Road Tunnels Manual
Manual call points (also named Alarm pushbuttons) allow a user to send an alarm to the control-command centre in case of an incident in a tunnel. These manual call points are not very expensive so they can be installed at frequent intervals, typically every 25m to 50m.
These devices are not often activated by tunnel users because users tend to prefer using emergency call stations (emergency telephones) that provide real-time audio conversations with an operator. Manual call points do not provide real-time feed back to the user.