Truck Rollover Warning sign
A ramp or curve ahead has a history of trucks and other high center of gravity vehicles tipping over at speed. Trucks in particular should slow well below the posted ramp speed.
Federal designation W1-13 in the MUTCD, the national standard every state signs to. Placed on highway interchange ramps and loop ramps where the curve radius is tight enough that loaded trucks have rolled over there before.
How to recognise it
This sign is a diamond stood on its point in yellow, the warning colour. Yellow diamonds telling you what the road is about to do. They are advisory rather than mandatory, but ignoring them is how people end up in ditches and how examiners end up failing you.
What the test wants you to know
This sign exists because standard curve advisory speeds are calculated for passenger cars, and a loaded truck's higher center of gravity can roll it before it would ever skid. The expected answer on a commercial license question is to brake before the curve, not during it, since braking mid curve on a tall vehicle can itself trigger a rollover.
Practise it
Reading about a sign is not the same as recognising it in half a second with an examiner watching. Every state road signs test on this site shows the sign and asks you to name it, then shows four faces and asks you to pick the right one.
Right Curve
Left Curve
Cross Road
Side Road
Merge
Lane Ends