Interruptions can be caused by many reasons, but some of the more common ones are stalls, stops, separations, or derailments. And within categories such as these there can be many types. For example, a locomotive may stall due to mechanical issues.
This can be costly to network performance. The ripple effect of a stall can take many hours or days to work itself out of the system. A key performance metric for the industry is “system velocity” – the average speed at which freight moves across the network.