Travelcard Zone 6 is the sixth outward concentric zone of the Transport for London zonal system used for calculating co-ordinated inter-modal Travelcard fares within Greater London. In this zonal system, Greater London is split into six (approximately concentric) zones for the purpose of determining the cost of a Travelcard. The zones are also used for pricing London Underground and Docklands Light Railway single journeys, but not single journeys undertaken entirely by bus or tram, for which a system-wide flat fare applies. 