New Delhi (PTI): Delhi Metro will touch its highest point in Dhaula Kuan on the Airport Express Line, with one of the pillars in a 542-metre stretch of road bridge reaching the height of 20 metres.

At present, the highest point of the Metro is 19 metres at Karkardooma crossing in east Delhi.

The viaduct or bridge above Dhaula Kuan -- in which an innovative technology is being used to ensure smooth traffic flow during construction -- will have 15 pillars which will support four special spans, the longest being 168 metres.

This will be the longest in India and the third-longest in the world to be built using the post-tensioned continuous casting technique and will be supported on five pillars, Delhi Metro spokesperson Anuj Dayal said.

The Metro said it is using the technology of setting up temporary steel structures to construct the 542-metre viaduct at the busy intersection in Dhaula Kuan to ensure that traffic flow is not disrupted.

The viaduct on the Airport Express Line is being built over eight roads which carry a heavy volume of traffic, including the Ring Road, National Highway-8, Ridge Road and Sardar Patel Marg intersect, Mr. Dayal said.

The viaduct will cross a railway track and one of the 15 pillars being built will be Delhi Metro's tallest so far at 20 metres, he said.

Vehicles going towards the Indira Gandhi International Airport and Gurgaon pass through this intersection because of which it was not possible to stop traffic movement even for a day or set up barricades, he said.

"So temporary steel structures are set up to support the construction of the viaduct. A total of 2,300 tonnes of steel are being used to set up these structures. This is being done only during the night so that traffic movement is not affected during the day," Mr. Dayal said.

The work at Dhaula Kuan inter-section is likely to be completed by October 2009.

The Airport Express Link connecting the New Delhi railway station to the Indira Gandhi International Airport will be 22.7 kilometres long with six stations.

While five of them (New Delhi Railway Station, Shivaji Stadium Terminus, NH 8, IGI airport, Dwarka Sector 21) will be underground, one (Dhaula Kuan) will be elevated.

Commuters will be able to reach the IGI airport in 18 minutes.