Method for controlling the power supply of an electric motor of a transport vehicle during a journey along a route, the transport vehicle comprising a main source of electrical energy and a secondary source of electrical energy, the secondary source being distinct from the main source and comprising an electrical energy storage member, the electric motor being powered by at least one source out of the main source and the secondary source, the method being implemented by a controlling electronic device and comprising the following steps: - estimation of an instantaneous electrical power (P(t)) necessary to the movement of the vehicle during the journey, - determination of a frequency spectrum of the estimated instantaneous power (P(t)), - computation of a first and of a second quantities (Q 1 (t), Q 2 (t)) of electrical energy for powering the electric motor, the computation being implemented on the basis of the determined power spectrum, the first quantity (Q 1 (t)) of electrical energy being supplied by the main source and the second quantity (Q 2 (t)) of electrical energy being supplied by the secondary source, and - controlling of the main source and of the secondary source as a function respectively of the first and second computed quantities (Q 1 (t), Q 2 (t)) of electrical energy, the step of estimation of the instantaneous power (P(t)) being implemented on the basis of a default instantaneous power (P 0 (t)) corresponding to the journey along the route and of current external data, the current external data comprising at least one element out of the group consisting of: - a total weight of the vehicle, - meteorological data, such as the force of the wind and the wind direction, the presence of snow or of ice, the presence of bad weather and the location of bad weather, - the time of departure of the vehicle, and - any operating incidents, the steps of the method being implemented on the basis of a knowledge base, the knowledge base containing instantaneous powers corresponding to preceding journeys along the route, each instantaneous power being associated in the knowledge base with external data corresponding to said journey, the knowledge base containing first and second quantities corresponding to preceding journeys along the route, the computation of the first and second quantities (Q 1 (t), Q 2 (t)) being implemented on the basis of first and second quantities stored in the knowledge base. - estimation of an instantaneous electrical power (P(t)) necessary to the movement of the vehicle during the journey, - determination of a frequency spectrum of the estimated instantaneous power (P(t)), - computation of a first and of a second quantities (Q 1 (t), Q 2 (t)) of electrical energy for powering the electric motor, the computation being implemented on the basis of the determined power spectrum, the first quantity (Q 1 (t)) of electrical energy being supplied by the main source and the second quantity (Q 2 (t)) of electrical energy being supplied by the secondary source, and - controlling of the main source and of the secondary source as a function respectively of the first and second computed quantities (Q 1 (t), Q 2 (t)) of electrical energy, - a total weight of the vehicle, - meteorological data, such as the force of the wind and the wind direction, the presence of snow or of ice, the presence of bad weather and the location of bad weather, - the time of departure of the vehicle, and - any operating incidents,