You're driving into thick fog on an Oregon road. Which lights should you use?
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A.
Hazard lights only.
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B.
Low beams, because high beams cause glare in fog. Correct
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C.
Parking lights only, because they reduce glare in fog.
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D.
High beams, because they cut through fog better.
The answer is "Low beams, because high beams cause glare in fog."
Use low beams in fog, dust, smoke, or any area of low visibility. Light from high beams reflects off the suspended particles in the air, causing glare and making it harder, not easier, to see ahead. Low beams direct light down at the road and reduce backscatter. The folk belief that high beams cut through fog drives choice D, which inverts what actually happens when the brighter beam meets airborne water.
The traps in the wrong answers
A. Hazard lights only.
Hazard lights are not headlights; you still need low-beam headlights for visibility. This answer substitutes hazard lights for headlights; the manual specifies low-beam headlights in low visibility.
C. Parking lights only, because they reduce glare in fog.
It is illegal to drive at night or in bad weather with only parking lights on; you need low-beam headlights. This answer confuses parking lights with headlights; the manual states it is illegal to drive at night or in bad weather with only the parking lights on.
D. High beams, because they cut through fog better.
High beams reflect off particles in the air and create glare. This answer inverts the rule; the manual says high-beam light reflects back, causing glare and making it more difficult to see ahead.
This question tests your knowledge of Adverse Conditions in Oregon. Source: Oregon Driver Manual, "Fog, Dust and Smoke," p.77..
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