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Difficulty: MediumSpace Ahead and Following Distance

A commercial driver is operating a 50-foot50\text{-foot} flatbed truck through suburban traffic at a steady cruising speed of 35 mph35\text{ mph} on dry pavement. According to official CDL safety standards, what is the minimum safe following distance the driver should maintain behind the lead vehicle?

  1. A
    6 seconds6\text{ seconds}
  2. 5 seconds5\text{ seconds}Answer
  3. C
    3 seconds3\text{ seconds}
  4. D
    7 seconds7\text{ seconds}

Answer

5 seconds5\text{ seconds}
Under standard CDL guidelines, commercial drivers must maintain at least 1 second1\text{ second} for every 10 feet10\text{ feet} of vehicle length when operating at speeds below 40 mph40\text{ mph}. For a 50-foot50\text{-foot} vehicle traveling at 35 mph35\text{ mph}, dividing 5050 by 1010 gives 5 seconds5\text{ seconds}. Because the speed is under 40 mph40\text{ mph}, no additional second is added.

Step-by-Step Solution

1
Calculate base following distance based on vehicle length
50 ft÷10 ft/sec=5 seconds50\text{ ft} \div 10\text{ ft/sec} = 5\text{ seconds}
The standard CDL formula requires 1 second1\text{ second} of following distance for every 10 feet10\text{ feet} of vehicle length.
2
Evaluate operating speed against the speed threshold
Operating speed is 35 mph35\text{ mph}, which is below 40 mph40\text{ mph}
An additional 1 second1\text{ second} is added only for speeds at or above 40 mph40\text{ mph}.
3
Determine total required following distance
5 seconds5\text{ seconds}
Since the vehicle is traveling below 40 mph40\text{ mph}, no extra speed second is added to the 5-second5\text{-second} base distance.

Key Concept

CDL Space Ahead and Following Distance Formula
Estimated Time:1m 0s
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Topics

Space Ahead and Following Distance

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