Security at the Heart of the Double-Deck Tunnel on the A86 West of ParisThe A86 is currently an incomplete orbital highway around the Greater Paris area. Two tunnels will provide the missing links west of Paris. Construction of the 10 km-long eastern tunnel, restricted to light vehicles, is ongoing between Rueil-Malmaison and Pont Colbert in Jouy-en-Josas, southeast of the Chateau de Versailles. It is an innovative single bored double-deck roadway. View alignment maps here. The 7.5 km-long western tunnel, to be built between Rueil-Malmaison and the A12 interchange in Bailly, west of the Chateau de Versailles, will provide a two-way single-deck carriageway open to all types of vehicles. Double-deck tunnels for vehicles are unusual around the world. The first such tunnel ever built is the 2,785 m Fuxing Road tunnel across the Huangpu River in Shanghai, opened in September 2004. The A86 is operated by Cofiroute (Compagnie Financière et Industrielle des Autoroutes). Its shareholders are Vinci (65.34%), Eiffage (16.99%) and Colas (16.67%), a Bouygues affiliate. SOCATOP (Société de Construction de l'Autoroute de Traversée de l'Ouest Parisien), a consortium of the same companies, is the project manager and contractor. Visit www.cofiroute.frThe 4.5 km first section (VL1) of the east tunnel broke through in October 2003 using a Herrenknecht TBM from the north in Rueil-Malmaison. Click here. The machine, christened 'Emma', went back to work on 14th June, 2005 to drive from the south in Pont Colbert the second 5.5 km section (VL2) in the opposite direction from Pont Colbert to the breakthrough point at the A13 highway interchange in Vaucresson. On 23rd January, 2006 the first kilometre had been bored. There was then still 4.5 km of tunnel to go. Commissioning is planned for October 2007 for the first north section between Rueil-Malmaison and the A13 interchange and in December 2009 for the second south section. Visit www.herrenknecht.comConstruction of the upper and middle decks is under way, with a hundred metres built every week. In January, 2.5 km of the upper deck and 2 km of the middle deck (for the upper traffic level) had already been installed within the tunnel.The operation and control centre is located by the Rueil-Malmaison intersection. This is the nerve centre of the safety system, operating around the clock and collating traffic information received in real time. The A86 West will be permanently monitored by 350 video cameras. In less than 10 seconds, the operation and control centre will be alerted and receive the images of any traffic anomaly detected (stationary vehicle, abnormally slow traffic, etc.). In less than 30 seconds of an incident being detected, warning messages will be displayed on the luminous overhead panels installed every 400 metres, and broadcast on FM radio.Citilog will provide the automatic incident detection system. Citilog's system will be monitoring input from 700 video cameras deployed throughout the eastern and western tunnels. The company's software will automatically alert traffic operators of any incident in the tunnels. Visit www.citilog.comWell signalled safety niches will provide drivers with shelter until the emergency crews arrive. There is a niche every 200 metres. All niches will be fitted with fire extinguishers and a direct telephone line to the operation and control room. They will connect with sealed, fire-proof shelters that will be under constant video surveillance. Each shelter can hold around 100 persons. A staircase inside each shelter links the two tunnel levels so that in the event of a serious accident on one level, the other can be used for evacuation and emergency service access. The first section of the tunnel (Rueil-Malmaison - A13) is equipped with 31 niches, either niches with staircases between the two levels or extraction niches between the lower deck and the extraction / fresh air ducts under it. Thirteen smoke extraction niches and 18 niches with staircases between levels are completed or nearing completion. View pictures here.To build the niches, prior treatment of the subsoil behind the segments is required, in particular by ground freezing to improve the consistency of the material, which is too liquid between Le Butard and the A13 for example, then the segments installed by the TBM are cut out and demolished, the ground is dug by a hydraulic breaker followed by waterproofing, installation of rebars and concrete pouring. In the event of fire, a powerful smoke extraction system will be triggered automatically. The system is designed to cope with a fire at least 10 times as large as a standard small vehicle fire. Smoke will be blown in the direction of traffic flow and extracted at a point no more the 400 metres downstream of the fire. This prevents any smoke from drifting upstream towards drivers blocked by the incident. Naturally, drivers already ahead of the accident will be able to continue normally to the tunnel exit. Emergency services will be able to access an incident in the eastern tunnel in one of three ways, depending on its nature and location: by the deck on which the incident occurred, in the direction of normal traffic flow; by the unaffected deck, using the refuge staircases between levels, located every 200 metres; and by the emergency shafts located at least every 1,000 metres, which are fitted with stairs and elevators. Safety specialists, trained to assist drivers, will be on permanent duty, ready to respond immediately when notified of any incident. They will be stationed by each intersection and will conduct regular patrols through the tunnel. They will be equipped with traditional road safety resources (road markers, towing equipment) and will intervene whenever necessary. They will be trained to provide first aid and control small fires until the fire service arrives.The tunnel will be fitted with twelve deep emergency access shafts with depths, from north to south, comprised between 20 m and 90 m on average, including five emergency access shafts coupled with ventilation units for fresh air and/or extraction at about 15 to 20 metres of depth.The construction by Cofiroute of the 10 km double-deck single-tube eastern tunnel with its reduced gauge (2.55 m from floor to ceiling) revived the debate on safety. What would happen in case of accident causing a fire at the end of a queue of vehicles formed by a traffic disruption (or first accident)? Would the fire propagate to other vehicles? What would be the evacuation conditions downstream of the fire? What would be the conditions faced by the firefighters? Would fixed fire-fighting systems improve the escape conditions and diminish the risk of fire spreading?To answer these questions, Cofiroute commissioned several test campaigns to consulting engineers Bonnard & Gardel. The tests were carried out by VSH at the Hagerbach test galleries in Switzerland and involved the following players: EMPA (research institution belonging to the Swiss Federal Institute of Technology in Zurich) for measuring the gas toxicity, CSTB (Centre Scientifique et Technique du Bâtiment) for external quality control of the measurements and water mist equipment supplier Aquasys. These tests will help Cofiroute select the technology best suited for its tunnel. The tunnel used during the test was approximately 220 m long, 150 m of which recreated the future 2.55 m-high and 9.3 m-wide A86 tunnel. Visit www.bg-21.com, www.hagerbach.ch, www.empa.ch, www.cstb.fr and www.aquasys.atThe objectives of these tests were, in a situation called "second accident" (accident at the end of a queue of vehicles) and in real conditions, to observe and measure the fire propagation conditions between the vehicles; measure the ambient conditions downstream the fire place, zone where vehicles might be blocked; test and qualify the equipment of the Cofiroute emergency services; test different fire detection and signalling systems and observe and measure the benefits and possible disadvantages of using fixed fire-fighting systems (water mist). Read E-News Weekly 16/2004, 40/2003, 42/2002, 22/2002 & 5/2002. Click fr/21. Visit www.a86ouest.com for more. 10/06.