CDL COMBINATION VEHICLES ACTUAL FINAL EXAM |
WITH COMPLETE QUESTIONS AND ANSWERS | 2025/2026
LATEST UPDATED | 100 % RATED AND VERIFIED SOLUTIONS
| GET AN A+
A fully loaded rig is _________ times more likely to roll over in a crash than an empty rig.
A. 5
B. 10
C. 15
D. 20 - (ANSWER)10. When a truck has cargo, the center of gravity moves higher which
increases the likelihood of rollover.
When following behind other vehicles, you should follow
A. At least one second for every 20 feet of your vehicle length
B. At least two seconds for every 10 feet of your vehicle length
C. At least two seconds for every 10 feet of your vehicle length, plus one second if going over 50
MPH
D. At least one second for every 10 feet of your vehicle length, plus one second if going over 40
MPH - (ANSWER)At least one second for every 10 feet of your vehicle length, plus one
second if going over 40 MPH. You should insure that you have a safe following distance to
lessen the chance of making a sudden steering change.
,A trailer jackknife is likely to happen when
A. The vehicle has a high center of gravity
B. The wheels of the trailer lock up
C. The front drive wheels lose traction
D. There is too much weight on the steering axles - (ANSWER)The wheels of the trailer lock
up. When the wheels of the trailer lock up, the trailer may swing around resulting in a trailer
jackknife. Trailer jackknifes are more likely to happen when the trailer is empty or lightly
loaded. When a vehicle has a high center of gravity, a rollover may happen. When there is too
much weight on the steering axles, hard steering can occur.
What is the fastest and best way to recognize that your trailer has started to skid?
A. Feeling your steering wheel shake
B. Listening for the distinctive skidding sound
C. Seeing it in your mirrors
D. Feeling your vehicle pull to the side - (ANSWER)See it in your mirrors. The best and
earliest way to determine that your trailer has started to skid is by seeing it in your mirrors. You
should check your mirrors regularly, especially after applying the brakes hard.
If your trailer begins to skid, you should
,A. Maintain light pressure on your brakes until the trailer straightens out
B. Release your brakes until the trailer wheels grip the road again
C. Turn the steering wheel in the direction of the skid
D. Apply to the trailer hand brake to straighten out the trailer - (ANSWER)Release your brakes
until the trailer wheels grip the road again. If your trailer skids (jackknife) your best course of
action is to release the brakes until you get traction back. You should not apply the trailer hand
brakes, since the skid was caused by wheel lock up in the first place.
Which of the following will help prevent a rollover:
A. Keep the cargo load centered on the rig
B. Drive slowly around turns
C. Keep the cargo as close to the ground as possible
D. All of the above - (ANSWER)All of the above. Risk of rollover is increased by a high center
of gravity. Keeping the cargo as close to the ground will lower the center of gravity and decrease
the risk of rollover. Keeping the cargo centered and driving slowly around curves will also help
reduce the risk of a rollover.
On the trailer air lines of a combination vehicle, the service line connects to the _________ on
the trailer to control the pressure to the trailer brakes.
Glad hands
, Trailer hand valve
Relay valves
Tractor protection valve control - (ANSWER)Relay valves. The service line is connected to the
relay valves on the trailer to apply more or less pressure to the trailer brakes. They connect the
trailer air tanks to the trailer air brakes. Glad hands connect tractor service and emergency lines
to the trailer service and emergency lines. The trailer hand valve works the trailer brakes. The
tractor protection valve control keeps air in the brake system in case the trailer breaks away or
develops a bad leak
On older trailers, what will happen if the emergency and service air lines are crossed?
A. Nothing will happen, they are designed to be interchangeable
B. The trailer spring brakes will release
C. Water and oil will build up in the air tanks
D. You could drive away, but you will not have trailer brakes - (ANSWER)You could drive
away, but you will not have trailer brakes. Older trailers don't have spring brakes so if the air
supply in the trailer air tanks has leaked away, there will be no emergency brakes.
When hoses are not in use, why should the trailer gland hands be locked together or attached to
dead end or dummy couplers?
