[luckroy]

Sounds like CA and IA work differently. 45 is the speed limit for that highway because it's windy. On the straighter roads, the limit is usually 50-55. However, there are still no speed zones (as you call them) for small clusters of houses.

[seanmcdirmid]

The whole west works different I think. I mean, who in their right mind would build their house right next to the highway (without a fairly long highway) if they didn't have to? As long as you have the land, you would build it 50-100 meters back!

The only time I see otherwise is if mountains or rivers are involved, or there is density (in which case it is sure to be zoned!).

[YSFEJ4SWJUVU6]

There are many types of highways. You might even call these rural roads just roads, even if they share the default speed limit for the area (80 km/h here).

With very low traffic density, you might build the house closer to the road (maybe 10m off, separated with trees) for just that reason – to save land. (Not all rural houses are farms.)

[sjg007]

It's common in the midwest and becoming an issue when towns expand and traffic picks up. Mailboxes on the opposite side of a county road should be illegal. I'm surprised actually that they are not.