Missouri Combination Vehicles Practice Questions

Combination Vehicles questions

1. 1. What must be checked about the fifth wheel before coupling?

   1. A. That it is greased and the jaws are open
   2. B. That the trailer lights are working
   3. C. That the landing gear is fully down

   Answer: A — That it is greased and the jaws are open

   A dry fifth wheel causes steering problems, and the jaws must be open to receive the kingpin.

2. 2. How do you test that the coupling is secure after connecting?

   1. A. Sound the horn and listen
   2. B. Rock the trailer from side to side
   3. C. Pull gently against locked brakes

   Answer: C — Pull gently against locked brakes

   A gentle tug test against locked trailer brakes confirms the kingpin is captured.

3. 3. What is the correct height of the trailer before backing under it?

   1. A. Exactly level with the fifth wheel
   2. B. Slightly lower than the fifth wheel
   3. C. Well above the fifth wheel

   Answer: B — Slightly lower than the fifth wheel

   Backing under a trailer set slightly low ensures the fifth wheel lifts it rather than striking the nose.

4. 4. What is a common cause of the trailer separating from the tractor?

   1. A. Jaws closing on the apron, not the kingpin
   2. B. The landing gear being left far too low
   3. C. Air lines being connected far too early

   Answer: A — Jaws closing on the apron, not the kingpin

   A high hitch leaves the jaws closed under the apron, which looks connected but is not.

5. 5. What should you do before uncoupling a trailer?

   1. A. Release the coupling first, then lower the landing gear
   2. B. Drive out immediately after releasing the brakes
   3. C. Lower the landing gear until it takes the weight

   Answer: C — Lower the landing gear until it takes the weight

   The landing gear must carry the trailer before the fifth wheel is released.

6. 6. What is offtracking?

   1. A. Tyre wear on the trailer axle
   2. B. The rear wheels cutting inside the front wheels
   3. C. The trailer swinging outward in a turn

   Answer: B — The rear wheels cutting inside the front wheels

   Longer vehicles offtrack more, which is why drivers must swing wide enough for the rear to clear.

7. 7. How should a long combination vehicle make a right turn at an intersection?

   1. A. Swing wide only as the turn is completed
   2. B. Swing wide before starting the turn
   3. C. Turn as tightly as possible

   Answer: A — Swing wide only as the turn is completed

   Swinging wide on entry invites a driver to squeeze up the right side into the path of the trailer.

8. 8. What are the two main causes of commercial vehicle rollovers?

   1. A. Under-inflated tyres and a very light load
   2. B. Braking too gently on a long downgrade
   3. C. Speed in turns and a high centre of gravity

   Answer: C — Speed in turns and a high centre of gravity

   Speed in curves and a high centre of gravity together account for the majority of rollovers.

9. 9. How should cargo be loaded to reduce rollover risk?

   1. A. Concentrated over one axle
   2. B. As low in the trailer as possible
   3. C. High and toward the front

   Answer: B — As low in the trailer as possible

   Keeping the load low is the single most effective way to reduce rollover risk.

10. 10. Which trailer should be placed first in a set of doubles?

    1. A. The more heavily loaded one
    2. B. The lighter trailer
    3. C. Either order is acceptable

    Answer: A — The more heavily loaded one

    Placing the heavier trailer first reduces the whipping effect on the rear trailer.

11. 11. What is rearward amplification, sometimes called the crack-the-whip effect?

    1. A. The trailer brakes apply before the tractor's
    2. B. The rear trailer runs at a lower speed
    3. C. The rear trailer swings farther than the tractor

    Answer: C — The rear trailer swings farther than the tractor

    A quick steering input at the front is multiplied at the rear, which can overturn the last trailer.

12. 12. How should a driver of doubles or triples steer to avoid rollover?

    1. A. Brake hard while steering
    2. B. Gently, avoiding sudden lane changes
    3. C. Steer quickly to complete manoeuvres fast

    Answer: B — Gently, avoiding sudden lane changes

    Gentle inputs prevent the amplified swing that overturns the rear trailer.

13. 13. How does stopping distance change for a loaded combination vehicle compared with an empty one?

    1. A. An empty vehicle can take longer to stop
    2. B. A loaded vehicle always stops faster
    3. C. Load has no effect

    Answer: A — An empty vehicle can take longer to stop

    Empty trucks have less traction and stiff suspension, so they can require more distance than a properly loaded one.

14. 14. What should you check about the trailer's air lines before coupling?

    1. A. That the hoses are brand new
    2. B. That the couplings are wet
    3. C. That the glad hands are clean

    Answer: C — That the glad hands are clean

    A damaged seal leaks air, which eventually applies the trailer's spring brakes.

