Well, to keep it real looking, you would want to avoid any kind of tubular track; just too wide at the top. Lay your track without ballast, then put down the roadway to the outside edges of the track. Cut narrow pieces to fit between the rails, being sure to leave enough space for wheel flanges on each inside. Any kind of curve, switch or crossing built into the roadway will also call for special "road" work. Just remember that street height has to match track height for the project to look good.
Chuck
