Prepare for the Class A CDL Combination Vehicles test with these practice questions and answers. This guide covers coupling procedures, uncoupling, rollover prevention, and trailer safety.
Q: A tractor with a(n) ________ trailer requires the shortest amount of stopping distance .1. empty2. fully loaded3. lightly loaded
Answer: fully loaded
Q: The air leakage rate for a combination vehicle ( engine off, brakes on) should not be more than _____ psi per minute .1. 42. 63. 2
Answer: 4
Q: If you do not do the final air brake check for air leaks and fix them before driving,1. you could lose your brakes while driving2. your fuel usage will increase3. tire pressure will drop
Answer: you could lose your brakes while driving
Q: Which part of the kingpin should the locking jaws close around?
Answer: The shank
Q: Glad hands are used to connect the ….1. kingpin from the trailer to the locking jaws of the fifth wheel2. electrical lines from the tractor to the trailer3. service and emergency air lines from the truck or tractor to the trailer
Answer: service and emergency air lines from the truck or tractor to the trailer
Q: Trucks roll over more easily when fully loaded and are1. ten times more likely to roll over in a crash than empty rigs2. five times more likely to roll over in a crash than empty rigs3. two times more likely to roll over in a crash than empty rigs
Answer: ten times more likely to roll over in a crash than empty rigs
Q: In general, the higher your trucks center of gravity, the …1. easier it is to turn over2. more stable it is when turning3. easier it is to turn around corners
Answer: easier it is to turn over
Q: You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and …1. the tractor to lose all air pressure2. the tractor protection valve to close3. the trailer supply valve to stay open
Answer: the tractor protection valve to close
Q: When you drive a set of doubles, which shut-off valve must be closed in the last trailer?1. Middle section2. front section3. back section
Answer: back section
Q: The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that…1. the parking lock is off and you may drive away2. the trailer will not swivel on the fifth wheel3. the coupling is not right and should be fixed before you drive the coupled unit
Answer: the coupling is not right and should be fixed before you drive the coupled unit
Q: What gear should the tractor engine be in after you uncouple the trailer and are inspecting the trailer?1. neutral2. low reverse3. high reverse
Answer: neutral
Q: After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by ..1. lifting the brake pedal2. applying and releasing the trailer brakes and listening for brake sounds3. turning on the parking brake from the cab
Answer: applying and releasing the trailer brakes and listening for brake sounds
Q: If the brakes did not release when you pushed the trailer air supply valve, you should …1. cross the air lines,2. check the air line connections3. check the electrical cables
Answer: check the air line connections
Q: You have a major leak in the service line, and you apply the brakes. Service air pressure will escape and cause the1. trailer tank pressure to be lost2. trailer emergency brakes to come on3. tractor spring brakes to lock on
Answer: trailer emergency brakes to come on
Q: You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should1. immediately apply your tractor parking brakes2. begin to lower the trailer landing gear3. back up gently and ease pressure on the fifth wheel locking jaws
Answer: back up gently to ease pressure on the fifth wheel locking jaws
Q: When should you use the hand valve to park a combination vehicle?1. To park at loading docks2. To park on a grade3. never
Answer: Never
Q: The front trailer supports are up, and the trailer is resting on the tractor. Make sure that1. there is enough clearance between the upper and lower fifth wheel2. there is enough clearance between the tractor frame and the landing gear3. the safety latch is in the unlocked position
Answer: there is enough clearance between the tractor frame and the landing gear
Q: The trailer hand valve works the trailer brakes. Which of these statements is true?1. the foot brake sends air to all the brakes on the vehicle ( including the trailer(s))2. The trailer hand valve should be used only to test the trailer brakes3. all the above
Answer: all the above
Q: Where should the tractor be when you inspect the landing gear after uncoupling the trailer?1. With the fifth wheel directly beneath the kingpin2. completely cleared from the trailer3. with the tractor frame under the trailer
Answer: with the tractor frame under the trailer
Q: After you lock the kingpin into the fifth wheel, you should check the connection by pulling1. the tractor ahead gently with the trailer brakes locked2. forward 50 feet, then turning right, and then left3. the tractor ahead sharply to release the trailer brakes
Answer: the tractor ahead gently with the trailer brakes locked
Q: At night, when a vehicle is carrying a load that extends four feet or more beyond the rear of the body, there must be ________ at the extreme end of the load.1. red lights2. red flags3. a red flag
Answer: red lights
Q: Which type of truck-trailer combination has the greatest chance of a “crack-the-whip” rollover?1. A tractor pulling three trailers2. A single tractor trailer3. A tractor pulling two trailers
Answer: A tractor pulling 3 trailers
Q: Air and electrical lines from the tractor to the trailer should be…1. pulled tight with very little slack2. secured but with enough slack for turns3. resting on the frame of the tractor.
