When you go to sign up for your driving permit, they hand you an entire book on road signs, markings, and traffic signals. They don't just explain what is around your neighborhood and on your daily commute, they explain how the entire system works and how to read it fluently.

Later, they test you on it. Obviously, testing people on riding the metro would be ridiculous. But there is a huge difference in having a map and signing system in place versus knowing how to read them.