CMRL mulls testing driverless trains before April 2025 along sharpest curve in Porur

CHENNAI: In all of phase II, the sharpest curve of 127.55-metre radius in Porur, the Chennai Metro Rail Limited (CMRL) will begin testing driverless trains before April 2025. This is part of the first phase of commissioning from Poonamallee to Porur junction on corridor 4, which is likely to be completed by December next year.

Also, CMRL achieves a unique feat by marking the first among all Metro Rail projects in India to design the composite girders, which carry rail tracks in a curved manner at Porur.

Following suit, the Delhi Metro Rail Corporation (DMRC) is adopting the same design for its construction in Patna. “The DMRC has already completed the design for construction in Patna. Such a design is first in India but exists in Seoul, South Korea,” said T Archunan, director of projects (DP), CMRL.

Corridor 4 (stretching 26.1 km from Light House to Poonamallee Bypass) is a priority corridor in phase II construction. The CMRL is already expediting work in this elevated line by laying tracks.

Speaking to DT Next, a CMRL official stated, “Testing at this stretch will begin before April 2025. And, importantly testing of the rolling stock coupled with the track will be done at the sharpest curve during the same period.”

At the stretch to be operated next year, the trains will pass through 10 Metro stations: Poonamallee Bypass, Poonamallee, Mullaithottam, Karayanchavadi, Kumananchavadi, Kattupakkam, Iyyappanthangal, Thelliyaragaram, Porur Bypass and Porur Junction.

“The work at Mullaithottam and Kattupakkam is still underway. Once completed, the trains (on a straight line here) will be tested at a maximum speed of 90 km/h. At the Porur curve, trains will be tested at the speed of 45-50 km/h. But, the average commercial speed of trains in phase II will be at 35 km/h,” explained Archunan. “For testing at the sharpest curve in Porur, check rails will be installed near the tracks as per safety norms.”

Almost five months prior to testing, CMRL has completed the erection of a composite girder on the elevated line in Porur along with contractor L&T and general consultant AEON. But, due to lack of space and heavy utilities, the CMRL and team, to prevent further land acquisition and demolition of buildings in Porur, planned the design in a curved manner (over the Porur flyover) and began erecting the steel portal beams (an element of viaduct) at that particular junction in August.

Rekha Prakash, chief general manager (planning and design), CMRL, explained, “To minimise land acquisition by the side of the flyover, which is lined with multi-storied buildings, the alignment was revised with a sharper curve of 127.55-metre radius.”

Steel composite girders are proposed to reduce the overall weight of the structural elements by 40%. “The girders were placed in a skew (to distort it from its original shape) and positioned on either side of the flyover without hindrance to traffic flow on Porur flyover. The complete spans were erected in four months,” she said.

Transported from Bhopal, the girders of eight spans (the centre distance between two piers) have been erected with a combined weight of 2,415 tons above Porur flyover (also called MGR flyover). The design was chosen to address spans ranging between 25 and 49.42 metres.

In phase II, which comprises 300 curves, Porur is the sharpest curve, followed by Koyambedu with a 127-metre radius and Alandur with 126-metre radius. As per required standards, the radius of the curve cannot dip below 120 metre-radius, pointed out CMRL officials. Corridor 5 between Madhavaram and Sholinganallur (44.6 km) has a maximum number of curves.