The wikipedia page on some of the considerations is a good introduction on where the real world goes beyond this:

https://en.wikipedia.org/wiki/Geometric_design_of_roads

It's tempting to think that the cross-section geometry of a road only applies in three dimensions and can be elided for 2D overheads, but the parabolas that smoothly connect straights and curves in the overhead perspective are often subtly warped to permit any requirements of cant and superelevation.