^^ Yeah, it sort of is, but u're talking about my system currently in use. He wants a start / stop train. And that I've yet to figure out.
But the only other idea I've had and tried is a cart that is being stopped by a detector piston, and then started by having a piston place a block behind it, and then boost. ONLY problem with this is that the damn timing was a pain and it took way to much space to look any good.
Also you had to have double wires and timers setup to push / pull back the track behind the cart.
I did have a pic, but not any more. Will check in any of the backup folders if I still have the save, if so you can see the concept and perhaps make it work...