All traffic on that street moves in the direction of the arrow. Cross traffic, parked cars, and signals on that street are all arranged for one direction only.
Turn only in the direction the arrow points. Before turning onto any unfamiliar downtown street, glance for this sign; it is usually mounted at the corner.
The arrow is the entire law: everyone goes where it points, including you.
Turning left onto a one-way street going right, usually at night, usually while following a navigation app too literally. Look at the sign, not just the map.
Signs that live in the same family, or get confused with this one.
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