A sample tube transport system comprising: a track adapted to provide a path for one or more carriers between a plurality of modules; at least one upper conveyor system comprising: a first upper pulley configured to rotate around a first axis; a second upper pulley spaced horizontally from the first upper pulley and configured to rotate around a second axis; an upper belt located adjacent the track and configured to wrap around the first upper pulley and around the second upper pulley; and a plurality of upper magnets affixed to the upper belt, each of the plurality of upper magnets being positioned to attract the one or more carriers for moving the one or more carriers along the track adjacent the upper belt; and at least one lower conveyor system comprising: a first lower pulley spaced vertically below the first upper pulley and configured to rotate around the first axis; a second lower pulley spaced horizontally from the first lower pulley and configured to rotate around a third axis; a lower belt spaced vertically below the upper belt, located adjacent the track and configured to wrap around the first lower pulley and around the second lower pulley; and a plurality of lower magnets affixed to the lower belt, each of the plurality of lower magnets being positioned to attract the one or more carriers for moving the one or more carriers along the track adjacent the lower belt, and wherein the upper and lower conveyor systems (110, 114) are adjacent to different parts of the track and the first, second and third axes (120, 122, 132) are vertical. a track adapted to provide a path for one or more carriers between a plurality of modules; at least one upper conveyor system comprising: a first upper pulley configured to rotate around a first axis; a second upper pulley spaced horizontally from the first upper pulley and configured to rotate around a second axis; an upper belt located adjacent the track and configured to wrap around the first upper pulley and around the second upper pulley; and a plurality of upper magnets affixed to the upper belt, each of the plurality of upper magnets being positioned to attract the one or more carriers for moving the one or more carriers along the track adjacent the upper belt; and a first upper pulley configured to rotate around a first axis; a second upper pulley spaced horizontally from the first upper pulley and configured to rotate around a second axis; an upper belt located adjacent the track and configured to wrap around the first upper pulley and around the second upper pulley; and a plurality of upper magnets affixed to the upper belt, each of the plurality of upper magnets being positioned to attract the one or more carriers for moving the one or more carriers along the track adjacent the upper belt; and at least one lower conveyor system comprising: a first lower pulley spaced vertically below the first upper pulley and configured to rotate around the first axis; a second lower pulley spaced horizontally from the first lower pulley and configured to rotate around a third axis; a lower belt spaced vertically below the upper belt, located adjacent the track and configured to wrap around the first lower pulley and around the second lower pulley; and a plurality of lower magnets affixed to the lower belt, each of the plurality of lower magnets being positioned to attract the one or more carriers for moving the one or more carriers along the track adjacent the lower belt, and wherein the upper and lower conveyor systems (110, 114) are adjacent to different parts of the track and the first, second and third axes (120, 122, 132) are vertical. a first lower pulley spaced vertically below the first upper pulley and configured to rotate around the first axis; a second lower pulley spaced horizontally from the first lower pulley and configured to rotate around a third axis; a lower belt spaced vertically below the upper belt, located adjacent the track and configured to wrap around the first lower pulley and around the second lower pulley; and a plurality of lower magnets affixed to the lower belt, each of the plurality of lower magnets being positioned to attract the one or more carriers for moving the one or more carriers along the track adjacent the lower belt, and wherein the upper and lower conveyor systems (110, 114) are adjacent to different parts of the track and the first, second and third axes (120, 122, 132) are vertical.