As much as I appreciate the guy, I don't think he thought this one through. A simple back of the envelope calculation would reveal just how hard it is to compete with a subway in terms of people per hour for a given width of road/track. Even bicycles, which are pretty compact, still need a safe stopping distance which wrecks the space efficiency. If you eliminate the stopping distances you probably also want to connect the vehicles to reduce crashes, and tada, it's a train.