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A Viable Option for Mass Transit Expansion, ET Infra

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It was in the late 1990s that the transformation of the city started with a slew of flyovers beginning to take over the landscape. With rapidly increasing vehicular density and limitation of horizontal expansion in the city, the flyovers today are stretched to the utmost.

As bridges and elevated metro corridors criss-cross all parts of the city, planners feel that going underground, though costly, is a viable option for not only metro projects but also road corridors. Today, there are at least 11 tunnel-based projects in the making, ranging from east-west corridors to rail systems like the metro and the bullet train, across the Mumbai Metropolitan Region (MMR).

The Metro 3 underground corridor (Colaba-Bandra-Seepz), one of the first underground mass transit projects in the city, is almost ready. The country’s first undersea twin tunnels, which are a part of the Mumbai Coastal Road project, are getting finishing touches.

Authorities have finalised contractors for three east-west tunnel-based road corridors, invited tenders for four of the nine underpasses on Western Express Highway (WEH) and Eastern Express Highway (EEH) for grade separation projects, and work is in progress on the bullet train tunnel and Metro Line 7A (Andheri to domestic airport).

Planners said that although late in the game, the city will find an apt solution in underground mass transit expansion given that it is an island and cannot spread itself horizontally.

With a vehicle count of 45 lakh, including 13 lakh private cars, the city faces perpetual traffic chaos. The congestion often leads to long jams, pollution and wasteful fuel expenditure. The city has the highest density of private cars in the country at 650 per kilometre of road.

In densely populated urban areas, tunnels can help minimise disruption by allowing trains to pass underneath while avoiding the need for extensive land acquisition or causing disturbances on the surface.

Govt officials said that going underground may be a little more expensive compared to building on top of a road, but delays caused by land encroachments, legal cases and traffic diversions can be avoided.

“London had its first underground metro in 1863. Mumbai is at least 100 years behind, but it is a much-needed start,” an official said.

Mumbai Metropolitan Region Development Authority (MMRDA) has been entrusted with the task of creating the Borivli-Thane tunnel that will pass under the eco-sensitive Sanjay Gandhi National Park and link Western Express Highway to Ghodbunder Road. Metropolitan commissioner Sanjay Mukherjee said tunnelling technology becomes necessary for projects in congested areas where road width cannot be compromised by flyovers. Tunnels even help protect environmentally sensitive areas and wildlife habitats.

“By routing traffic beneath forested regions, natural habitats are shielded from both vehicular and noise emissions,” Mukherjee said.

Another tunnel-based project is planned in the island city and will pass through one of the densest areas of the city to link the Coastal Road on the western seaboard to the Eastern Freeway near Orange Gate.

MMRDA had earlier planned an elevated link that would mean not only crossing over the railway tracks on both Central Railway and Western Railway as well as JJ flyover but also undertaking works in extremely congested areas.

The National High Speed Rail Corporation Ltd (NHSRCL) has opted for a 21-km underground tunnel from BKC to Shil Phata for the bullet train project. A 7-km portion of the tunnel will run below the sea.

“In Mumbai, land acquisition was a challenge. Also, there are elevated metro corridors and bridges already planned in MMR. The underground corridor was also planned to save the mangrove plantation and flamingo sanctuary,” an NHSRCL spokesperson said.

Experts said that apart from offering space, tunnels enhance safety by avoiding level crossings, reducing the risk of collisions with road traffic. They offer security advantages by providing a controlled and confined space. Tunnels allow for grade separation, meaning the road or railway can pass beneath existing transportation infrastructure like roads and highways without impeding surface traffic flow.

Tunnels in railway networks have been used for a long time because of the peculiar topography in the Sahyadri ranges. In regions with challenging topography, such as mountains, hills, or water bodies, tunnels provide a means to navigate through obstacles, allowing for a more direct and efficient rail route.

Mumbai Railway Vikas Corporation (MRVC) is digging a tunnel for extension of the Harbour line from Panvel to Karjat. So far it has excavated a tunnel over a length of 2 km.

  • Published On Feb 18, 2024 at 10:32 AM IST

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