Soft Shoulder Sign
MUTCD W8-4
The road shoulder is soft; stay on the pavement.
What it looks like
A yellow diamond-shaped warning sign with a black legend reading SOFT SHOULDER.
When you'll see it
Along roads where the shoulder is unpaved or not firmly compacted, often on rural highways or newly built sections.
What to do
Stay on the pavement and keep your wheels off the shoulder; a soft shoulder can grab a tire and pull the vehicle off the road.
Related signs
Source: Manual on Uniform Traffic Control Devices (MUTCD), 11th Edition — FHWA.