A commercial driver is operating an 80-foot combination vehicle at a steady cruising speed… — Commercial Driver's License (CDL) General Knowledge Exam

A commercial driver is operating an $80$ -foot combination vehicle at a steady cruising speed of $45\text{ mph}$ on a clear, dry highway. According to the standard CDL following distance rule, what is the minimum safe following distance, in seconds, that the driver should maintain behind the vehicle ahead?

Answer: 9 seconds

Answer

9 seconds

For an

80

-foot vehicle, the base following interval is

\frac{80}{10} = 8\text{ seconds}

. Because the vehicle is operating at

45\text{ mph}

(which is

\geq 40\text{ mph}

1\text{ additional second}

must be added, resulting in a total minimum following distance of

8 + 1 = 9\text{ seconds}

Step-by-Step Solution

Calculate the base space cushion based on total vehicle length.

8 seconds

The standard CDL formula requires 1 second of following distance for every 10 feet of vehicle length.

Apply the speed-based adjustment for speeds at or above 40 mph.

9 seconds

When traveling at speeds of 40 mph or greater, an additional 1 second must be added to account for increased stopping distance.

Key Concept

CDL Following Distance Rule (1 second per 10 feet of vehicle length plus 1 additional second at or above 40 mph)

Estimated Time:45s

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