Have you ever wondered how business like UPS or FedEx pick their routes? Identifying the most efficient way to deliver packages is a massively complex mathematical problem, but all complex solutions begin as small solutions to simpler problems.
Here is a simple variation in which the shortest route from "start" to "end is in red. Drag the points around and you will see the route change. This file was created using the free GeoGebra software.
Note: lines that cross below without a point labelled can be thought of like those interstate bridges, where two roads cross without actually intersecting.
I put this same file on the web at geogebratube. Click here
UPS is in the process of rolling out a massive program to help deal with its efficiency. You can read about it at FastCompany.
Search for info on the Traveling Salesman Problem and you will be amazed at what you find.