Abstract: The disclosure relates to an indicator assembly for use in push-back storage systems, comprising a rail having an indicator portion comprising an opening therethrough and an indicator mounted at the indicator portion. When a cart wheel rollingly engages the indicator portion, the indicator is triggered thereby providing an indication of passage of the wheel over the indicator portion. The disclosure also relates to a rail cleaning assembly comprising a frame configured to be mounted to a cart wheel that rollingly engages a rail along the length of the rail; and at least one cleaning element positioned to engage the rail, thereby removing debris accumulated on the rail as the wheel rollingly engages the rail.