One of our most interesting and complex tasks is controlling the tunnel under the Martwa Wisła river. The control system is based on Siemens Simatic S7-400-H components and the supervisory SCADA WinCC system. It is a redundant system at every level and at every layer. Starting from redundant CPUs located on both sides of the river, through I / O redundancy ET200M on redundant Profibus buses, to SCADA redundancy and cooperation with external environments of intelligent vision cameras, fire protection systems, induction loops in roads and many others. For the tunnel, an environment has been implemented that allows the simulation of several dozen different scenarios, reactions to various events in the tunnel. The simulation is performed live on SCADA panels. The activation of a given scenario takes place automatically in cooperation with the operator, but it can also be implemented manually by an authorized operator.