A belt-driven transportation system including a first set of pulleys rotatably attached to a first member and a second set of pulleys rotatably attached to a second member. The first and second members have relative movement to each other. The system further includes a unitary belt that is guided through a path defined by the first and second sets of pulleys with the path substantially lying in a stationary plane, and a plurality of retention rollers. A retention roller is disposed adjacent each pulley, with the belt extending about the pulley and between the pulley and the retention roller. The positioning of the belt substantially on the path is maintained by the plurality of retention rollers, and the first and second members are moved relative to each other with changes in the length of the path.