Originally Posted by AK370Z

Have you ever driven in heavy fog? you live in NJ. You should see heavy fog every now and then. This fog light is BRIGHTER than the taillight (on purpose) to show the car behind you there is a car in front. I have driven in situation where I couldn't see anything in front of me. I can barely see the car in front. I'm not saying it will save you from "rear ending" incident if fog is heavy ( and the driver behind you is an idiot) BUT it will help a little. I usually use it during snowing (blizzard), heavy rain, fog/heavy fog etc.

As far as legality, I can't answer that question. But I'm pretty sure cops will APPRECIATE your effort on keeping the highways/road accident free by using your fog light.