Double-Decker Highway and Metro Planned on GST Road

India’s longest double-decker viaduct has been proposed on GST Road in Chennai.
The project will have a six-lane elevated highway on the lower level and a metro
rail line on the upper level. It will cover an 18.4-km stretch from the Kalaignar
Centenary Bus Terminus (KCBT) at Kilambakkam to Chettipunniyam near Mahindra City.

The Tamil Nadu government has given in-principle approval to the National Highways
Authority of India (NHAI) to build the six-lane elevated road. The pillars will be
designed so that a metro line can be built above it in the future.

Once completed, this is expected to be the longest double-decker viaduct in India,
and possibly in the world. At present, the longest double-decker metro viaduct is
a 5.6-km stretch on Kamptee Road built as part of the Nagpur Metro project.

The decision was taken at a recent meeting chaired by Chief Secretary N Muruganandam,
attended by officials from the state highways department, Chennai Metro Rail Limited
(CMRL), NHAI, and other agencies.

Officials said tenders will be invited after the revised Detailed Project Report (DPR)
gets approval. After the Airport–KCBT Metro line of 15.46 km is completed, the next
phase of the metro project will extend from KCBT to Chengalpattu. This airport–KCBT
line is still awaiting approval from the Union government.

Meanwhile, under Corridor 5 of CMRL’s Phase II project, a 3.14-km-long four-lane
elevated flyover has been built on Mount–Poonamallee Road between Mugalivakkam and
Ramapuram near MIOT Hospital. This structure also has space for a metro line above
the road, but it has not yet been opened to the public.