Routes that parallel state borders

[hotdogPi]

It has to be obvious, like I-91 at the NH/VT border (along with US 5).
These will probably more common when the state border is a river.

IL 1
I-29 in Nebraska, and across the border, US 75
All of US 166
All of NY 22, and across the border, US 7
I-80 and I-90 in Indiana
US 52 northwest of Williamson WV, probably the longest parallel to a state border.
Eastern segment of Mexico 2 (yes, it's still a state border!)

[Big John]

WI 11, WI 35

[agentsteel53]

the western segment of MX-2 runs within 10 feet of the border in some places between Sonoyta and San Luis Rio Colorado.

[hbelkins]

US 23 in Kentucky would count. So too would the various segments of KY 8.

And so would WV 2, which but for a few deviations runs mostly within sight of the Ohio River and Ohio state line for the entire length of its border.

[bzakharin]

PA 32 and NJ 29 on either side of the border. Further south, I-95 on the PA side of the NJ border from the non-interchange with the PA Turnpike to the Delaware state line. Is the ocean a state line? If so, Garden State Parkway parallels it from the Driscoll Bridge south to its terminus.

[NE2]

MSR 120

[PHLBOS]

DE 92 (Naamans Road) and DE/PA 491 (Naamans Creek Road) run mostly parallel to the DE-PA border.

[corco]

The US 89/ID 61/WYO 89/UT 30/UT 16/WYO 89 chain of routes

[NE2]

AR 43/OK 20

[getemngo]

DE 54/MD 54, which spends about 10 miles with the state line right down its center.

MSR 120

Might want to specify the states for people who don't know every MSR. (It's Indiana/Ohio, with the Michigan section connecting them decommissioned in 1961.)

[formulanone]

US 1 and A1A in Florida. 

[SteveG1988]

NJ35

[Kacie Jane]

Washington SRs 4 and 14.  And US 30 and I-84 across the river in Oregon.

[NE2]

M-185

[bulldog1979]

M-185

M-185 may follow the shoreline of Mackinac Island, but it's nowhere near the Michigan state line. Now US 2 roughly parallels the state line between Ironwood and Iron River before running further away and turning to cross back into Wisconsin.

[Alps]

every road around each Hawaiian island

[SD Mapman]

SD 109 and part of US 18 West River.

[empirestate]

It has to be obvious, like I-91 at the NH/VT border (along with US 5).
These will probably more common when the state border is a river.

IL 1
I-29 in Nebraska, and across the border, US 75
All of US 166
All of NY 22, and across the border, US 7
I-80 and I-90 in Indiana
US 52 northwest of Williamson WV, probably the longest parallel to a state border.
Eastern segment of Mexico 2 (yes, it's still a state border!)

US 9 (New York), then. It parallels the border as obviously as NY 22 does, just further to the west. So does I-81, for that matter. Methinks there may be a missing criterion here...

[NE2]

Damn. I missed that.

[mrose]

I-2 and I-8 come to mind.

[national highway 1]

NR44, Bruxner Hwy
NR42, Cunningham Hwy
NR58, Riverina Hwy
B400, Murray Valley Hwy

[dgolub]

NY 120A goes right along the New York-Connecticut border.

[CNGL-Leudimin]

Almost every road in CO East of I-25.

[getemngo]

M-185

M-185 may follow the shoreline of Mackinac Island, but it's nowhere near the Michigan state line. Now US 2 roughly parallels the state line between Ironwood and Iron River before running further away and turning to cross back into Wisconsin.

...since people started counting oceans as state boundaries.

[jeffandnicole]

Wouldn't every road that runs the same direction as any one of a state's state line count as a parallel road, regardless of it's location within the state?