Maybe there should be a generic oyster card, that should work for all public transportation systems in uk. One physical token, linked to many accounts.
The standard for this exists, it is named ITSO. You will not be surprised to learn that although many local transport systems issue cards with ITSO logos they don't actually interoperate in a useful fashion since different local authorities and operators have contradictory requirements.
For example in Bingley (Yorkshire) where my mother lives, and in Southampton (on the South Coast) where I live, the buses use ITSO smartcards. But you can't take a ride on her bus with my smartcard.
Contactless bank cards do work on both systems though, and on the London transport network. So "Use a credit card" ends up being the "one physical token" solution.
> But you can't take a ride on her bus with my smartcard.
Even if I put some money on that card, via her bus' payment system? As in, I go to a tfl ticket machine, touch, put money on, touch again and then I can use the card on the underground. Then I go to Southampton, go to a ticket machine, touch, put money on, touch again, then I can use the card on the Southampton's transit system.
Unlike Oyster, you usually can't load "money" into ITSO cards. In Southampton you can load "journeys" or "season tickets" and I think the same in Bingley. I put journeys on my Southampton card because I don't use a bus for weeks at a time. But you do that by going to a web site with ID for the local card, there's no way that I've found to go "Er, I have a different ITSO card from somewhere else".
> As in, I go to a tfl ticket machine, touch, put money on, touch again and then I can use the card on the underground. Then I go to Southampton, go to a ticket machine, touch, put money on, touch again, then I can use the card on the Southampton's transit system.
Literally just tried this with the Southampton card in London against a tfl machine. No Dice.
It's Southampton that I'm in too, as of about two weeks ago you can now get the card that operates the train gates at central and oyster gates in London. About 8 years after they put in the gates...
Just two weeks ago I was finally able to get an oyster-like card from South West Rail that works with the train and the tube. Progress, finally!