Diagonal Interstates

[BridgesToIdealism]

Does anyone know what the official AASHTO rules are for diagonal interstates? (i.e. interstates that don't run exclusively N-S nor E-W). Is there an official rule for how such interstates are supposed to be signed with the grid?

[Takumi]

Not really. I-85 is probably more E-W than N-S, and I-26 is definitely more N-S than E-W.

[hotdogPi]

Not really. I-85 is probably more E-W than N-S, and I-26 is definitely more N-S than E-W.

There's a pattern there, though: NE/SW is signed as N-S, and NW/SE is signed as E-W. 22, 24, 26, 71, 81, 85, and the southern 87 follow this rule. However, this does not apply in other parts of the country; 4, 44, and 89 break the pattern.

[Scott5114]

There aren't any rules, per se. The only rules are based on Interstates being purely NS or EW. Thus, whenever the system was being drawn up, there were a lot of judgement calls where they had to give something an even number or an odd one.

The same thing happened with the US route system. Some states tried to "correct" for this by signing routes with banners like "N-EAST" or "S-WEST".

[zzcarp]

I-76 (west) doesn't follow any pattern. It goes northeast-southwest and is signed east-west in Colorado and signed north-south in Nebraska.

[sturmde]

I-76 (west) doesn't follow any pattern. It goes northeast-southwest and is signed east-west in Colorado and signed north-south in Nebraska.

At least it lies completely between I-70 and I-80, as even numbers 72, 74, 76, and 78 should.

[ilpt4u]

I-76 (west) doesn't follow any pattern. It goes northeast-southwest and is signed east-west in Colorado and signed north-south in Nebraska.

At least it lies completely between I-70 and I-80, as even numbers 72, 74, 76, and 78 should.

Am I missing something? I-72 is entirely between I-70 and I-80

There's a pattern there, though: NE/SW is signed as N-S, and NW/SE is signed as E-W. 22, 24, 26, 71, 81, 85, and the southern 87 follow this rule. However, this does not apply in other parts of the country; 4, 44, and 89 break the pattern.

I-69, (original) 74, and 57 are pretty diagonal - 57 moreso as it ends up extended to Little Rock

And those 3 fit the pattern above

[Bickendan]

Both I-5 and 15 have significant diagonal portions, and it's only because of I-11's recent addition that 15 has any resulting grid issues.
I-5 will likely never have any issues, even when CA 99 gets upgraded and if a Weed-Bend-Tri Cities-Spokane corridor were to be upgraded/built.

[jp the roadgeek]

I-89 is almost exclusively diagonal (SE-NW) from its beginning at I-93 in Concord, NH until just beyond the first numbered exit in VT.  It later returns to its diagonal trajectory between Barre and Burlington before turning exclusively north. 

[mrsman]

A few posts on the subject of diagonal interstates moved here from the I-57 Approved thread in Mid-South.

One proposed turnpike in Oklahoma long ago would have linked Oklahoma to Woodward (and Boise City, IIRC).

Finally looked it up.

§69-1705.  Authority - Powers and duties.
the Authority shall be authorized to construct and operate toll turnpikes only at the following locations:
(15)  A turnpike or any part or parts thereof beginning in the vicinity of Watonga and extending south and/or east to the vicinity of north and/or west Oklahoma City.

IIRC, the remaining 'Northwest Passage' was just to give 4-lane access as far as Guymon. Since that was nearly 25 years ago, I may be misremembering.

That would have built a decent chunk of the diagonal I'm talking about (and Scott5114 illustrated). Without a bigger picture corridor there's little need to build such a turnpike. There's probably not enough people driving just between OKC and Woodward for a toll road like that to pay for itself. However OTA operates a couple or so other turnpikes that don't turn a profit. A turnpike that was serving long distance interstate traffic between Denver and OKC would generate a lot more revenue. OTOH, I would prefer such a route to be built as a freeway if possible; it would attract even more traffic.

