Want to review your answers at any time?
Submit your email at the end of the test.
Combination Vehicle Endorsement Test
What will happen if the service air line comes apart while you are driving a combination vehicle?
nothing at all is going to happen
the trailer's air tank will exhaust through the open line
nothing is likely to happen until you put on your brakes
the emergency trailer brakes will come on
When uncoupling, it's a good practice to
hang the electrical cable with the plug end down
couple the glad hands together
couple the glad hands to dummy couplers
all of the above are acceptable
If you cross your air lines on a new trailer with spring brakes...
you won't have any operational brakes
you'll have no way of knowing there's a problem
you won't be able to release the tractor brakes
you won't be able to release the trailer brakes
When traveling under 40 mph, you should follow other vehicles...
With a distance of one second for every twenty feet of your vehicle length
With a distance of one second for every ten feet of your vehicle length
As close as possible so others don't cut in
Only during the day
In order to supply air to the trailer, you must first...
Push in the tractor protection valve
Cross the air lines to check for leaks
Pull out the "air supply' knob
Stop engine so you can hear the brakes
If one of the glad hands on your blue air line is missing a seal...
you might end up with a service line air leak
you could experience an emergency line air leak
it's not a major problem and you should continue coupling
take one off the red air line and use that as a temporary replacement
When you inspect the coupling, check to ensure that...
the electrical cable is unplugged
the landing gear handle is hanging free
there's a little slack in the air lines
there's no slack in the air lines
What is the correct setup for shut-off valves?
All shut-off valves should be open.
The front trailers shut-off valves open and the rear closed
The rear trailers shut-off valves open and the front closed
All shut-off valves should be closed.
If the trailer is too high when you try to couple, what may happen?
The king pin may fall off.
It may not couple correctly.
The trailer may tip and flip over.
All of these
What is the emergency air line for?
It supplies air to the tractor air tanks and controls the emergency brakes on combination vehicles.
None of these
It supplies air to the trailer air tanks and controls the emergency brakes on combination vehicles.
It supplies air to the tractor air tanks and controls the service brakes on combination vehicles.
It supplies air to the trailer air tanks and controls the service brakes on combination vehicles.
Two things that are important to prevent rollover are _______.
...keeping the cargo center of gravity as high as possible and driving slowly around turns
....the weight and length of the vehicle
...keeping an evenly loaded trailer and keeping properly inflated tires
...keeping the cargo as close to the ground as possible and driving slowly around turns
The trailer hand valve should be used...
Only to test the trailer brakes
Both B & C above
Only when parking
Only at highway speeds
Which one of the following statements about tractor protection valves is NOT true?
It is controlled by the trailer air supply valve in the cab
It will close automatically if air pressure is low
When it closes it allows air to leak from the tractor line
It keeps air in the tractor in the event the trailer air leaks
Which of the following is the definition of "off-tracking"?
When the rear wheels follow a different path than the front wheels
When the rear wheels go into a skid and the front wheels continue in a straight line
When the front wheels go one direction and the trailer wheels go in the other direction
None of these
After coupling, there should be _____ space between the upper and lower fifth wheel
None of these
Which trailer is most likely to turn over when you turn suddenly while pulling double trailers?
The rear trailer
The front trailer
Neither trailer is more likely to turn over.
Before driving, you need to raise the landing gear only until it just lifts off the pavement.
You can damage the landing gear if you...
position the trailer kingpin in the center of the fifth wheel
align the tractor and trailer
back under the trailer in a straight line
back under the trailer at an angle
Which one of the following is controlled by the foot brake?
The hose coupler
The shut off valve
The emergency air line
The service air line
To straighten out a jackknifing trailer, why should you NOT use the trailer hand brake?
The trailer wheels caused the skid in the first place. Once the trailer wheels grip the road again, the trailer will start to follow the tractor and straighten out
None of these
This is the only time that you should use the trailer hand brake.
The tractor wheels caused the skid in the first place. Once the trailer wheels grip the road again, the trailer will start to push the tractor and straighten out.
About the Combination Vehicles CDL Test
The Combination Vehicles test:
- 20 questions.
- You need 16 correct answers (80%).
- You may be timed. Time limit varies by state.
For those of you going for the Class A CDL, you will have to pass the written test covering information on combination vehicles. A combination vehicle is defined as any tractor-trailer set up, including a tractor with a single trailer, double trailers, triple trailers, and straight truck with a trailer.
While this test is separate from the general knowledge test, these are the vehicles that Class A drivers want to drive. The information tested in the Combination Vehicles test will only qualify you for common combination vehicles, not for doubles and triples. There’s a separate test for those!
The fact that most combination vehicles are typically heavier, longer, and require greater driving skill than single vehicles means that you will need specialized knowledge to safely operate one.
Now, don’t get in a rush to just buzz through the exam. Make sure you read and understand each question before selecting your answer because there are a lot of peculiarities with combination vehicles that can make them very dangerous.
Topics covered in the Combination Vehicles Test are as follows:
- Safe driving
- Rollover risk
- Railroad-highway crossings
- Preventing skids
- Combination vehicle air brakes
- Antilock brake systems
- Coupling and uncoupling
- Inspecting a combination vehicle
Be ready to answer a variety of questions. Why should you not use the trailer hand brake to straighten out a jack-knifing trailer? What is off-tracking? Why should you use chocks when parking a trailer? How can you test the trailer service brakes?