MUMBAI sub urban land area in WR and CR are very limited for the additional lines in the ground level.So vertical space in the available WR and CR Sub Urban Land Area also effectively utilized for the additional infrastructures in the MUMBAI METRO area.
Since Metro land acquisitions are highly impossible one and very much delays the project implementation period..
So further Additional SUB URBAN RAILWAY LINES may be constructed over the existing Ground level WR and CR tracks Land Area effectively.