As regards the back-breaking journey from Tindivanam, I agree it is, but I think you can put up with it, assuming you can travel 3 hours on road. The VM rail route has never been a sought-after one, from Chennai. Even the Chennai-Tiruvannamalai passenger, during the time it ran, did not live up to the hype it generated.
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As for a dedicated bus forum, I am not aware of anything comprehensive existing right now, kind of bits and pieces, but there are some allied road-travel fora like Team-BHP, whic provide...
more... info on routes, road conditions, eateries, etc.
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Thanx for your compliments, credit goes to Moderator.