3 Zone 4 Zone 5 Zone 6 Zones 7–9, C, G and W Travelcard Superimposed on these mode-specific regimes is the Travelcard system, which provides zonal tickets with validities from one day to one year, and off-peak variants. These are accepted on the DLR, buses, railways, trams, and the Underground, and provide a discount on many river services fares. Oyster card The Oyster card is a contactless smart card system introduced for the public in 2003, which can be used to pay individual fares (pay as you go) or to carry various Travelcards and other passes. It is used by scanning the card at a yellow card reader. Such readers are found on ticket gates where otherwise a paper ticket could be fed through, allowing the gate to open and the passenger to walk through, and on stand-alone Oyster validators, which do not operate a barrier. Since 2010, Oyster Pay as you go has been available on all National Rail services within London. Oyster Pay as you go has a set of daily maximum charges that are the same as buying the nearest equivalent Day Travelcard. Contactless payments Almost all contactless Visa, Maestro, MasterCard and American Express debit and credit cards issued in the UK, and also most international cards supporting contactless payment, are accepted for travel on London Underground, London Overground, Docklands Light Railway, most National Rail, London Tramlink and Bus services. This works in the same way for the passenger as an Oyster card, including the use of capping and reduced fares compared to paper tickets. The widespread use of contactless payment - around 25 million journeys each week - has meant that TfL is now one of Europe's largest contactless merchants, with one in 10 contactless transactions in the UK taking place on the TfL network. Mobile payments - such as Apple Pay, Google Pay and Samsung Pay - are also accepted in the same way as contactless payment cards. The fares are the same as those charged on a debit or credit card, including the same daily capping. In 2020, one in five journeys are made using mobile devices instead of using contactless bank cards, and TfL had become the most popular Apple Pay merchant in the UK. TfL's expertise in contactless payments has led other cities such as New York, Sydney, Brisbane and Boston to license the technology from TfL and Cubic. Identity and marketing