Design Proposal - Low Cost Location System

One of the problems we are facing with the small scale project is locations. I have thought of a back up solution in the case where a miniaturized GPS system that our controls team is researching may fail. We would like to have wireless triangulation for the carts to find their position on the track, however if that is not possible we would then need some way to locate the carts to determine the route it will have to travel. This is a design I thought of in the shower, and its pretty basic as the sketch shows the placement of bar codes and the process the system would take for each cart to locate itself on the track.

Starting with the hardware diagram, there will be a laser or a light source that will illuminate the bar code and then have the information read by a sensor. The bar code is designed with a piece of foil to signal the beginning of a bar code read, then the cart would take a measurement every unit of time derived from the length of time it read the high signal from the foil and the carts velocity. This is then interpreted as a binary number, converted to an integer and then that information is relayed back to the command center as a track piece location on the grid. The central computer would then calculate its fastest route and give information to the cart as it moves along the track.