evidence: To eliminate the previously open discharge toilet system, zero discharge Bio-toilet system with ventilation has been adopted for coaches of Indian Railways. [...] Initially complaints regarding choking of bio toilets in coaches were investigated and it was found that it was largely due to passengers throwing non Bio-degradable items like plastic bottles, huggies, tea cups, papers / polythene bags, napkin etc. in the toilet pans because of their unawareness about the provision of Bio-toilets in respective coaches which were resulting in choking and foul smell. [...] - To further address the issue of the foul smell in coach toilets and remove waste from toilet pan to Bio-tank, Bio-Vacuum toilet systems have been developed and are being fitted/retrofitted in coaches.