15. 15. Which glad hand supplies air to the trailer's emergency system?

    1. A. Either one
    2. B. The red one
    3. C. The blue one

    Answer: B — The red one

    Red is the emergency line and blue is the service line; crossing them disables the trailer brakes.

16. 16. What happens if the air lines are crossed when coupling?

    1. A. The trailer brakes may not work when needed
    2. B. The trailer marker lights will fail too
    3. C. The trailer brakes will lock on hard

    Answer: A — The trailer brakes may not work when needed

    Crossed lines can leave the trailer with no working service brakes without any obvious symptom.

17. 17. How should the fifth wheel be positioned relative to the kingpin before backing under?

    1. A. Offset to one side
    2. B. At a 45 degree angle
    3. C. Lined up directly with it

    Answer: C — Lined up directly with it

    A straight, slow approach is what lets the jaws capture the kingpin correctly.

18. 18. What should you inspect visually under the trailer after coupling?

    1. A. That the mud flaps hang straight
    2. B. That no gap shows at the fifth wheel
    3. C. That the tyres are fully inflated

    Answer: B — That no gap shows at the fifth wheel

    A visible gap means the jaws closed under the apron rather than around the kingpin.

19. 19. How should a driver back a trailer in a straight line?

    1. A. Steer opposite the drift, in small moves
    2. B. Steer in the same direction as the drift
    3. C. Hold the wheel fixed

    Answer: A — Steer opposite the drift, in small moves

    Small early corrections prevent the trailer from developing an angle that cannot be recovered.

20. 20. When backing, which side should a driver back toward if there is a choice?

    1. A. The passenger side
    2. B. Whichever is closer
    3. C. The driver's side

    Answer: C — The driver's side

    Driver-side backing keeps the trailer visible in the mirror throughout the manoeuvre.

21. 21. What should a driver do before backing in an unfamiliar area?

    1. A. Back slowly and correct as needed
    2. B. Get out and walk the area first
    3. C. Rely on the mirrors alone

    Answer: B — Get out and walk the area first

    A get-out-and-look is the only way to see what the mirrors do not cover.

22. 22. How does trailer length affect offtracking?

    1. A. Longer trailers offtrack more
    2. B. Length has no effect
    3. C. Longer trailers offtrack less

    Answer: A — Longer trailers offtrack more

    The longer the wheelbase, the tighter the rear wheels' path relative to the front.

23. 23. At what point in a turn is rollover risk highest?

    1. A. At the exit, when accelerating
    2. B. In the middle, when steady
    3. C. On entry, if speed is too high

    Answer: C — On entry, if speed is too high

    Speed must be set before the turn; braking hard mid-turn can itself trigger the rollover.

24. 24. Why is a partly loaded tank vehicle particularly prone to rollover?

    1. A. Its tyres are narrower
    2. B. The liquid shifts during a turn
    3. C. It is heavier than a full one

    Answer: B — The liquid shifts during a turn

    Side-to-side surge can throw weight outward exactly when the vehicle is already leaning.

25. 25. How should a driver take a highway exit ramp in a loaded vehicle?

    1. A. Slow below the advisory before the curve
    2. B. At the advisory speed
    3. C. At highway speed if the road is dry

    Answer: A — Slow below the advisory before the curve

    Ramp advisory speeds are calculated for cars, not for a high centre of gravity.

26. 26. How should a driver check the converter dolly before use?

    1. A. Check only that the tyres are inflated
    2. B. Check that the paintwork is undamaged
    3. C. Confirm the tow bar and chains are secure

    Answer: C — Confirm the tow bar and chains are secure

    The dolly is the connection point where a failure separates the rear trailer entirely.

27. 27. Why do doubles and triples require more space when changing lanes?

    1. A. They have shorter braking distances
    2. B. The rear trailer follows a delayed path
    3. C. They accelerate faster

    Answer: B — The rear trailer follows a delayed path

    The rear trailer arrives in the new lane well after the tractor does.

28. 28. What is the risk of using the trailer hand valve to slow the combination?

    1. A. It can cause a trailer skid or jackknife
    2. B. It applies the tractor brakes too hard
    3. C. It has no effect at speed

    Answer: A — It can cause a trailer skid or jackknife

    Braking the trailer alone can push it out of line with the tractor.

29. 29. What should a driver do to prevent a trailer jackknife when braking hard?

    1. A. Use the trailer hand valve on its own
    2. B. Release the brakes and steer sharply
    3. C. Use the foot brake, not the trailer brake

    Answer: C — Use the foot brake, not the trailer brake

    Coordinated braking through the foot valve keeps the combination in line.