How Do I Drive Safely in Fog?

Thick fog is a driving hazard in many areas of the Western U.S. In the Pacific Northwest, it comes up mostly in winter. In California’s Central Valley—where some roads have been called among the most dangerous in the world because of fog—the fog season starts with the first heavy rain in fall and goes until March.

How to drive in fog

Just like there are different types of snow, there are many types of fog. Oregon has freezing fog that can coat the road like black ice. California’s “tule fog” usually forms in low-lying areas that typically have bulrushes (tule, pronounced “ too-lee”) growing in them. Tule fog can reduce visibility on a stretch of highway to only a few feet, while other areas are nearly clear.

Photo by, under Creative Commons license

This is true of fog anywhere: You can be driving along with enough visibility and then suddenly go through a patch where you can barely see the road.

When fog’s an issue, here are tips to keep you safer on your drive.

  • Slow down and turn off your cruise control. Most crashes happen because the driver’s going too fast for weather conditions.
  • Drive with enough stopping space so you can stop in the distance you can see.
  • Don’t use high-beam headlights. They won’t shine through the fog but just reflect the light back in your eyes, making it worse for you and other drivers. Use low-beams.
  • In really dense fog, use front fog lights in addition to your low-beams if you have them. NEVER drive using only your parking or fog lights. It’s illegal and unsafe. Use rear fog lights if you have them when visibility is less than around 300 feet.
  • Fog lights should be turned off when visibility is normal. They can be distracting for oncoming drivers.
  • Oregon law says fog lights must be turned off when within 500 feet of an oncoming vehicle and within 350 feet when following another vehicle. 
  • Minimize distractions. Turn off music and don’t talk on your cellphone, so you can listen for traffic you might not be able to see. 

  • Keep your headlights clean. Get in the habit of wiping them off whenever you fill your gas tank.
  • Keep the windshield clear and use the defroster to avoid fogged windows.
  • Keep on the alert for slow-moving or stopped vehicles. Slow down more when you see red taillights ahead.
  • Avoid using your hazard lights while moving—other drivers may think you’ve stopped.
  • Use the right edge of the road, white fog line or roadside reflectors as a guide to stay in your lane.
  • In Oregon, a Dense Fog Advisory is issued when visibility is reduced to less than one-quarter mile. Check
  • Be patient. Don’t change lanes or pass other vehicles unless you really have to, and NEVER try to pass long lines of traffic in fog.
  • Don’t creep along; somebody else may crash into you. If visibility is extremely poor, exit the freeway or find a safe place to pull over. Some highways in California have signs that estimate road visibility and a 3-2-1 countdown pattern of reflective pavement markers to help motorists take exit ramps in heavy fog.
  • If you need to stop and there’s no nearby exit, pull off the pavement as far as safely possible. Turn off your lights, set the emergency brake and take your foot off the brake to be sure your taillights aren’t lit up. Turn on your emergency flashers. Wait it out until conditions improve.
  • Never stop in the travel lanes. If you can’t pull over, go slow and sound the horn occasionally.

What you should know about fog lights

Fog lights are designed to be used at low speed in fog, heavy mist, snow and other poor-visibility situations. They’re different from daytime running lights. They are an extra pair of lights mounted low on the vehicle, with the thinking that fog doesn't settle on the road surface but hovers 12 to 18 inches above it. They aim light into this layer of fog-free air. They also point to the right enough that the driver can see the solid, white “fog line” at the road edge as a guide.

Photo: Oregon Department of Transportation

The rules on using auto fog lights—also known as fog lamps—vary by state. The main thing to know: you can’t use fog lights in a way that creates glare for other drivers. They have to be pointed and used so they won't interfere with visibility for another driver within 25 feet. Here are specifics.

Basic fog light rules for Western states

  • No more than two fog lamps are allowed for highway driving.
  • They may be used with, not instead of, your regular headlights.
  • Fog lights have to be in a white to yellow color spectrum.
  • You can’t have more than four sets of the following types lighted at one time:
    1. Low-beam headlights
    2. High-beam headlights
    3. Fog lights
    4. Warning lights
    5. Spot lights
    6. Gaseous discharge lamps
  • If you pull over on the shoulder of the road, or are in standing traffic, you have to dim your fog lamps.
  • None of your car lights can create glare in the eyes of an oncoming driver within 500 feet.
  • For off-highway driving, a vehicle can have a max eight lamps for use as headlights when the vehicle is operated off-road. Whenever the vehicle is on a highway, the extra lights must be turned off and covered with an opaque hood.
  • Headlights and other white lamps are limited to a total of four.
  • Fog lights must be non-glaring.
  • They must be white, amber or any color in between white and amber.
  • Fog lamps may be used with but not instead of low-beams.
  • None of your car lights can create glare in the eyes of an oncoming driver within 500 feet. 
  • Two front-mounted fog lamps are allowed.
  • They may be used with low-beam headlights.
  • Your fog lights can’t create glare in the eyes of oncoming drivers. This means no part of the main beam can strike the body of a person, vehicle, screen or other object higher than the fog lamp centers 25 feet or more ahead. 
  • Headlights must be on in the daytime when vision is reduced to 500 feet or less.
  • Two fog lights providing a low, wide-angle light pattern are allowed.
  • Fog lamps may be used with your low-beams so long as they don’t project a stronger beam than your regular headlights.
  • They can’t be used as a substitute for your regular headlights.
  • None of the high-beam portion of the left light can project more than four inches above the center of the lamp at a distance of 25 feet.
  • Two front-mounted fog lamps are allowed, and may be used with your low-beams.
  • No more than four auxiliary lights (like fog lights, high-beam lights, spot lights) may be lit at once if any project a beam of 300 candlepower or more.
  • None of the high-beam portion of the left light can project more than four inches above the center of the lamp at a distance of 25 feet.
  • Fog lights must be used like your high-beams: turned off when within 500 feet of an oncoming vehicle and within 350 feet when following another vehicle.
  • Forward-pointing fog lights must be white, amber or yellow.
  • Rear-mounted fog lights must be red.
  • Fog lights must have a separate switch from regular headlights.
  • Fog lights may not be used instead of headlights. 
  • After-market fog lights have to meet federal rules. Products must be labeled; anything that is labeled “not for street use” can't be used on public roadways.
  • Two fog lights are allowed.
  • No red or blue lights showing toward the front are allowed.
  • No more than two extra driving lights are allowed.
  • A max of two, front-mounted fog lights are allowed.
  • They can only be used with low-beams, not your high-beam headlights.
  • They must be white or amber.
  • No more than four lights can shine to the front at once.
  • None of the high-beam portion of the left light can project more than four inches above the center of the lamp at a distance of 25 feet.

Each year, over 38,700 vehicle crashes occur in fog. Over 600 people are killed and more than 16,300 people are injured in these crashes annually. Treat low visibility driving with respect.

Get more winter driving how-tos in our ebook 19 Winter Driving Resources You Can't Do Without. See real-time road conditions for Western states here