From 16 September Londoners will be able to pay for all London Underground, London Overground and bus travel using their contactless debit cards. No more need for Oyster cards.
The really clever bit is that you'll never need to buy a travelcard in advance because TfL will just cap your payments when you reach a certain level.
At the moment Londoners have to pay up front for a weekly or a monthly travelcard and hope they make sufficient use of it.
For example, a commuter pays £57.20 a week for a Zones 1-6 travelcard in the expectation that they will travel enough over a seven day period to make it worthwhile. If they don't travel enough then they've wasted their money.
Under the contactless system travelcard prices will instead act as caps. A commuter travels as much as they want and TfL stops charging them when they reach a certain level.
So you don't have to guess at the start of the week whether a travelcard is the most cost-effective option, you just keep travelling and TfL will charge you the lower amount.
Matthew Hudson, TfL's head of business development, told BuzzFeed that it's been a massive task but said the switch will make it cheaper for TfL to sell tickets.
"We had to replace all our readers, upgrade communications and build a new back office. We have a team of about a hundred people doing software development, which we're then looking at selling on to around the world. On communications we've fitted out our entire system with Ethernet and we've changed all our buses to work on 3G so there's now a modem in every bus."
"Weekly tickets are one of the hardest products to sell because visitors come to London, don't know what zones or how long they need it. If we remove that and say we've got daily caps and a Monday-Sunday cap then most people don't have to do anything other than turn up and travel."
He says removing the need to buy a travelcard up front will increase the number of people on the tube because people won't worry about spending too much money.
All payments are recorded in an online account attached to the card.
That said, TfL aren't going to get rid of the Oyster card just yet. But this is the beginning of the end and Hudson reckons usage will decline pretty quickly.
"We surveyed our pay as you go customers and we got very positive results: a third of the people got it and wanted to do it now, a third wanted to wait and see, and a third of people said I don't think it's right for me."
"We're pretty confident it's going to be a success. As time goes on people will be using their Oyster card and they'll see a queue to top it up so they'll use their card instead."
He also suggested people could soon pay for tube journeys using phones equipped with wireless payment chips.
"At the moment phones [with a payment chip] can emulate a payment card and my readers can't tell the difference. It could happen now, it's just up to the mobile phones and the carriers and the card schemes to come to a deal."