In the last year, I've been through over a dozen cities and used public transport in all of them. It is wild just how confusing and complex buying a ticket can be. While some cities obviously take a user-centred approach to ticketing, others appear to take a Kafkaesque delight in a bureaucratic maze of zones, apps, and intricate restrictions. One of the seminal texts in computer systems design…
Honestly, I think, despite its massive amount of failures, Deutsche Bahn did a massive service with its app, as it doesn’t only show German train/tram/bus connection, but also does the same with other EU connections, with also often allowing you to buy it in the app as well.