CDL Doubles and Triples Practice Test 2026

1. Pregunta 1 de 25

   Compared with other combinations, how likely are doubles and triples to turn over?

   • AThey cannot turn over
   • BLess likely
   • CEqually likely
   • DMore likely
   Ver respuesta

   Respuesta: D. More likely

   Doubles and triples are more likely to turn over than other combination vehicles.

2. Pregunta 2 de 25

   Which trailer in a double or triple is most likely to turn over?

   • AThe tractor
   • BThe middle trailer
   • CThe first trailer
   • DThe last trailer
   Ver respuesta

   Respuesta: D. The last trailer

   Because of the crack-the-whip effect, the last trailer is the most likely to turn over.

3. Pregunta 3 de 25

   Compared with a five-axle tractor-semitrailer, how much more easily can the last trailer of a triple roll over?

   • AAbout 3.5 times as easily
   • BAbout 10 times as easily
   • CAbout the same
   • DAbout half as easily
   Ver respuesta

   Respuesta: A. About 3.5 times as easily

   Triples have the highest rearward amplification. The last trailer can roll about 3.5 times as easily.

4. Pregunta 4 de 25

   A speed that is safe for a single trailer on a curve is not always safe for doubles. Why?

   • ADoubles weigh less, so they slide in curves
   • BDoubles have better traction on curves
   • CDoubles have stronger brakes than singles
   • DDoubles and triples roll over more easily
   Ver respuesta

   Respuesta: D. Doubles and triples roll over more easily

   A speed that is fine for a straight truck or single trailer may be too fast for doubles or triples.

5. Pregunta 5 de 25

   What is the crack-the-whip effect?

   • AThe way the trailers bounce on rough roads
   • BThe loud sound air brakes make when released
   • CThe pull of the tractor as it climbs a hill
   • DA quick steering move swings the rear trailer much more
   Ver respuesta

   Respuesta: D. A quick steering move swings the rear trailer much more

   Sudden steering is amplified toward the back of the rig. This rearward amplification can tip over the last trailer.

6. Pregunta 6 de 25

   Why do doubles and triples need extra care in the pre-trip inspection?

   • AInspections are not required for doubles
   • BOnly the first trailer needs inspecting
   • CThey have more critical parts to check
   • DThey need less checking than single trailers
   Ver respuesta

   Respuesta: C. They have more critical parts to check

   With two or three trailers, there are more parts that must be checked.

7. Pregunta 7 de 25

   Why should you look far ahead when pulling doubles or triples?

   • ASo you can brake hard at the last moment
   • BSo you can follow other trucks closely
   • CSo you can slow down or change lanes gradually
   • DSo you can pass more often
   Ver respuesta

   Respuesta: C. So you can slow down or change lanes gradually

   Drive very smoothly to avoid rollover or jackknife. Looking far ahead gives you time for gradual changes.

8. Pregunta 8 de 25

   How should your following distance compare when pulling doubles or triples?

   • AAllow more following distance
   • BAllow less following distance
   • CFollowing distance does not matter
   • DUse the same distance as a car
   Ver respuesta

   Respuesta: A. Allow more following distance

   Doubles and triples are longer and cannot turn or stop suddenly, so leave more space ahead.

9. Pregunta 9 de 25

   Why are doubles and triples more likely to skid in bad weather?

   • ATheir tires are smaller than other trucks' tires
   • BGreater length and more dead axles mean less traction
   • CThey are always empty, so they are too light
   • DThey have no brakes on the trailers at all
   Ver respuesta

   Respuesta: B. Greater length and more dead axles mean less traction

   Be especially careful on slippery roads and in mountains. Length and extra axles raise the risk of skids.

10. Pregunta 10 de 25

    What should you avoid when parking doubles or triples?

    • AA spot you cannot pull straight out of
    • BParking on firm, level ground
    • CParking in truck stops or rest areas
    • DPulling forward through an open space
    Ver respuesta

    Respuesta: A. A spot you cannot pull straight out of

    Plan your parking so you can pull straight through and avoid a long, difficult way out.

11. Pregunta 11 de 25

    Converter dollies built on or after March 1, 1998 must have which safety feature?

    • AA second fifth wheel for a third trailer
    • BHydraulic brakes in place of air brakes
    • CAntilock brakes, with a yellow lamp on the left
    • DA spare tire mounted under the tow bar
    Ver respuesta

    Respuesta: C. Antilock brakes, with a yellow lamp on the left

    Converter dollies built on or after March 1, 1998 must have antilock brakes and a yellow ABS lamp on the left side.

12. Pregunta 12 de 25

    Which trailer should go first, right behind the tractor?

    • AThe shorter of the two
    • BThe lighter of the two
    • CThe more heavily loaded one
    • DThe empty one, if any
    Ver respuesta

    Respuesta: C. The more heavily loaded one

    Put the heaviest trailer first, behind the tractor. The lighter trailer goes at the rear.

13. Pregunta 13 de 25

    Where should the lighter trailer go in a set of doubles?

    • AIn the middle of a triple only
    • BAt the rear
    • CIt does not matter
    • DRight behind the tractor
    Ver respuesta

    Respuesta: B. At the rear

    The lighter trailer goes in the rear, and the heavier one goes first.

