Signs are posted showing which direction the vehicles can move in: commonly an upward arrow, or on a T junction where the main road is one-way, an arrow to the left or right. At the end of the street through which vehicles may not enter, a prohibitory traffic sign “Do Not Enter”, “Wrong Way”, or “No Entry” sign is posted, e.g. with that text, or a round red sign with a white horizontal bar. Sometimes one portion of a street is one-way, another portion two-way. An advantage of one-way streets is that drivers do not have to watch for vehicles coming in the opposite direction on this type of street.