How is the San Francisco public transportation system?

The San Francisco public transportation system, also called MUNI system, consists of a train network that includes the BART trains, buses, and their famous cable cars which are similar to tramways. A round trip with the BART train from SFO San Francisco international airport to San Francisco center costs around US$20 , depending on the exact exit stop. Airport San Francisco transportation to city A round trip from airport to city costs around US$20 , depending on the exact exit stop, and tickets can easily be bought on a machine before boarding the train. The BART schedule runs 24hours a day, therefore it is possible at any time to reach airport, or come to city center from there. The MUNI public transportation system covers city trains, buses and historic streetcars. A single ride costs US$2.5 , a day pass costs US$5, and a cable car ride costs US$7, all of them can be bought on the MuniMobile application. A San Francisco public transportation day pass with MUNI costs US$5 , and most be bought on the MuniMobile application - it does not include the cable car, but includes all the other means of transportation of the network. A cable car single ride costs US$7 , and can also be bought on the MuniMobile app, or in any case before boarding the cable car as it is not possible to buy tickets at the cable car.