Storage and retrieval system for containers comprising: a grid structure having a large number of grid cells, wherein each grid cell defines a storage column of a container storage structure which is arranged below the grid structure, wherein the storage columns are configured to each receive a vertical stack of containers , and wherein the grid structure defines longitudinal transport paths in a longitudinal direction (x) and transverse transport paths in a transverse direction (z), and at least one transport vehicle comprising a vehicle body , means for receiving, transporting and depositing containers which are stored in the container storage structure, a chassis which is connected to the vehicle body , wherein the chassis comprises two x wheel sets which are configured for movement of the transport vehicle along longitudinal transport paths in a longitudinal direction (x), and wherein the chassis comprises two z wheel sets which are configured for movement of the transport vehicle along transverse transport paths in a transverse direction (z), and a wheel positioning mechanism which is configured to selectively bring either the wheels of the x wheel sets into contact with the longitudinal transport paths or the z wheel sets into contact with the transverse transport paths in order to thus enable a movement of the transport vehicle either in the longitudinal direction or in the transverse direction, characterised in that the wheel positioning mechanism has four drive means each having a motor , wherein the drive means together act in each case on the wheels of a wheel pair, wherein a wheel pair in each case comprises a wheel of an x wheel set and a wheel of a z wheel set which is diagonally adjacent thereto, wherein a wheel set (2, 2'; 3, 3') comprises two wheels (2a, 2b, 2'a, 2'b; 3a, 3b, 3'a, 3'b) which are arranged adjacent to each other on a respective side wall of the vehicle body . a grid structure having a large number of grid cells, wherein each grid cell defines a storage column of a container storage structure which is arranged below the grid structure, wherein the storage columns are configured to each receive a vertical stack of containers , and wherein the grid structure defines longitudinal transport paths in a longitudinal direction (x) and transverse transport paths in a transverse direction (z), and at least one transport vehicle comprising a vehicle body , means for receiving, transporting and depositing containers which are stored in the container storage structure, a chassis which is connected to the vehicle body , wherein the chassis comprises two x wheel sets which are configured for movement of the transport vehicle along longitudinal transport paths in a longitudinal direction (x), and wherein the chassis comprises two z wheel sets which are configured for movement of the transport vehicle along transverse transport paths in a transverse direction (z), and a wheel positioning mechanism which is configured to selectively bring either the wheels of the x wheel sets into contact with the longitudinal transport paths or the z wheel sets into contact with the transverse transport paths in order to thus enable a movement of the transport vehicle either in the longitudinal direction or in the transverse direction, characterised in that the wheel positioning mechanism has four drive means each having a motor , wherein the drive means together act in each case on the wheels of a wheel pair, wherein a wheel pair in each case comprises a wheel of an x wheel set and a wheel of a z wheel set which is diagonally adjacent thereto, wherein a wheel set (2, 2'; 3, 3') comprises two wheels (2a, 2b, 2'a, 2'b; 3a, 3b, 3'a, 3'b) which are arranged adjacent to each other on a respective side wall of the vehicle body . <EOS>