The Mumbai Metro Rail Corporation (MMRC) has achieved 70% of tunnelling required for Colaba-Bandra-SEEPZ Metro-3 corridor. In all, 23 breakthroughs, totalling 38.25 km out of the 55 km has been completed in two years.

The Colaba-Bandra-SEEPZ Metro-3 corridor is the first and the only fully underground corridor, expected to overhaul the crumbling urban transport and the chock-a-block traffic conditions in the city. The total length of the 55 km tunnelling has been calculated based on an upline and downline tunnels across the 33.5-km long underground corridor, excluding the station box length.