In a first aspect, a substrate loading station is served by a conveyor which continuously transports substrate carriers. A substrate carrier handler that is part of the substrate loading station operates to exchange substrate carriers with the conveyor while the conveyor is in motion. A carrier exchange procedure may include moving an end effector of the substrate carrier handler at a velocity that substantially matches a velocity of the conveyor. A balancing mass is coupled directly or indirectly to a frame on which the substrate carrier handler is mounted and is adapted to accelerate in a direction opposite to the direction of end effector acceleration, as the end effector accelerates. Thus, inertial loads may be substantially balanced, and frame vibration reduced, despite potentially high rates of acceleration. Numerous other aspects are provided.