When driving under low-visibility conditions due to fog, you should:
- Turn on your high beam headlights.
- Slow down and use your low beam headlights. ✓
- Increase your speed so you do not cause an accident.
Answer: B. Slow down and use your low beam headlights.
When fog cuts your visibility, slow down and switch on your low-beam headlights.
Why this is the answer
The handbook's fog section says to drive slowly and use low beams, because high beams bounce light back off the fog and create glare. It also says to make sure you can stop within the distance you can see ahead and to leave more space between you and the car in front. Slowing down and using low beams work together: low beams keep the light from blinding you, and a lower speed lets you stop in the space you can actually see.
Why the other answers are wrong
- A. Turn on your high beam headlights. — High beams reflect off the fog and cause glare, which makes it harder to see, so the handbook says to use low beams instead.
- C. Increase your speed so you do not cause an accident. — Speeding up in fog goes against the handbook's advice to drive slowly and to be able to stop within the space you can see ahead.
Remember it
In fog, think low and slow: low beams on, foot off the gas.
Official handbook: California Driver Handbook (DL 600), Section 8: Safe Driving, p. 64