Free Florida 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 1Driving Techniques

   When driving a triple trailer combination on a highway with a posted speed limit of 65 mph, what is the maximum recommended speed for safely navigating curves, considering a typical trailer wheelbase and a desire to maintain a safety margin of 2 seconds between units?

   • A.60 mph
   • B.55 mph
   • C.50 mph(Correct)
   • D.45 mph

   Explanation

   Triple trailers are significantly longer and heavier, increasing the risk of jackknifing and off-tracking. A general rule of thumb for doubles and triples is to reduce speed significantly below the posted limit, especially for curves. While 2 seconds is a minimum following distance, the actual safe speed for a curve depends on many factors, but 50 mph is a more prudent maximum for triple trailers in a 65 mph zone to account for increased instability.

2. Question 2Pre-Trip Inspection

   You are performing a pre-trip inspection on a tractor-trailer combination with two trailing units. Which of the following is the MOST critical check related to the inter-axle or inter-unit slack adjusters to prevent a loss of braking effectiveness?

   • A.Checking for any visual signs of leakage from the air brake system, as this is the primary indicator of a problem.
   • B.Ensuring that the emergency and service lines are properly connected and free of kinks.
   • C.Verifying that all slack adjusters are set to the manufacturer's recommended stroke limit without any adjustment needed.
   • D.Manually actuating the brake pedal and checking the pushrod travel on all axles of all three units to ensure it's within the allowable range (typically 1-inch for S-cams).(Correct)

   Explanation

   The most critical check for slack adjusters is to verify the pushrod travel. Excessive pushrod travel indicates worn brake components or improperly adjusted slack adjusters, directly impacting braking performance. While leaks are important, they might not always be apparent during a static check, and proper connection of air lines is crucial but doesn't directly assess brake adjustment.

3. Question 3Driving Techniques

   During a lane change with a triple trailer combination, you notice significant trailer sway in the rearmost trailer. What is the IMMEDIATE and CORRECT action to take?

   • A.Accelerate slightly to regain stability.
   • B.Gently apply the service brakes on the tractor to stabilize the units.(Correct)
   • C.Apply the trailer brakes only to slow the sway.
   • D.Turn the steering wheel sharply in the opposite direction of the sway to counteract it.

   Explanation

   Trailer sway is often caused by excessive speed, improper loading, or road conditions. Gently applying the tractor's service brakes helps to slow the entire combination, which is usually the most effective way to regain control and reduce sway without causing a jackknife. Applying only trailer brakes can exacerbate the problem, and accelerating or sharp steering inputs are dangerous.

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