Describing a section of track where tunnels, bridges, platforms, or adjacent structures encroach on the standard loading envelope. Equipment routed through these areas must be measured carefully to ensure it will not strike lineside infrastructure. Routing systems flag these corridors to keep high-cube boxcars, double-stack trains, and oversized loads out.
Heard on the job
We've to route that transformer over the northern sub because the old tunnel makes the main line gauge-restricted.
Insider tip
Dispatchers rely on computerized clearance bureaus to catch gauge restrictions before a train ever departs the yard.