Warning Signs: Anticipating Hazards
Warning signs alert you to conditions ahead so you can adjust speed and position. The dominant format is a yellow diamond with a black symbol or legend. A few important variants exist: yellow pentagon (school zone/school crossing), yellow circular (railroad advance warning), and yellow rectangles for some advisory messages. Orange is reserved for construction; yellow is for permanent or general hazards.
Core warnings to know
- Curve and road geometry: curve ahead, sharp curve, winding road, reverse curve, hill, and winding-road chevrons.
- Intersection and merging warnings: crossroad, side road, Y-intersection, merge, lane ends, and added lane.
- Surface and condition warnings: slippery when wet, loose gravel, pavement ends, and bump.
- Traffic-flow warnings: two-way traffic, divided highway begins/ends, and reduced lane width.
- Advisory speed plaques: a yellow rectangular plaque below a warning sign shows a recommended (not legally posted maximum) speed for the hazard.
Traps to watch for
A frequent trap is confusing an advisory speed plaque with a regulatory speed limit. The advisory plaque is a recommendation for the hazard; the black-and-white SPEED LIMIT sign is the legal maximum. Another trap: the "lane ends" sign versus "merge" - lane ends means your lane disappears and you must merge; merge means two lanes combine and both drivers share responsibility. Also, a yellow diamond with a pedestrian symbol warns of pedestrians ahead, but a yellow pentagon means a school zone, and a fluorescent yellow-green pentagon emphasizes school children.
Rule of thumb
Yellow means "be ready" - slow down, increase following distance, and scan for the hazard. Warning signs do not change the right-of-way; they only tell you what is coming.
Worked example: You see a yellow diamond with a slippery-when-wet symbol and a 35 mph advisory plaque on a wet road. The correct response is to reduce speed toward 35 mph and avoid sudden braking or steering, not to assume 35 is a legal limit.