Abstract: A road/rail transport system is described and comprises rail bogies of the kind having two axles and a central bogie bolster arranged between the axles and transverse to the intended direction of travel and semi-trailers which are preferably of the kind having road wheels at the trailing ends and adapted for connection at their leading ends to a tractor unit. The rail bogie bolster has a pocket in which a mounting member is held, the pocket and mounting member having part spherical surfaces in engagement to permit limited movement of the mounting member relative to the pocket. The mounting member is adapted for releasable attachment to the frame of a semi-trailer which at one end is provided with an aperture for receiving the attachment of the mounting member and which at the other end is connectable to a similar semi-trailer so that a train may be constructed of semi-trailers and bogies with each bogie effectively supporting the weight of one semi-trailer.