Under ideal roadway conditions, a commercial driver operating a 50-foot vehicle at a cruis… — Commercial Driver's License (CDL) General Knowledge Exam

Under ideal roadway conditions, a commercial driver operating a $50$ -foot vehicle at a cruising speed of $45\text{ mph}$ must maintain a minimum following distance of $5\text{ seconds}$ to satisfy the standard CDL following distance formula.

Answer: Answer

Answer

False. The minimum required following distance for a

50

-foot vehicle at

45\text{ mph}

6\text{ seconds}

The statement is false because vehicles traveling at or above

40\text{ mph}

require an additional

1\text{ second}

buffer added to the length-based calculation. A

50

-foot vehicle traveling at

45\text{ mph}

requires

5\text{ seconds}

for length plus

1\text{ second}

for speed, giving a total minimum following distance of

6\text{ seconds}

Step-by-Step Solution

Calculate the baseline following distance based on vehicle length.

50\text{ feet} \div 10\text{ feet per second} = 5\text{ seconds}

The standard CDL formula requires allowing at least

1\text{ second}

for each

10\text{ feet}

of vehicle length.

Evaluate the operating speed and apply the speed modifier.

Since

45\text{ mph} \geq 40\text{ mph}

, add

1\text{ second}

(

5 + 1 = 6\text{ seconds}

At speeds of

40\text{ mph}

or greater, an additional

1\text{ second}

must be added to account for increased stopping distance.

Compare the calculated requirement with the statement.

The minimum requirement is

6\text{ seconds}

, not

5\text{ seconds}

, making the statement false.

Operating with only a

5

-second cushion leaves the vehicle under-buffered at highway speeds.

Key Concept

CDL Space Ahead Formula: 1 second per 10 feet of vehicle length, plus 1 second for speeds of 40 mph and above.

Estimated Time:45s

Question

Answer

Step-by-Step Solution

Key Concept

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