Alaska CDL: Combination Vehicles Practice Test

Not quite. The answer is spread evenly across the rig and as low as possible.

More than half of truck driver deaths in accidents are the result of truck rollovers. The higher the truck's center of gravity, the more likely it is to roll over. If the cargo is to one side, it will make the trailer lean, which can also make a rollover more likely. To help prevent rollover, spread your cargo evenly and keep it as low as possible. Drive slowly through curves and turns.

Not quite. The answer is back up gently to ease pressure on the fifth wheel locking jaws.

When uncoupling, ease pressure on the fifth wheel locking jaws by backing up gently. (This will help you release the fifth wheel locking lever.) Then apply the parking brakes while the tractor is pushing against the kingpin.

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 easier it is to turn over.

When you stack cargo high in a trailer, you raise its center of gravity, which makes the trailer more prone to rolling over. A fully loaded tractor-trailer is ten times more likely to roll over in a crash than an empty one.

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 Always

If there is a leak in the emergency air line, air will eventually leak out of the trailer air tank. If the trailer has air brakes but not spring brakes, the brakes will fail. Use chocks to prevent the trailer from rolling if its brakes fail.

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 Drive normally and get it fixed later.

Losing the ABS function does not change the basic parts of your truck, so you will still have the same brakes that you have always had. Simply use them and get the ABS repaired as soon as possible. There is no need to panic, unless your system shows other and more serious warnings.

Not quite. The answer is over the locking lever.

The safety latch should be in position over the fifth wheel locking lever. On some vehicles, you may have to position it manually.

Not quite. The answer is To prevent steering problems

One of the first steps in coupling a tractor to a trailer is to check that the fifth wheel skid plate is greased as required. If the fifth wheel plate is not properly lubricated, friction between the plate and the trailer apron could cause steering problems.

Not quite. The answer is to the driver's side.

If you must back your vehicle on a curved path, back toward the driver's side. You'll be able to watch the rear of your vehicle from your driver's-side window.

Not quite. The answer is 3 psi per minute.

To test the static air leakage rate, turn off the engine, release the parking brake (i.e., push the parking brake control knob in), and see how fast the air pressure drops. The air pressure should drop less than 2 psi in one minute for a single vehicle and less than 3 psi in one minute for a combination vehicle.

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 Pull the tractor ahead gently with the trailer brakes locked.

After you've backed under the trailer and locked the kingpin into the fifth wheel, raise the landing gear slightly off the ground. 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 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 red lights

According to federal regulations, if the load projects more than 4 feet behind the rear of the vehicle, the end of the load must be marked as follows: (1) with red flags, each 18 inches square, in the daytime; or (2) with two red lights at night. There are additional federal requirements on how to illuminate the rest of the load. US states may impose their own additional requirements on the transportation of oversized loads. You can learn about Alaska's detailed requirements by contacting the Alaska Department of Transportation or reviewing their document "Administrative Permit Manual: Oversize and Overweight Permits," which you can download from their website. [49 CFR 393.11],

Source: 49 CFR 393.87

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

Because of rearward amplification, the last trailer on a combination vehicle has the highest probability of rolling over. This is called the crack-the-whip effect.

Not quite. The answer is When you lock the drive wheels on the tractor and the tractor spins out sideways as the trailer continues to push forward

A jackknife is usually the result of a drive-wheel skid. The tractor's rear drive wheels lock, and the trailer starts to push the tractor sideways.

Not quite. The answer is hang it with the plug down.

After you disconnect the electrical cable, hang it with the plug down to keep moisture or rain from getting into it.