Free Maryland CDL Doubles & Triples Test Practice Test

Sample CDL Doubles & Triples practice questions

Try a few representative questions below. Each includes the correct answer and a short explanation — the same style you'll see in the full practice test.

1. Question 1Doubles & Triples Handling

   When driving a tractor-trailer combination with two (doubles) or three (triples) trailers, what is the primary concern regarding the 'off-tracking' or 'cutting the corner' effect, and how does it typically manifest?

   • A.All trailers will follow the exact same path as the tractor, eliminating any off-tracking concerns.
   • B.The middle trailer in a triple combination will exhibit the most significant off-tracking, necessitating specific lane positioning adjustments.
   • C.The lead trailer is most likely to veer into the oncoming lane during a left turn, requiring a wider swing than a single trailer.
   • D.The rear-most trailer has the greatest tendency to drift outwards, potentially striking curbs, other vehicles, or fixed objects on the inside of the turn.(Correct)

   Explanation

   The rear-most trailer in a doubles or triples combination experiences the most pronounced off-tracking. This is because each subsequent trailer pivots around the coupling point of the previous one, resulting in the last trailer deviating furthest from the tractor's path, especially during turns.

2. Question 2Speed & Braking Control

   A driver is approaching a steep downgrade with a doubles combination. What is the most critical safety consideration and recommended action to maintain control, assuming the vehicle is equipped with an engine retarder and air brakes?

   • A.Apply the service brakes continuously and firmly to maintain a steady speed, relying solely on the air brake system.
   • B.Engage the engine retarder at its highest setting and maintain speed without using the service brakes, as this is designed for steep descents.
   • C.Disengage the clutch and coast downhill to conserve fuel and reduce brake wear, only braking if absolutely necessary.
   • D.Downshift to a lower gear to allow the engine to provide braking assistance, then use the service brakes intermittently to supplement and control speed.(Correct)

   Explanation

   On steep downgrades, the primary strategy is to use a combination of engine braking and service brakes. Downshifting allows the engine to help control speed, reducing reliance on the service brakes, which can overheat and fail. Service brakes should be applied intermittently to maintain a safe speed, not continuously.

3. Question 3Coupling & Uncoupling

   When coupling a second trailer to a tractor that already has a lead trailer (doubles configuration), what is a key procedural step to ensure the air lines are properly connected and do not cause unintended braking or release?

   • A.Connect the air lines first, then connect the glad hands, ensuring the glad hand levers are fully engaged.
   • B.Ensure the air lines to the second trailer are connected to the correct ports (service and emergency) and that the glad hands are securely locked *before* connecting the fifth wheel to the kingpin.(Correct)
   • C.Connect the glad hands to the service and emergency lines of the second trailer, then connect the air lines to the tractor's air supply.
   • D.Test the air brakes on the lead trailer *after* connecting the air lines to the second trailer to confirm proper function.

   Explanation

   Proper air line connection is crucial. The glad hands must be securely connected to the correct service and emergency lines of the second trailer, and then locked. This ensures that the air brake system of the second trailer is properly integrated before the physical coupling is completed, preventing accidental braking or loss of air.

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