Abstract: This invention is a freight and mass transit system which utilizes a road-rail adaptive vehicle. The adaptive vehicle is self-powered, and, with its power unit intact, is able to travel both on roads and on rails. In one embodiment, the adaptive vehicle loads easily and rides securely on a flat-bed type rail car. In another embodiment, the wheels or axles of the vehicle adapt to cooperate with the rail-line rails for traction and guidance, and the vehicle rides directly on the rails. Preferably, the rail version of the adaptive vehicle is connectable with other similar vehicles, so that a set of adaptive vehicles may travel like a train down the rails. Also, preferably, the rail version of the adaptive vehicle is connectable with the freight and passenger compartments of other similar vehicles, so that passengers may move from one adaptive vehicle to another in order to make their necessary travel connections during the rail transit.