From SSC's Chennai airport thread (
link):
This shows the air traffic between MAA-BLR and MAA-HYD last month. See this (
link to DGCA publication) for the full list of stats.
That apart, Chennai-BLR has 7 dedicated daily trains, 3 of them all-AC (two Shatabdis and 1 double decker). The assumption being these are higher fare-paying passengers. All these trains run full irrespective weekdays or weekends. Then there are the AC Volvo services - KSRTC alone runs about 30-35 Volvo services one-way per day, not to mention the innumerable private operators. These numbers generally spike up over the weekends, of course.
Chennai-HYD dynamic is slightly different simply because of the distance. So the number of daily commuters are obviously lesser. However, the flight statistics show there is a good base to build upon. There are 3 dedicated daily trains between these two cities, and many train passengers would opt for a faster option if available. The sweet spot on this route is between the 2AC IR fare and air fare. Throw in a Tirupati or Vijayawada/Guntur as mid-way point, it becomes a sure-shot option.
The problem as I see it is BLR-HYD. While the demand between the cities is very good (1 lakh one-way pax per month according to DCGA), as of now, there are no mid-way points to generate additional revenue. Cities like Ananthapur or Kurnool are not big economic engines to drive a lot of traffic. But they could grow as exurbs for these cities, with 1-2 hr commute one-way.