Boston Science Museum Exhibit (Score 1)

I remember a few years back there was an exhibit on precicely this at the Boston Museum of Science. They had a four-wheeled car though, rather than three. One could sit in it and pedal it back and forth along a short piece of track they had constructed. I was extremely surprised at how well it worked and how smooth it was. It would have been impossible to tell that it wasn't a wheel on flat pavement without looking at it. A nifty trick indeed.