banking

Banking is the addition of one or more locomotives to the rear of a train to provide extra tractive effort on steep grades. The assisting locomotive, called a banker or banking engine, couples or remains in close contact with the train and pushes from behind while the lead locomotive pulls from the front. This distributed power allows heavier loads or faster speeds to be maintained on inclines that would otherwise require the train to reduce tonnage or crawl at minimal speed.

The practice became standard on railways with significant altitude changes, particularly in mountainous regions. British railways used banking extensively on lines like the Settle-Carlisle route and the approaches to Shap Summit. A banker might assist for a few miles or for an entire mountain section, depending on the grade, the tonnage of the train, and the power of the leading locomotive. Once the summit was passed, the banker would detach and return downhill, sometimes assisting other trains in descent or running light back to the depot.

Variants and application

Banking differs from banking in the sense of train dynamics (where a curve is tilted to reduce derailment risk). On very steep grades, particularly narrow-gauge mountain railways, even two or three bankers might work together. Some railways used dedicated banker locomotives optimized for low-speed, high-power operation rather than line-haul work. The banker typically operated without passengers and could be of older or smaller class than the main locomotive, provided it had sufficient adhesive weight and tractive effort for the specific gradient.

The need for banking declined with the arrival of more powerful diesel-electric and electric locomotives. Modern freight operations occasionally use helpers on mountain grades, though this is now less common on major routes. The term remains part of railway vocabulary, particularly in heritage railways and freight operations where heavy tonnage over steep terrain is still encountered. The economics of banking involved careful scheduling, as the banker tied up locomotive resources and required crew, offsetting fuel and wear against the ability to move train tonnage that would otherwise require split working or volume reduction.