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Difficulty: HardSpeed Control and Following Distance

When driving at night on an unlit highway using low-beam headlights, traveling at a speed of 60 mph60\text{ mph} allows a driver to safely bring the vehicle to a stop within the illuminated roadway ahead because standard low beams illuminate approximately 350 feet350\text{ feet}.

Answer: Answer

Answer

The statement is false because standard low-beam headlights only illuminate 160 to 200 feet160\text{ to }200\text{ feet} ahead, whereas stopping from a speed of 60 mph60\text{ mph} requires 300 to 350 feet300\text{ to }350\text{ feet}, resulting in 'overdriving your headlights.'
The statement is false because low-beam headlights only reach about 160 to 200 feet160\text{ to }200\text{ feet}. At 60 mph60\text{ mph}, total stopping distance is roughly 300 to 350 feet300\text{ to }350\text{ feet}. Driving at 60 mph60\text{ mph} with low beams means you are overdriving your headlights, as you cannot stop within the distance you can see.

Step-by-Step Solution

1
Determine the effective illumination range of standard low-beam headlights.
Low-beam headlights illuminate the roadway for approximately 160 to 200 feet160\text{ to }200\text{ feet} ahead (high beams illuminate up to 350 to 500 feet350\text{ to }500\text{ feet}).
Safe speed control at night depends directly on maintaining a stopping distance that does not exceed visibility distance.
2
Calculate total stopping distance at 60 mph60\text{ mph}.
At 60 mph60\text{ mph}, perception and reaction distance accounts for about 132 feet132\text{ feet} (1.5 seconds1.5\text{ seconds} at 88 ft/s88\text{ ft/s}), and braking distance adds roughly 170 to 200 feet170\text{ to }200\text{ feet}, yielding a total stopping distance of 300 to 350 feet300\text{ to }350\text{ feet}.
Total stopping distance equals the sum of driver reaction distance and mechanical braking distance.
3
Compare total stopping distance with low-beam visibility range.
Total stopping distance (300–350 feet300\text{--}350\text{ feet}) exceeds low-beam illumination distance (160–200 feet160\text{--}200\text{ feet}) by over 100 feet100\text{ feet}.
When stopping distance exceeds sight distance, the driver cannot stop for hazards that appear at the far edge of the light beam.

Key Concept

Overdriving Headlights and Night Speed Adjustment
Estimated Time:1m 30s
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Topics

Speed Control and Following Distance

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