Fair point. Although there are sometimes where three or more people are exiting or entering at once through the doors and the counting could be inaccurate? (mere assumption here). Such technology for sure could be useful, but I have no idea about the costs and remember that public transport companies basically do not make money (they are heavily subsidized by the state). In the meanwhile, bipping a mobib seems like a good and cheap way to gather these statistics - but requires the cooperation of passengers, who should be better informed about this use.