Method for monitoring a power supply device of a traffic system, in which a computer-based model of the power supply device is inter alia created with the aid of predetermined parameters relevant to the power supply device, characterised in that at least one current characteristic quantity, which is used to simulate the power supply device, is determined with a detection device, and at least one current characteristic value, which is used as a current comparison value relating to at least one characteristic value (KG3, KG4) calculated in the simulation, is determined with a detection device during ongoing operation of the traffic system, wherein the characteristic quantities are for instance a current timetable, current data of the rail vehicles or GPS positions or also current switching states, and wherein the characteristic values are for instance electrical characteristic values such as power, voltage and variables which can be derived therefrom, so that the operation of the power supply device is simulated at least with the aid of the model and the at least one characteristic quantity, - and consequentially the at least one calculated characteristic value (KG3, KG4) is compared with the at least one currently determined characteristic value in a current region, - and further consequentially at least one future characteristic value is precalculated with the aid of the simulation at least in a desired future time period, and the at least one precalculated future characteristic value is compared with at least one predetermined limit value in a preview area and - on the basis of the comparison results in the current region and the preview area with the aid of the simulation, stipulations for the future operation of the traffic system are calculated and when the at least one limit value is reached and/or exceeded, at least one warning message is automatically output and/or at least one measure, for instance the driving behaviour of the trains, is automatically introduced in an influential manner by way of an automatic train control. characterised in that at least one current characteristic quantity, which is used to simulate the power supply device, is determined with a detection device, and at least one current characteristic value, which is used as a current comparison value relating to at least one characteristic value (KG3, KG4) calculated in the simulation, is determined with a detection device during ongoing operation of the traffic system, wherein the characteristic quantities are for instance a current timetable, current data of the rail vehicles or GPS positions or also current switching states, and wherein the characteristic values are for instance electrical characteristic values such as power, voltage and variables which can be derived therefrom, so that the operation of the power supply device is simulated at least with the aid of the model and the at least one characteristic quantity, - and consequentially the at least one calculated characteristic value (KG3, KG4) is compared with the at least one currently determined characteristic value in a current region, - and further consequentially at least one future characteristic value is precalculated with the aid of the simulation at least in a desired future time period, and the at least one precalculated future characteristic value is compared with at least one predetermined limit value in a preview area and - on the basis of the comparison results in the current region and the preview area with the aid of the simulation, stipulations for the future operation of the traffic system are calculated and when the at least one limit value is reached and/or exceeded, at least one warning message is automatically output and/or at least one measure, for instance the driving behaviour of the trains, is automatically introduced in an influential manner by way of an automatic train control. - and consequentially the at least one calculated characteristic value (KG3, KG4) is compared with the at least one currently determined characteristic value in a current region, - and further consequentially at least one future characteristic value is precalculated with the aid of the simulation at least in a desired future time period, and the at least one precalculated future characteristic value is compared with at least one predetermined limit value in a preview area and - on the basis of the comparison results in the current region and the preview area with the aid of the simulation, stipulations for the future operation of the traffic system are calculated and when the at least one limit value is reached and/or exceeded, at least one warning message is automatically output and/or at least one measure, for instance the driving behaviour of the trains, is automatically introduced in an influential manner by way of an automatic train control.