Examkin

Question

Difficulty: MediumSpace Ahead and Following Distance

You are driving an 80-foot80\text{-foot} twin-trailer combination at a steady speed of 55 mph55\text{ mph} on a clear, dry highway. Under standard CDL safety guidelines, what is the minimum safe following distance you must maintain behind the vehicle ahead?

  1. A
    8 seconds8\text{ seconds}
  2. 9 seconds9\text{ seconds}Answer
  3. C
    4 seconds4\text{ seconds}
  4. D
    12 seconds12\text{ seconds}

Answer

The minimum safe following distance is 9 seconds9\text{ seconds}.
The standard commercial following distance formula requires 1 second for every 10 feet of vehicle length, plus an additional 1 second for speeds of 40 mph or greater. For an 80-foot vehicle traveling at 55 mph, this calculation is (80 / 10) + 1 = 9 seconds.

Step-by-Step Solution

1
Determine the base following distance based on vehicle length
An 80-foot80\text{-foot} vehicle requires 8010=8 seconds\frac{80}{10} = 8\text{ seconds} of space cushion.
CDL standards require a baseline of 1 second for every 10 feet of vehicle length.
2
Adjust following distance for operating speed
Since the vehicle is traveling at 55 mph55\text{ mph} (which is ≥40 mph\geq 40\text{ mph}), add 1 second1\text{ second}.
At highway speeds of 40 mph and higher, vehicles require an additional second of buffer due to increased stopping distance.
3
Sum the components to find total required following distance
8 seconds+1 second=9 seconds8\text{ seconds} + 1\text{ second} = 9\text{ seconds}.
Combining the vehicle length allowance and high-speed allowance yields the total minimum safe interval.

Key Concept

CDL Space Ahead Formula: 1 second per 10 feet of vehicle length under 40 mph, plus 1 additional second at or above 40 mph.
Estimated Time:1m 0s
Rate this question

Topics

Space Ahead and Following Distance

More questions from this topic