Politics. Those other pikes were created as tradeoffs to get the ones that were needed (Kilpatrick on OKC and Creek in Tulsa)

OK-3 from Watonga up to Woodward and Fort Supply runs on that diagonal. In Colorado, the SE bend of I-70 down to Limon and US-287 down to Kit Carson runs on the same diagonal. The road network is all mostly a N-S-E-W grid between Fort Supply, OK and Kit Carson, CO. The only diagonal routes out there (such as US-54 and US-56) run the opposite way, Northeast to Southwest.

The reason is the Class 1 railroads run (or in the case of US56) did run those directions.

The main railroads running on a general SW-NE basis in the area were the Santa Fe (AT&SF), which actually had two lines -- the one most of the passenger trains traversed, which generally followed US 50 west from Olathe, KS west to La Junta, CA, then headed southwest parallel to US 350 to Trinidad before generally following I-25 southwest to Belen, NM over Raton and Glorieta passes.  The second, which is now part of the BNSF "Transcon" line -- essentially a nonstop "conveyor belt" for L.A.-Chicago containerized cargo, essentially follows US 60 from the Belen, NM area (site of a substantial yard) east through Clovis, NM, then northeast, again following US 60, through Amarillo to near the TX/OK line, then along a diagonal route across NW OK, avoiding topographic anomalies, through Woodward, Alva into Harper, KS, then east along US 160 to Wellington.  It then strikes out northeast via Mulvane and El Dorado before crossing the Flint Hills and merging with the northern line near the town of Plymouth, a bit west of Emporia.  Finally, there's the old Rock Island "Golden State" line, named after the passenger service shared with SP that went from Chicago to Kansas City and then on to El Paso, where it turned west toward California.  It followed US 54 from El Paso to Santa Rosa, NM on SP tracks, segueing to the Rock Island there, but still remaining along US 54 to Pratt, KS, before turning NE along KS 61 to McPherson.  It then struck out ENE via Herington to McFarland, along I-70 west of Topeka, before turning east to Topeka and KC.  That line was purchased out of bankruptcy by SP in 1980 and later merged into UP along with all of SP.  It's still used extensively by UP as a competitor to the BNSF main conduit, although UP's major container hub east of L.A. is Fort Worth.  But a number of secondary lines, built to serve the grain business, did follow other SW-NE routes such as US 56 (and KS 45 before that) and the US 83/KS 383 diagonal in the northwest part of KS.  But the opposite diagonal -- SE to NW -- rarely was addressed by railroads until down into the Texas Panhandle, with the Fort Worth & Denver following US 287 between its namesake city and Amarillo, and then heading NW generally via US 87 to Trinidad, CO, where it turned north along the Front Range toward Denver.  The Santa Fe and Rock Island diagonals were intended to effect service to West Coast points, sometimes in concert with other railroads,  by attacking the Rockies well south of their highest points in Colorado, while the sole TX-Colorado line in the other direction was to provide an outlet for CO-originating mineral mining (including some coal and shale oil) down to refineries or Gulf ports in TX.  But there was never enough of that to warrant other rail firms' deploying competing lines for that traffic pattern, so that diagonal directionality was never fully established in the region -- hence the lack of impetus for a direct Denver-OKC route, since when the U.S. highway network in the area was developed -- routes which generally did follow existing rail lines -- there was little there to follow -- and little perceived need to do so.

The above discussion is very interesting and certainly explains why diagonal routes exist in certain places and not others. 

It should also be noted, with no surprise, that the density of freeways (N-S, E-W, as well as diagonal) is higher east of I-35.  So it should not be a surprise that we have an I-44 OKC - St Louis.  But you won't find as many diagonals west of OKC.   There are no MAJOR diagonals of any sort between I-25 and I-35 (except that I-35 itself is diagonal between Wichita and KC).  [Yes I'm aware of I-76 and its very useful to get I-80 to Denver but its relatively short compared to the discussed OKC-Denver routing.]

Salt Lake City is quite lucky having diagonals to the SW (LV, LA, San Diego), NW (Boise, Portland, Seattle) and more or less west (Reno, SF).  Every major city to its west is directly accessible on a more or less direct path via interstates.

[ilpt4u]

...So it should not be a surprise that we have an I-44 OKC - St Louis.  But you won't find as many diagonals west of OKC.

The only reason we have I-44 is because I-44 OKC-STL and then I-55 STL-CHI is the old diagonal US 66 route

[dvferyance]

I-43 is but only between Milwaukee and Beloit.

