This is a Minecart Station I have built often in terrain to travel between buildings in a huge world.
It's quite simple to build and can be modified a great deal and still work great.

How it works:
Get in to the minecart, click one of the 4 buttons (they determine the destination and launches the minecart).

I don't want to bore you with all the technical stuff that prevents it to bug etc...
download it and try it out instead.