CHENNAI: India’s longest double-decker viaduct, comprising a six-lane elevated highway on the lower deck and a metro corridor on the upper level, has been proposed for an 18.4-km stretch between the Kalaignar Centenary Bus Terminus (KCBT) at Kilambakkam and Chettipunniyam near Mahindra City on GST Road in Chennai.
The state government has granted in-principle approval to the National Highways Authority of India (NHAI) for constructing the six-lane elevated corridor with pillars designed to accommodate a future metro line.
Once completed, it is expected to be the longest double-decker viaduct in the country, and possibly the world. Currently, the longest double-decker viaduct in the metro category is a 5.6-km stretch on Kamptee Road under the Nagpur Metro project.
The decision for the proposed corridor was taken at a recent meeting chaired by Chief Secretary N Muruganandam with the state highways, CMRL, NHAI and other officials last week.
‘Tenders to be invited after revised DPR gets nod’
After the completion of the Airport-KCBT Metro line for 15.46 km, which is yet to receive approval from the union government, the second phase of the metro project will be taken up from KCBT to Chengalpattu, official sources said.
At present, under Corridor 5 (Madhavaram-Sholinganallur) of Chennai Metro Rail Limited’s Phase II project, CMRL has constructed a 3.14-km-long, four-lane elevated flyover on Mount-Poonamallee Road between Mugalivakkam and Ramapuram (MIOT hospital).
The structure also accommodates a metro line above the highway, though this stretch is yet to be opened to the public.
According to sources from the NHAI, concerns over the alignment for future metro expansion along the Kilambakkam-Chengalpattu stretch have been resolved by the state government.
“The government has granted in-principle approval for constructing the 18.4-km elevated corridor from the KCBT to Chettipunniyam. Earlier, the proposal had included a Bus Rapid Transit System (BRTS) along the highway to ease congestion in the southern Chennai corridor without significant land acquisition. The state government has now agreed to share the additional costs involved in providing structural provisions for future metro expansion,” a NHAI official told TNIE.
The official added that the detailed project report (DPR) will be revised to incorporate the updated metro alignment. “Once the revised DPR receives necessary approvals, tenders will be invited,” the official said.
The proposal to build the elevated corridor was first mooted in 2022, but progress was delayed due to issues related to the metro alignment for future expansion in South Chennai. “The dedicated bus lane proposed on the elevated corridor is likely to be retained in the revised DPR,” the official added.
Originally, the project envisaged entry and exit ramps at three locations, with the total cost estimated at Rs 3,400 crore. It may be recalled that two months ago, the state government approved the extension of the Chennai Metro’s Blue Line from the airport to KCBT, with stations planned at Pallavaram, Chromepet, Tambaram and Vandalur. Funds were also allocated for land acquisition and utility shifting.