Highways that are isolated from the state they are located in

[huskeroadgeek]

Not sure if there is a shorter name for this phenomenon-but these are highways that run through a portion of a state that is completely isolated from the rest of the state-i.e. you must go through an adjoining state to reach the rest of the state by road. The longest example of this would probably be I-15 in Arizona. Another would be I-684 which goes through a small portion of Connecticut. US 212 does this twice-in the northeast corner of Wyoming and again in Montana just NE of Yellowstone NP. Another one I know of is IA 165 in Carter Lake, IA-which is part of the road between downtown Omaha and Eppley Airfield. Other examples?

[agentsteel53]

there are some loops of the Alaska Highway that alternate between British Columbia and Yukon that share this property.

also, the town of Hyder, Alaska, can be reached only from Stewart, BC.

[corco]

US-191 also does it north of West Yellowstone, Montana- it enters Wyoming for a few miles. Montana maintains the road though.

[national highway 1]

WYO 70 dips southward into CO to pass through the town of Slater and it is maintained by WyDOT.

[Ian]

ME 113 enters New Hampshire twice and both are maintained by NHDOT. NHDOT even signs ME 113 with Maine's square. There is even a spur off of it, NH 113B, in Chatham.

[Quillz]

I know it doesn't strictly count, but CA-266 can only be accessed via CA-168. And the route itself is really just a connector between two Nevada State Routes.

[Bickendan]

there are some loops of the Alaska Highway that alternate between British Columbia and Yukon that share this property.

also, the town of Hyder, Alaska, can be reached only from Stewart, BC.

AK 7 may be the big fish for this.

Also, one I'm not 100% certain about, but it seems that NT 5 dips into Alberta a couple times, with its final portion in Fort Smith just a couple feet south of the 60° line (which would be in Alberta).

[jemacedo9]

State Rt 896 crosses into Maryland for a very short piece between PA 896 and DE 896...I don't remember if there is a side road intersection in Maryland.  Also, the I-84 bridge over the Delaware River bet PA and NY I believe barely touches NJ.

[vdeane]

Also I-95 and I-495 briefly pass through DC on the Woodrow Wilson Bridge.

[Quillz]

Isn't I-24 in Georgia for less than half a mile and uses Tennessee's mile markers?

[JREwing78]

MN-23 briefly enters Wisconsin just south of Duluth:
http://maps.google.com/maps?q=duluth,+mn&oe=utf-8&client=firefox-a&ie=UTF8&hq=&hnear=Duluth,+St+Louis,+Minnesota&gl=us&ei=jDLgTLqvDIjqnQfpkbi8CA&ved=0CB0Q8gEwAA&ll=46.656977,-92.288246&spn=0.125363,0.285988&t=h&z=12

[Grzrd]

Isn't I-24 in Georgia for less than half a mile and uses Tennessee's mile markers?

I-24 is in Georgia for 4.1 miles & has an interchange with I-59 in Georgia.

[signalman]

Isn't I-24 in Georgia for less than half a mile and uses Tennessee's mile markers?

I-24 is in Georgia for 4.1 miles & has an interchange with I-59 in Georgia.

There's also an exit that connects to US 11 in Georgia, but they both keep Tennesse's exit numbering.

[mightyace]

That exit serves GA 299 (Exit 169).  It's a good exit to stop at if you're just going to Chattanooga as gas prices are generally cheaper in GA than in TN.

[hbelkins]

Also, the I-84 bridge over the Delaware River bet PA and NY I believe barely touches NJ.

No. The state tripoint marker is in the shadow of the bridge, but is definitely south of it. Oscar Voss took a picture of me sitting on the marker and i was looking toward the bridge.

[Quillz]

Point Roberts, WA, can only be accessed (via land) through Canada. This includes the unnumbered roads that are located there.

[Dr Frankenstein]

QC-199 is only accessible by boat... from Prince Edward's Island.
(Well, there seems to be a Montreal ferry too on Google Maps, but I never heard anyone talk about it and I can't imagine the price...)

http://en.wikipedia.org/wiki/Quebec_Route_199

[elsmere241]

State Rt 896 crosses into Maryland for a very short piece between PA 896 and DE 896...I don't remember if there is a side road intersection in Maryland.

There is, it's called Little Egypt Road.

Also, just over the line in Pennsylvania, there's a turnoff called Elbow Lane that stays very close to the Pennsylvania/Maryland line.

[Coelacanth]

Point Roberts, WA, can only be accessed (via land) through Canada. This includes the unnumbered roads that are located there.

The same is true of the Northwest Angle in Minnesota, but there are no highways located there.

[english si]

N54, Ireland - the road here keeps on changing between N54 (in the Republic) and A3 (in Northern Ireland). While other sections of N54 and A3 in the borer wiggle have routes that link them back to the main road network of the country, this one doesn't.
here's something similar in England, where you have to drive through Wales to get there. A bit different, given the road numbers are the same.

[Alps]

Point Roberts, WA, can only be accessed (via land) through Canada. This includes the unnumbered roads that are located there.

The same is true of the Northwest Angle in Minnesota, but there are no highways located there.

There are numbered county highways there.  I plan to clinch a couple.

[Grzrd]

Isn't I-24 in Georgia for less than half a mile and uses Tennessee's mile markers?

I-24 is in Georgia for 4.1 miles & has an interchange with I-59 in Georgia.

There's also an exit that connects to US 11 in Georgia, but they both keep Tennesse's exit numbering.

I drove through there about a year ago and think I made a mental note that the section uses Georgia mileage markers but the exit numbers follow what would have been Tennessee mileage.  Don't know if my mind is playing tricks on me.  Can anyone confirm or deny?

[topay]

Isn't I-24 in Georgia for less than half a mile and uses Tennessee's mile markers?

I-24 is in Georgia for 4.1 miles & has an interchange with I-59 in Georgia.

There's also an exit that connects to US 11 in Georgia, but they both keep Tennesse's exit numbering.

I drove through there about a year ago and think I made a mental note that the section uses Georgia mileage markers but the exit numbers follow what would have been Tennessee mileage.  Don't know if my mind is playing tricks on me.  Can anyone confirm or deny?

You got it right.  Georgia mile markers, would-be Tennessee exit numbers. 

[Grzrd]

You got it right.  Georgia mile markers, would-be Tennessee exit numbers.  

I know I'm straying waaaaay off topic, but does this situation exist anywhere else on interstate system, i.e. mile markers reflect "home" state mileage, but exit numbers correspond to neighboring state's "would-be" mileage?

[dfilpus]

You got it right.  Georgia mile markers, would-be Tennessee exit numbers. 

I know I'm straying waaaaay off topic, but does this situation exist anywhere else on interstate system, i.e. mile markers reflect "home" state mileage, but exit numbers correspond to neighboring state's "would-be" mileage?

I 275 around Cincinnati uses exit numbers numbered based on mileage from the I 71/75 interchange, but each state uses its own mile markers.