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Question

Difficulty: MediumSpace Ahead and Following Distance

You are driving a 60-foot combination vehicle at a speed of 45 mph on a dry, clear highway. According to commercial driving safety guidelines, what is the minimum safe following distance you should maintain behind the vehicle ahead?

  1. A
    6 seconds
  2. 7 secondsAnswer
  3. C
    4 seconds
  4. D
    8 seconds

Answer

7 seconds
Under the standard CDL following distance rule, a driver must allow at least 1 second for every 10 feet of vehicle length under 40 mph, and add 1 additional second if traveling at 40 mph or faster. For a 60-foot vehicle traveling at 45 mph, the calculation is 6 seconds for vehicle length plus 1 second for speed, totaling 7 seconds.

Step-by-Step Solution

1
Calculate base following distance based on vehicle length
6 seconds
The standard CDL formula requires 1 second of following distance for every 10 feet of vehicle length (60 ft / 10 = 6 seconds).
2
Apply the speed-dependent safety adjustment
Add 1 second
Because the vehicle is traveling at 45 mph (which is 40 mph or greater), an extra 1 second must be added.
3
Sum the base following distance and speed modifier
7 seconds
Combining 6 seconds (length) + 1 second (speed) gives the minimum total following interval of 7 seconds.

Key Concept

Commercial Motor Vehicle Following Distance Formula
Estimated Time:1m 0s
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Topics

Space Ahead and Following Distance

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