I doubt that's practical in the US. The country has many miles of state highways (and the older US Routes; US 41 north of Chicago is a popular bypass for a toll

I doubt that's practical in the US. The country has many miles of state highways (and the older US Routes; US 41 north of Chicago is a popular bypass for a toll road) for which a limited-access road with no at-grade intersections is far too expensive to be worth it, but traffic is light enough that a 55 or 65 mile per hour speed limit is reasonable.