Upgradation of passengers are done in one class above only, said Indian Railways.
Indian Railways' auto upgradation scheme promotes full-fare paying passengers to higher class without any extra charge against the available vacant accommodation.
This not only benefits the waitlisted passengers but also help railways in terms of filling up vacant accommodation in various trains, said Indian Railways on it's website- indianrailways.gov.in.
The passengers for upgradation are selected automatically (except in cases where the passenger has shown his unwillingness to be upgraded) on random basis by the system at the time of preparation of reservation charts, noted Indian Railways.