You no longer need to be in the great outdoors to fast travel.
Fast traveling is a quality of life feature that makes it tremendously easier (and quicker) to explore the apocalyptic wasteland. With the constant threats of Super Mutants or radioactive storms, sometimes you just don't want to make that long trek across the map, especially if you're short on time. In previous Fallout games, players were only allowed to fast travel while they were outside. It appears that this is no longer the case in Fallout 76.
Full story from the WindowsCentral blog...