The standard US “Wrong Way” sign has a red background.
The sign is a red rectangular regulatory sign with a white border and the words WRONG WAY in white lettering. It warns a driver who has entered a one-way roadway or highway exit ramp in the prohibited direction. In the Manual on Uniform Traffic Control Devices, it is designated R5-1a.
Wrong Way signs are commonly installed as supplements to Do Not Enter signs. The Do Not Enter sign is generally placed nearer the point where a driver could enter incorrectly, while the Wrong Way sign may be positioned farther along the one-way roadway to provide another unmistakable warning.
The red field connects the sign visually with other urgent regulatory messages, including Stop and Do Not Enter. It should not be confused with orange work-zone signs, yellow general-warning signs or black-and-white one-way signs. Exact placement can vary with roadway geometry, but the standard sign’s red background is consistent.