After the major tunnel fires in the Mont Blanc and Tauern road tunnels in 1999 and the Gotthard Road Tunnel on 24 October 2001, the Federal Roads Office (FEDRO) reviewed all national road tunnels with a length of more than 300 metres for possible optimisation of tunnel safety. We spoke to Christian Gammeter, Head of Tunnel and Geotechnical Engineering in the Infrastructure Standards and Safety Division, about the current status of safety measures.
Systematic approach combines four fields
Safety in road tunnels, explains Christian Gammeter, results from the interaction between drivers, the vehicles, the tunnel infrastructure and tunnel operations. In all four fields, great efforts have been made in recent years to prevent critical incidents such as accidents and vehicle fires firstly. FEDRO's secondary safety objective is to be able to limit the consequences of such incidents as far as possible. It is to be achieved firstly by enabling tunnel users to react correctly to critical situations and to bring themselves to safety. Secondly, FEDRO is investing heavily in emergency services. It finances the Schadenwehr Gotthard, which we have already reported on in detail in a magazine article on the occasion of the 20th anniversary of the incident of 24 October 2001. And it finances the training of the fire services responsible for road tunnels at the International Fire Academy.
Target group drivers
Most accidents are the result of driver error, over which FEDRO generally has only limited influence. However, it tries to make it easier to use the tunnels, for example, through optimised lighting and signalling. Incidentally, FEDRO uses the necessary modification work to switch to LED lighting and thus reduce energy consumption.
Greater safety could also be achieved by making correct behaviour in tunnels a topic of driver training and by examinating critical knowledge in this regard. On the page FEDRO website, road users can find further information on the proper use of tunnels. According to Christian Gammeter, a special target group for FEDRO are lorry drivers and drivers of dangerous goods transports, who are offered special training and regularly tested on the safety-relevant aspects of their vehicles and their equipment.
Vehicle safety
When it comes to vehicle safety, says Christian Gammeter, the focus is on lorries, as they develop several times the thermal power of passenger cars in the instance of a fire. For this reason, lorries are checked annually for operational safety and must be equipped with fire extinguishers. In summit tunnels such as the Gotthard Road Tunnel, the risk of fire is particularly high because the lorries can overheat on the steeply rising access ramps. For this reason, thermal portals have been installed at both portals of the Gotthard Road Tunnel, which automatically scan the trucks with thermal sensors.
Stop in case of overheating
If the monitoring system indicates overheating, the lorry in question is pulled out of traffic and checked by Gotthard Schadenwehr. The lorries are not allowed to continue driving until they have cooled down or the detected temperature rise does not pose a danger. However, with this approach, lorry fires inside the tunnel cannot be completely ruled out. The major fire involving seven lorries on 24 October 2001 was caused by the collision of two lorry trains. «Even in this field,» says Christian Gammeter, «there is no such thing as absolute safety, which is why we design the infrastructure in such a way that the consequences of critical incidents for people, the environment, and the tunnel facilities themselves can be limited.»
Infrastructure designed with fire in mind
In the field of tunnel infrastructure, compared to the situation in 2001, «decisive safety gains have been achieved by optimising ventilation technology and escape routes», explains Christian Gammeter. The ventilation in the Gotthard Road Tunnel was redesigned in such a way that the smoke can no longer spread over long distances in the tunnel. It is drawn into the ventilation shafts above the false ceiling in front of and behind the fire site. With the smoke, a large part of the heat is also dissipated, which is why this extraction technology reduces the risk of fire spreading to other vehicles.
The diagram shows the principle of extraction, which can limit the spread of smoke.
Detail of a smoke flap as they were installed in the suspended ceilings of the Gotthard Road Tunnel after the incident in 2001. Each flap can be controlled individually to control the spread of smoke.
Trial run of the new smoke extraction technology in June 2008: The theatrical smoke is sucked into the ceiling, the area in front is practically smoke-free.
In 2001, the fire of the two lorries that had crashed had spread to five other lorries. «Today,» says Christian Gammeter, «it is unlikely. However, the best protection against the spread of fire is still a large distance between vehicles. It should be 150 metres for lorries - even and especially when stationary!» The escape routes in the Gotthard Road Tunnel have been optimised above all by significantly better signalling and illumination, thanks to which they can be recognised from a great distance even in dense smoke.
From traffic management to emergency services
The volume of traffic through the Gotthard Road Tunnel has more than doubled in the 31 years since it opened in autumn 1980. Whereas in 1981, just under 3 million vehicles passed through the tunnel, the FEDRO statistics for 2019 show almost 6.4 million vehicles passing through. This means that the tunnel repeatedly reaches its load limits, which is why a drop counter system was introduced that automatically limits the number of lorries in the tunnel and thus supports the observance of sufficiently large distances between lorries. It significantly reduces the risk of lorry fires – but does not rule it out. For this reason, FEDRO financed the development and construction of the training tunnel facilities in Balsthal and Lungern in 2005 and bears the annual training costs of the members of the fire services deployed in Swiss national road tunnels.
Efforts to improve safety go far beyond such measures, however. «We are constantly working to better understand and optimise the driver-vehicle infrastructure-tunnel operation system,» says Christian Gammeter, for which FEDRO also conducts or commissions its own research, for example, on the risks of electric vehicle fires.
In the third article of our retrospective on the major fire in the Gotthard Road Tunnel 20 years ago, we report on the significance of this incident for the International Fire Academy.
