An automated storage and retrieval system comprising: - a track system comprising a first set of parallel tracks arranged in a horizontal plane and extending in a first direction, and a second set of parallel tracks arranged in the horizontal plane and extending in a second direction which is orthogonal to the first direction, said first and second sets of tracks (10, 11) forming a grid pattern in the horizontal plane comprising a plurality of adjacent grid cells, each grid cell comprising a grid opening defined by a pair of neighboring tracks (10a, 10b) of the first set of tracks and a pair of neighboring tracks (11a, 11b) of the second set of tracks; - a plurality of storage columns each column being arranged to store a respective stack of storage containers wherein the storage columns are located beneath the track system, wherein each storage column is located vertically below a grid opening; - a plurality of container handling vehicles for lifting and moving storage containers stacked in the stacks, each container handling vehicle being configured to move on the track system above the storage columns, - a plurality of port columns, each port column forming a downwards vertical projection of a grid opening through which the container handling vehicles can drop off and pick up storage containers, - an access station, - a first continuous conveyor being adapted to transport storage containers to an access station, and - a second continuous conveyor being adapted for transporting storage containers from the access station, characterised in that the system comprises a plurality of relay modules arranged in series for relaying storage containers between the plurality of port columns and the access station, each relay module being arranged below its own respective port column, and comprising; - a port station for receiving storage containers dropped off from and to be picked up through its respective port column, - a first conveyor and a second conveyor, arranged at a side of the port station, - a lateral displacement device that is arranged for transporting storage containers between the port station and the first conveyor, and between the second conveyor and the port station, wherein the first conveyors of each of the plurality of replay modules cooperate to form the first continuous conveyor, and wherein the second conveyors of each of the plurality of relay modules cooperate to form the second continuous conveyor. - a track system comprising a first set of parallel tracks arranged in a horizontal plane and extending in a first direction, and a second set of parallel tracks arranged in the horizontal plane and extending in a second direction which is orthogonal to the first direction, said first and second sets of tracks (10, 11) forming a grid pattern in the horizontal plane comprising a plurality of adjacent grid cells, each grid cell comprising a grid opening defined by a pair of neighboring tracks (10a, 10b) of the first set of tracks and a pair of neighboring tracks (11a, 11b) of the second set of tracks; - a plurality of storage columns each column being arranged to store a respective stack of storage containers wherein the storage columns are located beneath the track system, wherein each storage column is located vertically below a grid opening; - a plurality of container handling vehicles for lifting and moving storage containers stacked in the stacks, each container handling vehicle being configured to move on the track system above the storage columns, - a plurality of port columns, each port column forming a downwards vertical projection of a grid opening through which the container handling vehicles can drop off and pick up storage containers, - an access station, - a first continuous conveyor being adapted to transport storage containers to an access station, and - a second continuous conveyor being adapted for transporting storage containers from the access station, characterised in that the system comprises a plurality of relay modules arranged in series for relaying storage containers between the plurality of port columns and the access station, each relay module being arranged below its own respective port column, and comprising; - a port station for receiving storage containers dropped off from and to be picked up through its respective port column, - a first conveyor and a second conveyor, arranged at a side of the port station, - a lateral displacement device that is arranged for transporting storage containers between the port station and the first conveyor, and between the second conveyor and the port station, - a port station for receiving storage containers dropped off from and to be picked up through its respective port column, - a first conveyor and a second conveyor, arranged at a side of the port station, - a lateral displacement device that is arranged for transporting storage containers between the port station and the first conveyor, and between the second conveyor and the port station, wherein the first conveyors of each of the plurality of replay modules cooperate to form the first continuous conveyor, and wherein the second conveyors of each of the plurality of relay modules cooperate to form the second continuous conveyor.