[jp the roadgeek]

Both I-84's.  The western one from the eastern part of Oregon to its terminus in Utah (NW-SE, and even SSE at times).  The eastern one at its very beginning when concurrent with I-380, from just east of the Taconic Parkway to just west of I-684 (both NW-SE), and pretty much exclusively SW-NE from Danbury, CT to its eastern terminus.

[ozarkman417]

I suppose I-44 is one, because it follows the diagonal portion of Route 66. Route 66 went west/east between LA and OKC, NE/SW between OKC and STL, but mostly north after that.

[sturmde]

...So it should not be a surprise that we have an I-44 OKC - St Louis.  But you won't find as many diagonals west of OKC.

The only reason we have I-44 is because I-44 OKC-STL and then I-55 STL-CHI is the old diagonal US 66 route

I-11 will be a diagonal of sorts.
.
Western I-84 is in a way a diagonal, too.

[ilpt4u]

I-43 is but only between Milwaukee and Beloit.

I suppose I-44 is one, because it follows the diagonal portion of Route 66. Route 66 went west/east between LA and OKC, NE/SW between OKC and STL, but mostly north after that.

I-55 is at least partially, if not mostly, diagonal betwen St Louis and Chicago. It is more Northerly than Easterly for Chicago-bound traffic than the segment of I-44 between St Louis and OKC, but is still on a decidedly NE/SW route

Litchfield-Springfield is about the only stretch of consistent due N-S along this segment of the route

[sprjus4]

^

I-59, I-26, I-22, and I-85 would also qualify.

[Takumi]

Not really. I-85 is probably more E-W than N-S, and I-26 is definitely more N-S than E-W.

There's a pattern there, though: NE/SW is signed as N-S, and NW/SE is signed as E-W. 22, 24, 26, 71, 81, 85, and the southern 87 follow this rule. However, this does not apply in other parts of the country; 4, 44, and 89 break the pattern.

As I remember it, the initial unofficial proposal for what is now I-87 II: Electric Boogaloo, was originally an eastern I-44.

[sprjus4]

Not really. I-85 is probably more E-W than N-S, and I-26 is definitely more N-S than E-W.

There's a pattern there, though: NE/SW is signed as N-S, and NW/SE is signed as E-W. 22, 24, 26, 71, 81, 85, and the southern 87 follow this rule. However, this does not apply in other parts of the country; 4, 44, and 89 break the pattern.

As I remember it, the initial unofficial proposal for what is now I-87 II: Electric Boogaloo, was originally an eastern I-44.

Which is odd considering I-46 and I-48 are both available.

I'm curious what ultimately switched it from east-west to north-south. While it is technically both, it's more east-west than it is north-south.

I-495 was north-south when it was briefly signed, despite being a clear east-west route. The only thing making it north-south would be that it takes Raleigh traffic to I-95 North and vice versa, and the same principal still applies with I-87. Raleigh to I-95 North / vice versa and Hampton Roads to I-95 South / vice versa.

Similarly, I-85 is more east-west than it is north-south.

[sparker]

Not really. I-85 is probably more E-W than N-S, and I-26 is definitely more N-S than E-W.

There's a pattern there, though: NE/SW is signed as N-S, and NW/SE is signed as E-W. 22, 24, 26, 71, 81, 85, and the southern 87 follow this rule. However, this does not apply in other parts of the country; 4, 44, and 89 break the pattern.

As I remember it, the initial unofficial proposal for what is now I-87 II: Electric Boogaloo, was originally an eastern I-44.

Which is odd considering I-46 and I-48 are both available.

I'm curious what ultimately switched it from east-west to north-south. While it is technically both, it's more east-west than it is north-south.

I-495 was north-south when it was briefly signed, despite being a clear east-west route. The only thing making it north-south would be that it takes Raleigh traffic to I-95 North and vice versa, and the same principal still applies with I-87. Raleigh to I-95 North / vice versa and Hampton Roads to I-95 South / vice versa.

Similarly, I-85 is more east-west than it is north-south.

