Transport for London is planning to allow customers to pay for journeys using their smartphones.
According to a Financial Times report, TfL is in talks with mobile operators including EE and Vodafone to make it possible for travellers to scan their phone in the same way as Oyster cards.
Most smartphones produced today use the same Near Field Communications technology as Oyster Cards.
TfL said the upgrade to readers to accept contactless payment cards also makes them capable of accepting suitable payment applications on mobile phones.
"In principle, mobile phones with a Visa, Mastercard or Amex payment application could be accepted on our services,” said a TfL statement.
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"At this stage, mobile phones with pre-paid cards will not be accepted. We are testing to see how the devices perform on the system and welcome any innovations which improve the services and choices we are able to offer customers.”
Gartner expects NFC will account for 5% of the total transaction value in 2017. Gartner said the fall in NFC payments is due to “disappointing adoption of NFC technology in all markets in 2012 and the fact that some high-profile services, such as Google Wallet and Isis, are struggling to gain traction."