Redundancy built into a road tunnel
On a typical weekday, 100,000 cars are expected to pass Norra Länken, which of course makes tremendous demands on safety and technical solutions.
"The redundancy built into a road tunnel has the task of ensuring that there is always access to information about what is happening there. If something turns wrong, there should be a back up. You should be able to view the situation through the cameras, shut off the tunnel, change the signs, send messages and so on", says Urban Wiklund, Goodtech in charge of systems installations for the construction company Tunnelentreprenad.
300 automatic activities in case of an accident
When a truck caught fire in Södra Länken (the South Link) in June 2008, the following happened:
The tunnel was closed off , as all the bars dropped down. Road signs in that part of the road got changed to lead the traffic out. The opposite direction lane was closed off to make way for the emergency services.
Tunnel ventilation was shut down and minimal smoke ventilation got started instead. The lighting got increased and guidance lighting lit. Information sign with "Evacuate the tunnel" was lit, a pre-recorded message was broadcast on the FM band, and a pre-recorded evacuation instructions were played through the speakers of the relevant parts of the tunnel.
The accident started a total of about 300 automatic activities. In Norra Länken's new tunnels, the ABB 36 kV switchgear
secures the availability of power supply and 800xA control system
ensures that all these activities are carried out.
A total of more than 14,000 objects are to be controlled or monitored, including doors, mobile phones, cameras, fire alarms, traffic signs and ventilation. And all of this is fully automated. For example, if a car stands still somewhere, the system will detect this, it send an alarm and everything can be supervised via the cameras.