The double deck rail carriage was first operated in Britain. A Bulleid design. Although having seen one in a museum it certainly isn't to the same modern standard as the Indian one shown.
ISTR that under Indian law (I don't know of Pakistan and Bangladesh) but there was not supposed to be any charge for passengers travelling on the roof anyway.
Given the price of worst great western here, I might perhaps ask them if I can travel cheaper if I sit on the roof (just forget the low roof clearance of the IKB tunnel!)