The chain of events resulting in the southern I-87 more or less went as follows:
(1) NC submitted I-44 because it was a familiar number although obviously duplicative.  AASHTO said "try again" and threw out 46, 54, and 56 as being acceptable in both states served by HPC #13, the corridor to be upgraded.
(2) NC pissed & moaned because of the proximity of same-numbered state highways to the corridor, and because renumbering the state routes would cause internal problems.  Citing the trajectory of I-85, they submitted a southern I-89 as their selection, since that state highway was well to the west, avoiding confusion. 
(3) There was reportedly an open bar at AASHTO's SCOURN meeting in Des Moines in the spring of 2016, which likely led to:  (4) In a fit of deliberate stupidity or dysfunction (see (3) above), SCOURN openly rejected the state-highway conflict argument -- but accepted the odd-number concept, despite the corridor being plainly longer E-W than N-S.
(5) The I-87 designation was arbitrarily substituted for the submitted I-89, with two reasons cited:  the longitudinal position of the southern corridor was closer to that of I-87 than I-89 -- and the "87" number tied in with a few obscure historical aspects pertaining to the served area (IIRC a regional university founding in 1787 was cited as one of these). 
(6) However, the SCOURN delegation regained its senses enough to actually designate a completely appropriate number, I-42, for the US 70 corridor from Raleigh to Morehead City (NC had submitted I-36, an out-of-grid number but not in use within the state).  Ironically, NC 42 actually crosses the new I-42 corridor.   I-42 was the last 2di commissioned in the 5-year period from 2012 through 2016 which saw one new Interstate trunk legislated per year (in chronological order, 11, 2, 41, 14, 42).
(7) Everyone went home, leaving NC and VA with one of the weirdest I-numberings in recent memory.   

[sprjus4]

^

As I've said before, while I get the corridor is more east-west, there is still a north-south aspect to it. It's not a number that will cause confusion to the public, say like I-587 being north-south, moreso it seems to be an issue within the roadgeek community. Outside this forum, there is likely little thought on east-west vs. north-south.

US-64 between Raleigh and Williamston is around 100 miles of east-west designation, and US-17 between Williamston and I-64 is also around 100 miles of north-south designation, though follows a northeast / southwest path.

I also would've liked to see an east-west route, but the prospect of it being north-south has never crossed my mind as "weird" . I'd give that title to the proposed I-587, a due east-west route set to be designated as north-south.



I-85 follows a corridor that is similarly more east-west than north-south, yet its accepted for what it is today.

[jeffandnicole]

Generally speaking, look at the endpoints and see if its more E-W than N-S.

Even I-95 is heavily diagonal. From Maine to near DC, it goes more E-W than N-S. Only once you get south of DC does it become more of a N-S highway.

I-495 was north-south when it was briefly signed, despite being a clear east-west route. The only thing making it north-south would be that it takes Raleigh traffic to I-95 North and vice versa, and the same principal still applies with I-87. Raleigh to I-95 North / vice versa and Hampton Roads to I-95 South / vice versa.

Cardinal direction rules don't apply to 3dis.

[sprjus4]

I-495 was north-south when it was briefly signed, despite being a clear east-west route. The only thing making it north-south would be that it takes Raleigh traffic to I-95 North and vice versa, and the same principal still applies with I-87. Raleigh to I-95 North / vice versa and Hampton Roads to I-95 South / vice versa.

Cardinal direction rules don't apply to 3dis.

Never said they did.

[sparker]

^

As I've said before, while I get the corridor is more east-west, there is still a north-south aspect to it. It's not a number that will cause confusion to the public, say like I-587 being north-south, moreso it seems to be an issue within the roadgeek community. Outside this forum, there is likely little thought on east-west vs. north-south.

US-64 between Raleigh and Williamston is around 100 miles of east-west designation, and US-17 between Williamston and I-64 is also around 100 miles of north-south designation, though follows a northeast / southwest path.

I also would've liked to see an east-west route, but the prospect of it being north-south has never crossed my mind as "weird" . I'd give that title to the proposed I-587, a due east-west route set to be designated as north-south.



I-85 follows a corridor that is similarly more east-west than north-south, yet its accepted for what it is today.

