[Johnny555]

This is pretty common among transit agencies, I got on the wrong platform in Japan once and couldn't get back out until I talked to a station agent, the fare gate gave an error and wouldn't open the gates. Not sure if that's better or worse behavior than charging a fare.

It's called an "excursion fare", which is meant for those that just ride the train without getting off and come back to the same station. You can talk to a BART station agent (assuming you can find one) and they'll let you out, or call customer service and they'll reverse the charge.

Modern fare systems should be able to figure out when you've exited right after entering and not charge you. BART is supposed to be adding a 30 minute grace period so if you go in and out of the station within 30 minutes, you won't be charged.

https://www.bart.gov/guide/faq#3

[kelnos]

Heh, I was in Japan a few weeks ago, and had left my bag in a locker at a station (inside the fare gates). I went back to get it later in the day (when I could check into my hotel), and the station attendant charged me 150 yen just to go in to get it and come right back out!

I get that they want to charge people who ride the trains for... fun?... and then get off at the same station, but it felt really silly.

[landedgentry]

I think those tickets are for people who train watch on the platform or see off friends/family from the platform.

[Symbiote]

If it was good enough in 1980, Japan might computerise it but they won't change it.