A commercial driver operating an 80\text{-foot} double-trailer combination at a steady cru… — Commercial Driver's License (CDL) General Knowledge Exam

A commercial driver operating an $80\text{-foot}$ double-trailer combination at a steady cruising speed of $55\text{ mph}$ on a dry highway tracks a stationary roadside marker to gauge space ahead. The driver observes the preceding vehicle pass the marker and counts exactly $8\text{ seconds}$ before their own front bumper reaches that same marker. Under standard commercial vehicle safety guidelines, this driver is maintaining the required minimum following distance.

Answer: Answer

Answer

False (The required minimum following distance is

9\text{ seconds}

, so an interval of

8\text{ seconds}

is insufficient).

Evaluating the statement as False is correct because an

80\text{-foot}

vehicle operating at

55\text{ mph}

requires

8\text{ seconds}

based on length plus

1\text{ second}

for traveling at or above

40\text{ mph}

, totaling at least

9\text{ seconds}

of following interval.

Step-by-Step Solution

Calculate base following interval from vehicle length.

80\text{ ft} \div 10\text{ ft/s} = 8\text{ seconds}

Commercial driving standards allocate

1\text{ second}

for every

10\text{ feet}

of total vehicle length.

Apply the highway speed adjustment rule.

8\text{ seconds} + 1\text{ second} = 9\text{ seconds}

When operating at speeds of

40\text{ mph}

or greater, drivers must add

1\text{ additional second}

to the base following distance.

Compare the driver's measured following distance against the calculated requirement.

Measured distance (

8\text{ seconds}

) is less than the required minimum (

9\text{ seconds}

Maintaining an

8\text{-second}

gap fails to provide the required safety cushion for an

80\text{-foot}

vehicle traveling at

55\text{ mph}

Key Concept

CDL following distance formula (

1\text{ second}

per

10\text{ feet}

of vehicle length, plus

1\text{ second}

for speeds at or above

40\text{ mph}

)

Estimated Time:1m 30s

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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