I m worried that this 10 minute headway is 1 Completely arbitrary If there is no source for it then it really should be dropped 2 Many of these metros have less than 10 minute headway during periods of the day How is this accounted for I m trying to get to the criteria we use to determine what is a metro system The only reason we are having this argument is that the criteria for what is a metro is not well defined here No criteria should be proposed without a source to back it up No more arbitrary rules made up by random editors