A. To prevent mix-up of the emergency and service lines
WITH COMPLETE QUESTIONS AND ANSWERS | 2025/2026
LATEST UPDATED | 100 % RATED AND VERIFIED SOLUTIONS
| GET AN A+
A fully loaded rig is _________ times more likely to roll over in a crash than an empty rig.
A. 5
B. 10
C. 15
D. 20 - (ANSWER)10. When a truck has cargo, the center of gravity moves higher which
increases the likelihood of rollover.
When following behind other vehicles, you should follow
A. At least one second for every 20 feet of your vehicle length
B. At least two seconds for every 10 feet of your vehicle length
C. At least two seconds for every 10 feet of your vehicle length, plus one second if going over 50
MPH
D. At least one second for every 10 feet of your vehicle length, plus one second if going over 40
MPH - (ANSWER)At least one second for every 10 feet of your vehicle length, plus one
second if going over 40 MPH. You should insure that you have a safe following distance to
lessen the chance of making a sudden steering change.
,A trailer jackknife is likely to happen when
A. The vehicle has a high center of gravity
B. The wheels of the trailer lock up
C. The front drive wheels lose traction
D. There is too much weight on the steering axles - (ANSWER)The wheels of the trailer lock
up. When the wheels of the trailer lock up, the trailer may swing around resulting in a trailer
jackknife. Trailer jackknifes are more likely to happen when the trailer is empty or lightly
loaded. When a vehicle has a high center of gravity, a rollover may happen. When there is too
much weight on the steering axles, hard steering can occur.
What is the fastest and best way to recognize that your trailer has started to skid?
A. Feeling your steering wheel shake
B. Listening for the distinctive skidding sound
C. Seeing it in your mirrors
D. Feeling your vehicle pull to the side - (ANSWER)See it in your mirrors. The best and
earliest way to determine that your trailer has started to skid is by seeing it in your mirrors. You
should check your mirrors regularly, especially after applying the brakes hard.
If your trailer begins to skid, you should
,A. Maintain light pressure on your brakes until the trailer straightens out
B. Release your brakes until the trailer wheels grip the road again
C. Turn the steering wheel in the direction of the skid
D. Apply to the trailer hand brake to straighten out the trailer - (ANSWER)Release your brakes
until the trailer wheels grip the road again. If your trailer skids (jackknife) your best course of
action is to release the brakes until you get traction back. You should not apply the trailer hand
brakes, since the skid was caused by wheel lock up in the first place.
Which of the following will help prevent a rollover:
A. Keep the cargo load centered on the rig
B. Drive slowly around turns
C. Keep the cargo as close to the ground as possible
D. All of the above - (ANSWER)All of the above. Risk of rollover is increased by a high center
of gravity. Keeping the cargo as close to the ground will lower the center of gravity and decrease
the risk of rollover. Keeping the cargo centered and driving slowly around curves will also help
reduce the risk of a rollover.
On the trailer air lines of a combination vehicle, the service line connects to the _________ on
the trailer to control the pressure to the trailer brakes.
Glad hands
, Trailer hand valve
Relay valves
Tractor protection valve control - (ANSWER)Relay valves. The service line is connected to the
relay valves on the trailer to apply more or less pressure to the trailer brakes. They connect the
trailer air tanks to the trailer air brakes. Glad hands connect tractor service and emergency lines
to the trailer service and emergency lines. The trailer hand valve works the trailer brakes. The
tractor protection valve control keeps air in the brake system in case the trailer breaks away or
develops a bad leak
On older trailers, what will happen if the emergency and service air lines are crossed?
A. Nothing will happen, they are designed to be interchangeable
B. The trailer spring brakes will release
C. Water and oil will build up in the air tanks
D. You could drive away, but you will not have trailer brakes - (ANSWER)You could drive
away, but you will not have trailer brakes. Older trailers don't have spring brakes so if the air
supply in the trailer air tanks has leaked away, there will be no emergency brakes.
When hoses are not in use, why should the trailer gland hands be locked together or attached to
dead end or dummy couplers?
A. To prevent mix-up of the emergency and service lines
