Kolkata Metro rolling stock
The rolling stock of Kolkata Metro consists of five classes, three classes for Blue and Yellow Lines, one of which is also used for Purple and Orange Lines, and one class for Green Line.
All trains receive 750 V DC using third rail electrification system. Trains can operate up to eight (Blue, Purple, Orange and Yellow Lines) and six (Green Line) cars in length.
Since Kolkata Metro was constructed in 1970s, there were some technical limitations. Due to the tunnel dimensions, and being under Indian Railways, Kolkata Metro opted Indian metre gauge shell (22.7 m (74 ft 6 in)) with 1,676 mm (5 ft 6 in) tracks for Blue Line, which was later used for Purple, Orange and Yellow Lines. So the options of rake manufacturers for Blue, Purple, Orange and Yellow Lines are very limited. On the other hand, Green Line uses the 1,435 mm (4 ft 8+1⁄2 in) standard gauge tracks similar to most other Indian metro networks.