Rail Capacity Is Terminal Dwell

01The evidence

• Lean railroading work has identified classification terminal performance as the bottleneck in freight rail, with dwell time determining how much traffic the network can absorb.Transportation Research Board
• Track capacity studies note that stations with long dwell times can require additional tracks to match line capacity, which places the constraint at the interface rather than on the line.National Academies

02The tension

Rail capacity is planned in train paths per day, derived from track and signalling. Terminals are treated as fixed constraints. When demand rises, the response is to add track, and the queue persists because the bottleneck was never the line.

03The theory

A wagon only generates revenue when it moves. Time spent in a yard is capacity consumed without output, and a terminal that holds wagons for a day removes them from the network for that day at both ends.

If dwell dominates, then throughput should scale with terminal cycle time rather than with track length, and improvements in classification should raise capacity more than equivalent track investment.

The prediction is that network throughput should correlate with terminal dwell better than with track mileage, and that reducing dwell should increase capacity without new construction.

The practical consequence is that capacity planning should model terminals as the constraint and that investment should be directed at classification automation and yard layout.

04What this is not

05Predictions

• P1Network throughput should correlate with terminal dwell better than with track mileage.
• P2Reducing dwell should raise capacity without new track.
• P3Yard investment should outperform line investment per unit cost.

06What would refute it

Throughput tracking track capacity at controlled dwell would restore the line model.

07What it would change

It would redirect rail investment toward yards and classification.