CDL Combination Vehicles Practice Test 2026

1. السؤال 1 من 25

   What causes more than half of truck driver deaths in crashes?

   • ANight driving
   • BBrake failures
   • CTruck rollovers
   • DTire blowouts
   أظهر الإجابة

   الإجابة: C. Truck rollovers

   More than half of truck driver deaths in crashes are the result of truck rollovers.

2. السؤال 2 من 25

   Compared with an empty rig, how much more likely is a fully loaded rig to roll over in a crash?

   • AAbout 10 times more likely
   • BAbout the same
   • CLess likely, because it is heavier
   • DAbout 2 times more likely
   أظهر الإجابة

   الإجابة: A. About 10 times more likely

   Fully loaded rigs are ten times more likely to roll over in a crash than empty rigs.

3. السؤال 3 من 25

   How should you load cargo to help prevent a rollover?

   • AAs low as possible, centered and spread out
   • BStacked as high as possible in the middle
   • CHigh and toward one side
   • DAll at the very back
   أظهر الإجابة

   الإجابة: A. As low as possible, centered and spread out

   Keep the center of gravity low, and keep cargo centered so the trailer does not lean.

4. السؤال 4 من 25

   Which driving habit helps prevent rollovers?

   • AChanging lanes quickly to avoid traffic
   • BGoing slowly around corners and ramps
   • CBraking hard in the middle of curves
   • DTaking ramps at the posted highway speed
   أظهر الإجابة

   الإجابة: B. Going slowly around corners and ramps

   Drive slowly in turns and on ramps, and avoid quick lane changes, especially when fully loaded.

5. السؤال 5 من 25

   What is rearward amplification?

   • AThe extra noise made by the rear axles
   • BThe way mirrors make trailers look longer
   • CThe crack-the-whip effect that can tip over a trailer
   • DThe longer stopping distance of a heavy load
   أظهر الإجابة

   الإجابة: C. The crack-the-whip effect that can tip over a trailer

   Rearward amplification makes the rear trailer swing more than the tractor in a sudden move. It can tip the trailer over.

6. السؤال 6 من 25

   Which part of a combination is most likely to turn over in a quick lane change?

   • AThe tractor
   • BThe last trailer
   • CThe first trailer
   • DThe converter dolly
   أظهر الإجابة

   الإجابة: B. The last trailer

   Because of rearward amplification, the rearmost trailer is the most likely to turn over.

7. السؤال 7 من 25

   A combination has a rearward amplification of 2.0. What does that mean?

   • AThe rear trailer is twice as likely to tip as the tractor
   • BThe rig is twice as long as a normal tractor-trailer
   • CThe rig takes twice as long to stop as a car
   • DThe trailer needs twice as much air pressure
   أظهر الإجابة

   الإجابة: A. The rear trailer is twice as likely to tip as the tractor

   A rearward amplification of 2.0 means the rear trailer is twice as likely to turn over as the tractor.

8. السؤال 8 من 25

   How should you steer a combination vehicle?

   • AWith one hand
   • BGently and smoothly
   • CQuickly, to correct problems fast
   • DWith sharp, short turns
   أظهر الإجابة

   الإجابة: B. Gently and smoothly

   Sudden steering can tip a trailer over. Steer gently and smoothly.

9. السؤال 9 من 25

   Compared with a loaded combination, how does an empty combination behave when you brake?

   • AIt always stops in a much shorter distance
   • BIt stops in exactly the same distance
   • CIt may take longer to stop, as wheels lock easily
   • DIt cannot skid because it is so light
   أظهر الإجابة

   الإجابة: C. It may take longer to stop, as wheels lock easily

   Empty rigs have stiff springs and strong brakes but poor traction, so wheels lock easily and stopping takes longer.

10. السؤال 10 من 25

    What is a bobtail tractor?

    • AA tractor pulling three trailers
    • BA truck with a short wheelbase and a box
    • CA tractor with no sleeper
    • DA tractor driving without a semitrailer
    أظهر الإجابة

    الإجابة: D. A tractor driving without a semitrailer

    A bobtail is a tractor without a trailer. It can be hard to stop smoothly and may take longer to stop than a loaded rig.

11. السؤال 11 من 25

    Which trailers are most likely to get stuck on a raised railroad crossing?

    • AFlatbeds with high loads
    • BLow-slung units like lowboys, car carriers and moving vans
    • CEmpty dry vans
    • DShort single-axle trailers with normal clearance
    أظهر الإجابة

    الإجابة: B. Low-slung units like lowboys, car carriers and moving vans

    Trailers with low underneath clearance can hang up on raised crossings.

12. السؤال 12 من 25

    What is a trailer jackknife?

    • AWhen locked trailer wheels let the trailer swing around
    • BWhen the trailer tips over onto its side
    • CWhen the tractor's front steering wheels lock up
    • DWhen the fifth wheel comes unlocked while driving
    أظهر الإجابة

    الإجابة: A. When locked trailer wheels let the trailer swing around

    A trailer jackknife happens when the trailer wheels lock and the trailer swings out. It is more likely with an empty or light trailer.

13. السؤال 13 من 25

    How can you spot a trailer skid early?

    • AFeel for the steering wheel to shake
    • BWatch the air pressure gauge
    • CListen for squealing tires
    • DCheck your mirrors when you brake hard
    أظهر الإجابة

    الإجابة: D. Check your mirrors when you brake hard

    Check the mirrors any time you brake hard. Once the trailer is out of your lane, a jackknife is hard to stop.

