The PRT is a lost form of public transport which is basically taxis on a rail network. Just like light rail, you go to a special station to use the system. But like a taxi, you tell the system where you wish to go, wait for a small car to come pick up you and other travellers going to the same place, then the car brings you directly to your destination, navigating the grid of intersections and never stopping along the way. PRTs were thought to be the future of transport, but the high cost and complexity means it never caught on.