A railway traction vehicle comprising: - a plurality of axles; - a power unit adapted to generate at least a part of the vehicle's traction power using fuel gas; - a fuel gas storage assembly adapted to provide fuel gas to the power unit and including a predetermined number of fuel gas storage modules; and - a fuel gas delivery network for delivering fuel gas from the fuel gas storage assembly to the power unit, wherein: • the fuel gas storage assembly comprises: - a plurality of identical fuel gas storage module receiving devices, each receiving device being adapted to receive one fuel gas storage module; and - for each of said receiving devices, an identical fuel gas coupling for coupling a fuel gas storage module received in the receiving device with said fuel gas delivery network, • said fuel gas storage modules: - share a standardised configuration such that each of them can be received in any of said receiving devices and coupled to the corresponding fuel gas coupling, and - are distributed over said fuel gas storage module receiving devices such that the load on the railway traction vehicle's axles is optimised, and • said predetermined number of fuel gas storage modules is adapted to the amount of fuel gas needed by the railway traction vehicle to operate on a predetermined railway line, characterised by a guiding arrangement, preferably including two parallel guide rails, in which the receiving devices are displaceably guided. - a plurality of axles; - a power unit adapted to generate at least a part of the vehicle's traction power using fuel gas; - a fuel gas storage assembly adapted to provide fuel gas to the power unit and including a predetermined number of fuel gas storage modules; and - a fuel gas delivery network for delivering fuel gas from the fuel gas storage assembly to the power unit, • the fuel gas storage assembly comprises: - a plurality of identical fuel gas storage module receiving devices, each receiving device being adapted to receive one fuel gas storage module; and - for each of said receiving devices, an identical fuel gas coupling for coupling a fuel gas storage module received in the receiving device with said fuel gas delivery network, - a plurality of identical fuel gas storage module receiving devices, each receiving device being adapted to receive one fuel gas storage module; and - for each of said receiving devices, an identical fuel gas coupling for coupling a fuel gas storage module received in the receiving device with said fuel gas delivery network, • said fuel gas storage modules: - share a standardised configuration such that each of them can be received in any of said receiving devices and coupled to the corresponding fuel gas coupling, and - are distributed over said fuel gas storage module receiving devices such that the load on the railway traction vehicle's axles is optimised, and - share a standardised configuration such that each of them can be received in any of said receiving devices and coupled to the corresponding fuel gas coupling, and - are distributed over said fuel gas storage module receiving devices such that the load on the railway traction vehicle's axles is optimised, and • said predetermined number of fuel gas storage modules is adapted to the amount of fuel gas needed by the railway traction vehicle to operate on a predetermined railway line,