Pretty sure it doesn't even go that far most of the time. Around here, there seem to be a few simple rules based on the road's intended use and the area it's in

Pretty sure it doesn't even go that far most of the time. Around here, there seem to be a few simple rules based on the road's intended use and the area it's in. Lower-traffic residential streets are 25MPH, as are somewhat busier streets in dense areas. Other roads that connect more distant places are 35MPH. And that's about it. One road I frequent has a broad section with parking on both sides, one lane in each direction that would be plenty wide enough for two cars abreast, and a center turn lane. And then there's a narrow section barely wide enough for one lane in each direction, with densely packed houses whose driveways connect straight to the road, and a hill that sharply limits visibility. People tend to go 25MPH in that section and 40+ on the wide section. The limit in both places is 35. About two miles away there's a major connector with 3-4 lanes each way, divided by a median. People often go 50 there. The limit is, you guessed it, 35.