Some train passengers could face season ticket fare rises of more than 5% under new year increases expected to be announced tomorrow.
Recent Government announcements have meant the annual rise in regulated fares, which include season tickets, will not be so severe for 2014.
But the new price-rise formula, which will kick in on January 2, still allows for average regulated fare increases of 3.1%.
And train companies can use a 2.0% "flex" regulation which lets them put some regulated fares up by 5.1% as long as their overall average does not exceed 3.1%.
The increase for any January is calculated from the RPI rate of inflation figure for the previous July. In July this year the RPI figure was 3.1%.
Campaign for Better Transport chief executive Stephen Joseph said: "We're very disappointed that the higher RPI figure is still being used when it comes to passengers having to find money for their annual increase.
"Yet when it comes to pensions and other benefits, the lower CPI inflation figure is used."
The announcement of the rise has been delayed this year after Chancellor George Osborne announced in his Autumn Statement earlier this month that the increase formula for regulated fares was changing from RPI plus 1% to RPI plus 0%.
Earlier the Government had also announced that the "flex" rule, which originally allowed companies to put up some fares by up to 5% above the RPI plus 1% figure, would be limited to 2% above.
Before these changes, some passengers could have faced season ticket rises of as much as 9%. However, even with the new formula, many passengers will be finding their fare rise far outstripping their wage rise.
Some passengers might have to wait a few more days to find out what their January rise will be as it is thought that some train companies may not yet be ready to announce the new fares.