Sounds like BART is cracking down seat hogs or as they call them, "manspreaders".
http://www.citylab.com/commute/2016/04/in-san-francisco-hog-a-train-seat-and-get-a-100-ticket/478587/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+TheAtlanticCities+%28CityLab%29
http://www.citylab.com/commute/2016/04/in-san-francisco-hog-a-train-seat-and-get-a-100-ticket/478587/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+TheAtlanticCities+%28CityLab%29