When driving a 45-foot intercity bus at 50\text{ mph} in clear weather, the minimum safe f… — Commercial Driver's License (CDL) General Knowledge Exam

When driving a $45$ -foot intercity bus at $50\text{ mph}$ in clear weather, the minimum safe following distance is $4.5\text{ seconds}$ .

Answer: Answer

False (the minimum following distance must be

5.5\text{ seconds}

)

The statement is false because commercial drivers must add

1\text{ second}

for speeds at or above

40\text{ mph}

. A

45

-foot vehicle requires

4.5\text{ seconds}

based on length (

1\text{ second}

per

10\text{ feet}

) plus

1\text{ second}

for operating at

50\text{ mph}

, totaling a minimum of

5.5\text{ seconds}

Calculate the base following distance using the vehicle length rule.

45\text{ feet} / 10 = 4.5\text{ seconds}

Commercial driver rules specify

1\text{ second}

of following distance for every

10\text{ feet}

of vehicle length.

Apply the additional time adjustment for operating speed.

4.5\text{ seconds} + 1.0\text{ second} = 5.5\text{ seconds}

For speeds at or above

40\text{ mph}

, an additional

1\text{ second}

must be added to the base calculation.

Compare the calculated requirement against the statement.

5.5\text{ seconds} > 4.5\text{ seconds}

The statement claims

4.5\text{ seconds}

, which improperly omits the extra second required for traveling at

50\text{ mph}

Commercial vehicle following distance calculation using vehicle length and the speed threshold modifier

Estimated Time:45s

Question