I suggest publishing Metro route schedule on internet, with info about at what time the train will be in certain station. Also the information can be posted in metro stations.
Metropolitan is the post proper working transport system in Yerevan.Timetable information is certain ( not like the bus timetable) and subway workers have such kind of information. It just needs to be published and available for everyone. This even does not require much expenditure, it's just an organizational question. The information can be even posted on municipality website or to make a separate layout for timetable in myyerevan.am.