A transportation system including a tubular rail assembly, a displacement device with at least one helical propulsion system located in a first position to be received in one rail and movable to a second position to be received in another rail, a switching mechanism engaged to each propulsion system for movement between the first and second positions, and a transportation device outside of the rail assembly and attached to the displacement device. Also, a displacement device with at least one pair of support members each supporting a helical propulsion system, and a biasing member circumferentially biasing the support member of each pair in opposite directions. Also, a displacement device with at least one tubular support member surrounding the body and circumferentially movable with respect thereto and supporting a set of angled wheels, and a switching mechanism engaged to each member for actuating the circumferential movement.