Keep radiation. It's a big part of Fallout.
what about highlighted grids, maybe if you have a Geiger counter in inventory or in one of your hand/weapon slots?
If you have one on you, areas of radiation show up on your world map highlighted so you know it's going to be getting pretty hot soon if you don't move.
It seems like the best way to find out where is radiated and where isn't is to wander into it, and as your face peels off, say to yourself "Hmm, yes, this area's full of it. Shouldn't go here anymore in the futureahaghahgsdjgbjghhsngs..."
Just ought to say, because when almost anyone suggests anything all you get is "lol new players dun know shit" etc.
I know what areas are radioactive. I'm just suggesting an additional use for Geigers. I mean that's how they work IRL (almost).