The Guardian (and other papers) report on the increase in cash fares for public transport in London Most expensive in the world: London's fares rise again .
The key issue is driving passengers toward electronic payment (Oyster-based smartcard prices have been frozen simultaneous with the cash increase). This is essentially the same as the model I developed a few years ago for toll roads with electronic toll collection, though in that case I suggested pushing travelers to electronic payment through delay reduction and ETC discounts, suggesting that it would be better overall to move travelers toward electronic payment sooner rather than later.
The more relevant point is that the Oyster fare is still more expensive than smartcard fares in other cities. Is that because London is recovering a higher share of its costs directly from passengers (rather than having a larger subsidy from general revenue), or because its costs are higher. The first would be a good reason for higher fares (why should bus users subsidize rail users, or bicyclists subsidize either?), the latter might suggest management problems, especially since there is no notable higher quality of service on the underground than on other large city metros. The network is more extensive, and more as a result more widely used, but on the other hand, it is far less reliable than any other city's system I have used.
The increase in National Rail fares is another issue entirely ...