[tialaramex]

In this particular context by the way (enter and exit same station, assume you just tapped in and out as you would normally) LU may actually charge "Same station fare" and the rules are pretty esoteric.

https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets...

[Edited to add: Stupid web site doesn't have working fragment markers, click "Same Station Exits" near the top... ]

In practice, as it explains elsewhere on the site, these charges are mostly to discourage attempted fare evasion, and if you're a regular user who just does this once in a while it'll delete the journeys after it decides this isn't suspicious after all, otherwise you need to talk to a human if you really didn't travel anywhere.

[rahimnathwani]

The 'same station exits' section of that page is fascinating. The great thing is that most people will never need to worry about this, so they discourage fare evasion without inconveniencing honest passengers.

I wonder: if there were better enforcement of fares in San Francisco, would public transport be better? Right now, I almost never use public transport in SF because ~100% of my journeys would take 2x to 3x as long as they do by car. This is very sad for me, having previously lived in two cities with excellent public transport (London and Beijing).