Interstate designations that maintain the through movement

[roadman65]

Interstate 37

[bassoon1986]

The southern I-49  (for now)

[Alps]

I-99?

No, US 322 is the through movement at State College.

I'd have to disagree... having driving thru it a couple of times, the interchange was set up to make I-99 clearly the thru movement. (even though, historically, US-322 was the through movement.)

And ya know something? I've been through there several times, and it just FEELS like it's not the through movement, the way it rises up so high and comes back down, whereas US 322 stays at ground level.

[kkt]

I-238

How do you figure?  I-238 looks straight through between its endpoints at I-580 and I-880.

[deathtopumpkins]

I-99?

No, US 322 is the through movement at State College.

I'd have to disagree... having driving thru it a couple of times, the interchange was set up to make I-99 clearly the thru movement. (even though, historically, US-322 was the through movement.)

And ya know something? I've been through there several times, and it just FEELS like it's not the through movement, the way it rises up so high and comes back down, whereas US 322 stays at ground level.

While that's a valid point, both of the 2 lanes approaching the interchange go to 99, while the two 322 lanes are added, both north- and southbound 99 is on the left, and, while the signs all just use straight down arrows (not even any exit only), 322 is signed as an exit. I think 99 is definitively the through movement.

[formulanone]

Decide for yourself:

[kj3400]

Yeah, I-99 is the through movement. I usually qualify through movements on whether the road merges on the right or not. I-99 doesn't merge with anything, and both carriageways are side by side through the interchange. If that isn't a through movement, I don't know what is.

[roadman65]

This photo here is not interstate, but being that people here are talking about the I-99 and US 322 split in State College brings up an interesting point.

It can easily be considered a 50/50 with such a diverge.  If this here split near Shreveport were two interstates splitting it could be arguable here of which is the straight through route here. 

US 71 goes straight, but LA 1 goes left and diverges, but US 71 drops to one lane while LA 1 takes the two lanes leading into this.  US 71 traffic MUST use the right lane to continue while LA 1 has to make no adjustment.

[froggie]

Wouldn't the two I-70 intersections disqualify it?

You're right...totally forgot about the I-70 junctions.  The western 70/79 junction is arguable, but the eastern junction clearly favors I-70.

[briantroutman]

This photo here is not interstate, but being that people here are talking about the I-99 and US 322 split in State College brings up an interesting point.

Right–as I mentioned above, there are lots of gray areas. If we wanted to be objective get really obsessive about this, we would probably have some kind of point system to assess which route is more "through"–and by how much.

It would look something like this. Each route starts with 50 points.

- Line-of-sight grading (assumably the original alignment) appears to heavily favor US 71
(+ 20, US 71)
(- 10, LA 1)

- Multiple lanes to LA 1
(+ 50, LA 1)

- Single lane to US 71
(-25, US 71)

- Pull through arrow for US 71
(+20, US 71)

- Diagonal exit arrows for LA 1
(-10, LA 1)

US 71: 65 points
LA 1: 80 points

So I'm not saying that these are the absolute right criteria or the appropriate point values, but you get the idea.

[Brandon]

A lot of 3dis seem to maintain the through route, but not all of them.  Looking locally,

* I-190 maintains the through route between I-90 and O'Hare.
* I-290 does not maintain the through route at I-355 and at I-88.  In both cases, the new interstate is on the left.  In the case of I-88, it's close to a 50/50 split.  In the case of I-355, it's most definitely I-355 as the through route with I-290 exiting itself.
* I-294 maintains the through route for its entire length.  I-80 exits off I-294.
* I-355 maintains the through route for its entire length.

* I-88 (W) maintains the through route from I-80 to I-290.

Now, a good question is, what is the shortest interstate (2di or 3di) not to maintain the through route for its entire length?

[agentsteel53]

Now, a good question is, what is the shortest interstate (2di or 3di) not to maintain the through route for its entire length?

I-676 turns sharp south in Camden with US-30 continuing east.  what it does just to the west, before I-95, is ... odd at best.

[TheStranger]

Another short one, though it no longer exists as of this year: In Washington, I-295 originally exited off of the Anacostia Freeway at what is now the 695/295 junction, then continued north along the 11th Street Bridge - a vestige of when 295 was supposed to continue northeast via the Pennsylvania Avenue/Barney Circle offramps from 695, as noted in this map from Scott Kozel's website:

http://www.roadstothefuture.com/DC_Area_Map_XL.jpg

[vtk]

Columbus's I-270 maintains through-route geometry for its entire 55 miles, beating I-97.

