The Delhi Airport, Metro, BRTS, RRTS and Monorail projects have separate threads in the Infrastructure and Transportation forums (http://www.skyscrapercity.com/forumdisplay.php?f=1247). Here are the links -


Delhi Airport Updates
http://www.skyscrapercity.com/showthread.php?t=347516


Delhi Metro Pics and Updates
http://www.skyscrapercity.com/showthread.php?t=516812


Gurgaon Metro | Rapid Metro Rail Gurgaon
http://www.skyscrapercity.com/showthread.php?t=913954


Delhi BRTS
http://www.skyscrapercity.com/showthread.php?t=613414


NCR RRTS
http://www.skyscrapercity.com/showthread.php?t=1043705


Delhi Monorail
http://www.skyscrapercity.com/showthread.php?t=1480675