The world’s safest tunnel

The world’s safest tunnel :The Fehmarnbelt Fixed will not only be the world’s longest for combined rail and road transport, it will also be the safest. The high safety requirements also apply to the two contracts for the electrical and mechanical installations (E&M) and the establishment of a substation for the tunnel’s power supply, which Femern A/S will announce shortly.

One of the most important safety requirements for the future link stipulates that a car or train journey through the tunnel must be at least as safe as a car or train journey on a conventional road or rail line. Steen Lykke, Technical Director at Femern A/S, explains the necessary implications:

“The immersed tunnel under the Fehmarnbelt sets new standards in terms of safety. There will be no oncoming traffic, no approaches and exits and no disruptions caused by bad weather or darkness. Automatic ventilation systems will permanently ensure air quality and visibility in the tunnel. Both road tubes will have an emergency lane and the entire tunnel will be constantly monitored by means of a comprehensive monitoring and traffic control system, including dynamic signs and radio communication, so that drivers can remain informed during their journey or in the event of an accident. Approximately every 100 m, emergency exits to a safe adjacent tunnel tube will be located and there will be emergency stations with fire-fighting equipment and direct telephones to the control centre. We introduce a system of longitudinal ventilation in a very long tunnel, combined with active fire extinguishing, including sprinkler or water-spray extinguishing systems. This solution will enhance safety in case of fire considerably. All these measures show, that safety is a top priority for us,” says Steen Lykke.

The cornerstones of the tunnel’s safety concept include the prevention of accidents, the mitigation of accidents and the rescue of anyone caught up in a potential accident.

Accident prevention
The tunnel design and technical concept specifically aim at preventing accidents. Neither in the road or rail tubes will there be oncoming traffic. Moreover, the entire traffic operation in the tunnel will be monitored around the clock by a separate traffic control centre and CCTV cameras. An intelligent traffic management and monitoring system will automatically detect any abnormal incident and will trigger an immediate response. For example, if a car is stopping it will be immediately registered.

Continuous and varied coloured lighting will provide optimum visibility conditions and will help improve alertness and driving experience. In comparison to a conventional road or rail line, tunnel traffic will also not be exposed to adverse weather conditions such as wind, rain, snow, ice or fog.

While the road tubes will further be equipped with a continuous hard shoulder, step barriers for collision protection and acoustic and haptic road marking for accident prevention, there will be neither switches nor track crossings in the rail tubes, in order to also minimize the risk of a train accident. Furthermore, the escape ways on each side of the tracks in both railway tubes are designed to provide additional crash protection for derailed trains to reduce the effects of an unlikely derailment.

Limiting accidents
If an accident does occur despite all prevention measures, the tunnel is designed to minimize its impact. Again, the separate tunnel tubes play an important role, as a potential accident in one tube will not present a hazard for traffic in the rest of the tunnel.

The technical design also includes effective fire protection: deluge or sprinkler systems, which will be controlled from the traffic control centre, will keep the temperature in the tunnel low. This will in turn reduce the development of smoke and the risk of fire spreading to nearby vehicles.

Moreover, the powerful ventilation system in the Fehmarnbelt tunnel will blow smoke in the direction of the traffic tunnel out of the tube. The vehicles located and standing still in front of the seat of the fire will therefore receive fresh air from behind, whereas the vehicles located behind the seat of the fire will simply have driven out of the tunnel without being concerned about what occurs behind them.

In the case of an accident, an intelligent communication system will guarantee guidance of road users, who will receive clear warnings and instructions via variable traffic sign systems, loudspeakers and broadcast announcements. In addition, emergency stations with emergency alarm units, fire detectors and fire extinguishing equipment will be installed every 100 metres.

The traction current of the overhead electric cables in the rail tubes can also be switched off, both on site as well as remotely at the traffic control centres, when it comes to firefighting and rescue measures.

Rescue efforts
In case of an accident, it is crucial to ensure optimum rescue conditions for all passengers. They must have immediate access to a safe area, where they can wait until the arrival of rescue services.

Therefore, a fifth tube between the two road tubes – the so-called central gallery – will offer users of the tunnel a continuous rescue corridor for safe evacuation. In addition, all four traffic tubes will have emergency exits approx. every 100 metres, through which evacuation can take place to the adjacent safe tunnel tube. The distance to the nearest emergency exit – the most important factor in self-rescue – is therefore no more than ca. 50 metres and significantly exceeds the relevant safety standards.

At last, as with accident limitation, the communication system will also play an important role in self-rescue. Those affected will receive instructions and if necessary, will be able to make their way to safe areas themselves before the arrival of the rescue services.

The tunnel’s electrical and mechanical systems are essential for safety and Femern A/S demands that they comply with the latest and highest standards. Femern A/S will soon put contracts on the systems out to tender and, at an Industry Day in Copenhagen in January, the detail of the contracts will be set out.

From now and until the tunnel opens, Femern A/S will draw up a detailed rescue and emergency plan in collaboration with the relevant German and Danish authorities. At the beginning of 2014, a workshop of several days’ duration will be held at which a wide range of possible accident scenarios will be examined and assigned to specific accident types. The relevant rescue plans for these will then be developed and rehearsed.

“The safety of the tunnel will be based on all applicable national technical norms and standards as well as the latest international expertise. The new fixed link will of course meet, and in some cases surpass, the high safety levels required in Denmark and Germany as well as in the EU. This is true for both the road and rail tunnels and is documented in the risk analysis that has been reviewed by independent experts.”

In September 2013, with various specialists and tunnel experts from all over Europe present, the technical director of Femern A/S Steen Lykke accepted the prestigious European award for the Fehmarnbelt Fixed Link as “the most distinguished and innovative European tunnel project”.

Femern A/S has published a detailed report on safety in the Fehmarnbelt tunnel, which can be downloaded here .

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