DMRC is building 45 metro stations along 65.20 km of additional lines in three distinct corridors in the city as part of the Delhi Metro's Phase-4 expansion. These include the future Silver Line from Tughalakabad to Aerocity and the Magenta Line extensions from Janakpuri West to RK Ashram Marg (28.92km, 12.55km, and 12.92km, respectively). From the Violet and Airport Lines' respective endpoints, the Silver Line will join them. The overall subterranean length of the Janakpuri West-RK Ashram Marg corridor will be 9.41 km, whilst the Aerocity-Tughlakabad corridor would be 19.35 km. There would be no underground segment between Majlis Park and Maujpur. On the Janakpuri West-RK Ashram Marg corridor, the Delhi Metro has so far finished 2.2 km of underground tube (for up and down movement) between Krishna Park Extension and Keshopur. This new section of tunnel is an extension of the earlier Magenta line tunnel, which was built for the Botanical Garden-Janakpuri West corridor, which is still in use. The construction of the ramp and entry/exit points as well as around 70% of the Krishna Park Extension station have been finished on this underground section, in addition to the twin tunnels. Although the full Janakpuri West-RK Ashram Marg corridor won't be finished until September 2025, the civil construction of this particular underground portion will be finished by the beginning of the following year. Tughlakabad to AerocityOn the Silver line route, tunnelling is now under place between the stations of Chattarpur and Kishangarh. On March 3, the first Tunnel Boring Machine (TBM) on the Aerocity-Tughlakabad Corridor began its work to bore a 1.27-kilometer tunnel connecting the stations of Chhatarpur and Kishangarh. The Janakpuri West-RK Ashram Marg corridor's Sangam Vihar-Anandmayee (Aerocity-Tughlakabad corridor), Derawal Nagar-Pulbangash, and Nabi Karim-Pulbangash segments will all see the start of tunnelling drives in the upcoming months. While the digging on the RK Ashram Marg corridor will be a routine task, the Delhi Metro will face a significant engineering challenge on the Aerocity-Tughlakabad corridor since the line will travel under 17 pairs of operational railway tracks, which is a record in and of itself.