Payload transportation system

A method, comprising:

• providing a first FAB building and a second FAB building connected via a bridging area, wherein the first FAB building comprises a first set of fabrication tools configured to perform first plurality of fabrication processes, the second FAB building comprises a second set of fabrication tools configured to perform second plurality of fabrication processes;
• performing one or more fabrication processes of the first plurality of fabrication processes to a wafer in the first FAB building;
• configuring a first vehicle of the first FAB building to travel along a first overhead transfer (OHT) track and take the wafer to the bridging area, wherein a first portion of the first OHT is at the bridging area;
• configuring a second vehicle of the second FAB building to travel along a second overhead transfer (OHT) track and arrive at the bridging area, wherein a second portion of the second OHT is at the bridging area and in parallel with the first portion of the first OHT track;
• on condition that the first vehicle and the second vehicle are aligned and travelling at a same speed along a same direction along the first portion of the first OHT track and the second portion of the second OHT track, respectively, configuring the first vehicle to transfer the wafer to the second vehicle;
• and
• performing one or more fabrication processes of the second plurality of fabrication processes to the wafer in the second FAB building.