Driving in Fog

Reduce speed immediately and turn on your low-beam headlights if they're not already on. Fog is often patchy — you may enter a dense bank suddenly after driving in clear conditions. Slowing down before you're in the thick of it gives you more options than trying to slow down once visibility has already dropped. Do not use high beams in fog; they reflect off the moisture and reduce visibility further rather than improving it.

Yes, if your vehicle has them. Front fog lights sit lower on the vehicle and illuminate the road surface below the fog layer, which is more useful than high-mounted lights in dense fog. Rear fog lights make your vehicle more visible to drivers behind you. Turn fog lights off when visibility improves — they can dazzle other drivers in clear conditions, and in some states using them unnecessarily is a traffic violation.

More than normal. The principle is that you should be able to stop comfortably within the distance you can see clearly. In fog, that visible distance is often very short. Use the road's painted edge lines rather than the taillights of the vehicle ahead as your guide — following taillights too closely creates a false sense of security and leaves very little reaction space if the vehicle ahead stops suddenly.

Pull off the road completely. Look for a parking lot, driveway, or a spot well clear of the travelled lane. Once stopped, turn on hazard lights to make your vehicle visible. If you're on a highway shoulder and can't find a safer spot, turn on hazard lights but also consider turning off your headlights — a parked vehicle with headlights on in dense fog can draw other drivers toward it. Wait for conditions to improve before continuing.

No. In fog, cruise control removes your ability to react quickly to sudden hazards — a stopped vehicle, a road closure, an animal. Your foot needs to be ready to brake immediately, which isn't possible if the vehicle is maintaining speed automatically. Disable cruise control whenever visibility is significantly reduced.

Use the defroster and windshield wipers. Fog increases moisture in the air, which can condense on the inside of the windshield and reduce visibility independently of what's happening outside. Running the defroster on a warm setting and using the air conditioning (which dehumidifies the air) clears interior condensation faster than heat alone. Keep the windshield clean on the inside — a film of residue scatters light and makes glare and condensation significantly worse.