Rules in most of the US as far as I know... fog lights on with
low beams only. Might want to find a head light bulb that causes a good focussed cut off line. Philips makes one. I had them on my Vibe for a couple of years. I think you have to order them. Never found them in stores, X-treme Vision? Maybe in stores now.
Another thing that helps keep splaying light all over the place in fog is to keep the head light lenses polished. Scratches and haze spreads the light pattern in all kinds of directions and doesn't help in fog at all.
Unfortunately, there's not much driver's instruction going on, so if you talk to most people that drive with their fogs on all the time, you'll hear the "I can see the road much better" routine. And they are correct... you can see the road much better 5 to 15 feet in front of the car, but then can't see as well farther into the darkness where it's really important to see what's there. The iris diminishes the pupil size in the presence of that good expanse of bright light that you see when the fogs are on. Seeing the road much better 5 to 10 or even 20 feet ahead of the car will do little to help avoid contact when driving even as slow as 30 mph, never mind at 50 or 60 mph.
Fog lights are called fog lights, because they are used when fog is present and limits visibility severely. They shine low and allow you to see the edges of the road while you travel slowly and cautiously.
But old wives tales really die hard. Physics and physiology? Fergetabout it. Notice that Subaru (mostly the Outbacks) and pickup trucks run around with fogs on all the time when low beams are on. Lines of oncoming Subaru Outbacks and pickup trucks will blind you here in Maine, even the clearest nights. I don't think most of those Outback drivers even know how to turn their fogs off! I knew a guy that bought an Outback. I was telling him how most Outbacks always run around at night with fog lights on, fog or no fog. He said his weren't on. He went out to the parking lot to show me and turned on his lights. Fogs were on
. Surprise, surprise! He hadn't realized it. Had to look up in manual how to turn them off, too.
They sure "look" cool when they're on though, whether on Vibes, Outbacks or Pickups. Especially when there's no fog'!