A railway traction vehicle comprising a plurality of axles, a fuel gas power unit (112), a fuel gas storage assembly (118) including a predetermined number of fuel gas storage modules (122), and a fuel gas delivery network (120). The fuel gas storage assembly (118) comprises a plurality of identical fuel gas storage module receiving devices (124), and, for each of said receiving devices, an identical fuel gas coupling (126) for coupling a module (122) with said network (120). The modules (122) share a standardised configuration such that each of them can be received in any of said receiving devices (124) and coupled to the corresponding fuel gas coupling (126). They are distributed over said fuel gas storage module receiving devices (124) such that the load on the axles is optimised. The predetermined number is adapted to the amount of fuel gas needed by the vehicle to operate on a predetermined railway line. Preferred application to regional passenger multiple units.