CDL COMBINATION VEHICLE COMPREHENSIVE EXAMS
QUESTIONS AND SOLUTIONS RATED A+
✔✔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 connections
3. check the electrical cables - ✔✔check the air line connections
✔✔You have a major leak in the service line, and you apply the brakes. Service air
pressure will escape and cause the
1. trailer tank pressure to be lost
2. trailer emergency brakes to come on
3. tractor spring brakes to lock on - ✔✔trailer emergency brakes to come on
✔✔You are uncoupling a trailer. After you shut off the trailer air supply and lock the
trailer brakes, you should
1. immediately apply your tractor parking brakes
2. begin to lower the trailer landing gear
3. back up gently and ease pressure on the fifth wheel locking jaws - ✔✔back up gently
to ease pressure on the fifth wheel locking jaws
✔✔When should you use the hand valve to park a combination vehicle?
1. To park at loading docks
2. To park on a grade
3. never - ✔✔Never
✔✔The front trailer supports are up, and the trailer is resting on the tractor. Make sure
that
1. there is enough clearance between the upper and lower fifth wheel
2. there is enough clearance between the tractor frame and the landing gear
3. the safety latch is in the unlocked position - ✔✔there is enough clearance between
the tractor frame and the landing gear
✔✔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 brakes
3. all the above - ✔✔all the above
✔✔Where should the tractor be when you inspect the landing gear after uncoupling the
trailer?
1. With the fifth wheel directly beneath the kingpin
2. completely cleared from the trailer
3. with the tractor frame under the trailer - ✔✔with the tractor frame under the trailer
, ✔✔After you lock the kingpin into the fifth wheel, you should check the connection by
pulling
1. the tractor ahead gently with the trailer brakes locked
2. forward 50 feet, then turning right, and then left
3. the tractor ahead sharply to release the trailer brakes - ✔✔the tractor ahead gently
with the trailer brakes locked
✔✔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 lights
2. red flags
3. a red flag - ✔✔red lights
✔✔Which type of truck-trailer combination has the greatest chance of a "crack-the-whip"
rollover?
1. A tractor pulling three trailers
2. A single tractor trailer
3. A tractor pulling two trailers - ✔✔A tractor pulling 3 trailers
✔✔Air and electrical lines from the tractor to the trailer should be...
1. pulled tight with very little slack
2. secured but with enough slack for turns
3. resting on the frame of the tractor. - ✔✔secured but with enough slack for turns
✔✔Compared with a straight truck or bus, there are ________ things to inspect in
combination vehicles.
1. fewer
2. more
3. the same number of - ✔✔more
✔✔What is the emergency air line for?
1. To engage the trailer brakes in case of air pressure loss
2. To have extra air pressure in case you need it
3. To engage the front brakes of the tractor in case of an emergency - ✔✔To engage
the trailer brakes in case of air pressure loss
✔✔The tractor protection valve will close and the trailer _______ brakes will come on
when there is a major leak in the brake line.
1. parking
2. service
3. emergency - ✔✔emergency
✔✔A trailer is most likely to jackknife when it is ...
QUESTIONS AND SOLUTIONS RATED A+
✔✔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 connections
3. check the electrical cables - ✔✔check the air line connections
✔✔You have a major leak in the service line, and you apply the brakes. Service air
pressure will escape and cause the
1. trailer tank pressure to be lost
2. trailer emergency brakes to come on
3. tractor spring brakes to lock on - ✔✔trailer emergency brakes to come on
✔✔You are uncoupling a trailer. After you shut off the trailer air supply and lock the
trailer brakes, you should
1. immediately apply your tractor parking brakes
2. begin to lower the trailer landing gear
3. back up gently and ease pressure on the fifth wheel locking jaws - ✔✔back up gently
to ease pressure on the fifth wheel locking jaws
✔✔When should you use the hand valve to park a combination vehicle?
1. To park at loading docks
2. To park on a grade
3. never - ✔✔Never
✔✔The front trailer supports are up, and the trailer is resting on the tractor. Make sure
that
1. there is enough clearance between the upper and lower fifth wheel
2. there is enough clearance between the tractor frame and the landing gear
3. the safety latch is in the unlocked position - ✔✔there is enough clearance between
the tractor frame and the landing gear
✔✔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 brakes
3. all the above - ✔✔all the above
✔✔Where should the tractor be when you inspect the landing gear after uncoupling the
trailer?
1. With the fifth wheel directly beneath the kingpin
2. completely cleared from the trailer
3. with the tractor frame under the trailer - ✔✔with the tractor frame under the trailer
, ✔✔After you lock the kingpin into the fifth wheel, you should check the connection by
pulling
1. the tractor ahead gently with the trailer brakes locked
2. forward 50 feet, then turning right, and then left
3. the tractor ahead sharply to release the trailer brakes - ✔✔the tractor ahead gently
with the trailer brakes locked
✔✔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 lights
2. red flags
3. a red flag - ✔✔red lights
✔✔Which type of truck-trailer combination has the greatest chance of a "crack-the-whip"
rollover?
1. A tractor pulling three trailers
2. A single tractor trailer
3. A tractor pulling two trailers - ✔✔A tractor pulling 3 trailers
✔✔Air and electrical lines from the tractor to the trailer should be...
1. pulled tight with very little slack
2. secured but with enough slack for turns
3. resting on the frame of the tractor. - ✔✔secured but with enough slack for turns
✔✔Compared with a straight truck or bus, there are ________ things to inspect in
combination vehicles.
1. fewer
2. more
3. the same number of - ✔✔more
✔✔What is the emergency air line for?
1. To engage the trailer brakes in case of air pressure loss
2. To have extra air pressure in case you need it
3. To engage the front brakes of the tractor in case of an emergency - ✔✔To engage
the trailer brakes in case of air pressure loss
✔✔The tractor protection valve will close and the trailer _______ brakes will come on
when there is a major leak in the brake line.
1. parking
2. service
3. emergency - ✔✔emergency
✔✔A trailer is most likely to jackknife when it is ...
