I've looked around at the API and available data files (specifically for commuter rail), and don't see information on the Zone a station is in, so there's no way to calculate a fare in an app. Is that information available anywhere? Obviously I could hard code it for all stations, but that seems unpleasant. Would be great if it was in the StationOrder.csv that is already available.
Alternatively, any rule of thumb to get it mostly right? Something like, "Each 5 miles of distance is a zone"?