Various public address systems exist to help facilitate the evacuation of users through emergency exits, including sound beacons which can be found in certain tunnels.
These sound beacons are located in the part of the tunnel open to traffic and have the following objectives:
It is important to be able to adjust the sound level of these beacons in order to prevent reverberation phenomena and inaudibility.
The information that is announced can be:
In cross-border tunnels, announcements may be made in the language of each country on which the tunnel is located.