When a serious event (accident, fire, etc.) occurs in a tunnel, it must be possible to prevent at an early stage the users from entering into the tunnel. In fact, a device preventing efficiently and rapidly entry into the tunnel can allow not sending into a potentially dangerous situation users who are outside and will also help prevent further accidents underground.
In many countries, experience shows that if the tunnel is closed simply by means of a stop signal placed outside before the entrance, it is not quite effective. Therefore, this stop signal is often combined with barriers and variable message signs allowing the users to be informed of the reasons for closure.
The device closing the tunnel can be activated from the control-command centre or automatically in tunnels that are not monitored continuously.
The closing device is meant for being used in emergency situations but it can also be used in other situations, particularly during scheduled closures for maintenance interventions.