Kilambakkam to Chettipunniyam Double-Decker Highway and Metro Project Delayed

The Tamil Nadu government has requested the National Highways Authority of India (NHAI) to prepare an integrated double-decker design for the proposed 18.4-km elevated corridor on GST Road, stretching from the Kilambakkam bus terminus to Chettipunniyam near Mahindra City. This decision, which aims to combine a six-lane elevated highway on the lower deck with a metro rail corridor on the upper deck, is expected to delay the project by another year.

In December last year, the state government granted in-principle approval for the extension of the metro rail corridor from the Kilambakkam bus terminus to Chettipunniyam.

Due to the new request, the Detailed Project Report (DPR) prepared earlier for a single-deck elevated corridor must now be revised. Engineers will need to redesign the load-bearing capacity of the piers to support the weight of both the highway and the metro line.

The design finalisation process is expected to take nearly five months. Additionally, a new cost-sharing arrangement between the NHAI and the state government must be negotiated and finalised before the revised DPR can be completed.

According to an NHAI official, constructing the flyover and the metro line simultaneously is more feasible, as building a metro corridor above an existing elevated highway at a later stage presents severe practical constraints. Similar simultaneous construction was previously executed on the Mugaliwakkam-Ramapuram stretch of Mount-Poonamallee Road.

The NHAI is prepared to proceed with either simultaneous construction or building the elevated highway first with the metro corridor following later. However, the latter option would require separate approval from the Union government, which could cause further delays.

If the state government decides to develop the civil infrastructure for the metro—such as installing pier caps and launching U-girders and I-girders—during the highway construction, its financial contribution will increase. This integrated approach would prevent future traffic disruptions on the lower deck during subsequent metro construction, allowing tracks and electrical systems to be installed smoothly.

The proposed extension from Kilambakkam to Chengalpattu faces further timeline pressures, as the state's proposal to extend the Blue Line metro from Airport to Kilambakkam is still awaiting approval from the Union government. Activist Dayanand Krishnan noted that the DPR has been with the Union government for over a year and urged for an early approval to commence work.