Only in these two states...

[bassoon1986]

Tennessee and Georgia

The only two states that have three I-x5's


Arkansas and Ohio

The only two states with 7 as their longest highway.


Connecticut and Mississippi

The only two states with 15 as their longest highway.


iPhone

[Bruce]

Washington and California: Have unique I-x05s (I-705 and I-305/505/605/805, respectively). Oregon does not have a unique number.

[SkyPesos]

Washington and California: Have unique I-x05s (I-705 and I-305/505/605/805, respectively). Oregon does not have a unique number.

Georgia and Florida: Have unique I-x75s (I-575 and I-175 respectively). The other x75 numbers used are I-275 (5/6 states), I-375 (2/6), I-475 (3/6) and I-675 (3/6).

[ethanhopkin14]

Texas and Arizona:  Only states with a single digit interstate and an interstate ending in 7.

Also, only states with at least 2 intrastate two digit interstates that are built completely to plan.

[Henry]

WI and NC: 2di and 2dus of the same number using the same general routing

[Avalanchez71]

Florida and Indiana: A strict grid numbering system

I think they're also the only two states which officially use "State Road" instead of State Highway or State Route. Could be wrong about this, but I can't find the specific thread where we discussed how DOTs officially named their state inventory.

I think New Mexico is also a "state road" state.

GA and TN actually sign hidden state routes on US Highways.

TN does not. GA does very reliably, to the point that in multiple cases the state route number is the local name for the road rather than the US number. GA 365 instead of US 23, GA 400 instead of US 19, etc...

SR 6 is signed along US 31E on the Ellington Pkwy section.  Also the SR number is posted on the MM signs as well.

[Avalanchez71]

How many states use a substantially different shield blank for post-mounts as for BGS-mounts?

Texas
New Mexico ??? sort of
Idaho ??? sort of

others?

Once upon a time Florida used a substantially different SR sign on the BGS back in the Button Copy days.  Actually there were two versions. 

[SkyPesos]

GA and TN actually sign hidden state routes on US Highways.

I don't mind GA signing its hidden state on its interstates too. Nothing wrong with an Ontario v2 freeway system

[Avalanchez71]

Arizona and California:  Only states to have a section of a highway or highways where the carriageways cross over and mimic driving on the left side of the road due to the grade of a mountain pass.

I-840 exit to I-65 does this.

I want to say Tennessee has one too, but I may be wrong. Of course carriageways cross over and you drive on the left at every diverging diamond interchange.

Texas and Missouri:  Only states that extensively marks exit numbers as a tab above the gore sign, on a separate sign as opposed to on the gore sign itself.  I know it shows up in a lot of states, but I have only seen it widespread in those two.

I think Wyoming does this too.

I was going to say that Colorado and Texas were the only 2 states to refer to their state highways as SH-xx, but it turns out Idaho does too.

So does Oklahoma.

[X99]

Probably wrong on this, but:

Nevada and South Dakota: only two states with two massively separated population centers.

[ethanhopkin14]

California and New Jersey:  Only states with something consistently different about how they sign US highways.  New Jersey always has the black outline on BGSs and California has their unique US highway cutout shield. 

[hotdogPi]

Probably wrong on this, but:

Nevada and South Dakota: only two states with two massively separated population centers.

Missouri

[kphoger]

CA and NM:  do not have a river border with Mexico

Neither do 46 other states. Only AZ and TX have a river border with Mexico.

Dang it!  I kept telling thinking I had typed that wrong, then I kept telling myself it was actually correct the way it was.  The fact that it's a 2/2 split made it confusing for some reason.

[webny99]

CA and NM:  do not have a river border with Mexico

Neither do 46 other states. Only AZ and TX have a river border with Mexico.

Dang it!  I kept telling thinking I had typed that wrong, then I kept telling myself it was actually correct the way it was.  The fact that it's a 2/2 split made it confusing for some reason.

It could still fit the thread if you said they're the only states with a land-only Mexican border... but it doesn't sound quite as impressive that way.

[Mapmikey]

Also, only states with at least 2 intrastate two digit interstates that are built completely to plan.

I-87 and I-88 in New York say hello...

[StogieGuy7]

Utah uses "SR-XX". "U-XX" is a roadgeek urban legend that has not been used by "normal people" in several decades.

But the original point remains incorrect because there is a third state (not Utah). Nebraska uses "N-XX", "L-XX", "S-XX", and "R-XX" for state highways, links, spurs, and recreation roads.

Define "normal people" please.  That's a but rude.  Yes, apparently the use of "U-XX" is now limited to old timers and rural residents.  When I lived there (1985-97), hardly anyone was using SR-XX and in fact tended to refer to a state highway as a state highway.  Things change - and clearly now the SR-XX identifier is now what is in use.  But they did go by U-XX for many years.  A quick search turned up this example: "Ferron, Utah is located on U-10 at the mouth of Ferron Canyon, ten miles southwest of Castle Dale. It was named to honor A.D. Ferron, pioneer surveyor of Castle Valley, Emery, and Carbon counties." 

[Scott5114]

Define "normal people" please.  That's a but rude.

If you post on this forum you're abnormal. Them's the breaks.

[kphoger]

Utah uses "SR-XX". "U-XX" is a roadgeek urban legend that has not been used by "normal people" in several decades.

Define "normal people" please.  That's a but rude. 

Oh, come on.  We roadgeeks are not normal.  I have a feeling most of us on here would be the first to admit that.

Normal people don't have online discussions about official DOT terminology.

[roadman65]

I know NJ calls all Designations "Route"  regardlessly.  So I-80 is "Route 80"  and US 22 is " Route 22"  and NJ 27 is Route 27.

Is there a second?

[JCinSummerfield]

IL & MN - 2 states that have a water only boundary with Michigan.

[cl94]

/quote]

I-87 and I-88 in New York say hello...

Incorrect. I-88 was not built to plan. It was supposed to extend east to at least Troy, possibly into Vermont. NY had the extension to Troy on the books as late as the early 90s.

[kphoger]

Also, only states with at least 2 intrastate two digit interstates that are built completely to plan.

I-87 and I-88 in New York say hello...

Incorrect. I-88 was not built to plan. It was supposed to extend east to at least Troy, possibly into Vermont. NY had the extension to Troy on the books as late as the early 90s.

OK, it was about time someone fixed this quote string!

[TheHighwayMan3561]

Probably wrong on this, but:

Nevada and South Dakota: only two states with two massively separated population centers.

Missouri

Washington, North Dakota

[ethanhopkin14]

Define "normal people" please.  That's a but rude.

If you post on this forum you're abnormal. Them's the breaks.

Word

[jakeroot]

Probably wrong on this, but:

Nevada and South Dakota: only two states with two massively separated population centers.

Missouri

Washington, North Dakota

I don't think WA would count. Clark County, down in the southwest part of the state (containing Vancouver), is not substantially smaller than Spokane County nor the Spokane metro area. If you look at the Portland/Vancouver metro area as a whole, it obviously dwarfs Spokane.

If I were to name WA's big population centers, I would list Seattle, Spokane, and Vancouver.