The invention relates to an expansion joint (10) for connecting regions of a rail-based grid storage system (50, 50', 50"; 104, 104', 104"), the expansion joint (10) comprising:
- a first rail element (12) and a second rail element (11), the rail elements (12, 11) being elongate and configured to slide relative to one another in a longitudinal direction in a junction area where they overlap,
- the expansion joint (10) having a profiled upper surface that defines one or more tracks (27', 27") for supporting container handling vehicles (200, 300, 400), the tracks (27', 27") extending from the first rail element (12) through the junction area to the second rail element (11), wherein in the junction area, each rail element (11, 12) provides a portion of the or each track (27', 27") of the profiled upper surface so that there is a transition extending along the expansion joint (10) from the first rail element (12) to the second rail element (10) for the or each track (27', 27"). The invention further relates to an automated storage and retrieval system comprising said expansion joint (10) and a method of connecting regions (50, 50', 50"; 104, 104', 104") of a rail-based grid storage system and/or delivery rail system using one or more of the expansion joints (10)