The Gotthard Base Tunnel opens on June 1, 2016. Generally nobody is allowed to stay in the tunnel anymore. In order to prevent accidents when necessary maintenance work is performed and sections are blocked for the trains, the doors in the cross passages are monitored by the control system. If a door opens, train operation is stopped immediately. Each subsection from the sliding doors in the cross passages, to the emergency stops and the 50 Hz power supply is controlled by an independent control system. So-called head computers read the data from the local programmable logic controllers (PLC) and prepare it for the control systems, which are integrated in the tunnel and railway control technology. The information of the head computers is transferred to the higher-level tunnel control system.