Keep Right Sign
MUTCD R4-7
Keep to the right of the median or obstruction ahead.
What it looks like
A white square with a black arrow angled to show traffic should pass to the right of an obstruction or median ahead.
When you'll see it
Posted at the approach to a median, traffic island, toll booth, or other divider where drivers must pass on the right side.
What to do
You must keep to the right of the median or obstruction ahead rather than passing on the left.
Related signs
Source: Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition — FHWA.