In one embodiment, a sortation system has a conveyor system and mobile drive units. The conveyor system has a conveyor surface that carries payloads along a direction that extends from a first conveyor end to a second conveyor end. The conveyor system has support structure that supports the conveyor surface above a floor so as to define a space between the conveyor surface and the floor. The space is sized so that the mobile drive units can drive under the conveyor surface towards the second conveyor end. The conveyor system has sensors supported that are positioned to detect positions of the mobile drive units under the conveyor surface. The conveyor system moves at least a portion of the conveyor surface based on the sensors detecting the presence of each mobile drive unit so as to synchronize movement of the payloads from the conveyor surface to the mobile drive units.