Over 30m journeys have now been made using the bus Hopper fare, in under four months since its introduction in September 2016.
London mayor Sadiq Khan introduced the new bus Hopper fare enabling passengers to take a £1.50 bus or tram journey and then change onto another bus or tram for free within one hour of touching in at the start of their journey.
It's automatically given to anyone who uses pay as you go with a contactless bank payment or Oyster card.
Khan said: "I’m delighted that our new Hopper fare has already cut the cost of bus travel for millions of Londoners. The cost of transport must never become a barrier to work or study, and it was unfair that Londoners were charged twice simply for changing buses."
“It’s crucial that we continue to do more to encourage people onto public transport, and make our city a more affordable place to live and work," he added.
In the end of October, it was announced more than 10m journeys had been made in the first six weeks since the introduction of the Hopper fare.
Popular early routes included the 279 from Waltham Cross Buss Station to Manor House Underground station, the 53 from Orchard Road in Plumstead to Horse Guards Parade in Westminster and the 207 from the Hayes By-Pass near Southall to White City Bus Station in Shepherds Bush.
While Transport for London (TfL) says Hopper use is about in line with expectations, London Assembly members raised concerns over whether there had been "adequate funding" for it, during discussions of the mayor's first Budget on Tuesday.
Khan has said he thinks sufficient funding has been planned but it will be kept "under review".
Deputy chair of the London Assembly Transport Committee Keith Prince said the financial implications of underestimating the popularity of the fare "could be immense".
"From day one I welcomed this useful policy, but TfL haven't been able to adequately show me how they expect to pay for this, especially in light of mayor Khan's partial fares freeze crippling the transport budget," Prince said.
With the 30m journeys being reached in under four months, Prince said "the original projected £30m cost could be enormously wrong".