While driving a 40\text{-foot} single-unit truck at a steady speed of 35\text{ mph} on a d… — Commercial Driver's License (CDL) General Knowledge Exam

While driving a $40\text{-foot}$ single-unit truck at a steady speed of $35\text{ mph}$ on a dry roadway, what is the minimum safe following distance you must maintain behind the vehicle ahead?

A
$2\text{ seconds}$
B
$5\text{ seconds}$
$4\text{ seconds}$ Answer
D
$8\text{ seconds}$

Answer

4\text{ seconds}

Under standard commercial driving rules, a driver must maintain at least 1 second of following distance for every 10 feet of vehicle length when driving under

40\text{ mph}

. For a

40\text{-foot}

single-unit truck traveling at

35\text{ mph}

, the required following distance is

40 \div 10 = 4\text{ seconds}

Step-by-Step Solution

Calculate base following distance from vehicle length

40\text{-foot}

truck requires

4\text{ seconds}

(

40 \div 10 = 4

Commercial vehicle safety standards require 1 second of following distance for every 10 feet of vehicle length.

Check if an additional second is required for operating speed

Speed is

35\text{ mph}

, so

0\text{ additional seconds}

are needed.

An extra 1 second is only added when operating at speeds of 40 mph or greater.

Calculate the total minimum following distance

4\text{ seconds} + 0\text{ seconds} = 4\text{ seconds}

Sum the base vehicle length duration and the speed adjustment.

Key Concept

Standard commercial vehicle following distance formula based on vehicle length and speed thresholds.

Estimated Time:45s

Question

Answer

Step-by-Step Solution

Key Concept

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