Unless otherwise provided in this Act or the rules framed thereunder, any notice or other document required or authorised by this Act to be served on any person by a railway administration may be served--
         (a) by delivering it to the person; or
         (b) by leaving it at the usual or last known place of abode of the person; or
         (c) by registered post addressed to the person at his usual or last known place of abode.