The Chennai Suburban Railway is a commuter rail system in the city of Chennai (Madras), Tamil Nadu, India operated by the Southern Railway, one of the operating railway zones of Indian Railways. Chennai has a complex railway network. The system uses electrical multiple units (EMUs) operating on alternating current (AC) drawn from over-head cables through the catenary system. The total system spans around 900 km of which only 286 km have dedicated dual tracks for suburban EMUs, the rest share tracks with other trains and are called mainline EMUs (MEMUs). As of 2013, the suburban sector has 580 services, including 250 in the Beach–Tambaram section, 240 services in the Central–Tiruvallur section, and 90 in the Central–Gummidipoondi. As of 2011–2012, 1.46 million people use the suburban train