Several Tube stations in east London have been rezoned to recognise the capital's "shifting economic map".
Eight stations including Stratford and West Ham have been rezoned from Zone 3 to Zone 2/3.
It means the stations will be regarded in Zone 2 or 3 depending on which way the passenger is travelling, giving the cheapest travel option for the journey.
The Mayor of London said it was hoped 100,000 people per week would benefit from the change.
How a Zone 2/3 boundary station works
According to Transport for London a passenger would always pay the cheapest fare depending on which direction they were travelling in.
For example, if they were travelling from Zone 6 to Stratford they would pay a Zone 3-6 fare, whereas if they were travelling to or from Zone 1 from Stratford they would pay a Zone 1-2 fare.
The other stations that have been rezoned are Stratford High Street, Stratford International DLR station, West Ham, Canning Town, Star Lane and Abbey Road.
Sir Robin Wales, the Mayor of Newham, said: "We've been campaigning for this for some time. The truth is London's moving eastwards... and it's sensible to reduce the cost of travel.
"It's going to encourage people to come to Stratford, West Ham and Canning Town, which will be great."
Transport for London has made the changes as part of its 2016 plans, which include a ticket price hike of 1% in line with the July Retail Price Index and enabling children to travel for free on National Rail services in the capital.
The changes also include it becoming possible to use an Oyster or contactless card for journeys between London and Gatwick Airport on Southern, Gatwick Express and Thameslink services from 11 January.