Part of me says yeah, maybe they have a back-assed point -- but it still rankles me when designations are re-used when there's a whole pool of 30+ numbers that could be assigned and not in any way confused with a trunk route elsewhere.  When I first heard about the "I-44" proposal for this corridor, my first reaction was to drive cross-country to Raleigh and slap someone silly!  I-87 is only marginally more acceptable than that; but it's the compounding of errors that led to such a designation that is bothersome -- and in my lifetime, the only thing that repeatedly pisses me off is deliberate stupidity.  Needless to say, in my 71 years I've been pissed off more than a few times!  But with this corridor, the only saving grace (and way out) is that with the hits to funding NC has been taking, it'll probably be years if not decades before the substandard sections of US 64 are upgraded, and considerably longer than that for the US 17 section to be fully completed.  But the NC "master plan" must go on; by that time, a freeway along US 17 south of there to Wilmington or even the SC state line will likely be in the works.   Guessing that the NC idiom of seeking Interstate status for at least their main corridors (and US 17 would certainly qualify there) would likely apply here, there's the potential (please pardon the Fictional aspect of this) that, with a bit of legislative "massaging", all of US 17 could receive one odd number and an even designation can belatedly be applied to the E-W/US 64 section (now that we know SCOURN won't give in-state conflicts any consideration).  Numbers TBD; too early for speculation on that.

[Takumi]

Not really. I-85 is probably more E-W than N-S, and I-26 is definitely more N-S than E-W.

There's a pattern there, though: NE/SW is signed as N-S, and NW/SE is signed as E-W. 22, 24, 26, 71, 81, 85, and the southern 87 follow this rule. However, this does not apply in other parts of the country; 4, 44, and 89 break the pattern.

As I remember it, the initial unofficial proposal for what is now I-87 II: Electric Boogaloo, was originally an eastern I-44.

Which is odd considering I-46 and I-48 are both available.

I'm curious what ultimately switched it from east-west to north-south. While it is technically both, it's more east-west than it is north-south.

I-495 was north-south when it was briefly signed, despite being a clear east-west route. The only thing making it north-south would be that it takes Raleigh traffic to I-95 North and vice versa, and the same principal still applies with I-87. Raleigh to I-95 North / vice versa and Hampton Roads to I-95 South / vice versa.

Similarly, I-85 is more east-west than it is north-south.

The chain of events resulting in the southern I-87 more or less went as follows:
(1) NC submitted I-44 because it was a familiar number although obviously duplicative.  AASHTO said "try again" and threw out 46, 54, and 56 as being acceptable in both states served by HPC #13, the corridor to be upgraded.
(2) NC pissed & moaned because of the proximity of same-numbered state highways to the corridor, and because renumbering the state routes would cause internal problems.  Citing the trajectory of I-85, they submitted a southern I-89 as their selection, since that state highway was well to the west, avoiding confusion. 
(3) There was reportedly an open bar at AASHTO's SCOURN meeting in Des Moines in the spring of 2016, which likely led to:  (4) In a fit of deliberate stupidity or dysfunction (see (3) above), SCOURN openly rejected the state-highway conflict argument -- but accepted the odd-number concept, despite the corridor being plainly longer E-W than N-S.
(5) The I-87 designation was arbitrarily substituted for the submitted I-89, with two reasons cited:  the longitudinal position of the southern corridor was closer to that of I-87 than I-89 -- and the "87" number tied in with a few obscure historical aspects pertaining to the served area (IIRC a regional university founding in 1787 was cited as one of these). 
(6) However, the SCOURN delegation regained its senses enough to actually designate a completely appropriate number, I-42, for the US 70 corridor from Raleigh to Morehead City (NC had submitted I-36, an out-of-grid number but not in use within the state).  Ironically, NC 42 actually crosses the new I-42 corridor.   I-42 was the last 2di commissioned in the 5-year period from 2012 through 2016 which saw one new Interstate trunk legislated per year (in chronological order, 11, 2, 41, 14, 42).
(7) Everyone went home, leaving NC and VA with one of the weirdest I-numberings in recent memory.   

The sad thing is, 46 would have been an easy renumber because VA/NC 46 are one corridor and the route doesn't really go through anywhere significant.