Answer: secured but with enough slack for turns
Q: Compared with a straight truck or bus, there are ________ things to inspect in combination vehicles.1. fewer2. more3. the same number of
Answer: more
Q: What is the emergency air line for?1. To engage the trailer brakes in case of air pressure loss2. To have extra air pressure in case you need it3. To engage the front brakes of the tractor in case of an emergency
Answer: To engage the trailer brakes in case of air pressure loss
Q: The tractor protection valve will close and the trailer _______ brakes will come on when there is a major leak in the brake line.1. parking2. service3. emergency
Answer: emergency
Q: A trailer is most likely to jackknife when it is …1. loaded to full capacity2. overloaded3. empty
Answer: empty
Q: When you are uncoupling a loaded trailer, lower the landing gear until it …1. reaches the ground2. makes firm contact with the ground3. makes contact with the ground, and leave the trailer off the fifth wheel
Answer: makes firm contact with the ground
Q: How much space should there be between the upper and lower fifth wheel after coupling?1. Just enough to see light through it2. About 1/4 inch3. None
Answer: none
Q: After you have coupled the trailer, you should start to raise the landing gear by using1. low gear2. high gear3. intermediate gear
Answer: low gear
Q: The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that1. the parking lock is off and you may drive away2. the coupling is not right and should be fixed before you drive the coupled unit3. the trailer will not swivel on the fifth wheel
Answer: the coupling is not right and should be fixed before you drive the coupled unit
Q: When checking the trailer emergency brakes, make sure that the tractor protection control valve is placed in the _______ position.1. normal2. emergency3. neutral
Answer: emergency
Q: You should use chocks when parking a trailer without spring brakes because1. if the air supply leaks away, there will be no brakes2. some states require chocking of trailer wheels3. you dont want the trailer rolling down a hill
Answer: if the air supply leaks away, there will be no brakes
Q: You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should1. begin to lower the trailer landing gear2. immediately apply your tractor parking brakes3. back up gently to ease pressure on the fifth wheel locking jaw
Answer: back up gently to ease pressure on the fifth wheel locking jaw
Q: While you are driving, your emergency air line breaks or gets pulled apart. The loss of pressure will cause the1. air compressor to unload instead of pumping air2. trailer emergency brakes to come on3. trailer supply valve to open
Answer: trailer emergency brakes to come on
Q: You are coupling a tractor to a semi-trailer. You have backed up but are not yet under it. Before backing under the semi trailer, you should hook up1. the electrical service cable2. nothing. Back up and lock the fifth wheel3. The emergency and service air lines
Answer: the emergency and service air lines
Q: When backing a tractor under a trailer, you should expect that1. the trailer will be lifter slightly when the tractor backs under it2. the trailer landing gear is fully extended3. the end of the kingpin is even with the top of the fifth wheel
Answer: the trailer will be lifting slightly when the tractor backs under it
Q: When you drive a set of doubles, which shut0off valve must be closed in the last trailer?1. front2. back3. middle
Answer: back
Q: What is a tractor jackknife?1. When you lock up the drive tires on the trailer and the trailer spins out sideways as the tractor continues to push forward2. When you lock up the drive tires on the tractor and the tractor spins out sideways as the trailer continues to push forward3. Neither of the above
Answer: When you lock up the drive tires on the tractor and the tractor spins out sideways as the trailer continues to push forward