How about Atlanta's circumferential?



As for short routes that don't maintain through-route geometry...

I-670 exits itself westbound (in favor of Third St) and used to eastbound (in favor of I-71).

I-74 is certainly not the shortest, but it seems to have the a lot of non-through moments per mile built.  (Yet another new way to answer the thread topic...)

I want to say there's a half-innerbelt in northeast Ohio (I-277?) that has to exit itself in the middle.  And maybe another in Youngstown...

[Brandon]

Columbus's I-270 maintains through-route geometry for its entire 55 miles, beating I-97.

How about Atlanta's circumferential?

The western I-88 (IL) beats both at a bit over 140 miles with a maintenance of through route geometry.

As for short routes that don't maintain through-route geometry...

I-74 is certainly not the shortest, but it seems to have the a lot of non-through moments per mile built.  (Yet another new way to answer the thread topic...)

Geeze, I-74 has a lot of them.  Three complete changes in Illinois (with two of them in the Quad Cities) and two 50/50 splits in Illinois as well (one with I-55 eb and one with I-474 wb).  Then another two complete changes in Indiana.

[empirestate]

Interestingly, I-390 does not maintain the through route at its junction with I-590, as it forms the south and west legs of a semi-directional T with I-590 as the east leg.

However, I-390 at its other end causes I-86 to not take the through route; instead, I-86 forms the west and south legs of the interchange with I-390 as the north leg.

I-787 secretly does not take the through route where it turns across the Hudson River to Troy, and again at its south end where it secretly ends at the Thruway via ramps but publicly follows the through route to US 9W.

[Alex4897]

No single lane of I-95 continues the entire length of Delaware, most of the lanes getting thrown onto other roads at the "Megachange" southwest of Wilmington.

[vtk]

Geeze, I-74 has a lot of them.  Three complete changes in Illinois (with two of them in the Quad Cities) and two 50/50 splits in Illinois as well (one with I-55 eb and one with I-474 wb).  Then another two complete changes in Indiana.

Plus a few in North Carolina, I think...

[Joe The Dragon]

A lot of 3dis seem to maintain the through route, but not all of them.  Looking locally,

* I-190 maintains the through route between I-90 and O'Hare.
* I-290 does not maintain the through route at I-355 and at I-88.  In both cases, the new interstate is on the left.  In the case of I-88, it's close to a 50/50 split.  In the case of I-355, it's most definitely I-355 as the through route with I-290 exiting itself.
* I-294 maintains the through route for its entire length.  I-80 exits off I-294.
* I-355 maintains the through route for its entire length.

* I-88 (W) maintains the through route from I-80 to I-290.

Now, a good question is, what is the shortest interstate (2di or 3di) not to maintain the through route for its entire length?

for I-294 / tri state tollway that used to BE toll US 41 it was all one route. The area where US-41 and I-94 split seems like US-41 was the old main flow.

maybe one day I-355 or what ever will have one number when the IL-53 ext is build. Maybe some day I-290 can get put on to parts of the EOE? or maybe I-355 can go over parts of it?

Now talking about this didn't the quad city's area have some renumbering done?

[amroad17]

As far as Akron, it is I-76 that exits from itself (SW corner of the "beltway").  I-277/US 224 maintain the through route.

[SteveG1988]

I78 itself, all the roads that split from it are done on curves where the through route curves around as they exit, I.E. us22 in PA

I278

[NE2]

I78 itself, all the roads that split from it are done on curves where the through route curves around as they exit, I.E. us22 in PA

Except westbound at NJ 139. That's more of an equal split, and I-78 is signed as an exit (as of January 2013).

I278

[Alps]

I78 itself, all the roads that split from it are done on curves where the through route curves around as they exit, I.E. us22 in PA

Except westbound at NJ 139. That's more of an equal split, and I-78 is signed as an exit (as of January 2013).

I278

We need a trollface smiley, don't we. I-478, I-678, I-878, sure.

[TXtoNJ]

I-45?

[CNGL-Leudimin]

It seems to do so.

We need a trollface smiley, don't we. I-478, I-678, I-878, sure.

I give out one: .