Mumbai To provide better connectivity to suburban rail commuters, the authorities have decided to link Metro-4 with Metro -3 at the Chhatrapati Shivaji Maharaj Terminus. The partially underground extension of Metro 4 (Wadala-Thane-Kasarvadavali) from Wadala to the general post office (GPO) in south Mumbai will be linked to Metro-3 (Colaba-Bandra-Seepz) corridor at the CSMT, senior officials from the Mumbai Metropolitan Regional Development Authority (MMRDA) confirmed. The two Metro corridors will be linked underground at the CSMT Metro station being planned for Metro 3. While the extension of Metro 4 will cater to commuters from eastern suburbs, Metro 3 will help people commute from western suburbs to south Mumbai. The extension to the Metro 4 line will pass through the Mumbai Port Trust (MbPT) land on the eastern waterfront. Of the 9-km extension, 6 km on the southernmost part will be underground, officials said. The extension is being planned to provide connectivity up to south Mumbai via port land, which is going to be developed as a second Marine Drive by MbPT. The port trust is also keen that the part that will go through their land be underground. The partly-underground extension will cost Rs2,400 crore. “The detailed project report is in its final stages. Once the alignment is finalised, it will be presented to the executive committee and the cabinet for a final approval,” said UPS Madan, metropolitan commissioner, MMRDA. “This will be the second partially underground Metro for the city.” The 5-km Metro corridor from Western Express Highway to the city airport, which will be built to connect Dahisar-Andheri Metro-7 and Colaba-Bandra-Seepz Metro-3, will be underground. Metro-3 is the only fully underground corridor.