In the construction of a road tunnel project in Stockholm, workers’ safety underground has been buttressed by an RFID access control system together with emergency alarms linked to Tetra radios.  The aim of the Norra Länken project is to reduce the volume of traffic and noise pollution from the roads surrounding the Swedish capital by diverting traffic through new tunnels under the city. 

The safety system, from Identec Solutions and Zonith, uses RFID tags to monitor employees entering tunnel sections. In this way, safety staff can monitor how many people are in a section at any time. 

“With our RFID access control system linked to the alarm and communication system, we’re always aware of the safety level in the tunnels”, said Roger Zell, security manager at Norra Länken. “Instant emergency alarm information is key to us. With this solution, we automatically get updates in clear text on our radios and can react quickly to any emergency situation.”

Vital messages 

All construction workers and staff are individually identified to the system by their RFID tags. RFID readers are located at entrance and exit points to the tunnels.

The Tetra radios, provided as part of a system to support secure voice and data traffic, are used to display employee numbers in each location and to receive technical and critical alarm information via text messaging. Panic buttons on the radios and wall-mounted alarm points enable any employee to activate emergency evacuation alarms from anywhere within a tunnel. 

Zonith’s software is used to manage all technical and critical safety alarms. The software automatically dispatches information to the available resources over the Tetra radios via text message. Immediate action can then be taken, minimizing delays in construction. 

The Zonith Alarm Control System is installed on a server above ground. It links to remotely-located real-time control units (RTCUs) via Tetra. Each RTCU is connected to fire sensors, technical alarms and evacuation panic alarm buttons. 

When an alarm is raised, the RTCU immediately notifies the Alarm Control System, which instantly selects the safety staff from a duty roster. Staff are immediately notified with the exact emergency alarm details on their radios and managers can decide whether to order the evacuation of the tunnel or sections of tunnel.