Many airports in the US have some sort of system to get passengers from one terminal to the other. Here are just a few examples. Pittsburgh has a train that goes from baggage claim to the concourses. Atlanta has a train that goes between all concourses. Denver has a train that goes to some of the concourses. Seattle has a train that goes to some of the concourses. A train seems to make the most sense for airport transportation. You don't need a driver, it can move lots of people very quickly, it can be put underground as to not disturb airplanes, etc.

But then there is Washington Dulles. Why does Washington Dulles International Airport have these strange looking truck/bus shuttles that take passengers from terminal to terminal? Talk about a broken system. They have to be driven by a human? They have to yield to airplanes? That's really the solution you came up with?

I think this is how it went down:
Engineer 1: "Oh crap, we built these terminals so far apart, how are people going to actually get to these things in a reasonable time?"
Engineer 2 speaks up from the back: "Ummm, maybe we should put in a train system like almost every other airport which has this problem?"
Engineer 1: "No, No, trains are for European jerks and cattle. This is America, damnit! Now, my crazy half-stepbrother's dog's owner's nephew has an idea. His company makes these ugly, giant truck/bus looking things that will work much better. He hasn't found anyone else to buy them, but I think they would be great."
Engineer 2: "Sir, with all due respect, I'd rather have dental work done with an ice skate than ride in one of those. Don't you think there is a reason all the other airports chose trains?"
Engineer 1: "You again with the trains? Ha! Hey everyone, check out the European douche in the back with his trains. Haha!"

Check out a sweet picture of these ugly POSes...