The app is free to download and users can top up their Oyster card on the go or check journey history. The Oyster system checks that the Travelcard is valid in the zones it is being used in. Since the introduction of the Oyster card, the number of customers paying cash fares on buses has dropped dramatically. Two other names were considered  and "Oyster" was chosen as a fresh approach that was not directly linked to transport, ticketing or London. The Oyster name was agreed on after a lengthy period of research managed by TranSys and agreed by TfL.
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