Airports and flights cannot be alternative to railways and roadways for entire city travellers even if they create metro tracks. For instance buses take 5-5.5 hrs to reach electronic city and madiwala (south end) with just rs 600 while people of whitefield indiranagar marthahalli east areas tech within 6 hrs by using trains @rs 600. If they 50% use flight they have they reach airport in chennai 30min+ 60min check in +60 min travel +30min getting into city travel mode +60-150mns for reaching destination total 4-5 hrs of journey without much savings in time. Plus creating a metro line for 40-50km till city center requires rs10000 crs and still be not useful for sectors like chennai blore and I'll be helpful for long distance travellers. By investing in existing track even if 1or2 trains travrl@160-200kmph speed the avg speed of other trains and freights I'll also improve considerably.