Editing Loading gauge (section)

== Structure gauge ==
{{Main|Structure gauge}}
[[File:2014 Replacement of New Road Bridge, Milton Ernest, Bedfordshire.png|thumb|right|Increasing the structure gauge can involve substantial work. The UK's [[Midland Main Line]] being upgraded in 2014.]]

The structure gauge, which refers to the dimensions of the lowest and narrowest bridges or tunnels of the track, complements the loading gauge, which specifies the tallest and widest allowable vehicle dimensions. There is a [[Engineering tolerance#Clearance (civil engineering)|gap]] between the structure gauge and loading gauge, and some allowance needs to be made for the dynamic movement of vehicles (sway) to avoid mechanical interference causing equipment and structural damage.