Halcrow Group Ltd - Articles and news items
Issue 5 2009, Past issues • 28 October 2009 • Dr. Fathi Tarada, Director of Fire Safety Engineering, Halcrow Group Ltd, Co-Chairman of the PIARC Working Group on Air Quality, Fire and Ventilation, and member of the Technical Advisory Committee for the International Symposium on Aerodynamics and Ventilation of Vehicle Tunnels
Fire suppression is emerging as a key risk reduction measure for consideration in tunnels under construction or undergoing refurbishment. However, understanding the possible benefits, limitations and costs of fire suppression, and reflecting that understanding in the project decision-making process, is still a nascent science. This article describes some of the latest technical guidance available, and how it was applied to two tunnels in order to reduce societal costs related to fires, and to minimise construction costs and programmes.
Until relatively recently, the issue of tunnel fire suppression was considered very differently in various parts of the world. In Japan, fixed fire suppression systems are installed in tunnels with a length of 3,000m or longer, and which have a traffic volume of 4,000 vehicles per day or greater. The Australasian Fire Authorities Council’s fire safety guidelines for road tunnels require installation of fire suppression systems in long road tunnels in Australia. However, European tunnel designs generally followed World Road Association (PIARC) guidelines, which did not support the principle of tunnel fire suppression prior to 2008. The same reticence with respect to tunnel fire suppression was evident prior to 2008 in the National Fire Protection Association (NFPA)’s standard 502, which is widely used in North America and elsewhere.
Tunnels are no more dangerous than the rest of the road network; in fact, they are generally safer. However, in case of an incident in a tunnel, the possible consequences in terms of life safety, damage to infrastructure assets and disruption to traffic flow are significantly magnified.
A recent example is the fire on the double-decker bus in the Limehouse Link Tunnel in London, which occurred on 30 October 2005. Mercifully, the fire happened on a quiet Sunday morning with little traffic and there weren’t any injuries or fatalities. But traffic through the East End of London was severely disrupted during the immediate aftermath of the fire, as well as during the subsequent tunnel refurbishment; which required the full closure of the tunnel until 15 November 2005.