(16 Jan 2023, 2:36 pm)Adrian wrote Brighton & Hove, who use the same app, allow you to buy singles on it. It's really useful, and they work on the basis that they're valid for 15 minutes (to scan) from you hitting activate.
I don't think it'd ever work in an area without a flat fare or hopper-type system. People would get wise to it, buy the cheapest fare to get them on board, then over ride on it.
People do that anyway!