You must drive through fog at night. How should you set your headlights?
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A.
On dim, or use fog lights if the vehicle has them. Correct
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B.
Off, using only your hazard flashers.
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C.
On high beam so you can see farther ahead.
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D.
Off, using only your parking lights.
The answer is "On dim, or use fog lights if the vehicle has them."
In fog the manual sets headlights on dim, or fog lights if the vehicle has them. Choice C is the trap, since the reflex on a dark road is to reach for high beams for more distance; the light bounces off the water droplets and throws glare back at the driver.
The traps in the wrong answers
B. Off, using only your hazard flashers.
Hazards on a moving vehicle mislead other drivers and do not light the road. This answer uses the flashers as running lights, importing a shoulder-side behavior into traffic where it does not belong.
C. On high beam so you can see farther ahead.
High beams reflect off fog droplets and worsen visibility rather than improve it. This answer applies a clear-night habit to fog, where more light forward comes right back at the driver's face.
D. Off, using only your parking lights.
Parking lights alone are not enough for a moving vehicle in fog. This answer treats fog like a parked-and-idling setup rather than a driving one that needs a real forward beam.
This question tests your knowledge of Defensive Driving in Illinois. Source: Illinois Rules of the Road, "Chapter 11: Safe Driving Tips, Weather Conditions, Fog," p.84..
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