Warning Signs
Warning signs tell you what is coming, not what you must do. They are yellow diamonds with black symbols, and Idaho highways also use yellow rectangles and plaques that add distance or advisory speed.
Reading the yellow diamond
- Diamond shape means warning. The symbol shows the hazard: curve, hill, merge, pedestrian, deer, ice, wind, or signal ahead.
- A black-on-yellow advisory speed plaque (for example 35 MPH) is the recommended speed for a passenger car in good conditions. It is not a legal limit, but it is strong evidence that a higher speed is unsafe.
- Distance plaques such as 1 MILE or NEXT 3 MILES tell you how far the condition lasts.
- Warning signs never grant right-of-way and never override a regulatory sign, signal, or flagger.
Specific hazards the exam likes
- Curve and reverse-curve signs: slow before the curve, not in it.
- Deer and wildlife signs: common on Idaho rural routes; scan the shoulders at dawn and dusk and cover the brake.
- Hill and downgrade signs: shift to a lower gear before the descent instead of riding the brakes.
- Signal ahead, stop ahead, and yield ahead: move your foot off the accelerator and prepare to stop.
- Slippery when wet and crosswind: reduce speed and increase following distance.
Worked example
You see a curve sign with a 35 MPH advisory plaque and are traveling 55 mph in heavy rain. The advisory assumes good conditions, so in rain you should be well below 35 mph: brake before the curve, then steer through it. The plaque does not change the posted speed limit; it changes the safe speed.
Traps
Treating the advisory speed as the legal limit; missing a small plaque under the diamond; confusing a pedestrian warning sign with a marked crosswalk; assuming the hazard ends where the sign stands.