Artistic impression of the terminal

Elevated runways

While elevated runways have been there for a while – the first one came up in 1949 over the Van Wyck Expressway at Idlewild-Kennedy Airport, New York – they make for spectacular visual experiences. Planes passing over traffic command attention wherever they are, despite a number of airports now having elevated taxiways. As airports have needed to cater to an increasing number of passengers, they have expanded over existing infrastructure, often roads.

Of course, they are impressive feats of engineering in themselves and it was no surprise that busy airports have resorted to building them. LAX and Heathrow followed in 1953. Not to be outdone, Orly topped them within five years with the road tunnel not just under the taxiway, but also the main apron and the terminal building! Denver’s Stapleton Airport became the first to have a runway over an interstate highway, the I-70 in 1962, while the Toronto Pearson Airport built an island in the middle of the apron over the road tunnel.

The world’s busiest airport at the time, Chicago’s O’Hare, followed in 1966, while Sydney’s Mascot opened the year after (the first outside North America and Europe). Dallas/ Forth Airport opened in 1974 with four taxiways at once, while Singapore’s Changi and Hong Kong’s erstwhile Kai Tak airports opening elevated taxiways in 1981 and 1982 respectively. Delhi, and India have joined the bandwagon!

Changi Airport taxiway bridge; Credit: uZRudd97

Elevated runway: Quick check

• The new taxiways are 2.1 km long and 202 m wide elevated dual-lane taxiway connecting the Northern and Southern airfields of IGI Airport, reducing taxi distance for aircraft by 7 km, according to the airport operator.

• The purpose of the ECT is to reduce taxiing distances for aircraft, reduce aircraft emissions and save natural resources such as ATF, and enhance operational efficiency.

• The taxiway is expected to optimise taxiing routes and aircraft operations, resulting in a reduction of about 55,000 tonnes of CO2 per annum.

• The 2.1-km-long dual-lane elevated Code F taxiways are capable of handling large aircraft and wide-body jets such as A380, B777, and B747-8.

• The Eastern Cross Taxiway will have two 44m wide lanes with a gap of 47m between them to allow safe and simultaneous passage of two big aircraft.

• The taxiway central spine structure is a massive monolithic structure comprising 590 girders – each weighing 90 tonnes – capable of maintaining structural integrity even in the case of an explosion of TNT/ RDX.

• The ECT central spine structure comprises 156 piers. It is supported by 590 girders, each weighing nearly 90 tonnes. The structure is designed to withstand explosions of TNT/ RDX. The structure designs are made in conformity to Seismic Zone IV and designs are vetted by IIT Mumbai.

• The bridges are designed to carry the weight of the heaviest aircraft, such as the Airbus A380/B777/B747s. Each of its two lanes would be 44 m wide with a gap of 47 m between them to allow safe simultaneous passage of two big aircraft. It will also have carriageways on both ends to allow emergency vehicles such as fire tenders and tow tractors to move.