When a serious event (accident, fire, etc.) occurs in a tunnel, it must be possible to prevent users from entering as they risk encountering a potentially dangerous situation.
Devices are therefore used to warn users who are outside that the tunnel is closed and/or prevent them from entering.
In many countries, experience shows that if the tunnel is closed simply by means of a stop signal placed in front of the entrance, it is not always 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 (Fig.1)
The tunnel closure device can be activated from the control-command centre or automatically in tunnels that are not monitored continuously. Some road authorities also mandate that a ground responder has to be deployed at the tunnel entrance before the barrier can be safely lowered.
The closure device is meant for use in emergency situations but it can also be used in other situations, particularly during scheduled closures for maintenance interventions.