(14 Jul 2019, 10:53 pm)streetdeckfan wroteIt relies on honesty, but even with oyster systems you can pass minor's passes between people who aren't entitled to them. By the time the driver has realised it was a kid's passed being scanned, the person has already sat down.
I just couldn't bring myself to pretend to be under 19. When I was at college, I was given an 18 and Under day ticket instead of a Student day ticket so when I got to the interchange I asked to get it swapped for the right ticket
All you can do is reduce the need for doing it (cheaper simpler tickets) and then add repercussions for doing evading full fares. Revenue protections issuing more fixed fines and spot checks etc.