Green Line 4 of the Mumbai Metro, currently under construction, is part of the metro system for the city of Mumbai, India and is being developed by MMRDA and a consortium of international companies. The line is planned to be fully elevated, and is expected to consist of 32 stations from Wadala (Mumbai) to Kasarvadavali (Ghodbunder road, Thane) via Ghatkopar, Mulund and Teen Hath Naka, a popular traffic crossing in Thane. It is estimated to cost ₹14,549 crore. Its construction was expected to begin by June 2018. It is expected to be completed in 2022 and is expected to provide interconnectivity among the existing Eastern Express Highway, Central Railway, Mono Rail, the ongoing Metro Line 2B (D N Nagar to Mandale), and the proposed Metro Line 5 (Thane to Kalyan), Metro Line 6 (Swami Samarth Nagar to Vikhroli) and Metro Line 11 (Wadala to CSMT). It will provide rail based access to the commercial, government bodies and geographical landmarks in Mumbai. Dedicated depots are planned in Owale land in up to an extent of 20 ha. and in Godrej Land in up to 15.50 ha. area. It will reduce the current travel time by between 50% and 75% depending on road conditions. Alstom awarded to provide rolling stock for this line, but the contract has been cancelled in March 2022 due to delays and uncertainties of the project. Planning The Maharashtra Cabinet approved the Metro 4 corridor on 27 September 2016. Half of the project cost will be funded by the Centre and the State Government, while the remaining will be financed through loans from the AIIB and the World Bank. The foundation stone for Metro 4 was laid by Prime Minister Narendra Modi on 24 December 2016. The Maharashtra Coastal Zone Management Authority granted Coastal Regulation Zone (CRZ) to the project in February 2017. Over of the line passes over water bodies in Bhakti Park and Wadala, both areas classified as Coastal Regulation Zone II where CRZ rules limit construction activities. 48 piers are proposed to built in the CRZ II. The MMRDA will construct metro car depots for the line on a 30 hectare plot at Owala village in Thane district and another in Vikhroli. The MMRDA utilized a drone to carry out survey work for Metro 4. The drones were fitted with 360 degrees camera that provide up to accuracy. The aerial survey takes less time than