2014 August 13, Gwyn Topham, “Open data and driverless buses: how London transport heads to the future”, in The Guardian[1]:
From September passengers will be able to enter by tapping their credit card at the barriers – with the new Tannoy announcement "avoid card clash" joining the familiar "mind the gap" as the sound of the Underground. Card clash can be avoided with an even newer technology, contactless payments via mobile phones: […]
