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The Heathrow Airside Road Tunnel (ART) is a tunnel at London Heathrow Airport. It connects the airside roads around Terminals 1, 2 and 3 to those around Terminal 5. The tunnel was opened to traffic in March 2005 and is used only by vehicles with security clearance to drive airside.
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Map of Heathrow Airside Rd Tunnel, Longford, Hounslow TW6 1BP, UK
The ART is 1.42 kilometres (0.88 mi) long, consisting of 60 metres (200 ft) of twin-cell cut and cover box at each end, linked by a pair of 1.3-kilometre (0.81 mi) long bored tunnels. The ART was designed and built between 1999 and 2004 by a team of engineers from BAA (now Heathrow Airport Holdings, the tunnel's owner), AMEC, Laing O'Rourke, Morgan-Vinci JV and Mott MacDonald.
The bored tunnels have internal diameter of 8.1 metres (27 ft) and were driven by a 9.16-metre (30.1 ft) diameter Herrenknecht earth pressure balance tunnel boring machine. The excavations were lined with a bolted concrete lining 0.45 metres (1.5 ft) thick: these are unusually strong tunnel segments, required because the ART is so close to the surface and, at one point, passes 3 metres (9.8 ft) over the top of the Heathrow Connect tunnel to Terminal 4.
Each bore contains an unusual road layout, consisting of a single carriageway 6 metres (20 ft) wide; just wide enough to allow an airport bus (Cobus 2700) to drive past another bus stopped at the side of the road. The two tunnels are linked by escape cross-passages at intervals of 100 to 130 metres (330–430 ft).