A method for determining the required freight wagon fleet based on seasonal unevenness and wagon compatibility with cargo types

Determining the rational size and structural composition of the freight wagon fleet is essential for sustaining railway operational stability and capital efficiency. Conventional planning approaches either sum individual peak commodity demands – causing artificial fleet overestimation – or aggregate all network flows into a single pool, which overlooks physical wagon–cargo compatibility constraints. This study develops an analytical methodology that integrates the seasonal unevenness of monthly cargo loadings with the technical boundaries of wagon interchangeability. Commodities are categorised into closed interchangeability groups based on suitable wagon types. Monthly wagon requirements are computed for each group, and the maximum simultaneous demand over a 12-month horizon is selected as the required working fleet. The required inventory fleet is derived by incorporating reserve and repair shares. The methodology was tested on the railway network of JSC ‘Uzbekistan Railways’ across 14 cargo types and 9 wagon categories. The required working fleet determined by interchangeability groups was 26,569 wagons. Summing individual cargo maxima overstated the requirement by 907 wagons (3.4%), whereas network-wide aggregation understated it by 1,972 wagons (7.4%). Accounting for maintenance shares resulted in a required inventory fleet of 29,763 wagons against an available fleet of 22,494 wagons, revealing an overall deficit of 7,269 units and a structural imbalance index of 29.9%. Sizing the fleet within technical interchangeability groups eliminates aggregation biases and provides precise decision support for targeted procurement, leasing and modernisation of rolling stock.

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