If you would do this for Rail and Road, you would need to make Diagonal roads too.. not too mention diagonal waterways!
you would probably have to start working with octagons or hexagons instead of squares.
not thinking this is going to happen or if it does not in the near future
Hairysteed: Going over Diagonal Railroad would be cool i agree. Being able to go over road and rail junctions would be cool too. And being able to put signal lights under them would also be handy.
Diagonal bridges starts to mess my head up though...
There is one problem with placing signals on bridges though; imagine you have a piece of track and a railroad bridge spanning over it. You want to place a signal on that part of the bridge that overlaps the railroad underneath. How is the game supposed to figure out whether you want a signal on the bridge or under it?