CDL DOUBLE AND TRIPLE TRAILERS

CDL DOUBLE AND TRIPLE TRAILERS

ENDORSEMENT PRACTICE TEST

QUESTIONS AND CORRECT ANSWERS

(VERIFIED ANSWERS) PLUS RATIONALES

2025

• Which of the following is especially important when driving doubles

and triples?• Keeping the engine RPMs high • Preventing trailer rollovers • Accelerating quickly • Using cruise control Preventing trailer rollovers is critical because doubles/triples are more prone to rolling due to their articulation and length. 1 / 4

• What should you check before coupling a converter dolly to a second

trailer?• The weight of the trailer • The height of the landing gear • That the pintle hook is latched and secure • That the load is balanced The pintle hook must be properly latched and locked to prevent the dolly from detaching.

• What is the “crack-the-whip” effect?

• A method of steering trailers • A technique for checking brakes • A trailer rollover caused by quick steering • A type of tire failure Sharp steering with doubles/triples can cause the rearmost trailer to sway and flip, like cracking a whip.

• When backing doubles or triples, what is the best approach?

• Back at high speed • Use only your mirrors • Avoid backing if possible • Rely on the trailer’s self-alignment 2 / 4

Backing multi-trailer rigs is extremely difficult and should be avoided when possible.

• How should you handle turns with doubles or triples?

• Cut corners sharply • Make wide turns • Stay close to the curb • Use only one trailer brake Wide turns prevent the rear trailer from hitting curbs or objects.

• Which trailer is most likely to roll over?

• First trailer • Last trailer • Truck tractor • Middle trailer The rearmost trailer has the greatest chance of rolling due to the crack- the-whip effect.

• How do you test trailer service brakes?

• Press the accelerator • Use the hand valve while parked • Pull the parking brake • Apply the foot brake hard 3 / 4

The hand valve allows you to check brake function on the trailer independently.

• What should you do if the trailer brakes are not working?

• Drive slowly • Do not operate the vehicle • Use the dolly to slow down • Increase air pressure Trailer brake failure is a serious issue and the vehicle should not be driven.

• How should you check if air is flowing to all trailers?

• Check brake shoes • Open the emergency line shut-off valve • Use the foot brake • Apply trailer spring brakes Opening the shut-off valve should cause air to escape if air is reaching the trailer.

• Why is it important to have sufficient air pressure before

driving?• To ensure brakes work properly • For better fuel economy • To activate cruise control

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