I'd say "easy" is an overstatement. You have to install an app and master their weird terminology (to get a reasonable price you buy a "carnet" of 10 tickets).

I'd say "easy" is an overstatement. You have to install an app and master their weird terminology (to get a reasonable price you buy a "carnet" of 10 tickets). And of course it still only works with Android. Easy would be following what's being done in major transit systems all over the world: Let people immediately pay for rides without installing or thinking about anything, by tapping their phone on the turnstile. And for a bonus, adopt TfL's fare capping so people don't have to try to game the various discount options.