Advisory Speed Plaque on a Night Curve With a Tailgater
It is 9:15 p.m. in October and you are on a two-lane state route in rural Lycoming County, driving a passenger car with two sleeping children in the back. The posted speed limit is 45 mph. You pass a yellow diamond showing a black squiggly arrow, then a yellow rectangle reading 30 MPH, then a yellow diamond with a leaping deer. The road climbs, and just past the crest the pavement drops into tight curves you cannot see from here. A solid double yellow line runs down the middle, and there is no shoulder, only a grass bank on the right and a rock cut on the left. Headlights from an oncoming vehicle flicker through the trees, then disappear. You are running late for a 10:00 p.m. arrival, and the car behind you is close enough that its headlights fill your mirror.
1. Is 30 mph now the legal speed limit on this section? Explain how the plaque relates to the 45 mph sign and to your legal exposure.
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No. The black-on-yellow 30 MPH plate is an advisory speed plaque mounted below a warning sign. Warning signs are yellow diamonds because they warn; they do not set a limit. The white SPEED LIMIT 45 sign remains the posted maximum on this section.
The advisory speed is an engineer's judgment of the speed at which the curve can be taken comfortably in good conditions. Driving above it is not automatically a violation, but it is evidence. If you lose control or crash, Pennsylvania's requirement to drive at a speed reasonable for conditions supports a citation, and the plaque becomes persuasive proof that a safe speed was identified and exceeded. In practical terms, the plaque should be treated as a ceiling at night, in rain, or with a loaded car, because the figure assumes clear daylight and a competent driver.
2. Why do the warning signs appear where they do, and how should the tailgating car change your plan for the crest and curves?
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Advance warning signs are placed before the hazard so a driver has time to react and slow down before, not in, the curve. That is why the squiggly-arrow sign and the plaque come up while the road still looks straight: the curve is beyond the crest, and the crest itself hides it. The deer sign adds a second, separate hazard in the same stretch.
The car behind you is a reason to be smooth, not fast. Ease off the throttle early so your brake lights come on while you are still on the straight, giving the follower warning before you actually need to slow. Do not brake hard at the crest, and do not accelerate past your sight distance to create a gap for the other driver's comfort. If the tailgater stays glued to your bumper through the curves, the safest response on a road with no shoulder is a steady, predictable speed and, at the first safe pull-off or wide driveway, letting the car pass.
3. You are now at the crest with high beams on and a deer steps onto the pavement 120 feet ahead, with oncoming headlights approaching. What do the signs and the geometry tell you to do?
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Brake firmly and straight. The rock cut on the left and the absence of a shoulder mean there is no safe escape path; swerving left puts you into the oncoming vehicle the headlights announced, and swerving right puts you into the bank. A hard, straight stop keeps the car under control and uses the distance the warning signs were designed to give you.
Sound the horn, hold the wheel with both hands, and drop to low beams so the oncoming driver is not blinded and you keep some forward vision. Once stopped or past the animal, expect more: deer move in groups, and the sign is posted because this is a crossing corridor. The whole sequence shows how warning signs work together, shape and color first (yellow diamond equals caution, not command), then the specific hazard, then the advisory speed that tells you how much the hazard costs you.