When I was in Washington, DC last week with my SIL and a friend, we stayed in a suburb and took the Metro anywhere we went that wasn’t on the tour bus.
You got your ticket from a machine. And if you decided to go on to somewhere further than your original destination, you could put your almost depleted ticket into one of the machines and add money to it.
Someone I’ve talked to since we got back said that they had heard that the DC Metro was “scary”, but I never felt that. Of course, I was never traveling on one alone and we rode them almost exclusively during daylight.
When we had questions the “regulars” sitting around us were always very helpful. When I was talking to one young man about how we could make sure we didn’t miss getting off at the right stop, he told me that for our stop we should count three stops after daylight! Then he explained, because it was obvious we weren’t “locals”, he meant get off at the third stop after the train went from underground to above ground.
The trains were always on schedule and clean and the passengers were friendly and helpful. This was my first experience with a metro train system and it was a very positive one.