They may be out of scale, but they're fun! Here's a diagram explaining how to wire a Fastrack straight to run a postwar highway crossing flasher (Lionel 154, Marx 421 et cetera)...
1) Mark the track where you want to cut the insulating gaps.
2. Undo the tabs underneath and pull the rail from the base.
3. Solder wires to the rail. It's easier to do this before cutting the gaps.
4. Cut the gaps using a motor tool, saw or whatever you have handy. I don't recommend teeth, unless you share a dentist with Richard "Jaws" Kiel. 
5. Before reinstalling the rail, drill holes in the roadbed for the wires.
6. Reinstall the rail. Epoxy and clamp to the roadbed as needed.
The finished track. The red wire goes to the center rail, or, if you have a common ground, the accessory terminal.
And here's the track in action!
Mitch
