55% of the corridors in Phase I are underground and the rest are elevated. The first stretch of Phase I, covering seven stations from Koyambedu to Alandur over a distance of 10 kilometres (6.2 mi), began operation on 29 June 2015. As of March 2019, the entire Phase 1 stretching from Chennai Central to Alandur on the Green line and Washermanpet to Chennai International Airport on Blue line are commercially operational, bringing the total operational network over 45 km.