Arkansas CDL: Combination Vehicles Practice Test

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 make sure the ground is solid and can support the weight of the trailer.

Before uncoupling the trailer, be sure you're leaving it on firm ground that can support its weight.

Not quite. The answer is see it in your mirrors.

The earliest way to notice that your trailer is jackknifing is to see it swinging out in your mirrors.

Not quite. The answer is rollovers.

More than half of truck driver deaths in crashes are the result of truck rollovers. A full load increases the weight on the truck, making a jackknife less likely. But a full load also raises the truck's center of gravity, making a rollover more likely. Furthermore, many of America's expressways are old, with curved exit ramps that don't have the banking needed for today's combination vehicles.

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 check the air line connections.

If you cross the emergency and service air lines, air will flow to the service line instead of the trailer air tanks. Air won't be available to release the spring brakes. Therefore, if the spring brakes don't release when you push the trailer air supply control, check the air line connections.

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 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 release the brakes.

Once you realize your vehicle is in a skid, you should release the brakes so that the wheels can grip the road again. The trailer will start to follow the tractor and straighten out.

Not quite. The answer is To engage the trailer brakes in case of air pressure loss

The emergency air line has two main functions: (1) It supplies air to the trailer air tanks to keep the trailer brake system charged. (2) It controls the vehicle's emergency brakes. If air pressure in the emergency air line drops too low (say because of a bad leak or damage due to the trailer breaking loose), 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 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 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 No, because the brakes on the trailer wheels caused the skid to begin with.

The trailer skid was caused by the brakes locking the wheels. Applying the trailer hand brake might make that even worse. Instead, release the brakes so the trailer wheels can roll again and regain traction.

Not quite. The answer is It should not be done.

The trailer hand valve (also known as a spike, a trolley valve, or a 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 trailer skid.

Not quite. The answer is It takes 14 seconds to clear a single track and more than 15 seconds to clear a double track.

You can expect it to take more than 15 seconds for a typical tractor-trailer to clear a double track and at least 14 seconds to clear a single track.

Not quite. The answer is Rear

The shut-off valve should be closed only at the rear of the last trailer so that air will flow to the brakes of all trailers but no farther.

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 low gear.

Start to raise the landing gear by using the low gear range (if the landing gear is so equipped). Then switch to the high gear range once the trailer supports are free of weight.

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 Nothing is likely to happen until you try to apply the brakes.

If a leak has developed in the service line, air tank pressure may remain close to normal – until you try to brake. Then the air loss from the leak will cause the air pressure to drop quickly. If the air pressure drops far enough, the emergency brakes will come on.