14. السؤال 14 من 25

    Your trailer starts to skid sideways because its wheels are locked. What should you do?

    • AApply the trailer hand brake to straighten out
    • BRelease the brakes to get traction back
    • CBrake harder
    • DSpeed up sharply
    أظهر الإجابة

    الإجابة: B. Release the brakes to get traction back

    Release the brakes so the trailer wheels grip again. Do not use the trailer hand brake, because the trailer brakes caused the skid.

15. السؤال 15 من 25

    What is offtracking?

    • AThe trailer leaving the road on a sharp curve
    • BDriving partly in the wrong lane on a straight road
    • CThe fifth wheel sliding backward while driving
    • DRear wheels taking a shorter path than the front in a turn
    أظهر الإجابة

    الإجابة: D. Rear wheels taking a shorter path than the front in a turn

    In turns, the rear wheels cut inside the path of the front wheels. Longer vehicles offtrack more.

16. السؤال 16 من 25

    The diagram shows a right turn. Which wheels offtrack the most?

    • AAll wheels follow the same path
    • BThe tractor's front wheels
    • CThe rear wheels of the last trailer
    • DThe tractor's drive wheels
    أظهر الإجابة

    الإجابة: C. The rear wheels of the last trailer

    The rear wheels of the rearmost trailer offtrack the most.

17. السؤال 17 من 25

    The diagram shows a correct right turn. What is this "button hook" method?

    • ALet the trailer wheels roll over the curb to save space
    • BStop halfway, back up, and then finish the turn
    • CSwing into the left lane first, then turn right from there
    • DKeep the rear near the curb, then turn wide as you finish
    أظهر الإجابة

    الإجابة: D. Keep the rear near the curb, then turn wide as you finish

    The button hook turn stops cars from passing you on the right. The jug-handle turn, swinging left first, is wrong.

18. السؤال 18 من 25

    You are backing a trailer and want it to move to the right. Which way do you turn the top of the steering wheel?

    • ATo the right
    • BTo the left
    • CKeep it straight
    • DRight, then quickly back to center
    أظهر الإجابة

    الإجابة: B. To the left

    When backing a trailer, turn the wheel the opposite way from where you want the trailer to go.

19. السؤال 19 من 25

    You are backing a trailer and it starts to turn the way you want. What should you do next?

    • AStop and pull forward a long way
    • BKeep turning the wheel the same way
    • CLet go of the wheel and let it roll
    • DTurn the wheel the other way to follow it
    أظهر الإجابة

    الإجابة: D. Turn the wheel the other way to follow it

    Once the trailer starts to turn, turn the wheel the other way so the tractor follows the trailer.

20. السؤال 20 من 25

    If you must back a trailer on a curve, which way should you back?

    • AToward the right side
    • BUphill only
    • CIt does not matter
    • DToward the driver's side
    أظهر الإجابة

    الإجابة: D. Toward the driver's side

    Backing toward the driver's side lets you see the trailer better.

21. السؤال 21 من 25

    Your trailer drifts while you back up. How do you correct it?

    • ATurn the top of the wheel away from the drift
    • BSpeed up so the trailer straightens out
    • CTurn the top of the wheel toward the drift
    • DApply the trailer hand brake to stop the drift
    أظهر الإجابة

    الإجابة: C. Turn the top of the wheel toward the drift

    Correct drift right away by turning the top of the wheel toward the drift. Back slowly so you can correct early.

22. السؤال 22 من 25

    While backing a trailer, you get out of position. What should you do?

    • AKeep backing and turn the wheel harder
    • BBack faster so the trailer straightens
    • CUnhook the trailer and start again
    • DPull forward (a pull-up) to reposition
    أظهر الإجابة

    الإجابة: D. Pull forward (a pull-up) to reposition

    Use pull-ups to get back into position when needed.

23. السؤال 23 من 25

    Your combination is 70 feet long and you are driving at 55 mph. What following distance should you keep?

    • AAt least 7 seconds
    • BAt least 8 seconds
    • CAt least 4 seconds
    • DAt least 10 seconds
    أظهر الإجابة

    الإجابة: B. At least 8 seconds

    Allow 1 second per 10 feet of length (7 seconds) and add 1 second above 40 mph.

24. السؤال 24 من 25

    What is the trailer hand valve (trolley valve) for?

    • ATesting the trailer brakes
    • BReleasing the spring brakes
    • CNormal stopping while driving
    • DParking the trailer
    أظهر الإجابة

    الإجابة: A. Testing the trailer brakes

    Use the trailer hand valve only to test the trailer brakes. Do not use it while driving or to park.

25. السؤال 25 من 25

    Why should you use the foot brake rather than the trailer hand valve for normal stops?

    • AThe hand valve is too strong for normal stops
    • BThe foot brake only works on the tractor
    • CThe hand valve uses no air, so it wears out
    • DThe hand valve brakes only the trailer, so it may skid
    أظهر الإجابة

    الإجابة: D. The hand valve brakes only the trailer, so it may skid

    Using the trailer brakes alone can make the trailer skid. The foot brake applies air to all wheels.

لوحة المفاتيح: 1–4 للإجابة، وEnter للسؤال التالي.

الاختبار الحقيقي: 80% correct; the number of questions varies by state (20 in Washington, 30 in Utah)