The train covers the distance in 19 minutes, with a 30-second halt at each station.
The much-awaited Chennai Metro Rail was launched on Monday by Chief Minister J Jayalalithaa, from her office via video conference.
The first train, steered by two lady drivers, started from Alandur and headed to Koyambedu, a 10.1-km stretch which takes an hour by road.
The train covers the distance in 19 minutes, with a 30-second halt at each station. The service would be from 6 am to midnight.
Rail stations were akin to cinema halls, as excited people tried to grab tickets. The minimum fare is Rs 10 and the full fare for the entire stretch is Rs 40.
Special class fares are double. For the same full stretch, a city bus charges Rs 11; for an air-conditioned one, Rs 30 a passenger. An auto rickshaw fare would be Rs 200-250.
A look at Metro Rail across India
The Mumbai Metro charges Rs 32 one-way for 11 km (Ghatkopar to Versova), according to the Mumbai Metro website.
According to Delhi Metro Rail Corporation, a distance of 10.851 km (Adarsh Nagar to Chawri Bazar) would cost Rs 16, and the time taken 19 minutes.
Each train in the Chennai Metro can carry 1,276 passengers. Seats are available for 176. Coaches are installed with LEDs and speakers.
The 45-km first phase, with 32 stations, was originally estimated at Rs 14,600 crore (Rs 146 billion). Officials said it would have increased to Rs 20,000 crore (Rs 200 billion).
Of the project cost, the central and state governments would contribute around 20 per cent each; Japan International Cooperation Agency would fund the rest.
Project work began in 2007. Phase-I is to have two corridors, a 23.1-km stretch (Washermanpet to Airport) and another of 22 km (Chennai Central to St Thomas Mount).
Officials say they hope the project will be complete by next year.
The second phase was earlier estimated at Rs 36,000 crore (Rs 360 billion). Chennai Metro Rail Ltd has zeroed on three corridors here.
A presentation has been made to the government, for the 60 km here, all underground.