Railway power system planners and operators need a tool for testing their designs or new timetables. This paper presents a tool for the DC traction systems, an algorithm called decoupled AC/DC load flow. The main feature of this algorithm is to separate the solution of AC and DC equations. Therefore, a minimum number of iterations is needed to avoid any convergence problems. Electrical variables of AC and DC systems as a function of time and location can be determined. In this paper, for a better presentation of the real operating conditions, i.e. the uncertainties in the timetable, the train's departure time has been considered as a random variable. The Monte Carlo simulation method has then been implemented to the AC/DC load flow algorithm in order to determine the worst operating conditions of the system. Simulation results indicate the effectiveness of the suggested AC/DC load flow algorithm, and the importance of the mentioned stochastic simulation method.