All the train running in these routes are all broad gauge, Its really a good experience 2 travell in chennai trains, i like to travel in beach thambaram trains, though there are train for every 10 mins the trains are crowded fully in the peak hours. To avoid the crowd in the peak hours the railways had introduced automated ticket wending machines which uses a prepaid smartcard to lend the tickets but i dono why most of them dont use it, The rail way stations are better than before, they are maintained well nowadays, Train travelling in chennai is a great experience, Mainly Travelling in MRTS trains, they are also called as flying trains ( Parkkum Raiyil ) . chennai rocks 
Chennai Train Route:
Train route From CHENNAI BEACH to CHENGALPET:
Chennai Beach, Chennai Fort, Park, Egmore, Chetpet, Nungambakkam, Kodambakkam, Mambalam, Saidapet, Guindy, St.Thomas Mount, Pazhavanthangal, Meenambakkam, Tirusulam, Pallavaram, Chromepet, Tambaram Sanatorium, Tambaram, Perungalathur, Vandalur, Urappakkam, Guduvancheri, Potheri, Kattangulathur, Maraimalai Nagar, Singaperumal Koil, Paranur, Chengalpet
Train route From CHENNAI BEACH to VELACHERY:
Chennai Beach, Chennai Fort, Park Town, Chintadripet, Chepauk, Tiruvelikeni, Light House, Thirumayilai, Mandaveli, Greenways Road, Kotturpuram, Kasturiba Nagar, Indira Nagar, Thiruvanmiyur, Taramani, Perungudi, Velachery
Train route From CHENNAI BEACH to SULLURPETTA:
Chennai Beach, Royapuram, Washermanpet, Korukkupet, Tondiarpet, V.O.C Nagar, Thiruvottiyur, Wimco Nagar, Kathikivakkam, Ennore, Attipattu Pudunagar, Attipattu, Nandiambakkam, Minjur, Anuppambattu, Ponneri, Kavaraipettai, Gummidipundi, Elavur, Arambakkam, Tada, Akkampet, Sullurpetta
Train route From CHENNAI BEACH to TIRUTTANI:
Chennai Beach, Royapuram, Washermanpet, Vyasarpadi Jeeva, Perambur, Carriage Works, Loco Works, Villivakkam, Korattur, Pattaravakkam, Ambattur, Thirumullaivail, Annanur, Avadi, Hindu College, Pattabiram, Tiruninravur, Veppambattu, Sevvapet Road, Putiur, Thiruvallur, Egattur, Kadambattur, Senjipanambakkam, Manavur, Thiruvaiangadu, Mosur, Puliyamangalam, Arakkonam, Tiruttani
Train route From CHENNAI CENTRAL to TIRUTTANI:
Chennai Central, Basin Bridge, Vyasarpadi Jeeva, Perambur, Carriage Works, Loco Works, Villivakkam, Korattur, Pattaravakkam, Ambattur, Thirumullaivail, Annanur, Avadi, Hindu College, Pattabiram, Tiruninravur, Veppambattu, Sevvapet Road, Putiur, Thiruvallur, Egattur, Kadambattur, Senjipanambakkam, Manavur, Thiruvaiangadu, Mosur, Puliyamangalam, Arakkonam, Tiruttani
Train route From CHENGALPET to TIRUMALPUR:
Chengalpet, Reddypalayam, Villiambakkam, Palur, Palayasivaram, Walajabad, Nathapettai, Kancheepuram Old, Kancheepuram, Tirumalpur
Chennai Train Route Map:
Good informative material. First time person visiting chennai who need to travel in EMU finds it easy to get down at a specific station by looking at station name listed in this site. Request to provide local train timings also.