An interstate commercial carrier is operating a 55\text{-foot} bulk tanker along an open f… — Commercial Driver's License (CDL) General Knowledge Exam

An interstate commercial carrier is operating a $55\text{-foot}$ bulk tanker along an open freeway at a sustained cruising speed of $52\text{ mph}$ under clear, dry daytime conditions. According to standard commercial vehicle space management rules, what is the minimum safe following distance, in seconds, that the driver must maintain behind the vehicle ahead?

Answer: 6.5 seconds

Answer

The minimum required following distance is

6.5\text{ seconds}

According to the CDL space management formula, a commercial driver must allow at least

1\text{ second}

for every

10\text{ feet}

of vehicle length. For a

55\text{-foot}

tanker, the base following interval is

5.5\text{ seconds}

. Because the vehicle is traveling at

52\text{ mph}

(which meets or exceeds the

40\text{ mph}

threshold), an additional

1\text{ second}

must be added, yielding a total minimum following distance of

6.5\text{ seconds}

Step-by-Step Solution

Calculate the vehicle length buffer

5.5\text{ seconds}

(

55\text{ ft} \div 10\text{ ft/second}

)

Commercial driving safety guidelines allocate

1\text{ second}

of following distance for every

10\text{ feet}

of total vehicle length.

Determine the high-speed interval adjustment

Add

1.0\text{ second}

When operating at speeds at or exceeding

40\text{ mph}

, drivers must add

1\text{ extra second}

to compensate for increased stopping distance and reaction lag.

Sum the base buffer and speed adjustment

6.5\text{ seconds}

Adding

5.5\text{ seconds}

(length requirement) and

1.0\text{ second}

(speed requirement) gives the total required time interval.

Key Concept

Commercial vehicle following distance formula:

1\text{ second}

per

10\text{ feet}

of vehicle length plus

1\text{ additional second}

for travel speeds at or above

40\text{ mph}

Estimated Time:1m 0s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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