Use this guide to review when California requires headlights, which beams to use in fog or poor visibility, and the visibility rules that can appear on the knowledge test.
QUICK ANSWER
California DMV requires headlights in several situations beyond nighttime. The handbook says to use them when it is too dark to see from 1,000 feet away, from 30 minutes after sunset until 30 minutes before sunrise, in adverse weather when windshield wipers are needed, and when fog, smoke, dust, or other conditions reduce visibility. In fog or heavy smoke, use low beams—not high beams.
STUDY NOTES
When headlights are required
- When it is too dark to see from 1,000 feet away.
- Beginning 30 minutes after sunset and continuing until 30 minutes before sunrise.
- In adverse weather when you need windshield wipers because of fog, rain, or snow.
- When clouds, dust, smoke, fog, or similar conditions make other vehicles hard to see.
- On mountain roads and in tunnels, even during the day.
- Where a road sign requires headlights.
High beams have distance rules
Dim high beams to low beams within 500 feet of an oncoming vehicle or within 300 feet of a vehicle you are following. High beams can reduce other drivers' ability to see and can make your own vision worse in fog because the light reflects back toward you.
Fog and heavy smoke
DMV says it is best to avoid driving in heavy fog or smoke. If you must drive, slow down, use low beams, increase following distance, and make sure you can stop within the distance you can see. Do not drive using only parking or fog lights.
PRACTICE CHECKS
Check your understanding
Answer each question before opening the explanation.
1. Which headlights should you use in heavy fog?
Show answer
Answer: Low-beam headlights.
DMV warns that high beams reflect back in fog and create glare.
2. How close to an oncoming vehicle must you dim your high beams?
Show answer
Answer: Within 500 feet.
The handbook gives a 500-foot distance for oncoming traffic.
3. If rain requires your windshield wipers, what should you do with your headlights?
Show answer
Answer: Turn on your low-beam headlights.
California DMV lists this as an adverse-weather headlight requirement.
FAQ
Common questions
Are headlights required only at night in California?
No. DMV also requires headlights in adverse weather, poor visibility, on mountain roads and in tunnels, and wherever signs require them.
Can I use only parking lights in fog?
No. DMV says never drive using only parking or fog lights in heavy fog or smoke; use low-beam headlights.
When do I dim high beams for a vehicle I am following?
Dim to low beams within 300 feet of a vehicle you are following.
VERIFY THE RULE
Official sources
This study page was reviewed against the DMV material below. Open the source when you want the complete rule, exceptions, or surrounding context.
Last reviewed: August 16, 2026 · Reviewed by Master My Test