Warning Signs
What warning signs mean
Warning signs are yellow diamonds with black symbols (fluorescent yellow-green for school, pedestrian, and bicycle warnings). They tell you what is ahead so you can adjust speed and position. They are not themselves commands, but ignoring the hazard can still violate the basic speed law.
Core rules
- Curves: Right curve, left curve, reverse curve, and winding road signs warn of alignment. A yellow “35 MPH” plaque is an advisory speed for the curve, not a posted legal limit.
- Intersections: Crossroad, side road, T-intersection, Y-intersection, and roundabout signs warn of entering traffic. “STOP AHEAD” and “YIELD AHEAD” warn of a control device ahead, not the device itself.
- Narrowing: “LANE ENDS,” “ROAD NARROWS,” and “ONE LANE BRIDGE” tell you to merge or wait.
- Hills and surfaces: Steep grade signs warn of long descents; truck plaques advise lower gears. “SLIPPERY WHEN WET,” “LOOSE GRAVEL,” and ice warnings call for slower speed and gentler inputs.
- Pedestrians and schools: A pentagon-shaped school sign or a yellow-green pedestrian sign warns of crossings. A “SCHOOL SPEED LIMIT” sign is regulatory when its flashing beacon is active.
Worked example
You see a yellow diamond showing a right curve with a “40 MPH” advisory plaque. The road is wet. The plaque suggests 40 mph for the curve in good conditions; in rain you should enter slower because the advisory does not guarantee grip. Reasoning: advisory speeds are guidance for ideal conditions, while the basic speed law still requires a safe speed.
Traps
Treating a warning sign as a speed limit; missing the difference between “STOP AHEAD” and “STOP”; assuming an advisory plaque is enforceable as posted maximum; ignoring fluorescent yellow-green school signs; and failing to slow for a surface warning until you are already in the hazard.