transformed into a station from where mail and express trains operate. Nowadays the Dankuni Station is been given importance and many long route trains stop at this station. The electrified suburban rail network of the SER and the ER is extensive and stretches far into the neighboring districts of North 24 Parganas, South 24 Parganas, Howrah, Hooghly, Nadia, East Medinipur, West Medinipur and parts of East Barddhaman. The Kolkata Suburban Railway is the largest suburban railway system in India with 1501 km route length. The Circular Rail encircles the entire city of Kolkata, starting and terminating at Dum Dum Junction. However, the poorly-patronized branch line between Dum Dum Cantonment railway station and Biman Bandar railway station is now replaced by Line 4 (under construction) of the Kolkata Metro. Metro Railway Kolkata was the first city in South Asia to have an underground railway system that started operating in 1984. Kolkata Metro is jointly owned by Metro Railway, Kolkata and Kolkata Metro Rail Corporation. Kolkata Metro Line 1 (Blue Line) is under the administration of Metro Railway, Kolkata. It has the status of a Zonal Railway and is directly run by the Indian Railways. Kolkata Metro Line 1 is the oldest operating metro system in India which started operation in 1984. This metro system consists of elevated tracks as well as underground tunnels with electric current coming from a third rail. The rakes are both AC as well as Non-AC. Since October 2021, Non-AC metro services has been discontinued. Kolkata Metro Line 2 (Green Line) is under the administration of Kolkata Metro Rail Corporation. Green Line is going to have India's first underwater metro system. It consists only AC rakes. Lines which are operational are: Kolkata Metro Line 1 (North-South Metro) begins at Dakshineswar in the north and continues south through Esplanade in the heart of the city until the southern end in New Garia. Blue Line is mostly underground with few portion on elevated tracks which makes it a different metro system from the rest of metro systems in India. Kolkata Metro Line 2 (East-West Metro) begins at Bidhannagar Sector 5 in the east to Phoolbagan. Only Phase 1 is completed. The phase 1 is on elevated tracks. The Phase 2 from Phoolbagan to Howrah Maidan is under construction. The Phase 2 is mostly underground. This phase 2 of the Green Line will cross through the Hooghly River and it