14. Pregunta 14 de 25

    The rear trailer has no spring brakes. How can you secure it before coupling?

    • ALower the landing gear and do nothing else
    • BCharge its tank, then disconnect the emergency line
    • CTie it to a post with a strap or chain
    • DLeave it free to roll so it lines up easily
    Ver respuesta

    Respuesta: B. Charge its tank, then disconnect the emergency line

    Charging the tank and disconnecting the emergency line sets the trailer's emergency brakes (if the slack adjusters are right). Chock the wheels if in doubt.

15. Pregunta 15 de 25

    You are not sure the rear trailer's brakes will hold. What should you do?

    • AChock the wheels
    • BStart coupling anyway
    • CRaise the landing gear
    • DRelease the brakes
    Ver respuesta

    Respuesta: A. Chock the wheels

    If you have any doubt about the trailer brakes, chock the wheels.

16. Pregunta 16 de 25

    How do you release the brakes on a converter dolly that has no spring brakes?

    • AOpen the air tank petcock
    • BDisconnect the pintle hook
    • CDrain the tractor tanks
    • DPull the red knob
    Ver respuesta

    Respuesta: A. Open the air tank petcock

    Open the dolly's air tank petcock to release its brakes. If the dolly has spring brakes, use the dolly parking brake control.

17. Pregunta 17 de 25

    The converter dolly is close to the rear trailer. How can you move it into place?

    • AWheel it by hand so it lines up with the kingpin
    • BDrag it with a chain
    • CPush it with the tractor's front bumper
    • DDrive over it
    Ver respuesta

    Respuesta: A. Wheel it by hand so it lines up with the kingpin

    If the distance is short, you can wheel the dolly by hand into line with the kingpin.

18. Pregunta 18 de 25

    After hooking the dolly to the first trailer, what must you do with the pintle hook?

    • AGrease and remove it
    • BTie it with rope
    • CLeave it open
    • DLock it
    Ver respuesta

    Respuesta: D. Lock it

    Hook the dolly to the front trailer, lock the pintle hook, and secure the converter gear support in the raised position.

19. Pregunta 19 de 25

    Before backing the dolly under the rear trailer, how high should the trailer be?

    • ALevel with the top of the dolly's tires
    • BMuch higher than the dolly's fifth wheel
    • CResting on the ground with the gear up
    • DSlightly lower than the dolly's fifth wheel
    Ver respuesta

    Respuesta: D. Slightly lower than the dolly's fifth wheel

    The trailer must be a little low so it is raised slightly when the dolly is pushed under it.

20. Pregunta 20 de 25

    Why raise the rear trailer's landing gear slightly off the ground right after backing the dolly under it?

    • ATo make the trailer weigh less
    • BTo let the trailer brakes cool off
    • CTo prevent damage if the trailer moves
    • DTo check the trailer's tire pressure
    Ver respuesta

    Respuesta: C. To prevent damage if the trailer moves

    Raise the landing gear just off the ground so it is not damaged if the trailer moves during the tug test.

21. Pregunta 21 de 25

    How do you test the coupling between the dolly and the second trailer?

    • ABack up hard into the second trailer
    • BDrive away at highway speed and watch
    • CPull against the second trailer's kingpin
    • DRock the second trailer by hand
    Ver respuesta

    Respuesta: C. Pull against the second trailer's kingpin

    Test the coupling by pulling gently against the second trailer's kingpin.

22. Pregunta 22 de 25

    During the visual check of the dolly coupling, what should you see?

    • ANo gap between the fifth wheel plates, jaws closed on the kingpin
    • BThe trailer's landing gear resting on the ground
    • CA small gap between the fifth wheel plates, jaws open
    • DThe jaws open around the head of the kingpin
    Ver respuesta

    Respuesta: A. No gap between the fifth wheel plates, jaws closed on the kingpin

    There should be no space between the fifth wheel surfaces, and the jaws must be closed on the kingpin.

23. Pregunta 23 de 25

    After coupling the dolly, what must you connect between the trailers?

    • AA tow strap in place of the chains
    • BOnly the light cord, nothing else
    • COnly the safety chains, nothing else
    • DSafety chains, air hoses and light cords
    Ver respuesta

    Respuesta: D. Safety chains, air hoses and light cords

    Connect the safety chains, air hoses and light cords.

24. Pregunta 24 de 25

    After coupling doubles, what do you do with the shut-off valves at the rear of the second (last) trailer?

    • AOpen them
    • BRemove them
    • CClose them
    • DLeave them half open
    Ver respuesta

    Respuesta: C. Close them

    Close the dolly air tank petcock and the shut-off valves at the rear of the last trailer.

25. Pregunta 25 de 25

    After coupling doubles, what do you do with the shut-off valves at the rear of the first trailer?

    • ATape them shut
    • BRemove them
    • CClose them
    • DOpen them
    Ver respuesta

    Respuesta: D. Open them

    Open the shut-off valves at the rear of the first trailer, and on the dolly if it has them, so air reaches the second trailer.

Teclado: 1–4 para responder, Intro para la siguiente pregunta.

El examen real: Varies by state; usually 20 questions, with 16 correct needed (80%)