The method of nested simulations supporting decision-making process within a mesoscopic railway simulator

Abstract

While executing stochastic simulations, some unexpected (conflict) situations may occur thanks to which it is not possible to continue with the simulation in appliance to prescribed rules and it is necessary to decide on an alternative solution. There is a variety of tools for supporting the decision-making activities – methods of operational research, heuristic methods, etc. Another method is based on nested simulations with which the solution of a problem is searched using recursive simulations making a limited outlook into the future. At the moment when the problem occurs, alternative scenarios are created and simulated. After a certain period of time the nested simulations are stopped, their results are evaluated, the most suitable solution is selected and then the simulation continues in compliance with that solution. This contribution describes the issue of decision-making support in simulators, and it focuses mostly on the description of the method of nested simulations.