Abstract: An articulated ramp assembly is mounted in housing (22) fixed beneath floor (108) and aligned with a door opening of vehicle (100). Ramp body (12) is articulated along its length and movable along a predetermined trajectory path between an extended position and a retracted position by drive arrangement (20). In the extended position, ramp body (12) extends from floor (108) to ground (106), and in the retracted position, ramp body (12) is contained within housing (22). Drive arrangement (20) includes a reversible motor coupled to an endless chain drive (24) having sprockets (26-44) for moving ramp body (12) along a guide (48) to follow the trajectory path.