So what is your opinion?

Fog lights + Low beams

OR

Fog lights only?


My truck is wired in a way that allows the main headlights to be turned off while the fog lights still operate with the parking lights. When I turn off the low beams and fog and ONLY use the fog lights. Visibility of the road and tree line improves. My friend argues that it is against the law to do such things. however I hear over in Europe in heavy fog, it is common practice to run only the front fogs+parking lights+ rear fog with main beams off.

What is your opinion?

Here you have to look what the road legislation at your place says, it tends to differ.

Here the law says, at reduced visibility you need to use the "low beam", unless you use the front fog lights. Then the front fog lights you are allowed to use only if there is the fog or dense rain or snowing.

But some places require the main light (the low or high beam) to be ON anytime at reduced visibility, regardless whether the fog lights. So then you may use the fog lights with them, but you can not switch the main lights off.

Or some places (it was here till about some 20 years ago) you are not allowed to use the fog lights with high beam (or the high beam with the fog lights), although that combination really does not make much sense to me (creates the "white darkness" wall even during dusk/dawn).


If you have the "freedom", I would decide based on what gives better visibility at the given condition. When dark outside with a dense fog or so, too much light too high tend to create a "white darkness" - a kind of bright wall where you can not see a thing behind. On the other hand if there is daylight, it could create extra shadows behind obstacles so make them more visible for you (assume your eyes are way higher above the ground than your headlights). Also the fog lights may sometimes cause more glare to the oncoming traffic and you likely do not want that (so they then make some mistake because not seeing something in time).
So sometimes is better one way, sometimes the other. You have to try and learn to estimate yourself which condition is better in which situation.

@HomeBrewLamps - It is my understanding that USDOT regulations require fog lights (selective yellow works best) to only work in conjunction with low beams...OE fog lights are wired this way. I do however get your argument about wanting to have them run independently. I'd check with Michigan DOT just to make sure...don't need the  pulling you over.