Passengers with a contactless-enabled debit, credit or charge card can touch in on each bus' reader, as they would with an Oyster card, and pay an equivalent fare, rather than the higher cash fare.
This deployment is being treated as a pilot before contactless payments are rolled out to the London Underground, Overground and DLR over the course of 2013.
It's currently not fully featured, without the daily price capping of Oyster cards, but this will be introduced in the wider rollout, along with the introduction of mobile payments.
"Offering contactless payment on London's buses, alongside Oyster, is the first step in becoming the world's first transport network where customers can travel between bus, Tube and rail by touching in with a contactless payment card," said TfL director of customer experience Shashi Verma. "We look forward to seeing the number of people using this payment option increase over the next year as the banking industry issues more contactless cards to their customers."
The wider rollout will vastly increase the number of contactless payment points in the city. But perhaps the biggest knock-on effect of this move, in terms of mobile payments, will be introducing NFC to the public consciousness, and helping to push it into the mainstream. The concept currently doesn't have much traction at all, as seen in ICM's findings this week that half of the sales assistants working in stores accepting contactless payments weren't aware of it.