A motorist is driving on a two-lane roadway with a posted speed limit of 45\text{ mph}. He… — DMV Permit Practice Test

A motorist is driving on a two-lane roadway with a posted speed limit of $45\text{ mph}$ . Heavy fog suddenly reduces visibility to less than $60\text{ feet}$ , creating hazardous driving conditions. Under the Basic Speed Law, which of the following actions is legally required of the driver?

Reduce driving speed to a rate that is reasonable and prudent for the reduced visibility, even if it is significantly lower than $45\text{ mph}$ .Answer
B
Maintain $45\text{ mph}$ as long as the vehicle remains within its designated lane and emergency flashers are activated.
C
Increase speed slightly above $45\text{ mph}$ to clear the fog bank as quickly as possible and avoid rear-end collisions.
D
Drive at exactly $45\text{ mph}$ because posted maximum speed limits establish an absolute legal protection against speeding citations.

Answer

The driver must reduce speed to a rate that is reasonable and prudent for the reduced visibility, even if that speed is significantly lower than the posted

45\text{ mph}

limit.

Under the Basic Speed Law, drivers must never travel faster than is safe for current conditions, regardless of the posted maximum speed limit. When heavy fog severely limits visibility, the safe operating speed decreases significantly below the posted limit of

45\text{ mph}

Step-by-Step Solution

Identify the core law governing vehicle speed under adverse environmental conditions.

Recognize that the Basic Speed Law overrides posted maximum speed limits when conditions are hazardous.

Posted speed limits apply only under ideal driving conditions.

Evaluate the driver's legal duty when encountering heavy fog reducing visibility to under

60\text{ feet}

Determine that maintaining or exceeding

45\text{ mph}

creates an unsafe situation because stopping distance exceeds sight distance.

Safe speed selection requires matching vehicle speed to reaction time and visible distance ahead.

Select the option specifying speed reduction based on prevailing safety needs.

The driver must slow down to a safe speed appropriate for dense fog.

This directly fulfills the mandate of the Basic Speed Law.

Key Concept

Basic Speed Law vs. Posted Speed Limits

Estimated Time:1m 0s

Question

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Key Concept

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