if youre doing tokyo, please add SEVERAL touge tracks
they can span a huge mountain and be interconnected by side streets
make each touge track unique, one relatively open not too crazy, one tight technical, many hairpins, and one with elevation changes.
each touge track should have its own style; walls, gutters, sheer drop offs, guard rails, you name it. They should each also have a unique feature like a lane split or a bridge or a tunnel or a hazard or something.
If the setting is tokyo, maybe even reward players for just driving the touge over and over again as practice. its where a lot of people race naturally, and organically.