Under the standard commercial motor vehicle space management formula, an operator driving … — Commercial Driver's License (CDL) General Knowledge Exam

Under the standard commercial motor vehicle space management formula, an operator driving a $30\text{-foot}$ straight truck at a cruising speed of $45\text{ mph}$ on a dry, clear highway must maintain a minimum following distance of at least $4\text{ seconds}$ behind the lead vehicle.

Answer: Answer

Answer

True

The statement correctly applies both parts of the CDL space ahead formula:

3\text{ seconds}

for the

30\text{-foot}

length (

30 \div 10

) plus

1\text{ second}

for driving at

45\text{ mph}

(which is

\ge 40\text{ mph}

), giving a total required headway of

4\text{ seconds}

Step-by-Step Solution

Calculate the base following distance interval from vehicle length.

30\text{-foot}

vehicle requires a base interval of

3\text{ seconds}

(

30\text{ ft} \div 10\text{ ft/s} = 3\text{ s}

The commercial driving guideline allocates one second for each

10\text{ feet}

of total vehicle length.

Evaluate the travel speed to determine if a speed adjustment is required.

45\text{ mph}

, the vehicle exceeds the

40\text{ mph}

threshold, adding

1\text{ second}

An additional safety buffer of one second is mandatory at speeds at or above

40\text{ mph}

due to increased stopping distances.

Sum the base following time and speed adjustment.

3\text{ seconds} + 1\text{ second} = 4\text{ seconds}

Combining the base length interval with the speed adjustment yields the total required following headway under good conditions.

Key Concept

CDL safe following distance formula: one second per ten feet of vehicle length, plus one additional second for speeds at or above 40 mph.

Estimated Time:1m 0s

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