Large Airplane Ground Operations Simulator (LAGOS), the Boeing taxi rig for the 777, at Paine Field (PAE) in February 1994.
The self-propelled rig was built to test the wheel geometry of the B-777-300.
Sauce & moar: https://airfactsjournal.com/2020/08/the-strangest-45-minutes-in-my-logbook/
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