loading gauge

noun loading gauges

1. UK The maximum permitted height and width for a rail vehicle, governed by clearances in tunnels, under bridges and past lineside structures. In Russia, where experiments on a considerable scale have been made with condensing, the railways have the considerable advantage of a loading gauge 17 ft. high (the biggest in the world), as compared with the British 13 ft. or slightly over.
2. A physical structure, often a metal frame above a railroad track, to check the maximum height and width of a vehicle.