It's only Tamil, English in Chennai Metro rail system

 In Chennai, where people, including political outfits, have been known to stage anti-Hindi protests ever since Dravidian parties assumed power in the early 50s, any move to implement a new three-language policy, especially in Metro railway stations, would have triggered protests.

 In fact, all major political parties had recently protested across the state against the
Centre's move to include Hindi on milestones along the highways. Metro rail services in Chennai started only in 2015 with the signage at entry/exit points, ticket counters, toilets and escalators in Tamil and English only. “We do not have plans to add Hindi in the signage information as most people from the north who come to Chennai know English,” a senior spokesperson of Chennai Metro Rail Limited (CMRL) said.

 "Though CMRL is a joint venture of the government of India and government of Tamil Nadu with equal equity holding, the Central government or the company will not make any move to insert Hindi signage at stations as it would be against the state's interest," the CMRL official said. Tamizhar Munnetra Padai (TMP), a pro-Tamil outfit said if CMRL inserts Hindi signage, it will lead to adverse effects. “We will be the first to protest if that happens,” Ravikumar, district leader of TMP said.