Colloquial Terms for road types

[Henry]

The way I see it:

Interstates are referred to as "I-XX", with the lone exception being Texas, where "IH-XX" ("Interstate Highway") is used instead.

US and state routes are often designated as "Route XX" in the Northeast and Midwest, with a few exceptions; they are called "Highway XX" in the South and West, again with a few exceptions. In Georgia and Florida, for example, the official designation is "SR-XX" ("State Road" in FL, "State Route" in GA), but I imagine they are still called "Highway XX" when someone gives directions.

I've never heard a county/secondary route being called "Highway XXX", just "Route XXX". Of course, in Texas you have the "FM-XX" ("Farm to Market") roads, and AFAIK, no other state uses that designation.

Hope this helps.

[vtk]

I was going to point out the IH- quirk of Texas, but Henry beat me to it.

County roads in Ohio vary a bit by county.  In some counties, the county road number is the road's only designation, and so the road is called "County Road [ # ]".  The signage is usually just like a street name sign, but it says  "CR [ # ]" or "[NAME OF COUNTY] [ # ]".  In most counties, the roads are given names, and they are referred to by mane.  The county road number appears on the signs with the road's name, usually in much smaller type.  Usually the number is ignored by locals.  A few counties post county road numbers as prominently as state routes; I don't know if those numbers are used by locals.  

In counties that both name and number their roads, every county road has a name (to satisfy "common sense") and every county road has a number (for inventory or maintenance purposes) but these designations don't have to match.  For example, in Franklin County, part of CR 135 is called Grove City Rd, while the rest is called Kropp Rd.  CR 140 has segments called Lukens Rd, Kropp Rd, Darby Creek Dr, and (discontinuous from the others) Hubbard Rd.  On the other hand, Madison County keeps a strict one-to-one relation between county road names and numbers.

And then there's township roads (in some states which have townships).  Naming and numbering of township roads usually follow the conventions of the county they're in, though signage and maintenance are done with smaller budgets.

[Bickendan]

Oregon is a mixed bag. Interstates are called I-x (5, 82, 84, 105, 205, 405), US and state highways will be called either US x, Oregon x or Highway x. Written, state highways tend to be OR x (just saw a construction VMS refer to work being done on "OR213").

[xonhulu]

I've noticed that the Portland TV newspeople refer to Oregon's state and US routes as "highway" but refer to Washington routes as "SR."  I might be wrong, but I remember it starting several years ago when KATU had a Washington state trooper doing their morning Clark County traffic report.  However, I'm not an obsessive viewer of the local news, so I could easily be wrong on this.  I just know it seems to be that way now.

[Darkchylde]

About Texas:

Even though signage and TxDoT use the IH nomenclature, around Houston, Galveston, Beaumont, etc, everyday people still call them by I-xx.

[formulanone]

County roads/routes in Florida seem to vary, since some were former state routes, or even change in maintenance type, the local terminology varies; sometimes you'll hear "highway", "route", or even "state route/road" but the local name usually takes precedence.

Alternate signage usually denotes them as CR xxx, such as on street blades.

[SSOWorld]

In Minnesota and Wisconsin, Interstates are referred to as I-XX (like I-94), US and State Highways are generally referred to as Highway XX (Highway 10), and County Highways are referred to as County XX or County Road XX (County 81 or County Road C), although often in urban areas county roads are called their "name" instead of their number (like Penn Ave instead of County 2 in Minneapolis).

"County Highway" is much more common in Wisconsin than "County Road".  It is also very common to just skip the second adjective and just refer to "County A" or "County W" or "County CC".
"County Highway" is usually reserved for news reports and articles.

When in Wisconsin, anything that's not an interstate, but still numbered or lettered is a "highway".

I beg to differ on Interstates - many may refer to Interstates as "highway" as well.  Look at older signs - like on WIS 60 just east of US 41.  The a distance sign says "Hwy 45" and "Hwy 43".

[Brandon]

And in Michigan, we can tell the tourists very easily since they drop the "M" from the highway names, or substitute something else. It would be "M-28" that runs across the Upper Peninsula, although it isn't uncommon to see "State Highway M-28" on street signs in rural areas. We Michiganders tend to retain the type designator with I-75, US 23, M-28, although county roads might be just the number almost as much as "County Road 492" in the counties that post designated numbers.

However, the designator is often dropped when referring to interstates and US routes, i.e. I-75 is just "75", and US-23 is just "23".  However, the "M" is always used, i.e. M-14 is "M-14".

Of course, the freeway name is used in Detroit even though it does not appear on the signage, i.e. "The Lodge", "The Jeffries".

[Brandon]

In Illinois here is what we locally say.
Interstate - I-XX or XX (where X is the number)
US Routes - US XX or Route XX or XX
State Highway - Illinois Route XX or Route XX
County highway - Most times is given an actual name and is referred as such. For example, in Winnebago County, there is an exit off I-90/39 where the BGS sign says "Winnebago County 9, Rockton Rd" but is always referred to as Rockton Rd.
In the majority of counties in Illinois, the local name for a county highway is something like 1200 West Rd. The number, depending on the county, usually is in reference of a distance in miles from the county boundary at its farther cardinal direction point. For example, in La Salle County IL, which is generally a square except on the southern boundary, N 6th Rd means it is an east-west road that is 6 miles north of the LaSalle-Woodford County Line.

We also use XX for a state route as in "59" or "53" for IL-59 or IL-53.  Calling IL-59 just "59" is very common around Joliet and Plainfield.  It may be used since it fits in better with the numbered streets that 59 crosses (i.e. 59 and 95th - IL-59 and 95th Street).