lower berths are kept for the sr citizens as the railway gives priority to sr citizens for alloting lower berths but these are not kept safe for them, while booking you can mention you choice @ prs to the booking clerk to allot lower berths wheather you are sr citizen or not
while booking through irctc you can also opt for the option to book the tickets only in case of lower berths are alloted
As the blogger @ Oct 10 11:14AM says that there should be large no of vacant seats to...
more... book in lower berth quota this is also not 100 % true.
This totally depends upon the seats accomodation available @ the time of booking.
Sometimes with higher availbility(say more than 70) it refuses to allot a single lower berth & sometimes with less seats available(say less than 10) I got two lower berths.