What it looks like
A horizontal black rectangle with the words ONE WAY in white capitals and a white arrow showing the single direction of travel.
When you'll see it
Posted at intersections and along one-way streets, especially in downtown grids and where divided roadways separate opposing traffic.
What to do
You must travel only in the direction the arrow points; do not turn or drive against the marked flow.
Source: Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition — FHWA.
