Read this again:-
"tracks conditions in some sections , traffic /conjestion high speed trian ki ijjata nai deta
distance etc all factors"
Delhi - Agra -> 160 kph (Shatabdi) 130/140 (Rajdhani) 110 Mail/Express
Agra...
more... - Lalitpur -> 130 kph (Rajdhani/Shatabdi/Duronto) 110 Mail/Express
Lalitpur - Kazipet - Secunderabad/Vijayawada -> 120 kph (Raj/Shatabdi/Duronto) 110 Mail/Express
Secunderabad - Bangalore :- single track in 90% of the section, diesel line, 110 kph applicable to all trains, Rajdhani/Duronto may have exceptional.
Vijayawada - Chennai Central -> 110 kph (All Class trains.)
.
secondly, traffic en-route. the route handles more trains, where even freights do come n start disrupting normal run.
unless there is a proper clearance, ahead, even a TGV has to run on caution order, so a IR train too.
BZA - BPL section needs to b upgraded, but our coaches aren't fit to touch max limit i.e above 110 which is a default restriction for Mai, Super fast n Express trains.