Heathrow Airside Road Tunnel

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The Heathrow Airside Road Tunnel (ART) is a road tunnel at Heathrow Airport in the London Borough of Hillingdon, London, UK. It connects the airside roads around Terminals 1, 2 and 3 to the airside roads around Terminal 5.

The ART is 1.42 km long, consisting of 60 m of twin-cell cut and cover box at each end, linked by a pair of 1.3 km bored tunnels. The ART was designed and built between 1999 and 2004 by a team of engineers from BAA (who own the tunnel), AMEC, Laing O'Rourke, Morgan-Vinci JV and Mott MacDonald.

The bored tunnels have internal diameter 8.1 m and were driven by a 9.16 m diameter Herrenknecht earth pressure balance TBM. The excavations were lined with a bolted concrete lining 0.45 m thick: these are unusually strong tunnel segments, required because the ART is so close to the surface and, at one point, passes 3 m over the top of the Heathrow Express tunnel to Terminal 4.

Each bore contains an unusual road layout, consisting of a single carriageway 6 m 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 100–130 m.

The tunnel was opened to airside traffic in March 2005 and is used only by vehicles with security clearance to drive airside. At present, it is mostly used by buses taking passengers from Terminal 3 to aircraft on stands at the west edge of the airport. When Terminal 5 is opened in 2008, the ART will form the link between it and the other terminals at Heathrow.