 Color coding allows the map to specify each line in an easy way, allowing the users to quickly identify where each specific line goes; if it does not go to the desired destination, the colors and symbols allow the user to identify a feasible point of transfer between lines.Symbols such as aircraft may be used to illustrate airports, and symbols of trains may be used to identify stations that allow transfer to other modes, such as commuter or intercity train services.With the widespread use of zone pricing for fare calculation, systems that span more than one zone need a system to inform the use which zone a particular station is located in.