line up

To line up is to position all switches and signals along a route so that a train can move safely from its starting point to its destination. In railway operations, this means manually or automatically throwing switch points to align the rails, ensuring the train will follow the intended track rather than an adjacent line. The switches must be set before the train approaches; once it is moving, the switches remain locked in position to prevent dangerous derailment.

The process varies by signalling system and yard layout. In traditional manual yards, a dispatcher or switchman walks or drives along the track to physically throw lever-operated switches. Modern railways use interlocking machines or computerised systems that set multiple switches in sequence, often triggered by a single operator command. The system will not permit signal clearance until every switch in the route is correctly positioned and mechanically confirmed in place.

Switches, signals, and safety

A lining up procedure checks far more than just switch position. The dispatcher must ensure that no conflicting movements are authorised elsewhere on the same track section; that point heaters are working in winter conditions; and that any portable derails or portable switches are removed from the route. If a switch fails to move or lock properly, the system prevents signal clearance and alerts the operator to the fault, rather than allowing a train to proceed along an uncertain path.

The term is used across freight, passenger, and shunting operations, though the scale differs sharply. Lining up a route through a ten-track marshalling yard with multiple converging lines may involve dozens of switches; lining up a single-track rural branch line may involve only one or two. In either case, the act of lining up is the critical moment between planning a movement and executing it.