating." The longer the vehicle, the greater the difference. In a combination vehicle, the trailer's wheels will off-track more than the tractor's rear wheels. In a double or triple combination vehicle, the wheels of the last trailer will off-track the most.

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 tilted down toward the rear of the tractor.

Before coupling, make sure that the fifth wheel is in the proper position. For one thing, it should be tilted down toward the rear of the tractor so that the trailer can easily slide into it.

Not quite. The answer is Look under the vehicle for the ECU and wheel speed sensor wires coming from the back of the brakes.

You can tell if your vehicle has ABS by looking under the vehicle for the electronic control unit (ECU) and wheel speed sensor wires leading from the back of the brakes.

Not quite. The answer is slightly raised.

After you've backed under the trailer and locked the kingpin into the fifth wheel, raise the landing gear slightly. Then with the trailer brakes still locked, gently pull the tractor forward to check that the trailer is locked onto the tractor.

Not quite. The answer is the coupling is not right and should be fixed before you drive the coupled unit.

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 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 Normal

To test the trailer air brake system, first charge it with air. To do this, push in the red trailer air supply knob, or (in older vehicles) move the tractor protection valve control from the "emergency" position to the "normal" position. Wait until the air pressure reaches normal before you check for crossed air lines.

Not quite. The answer is Gently pull forward in low gear against the locked trailer brakes; then look at it carefully.

After you've backed under the trailer and locked the kingpin into the fifth wheel, raise the landing gear slightly. Then with the trailer brakes still locked, gently pull the tractor forward to check that the trailer is locked onto the tractor.