You are travelling against the permitted direction on a one-way road or ramp; turn back when it is safe.
This sign faces drivers travelling against the permitted direction. It is used on one-way roads and exit ramps, often beyond a Do Not Enter sign.
In the United States, R5-1a is a horizontal red rectangle. It has a white border and the words WRONG WAY in white.
Official sign in each country; the code is its number in the national rules. Signs that come in two directions show the left and the right version.
Sign images from Wikimedia Commons, used under their licences.
