Personally, I think the whole system of "control" cities and the signage thereof is in need of a rejig - with what we have now, we end up with a system in which long-distance interstate are signed to uberlocal control-cities that nobody outside the local area has heard of, and where mileage signs are woefully inconsistent, etc.
Control cities should be divided into 2 tiers: "control" and "super-control". "Super-Control" cities would be big places of national, strategic importance; I'm talking destinations like Boston, Chicago, New York, Phoenix and the like - these would be spread at a roughly equal distance along the route (though in really remote areas, they'll inevitably be more spread out). One would always appear on signage, and once reached, would be replaced by the next one.
"Control" cities would be other major destinations that a route passes through, or the location of a major junction.
Taking the I-10 as an example, working West, your Super-Control cities would be:
Jacksonville
Tallahassee
Mobile
New Orleans
Houston
San Antonio
El Paso
Phoenix
Los Angeles
And again using the I-10, the number of Control Cities are too many to list, but they'd include places like:
Lake City (for I-75)
Pensacola
Baton Rouge
Lafayette (for I-49)
etc, etc
Plus, you'd have any numerber of local destinations along your route .
On interchange directional signs, you'd have the following information:
- the next Super Control city
- the next Control city
So, for example, on the I-10 going west at Jacksonville, a direction sign would read "Lake City, Tallahassee".
Mileage signs would contain the following:
- the next super-control city
- the next 2 control cities
- plus one more local destination.