The shortest "major" Interstates

[Pink Jazz]

I was wondering, of the three shortest major Interstates (I-45, I-30, and I-85), does anyone have any idea why would AASHTO choose such designations for those routes?

I can see a rationale for I-85, since it is one of the nation's busiest and most important corridors.  However, I am not sure why I-30 and I-45 were chosen.  I do know that I-30 was originally supposed to be much longer than it is now, so perhaps AASHTO gave it the designation for potential future planning.  I-45 is a complete mystery.

[Max Rockatansky]

IMO the whole east/west grid north of I-40 is jacked up because the AASHTO thought motorists would confuse US 50/60 with an I-50/60.  But sparing that particular rant because it's probably worth another topic, basically the x0 routes should serve a major cross country traffic corridor and for what it's worth with I30 it seems to do just that connecting to I20 and I40 on both ends.  I would use I45 as a better example than I85 since 45 is only in Texas but still serves two of the biggest metro areas in the country. 

[GaryV]

Part of the rationale for I-45 staying in Texas (at least staying in the South) is that it enforces the separation of US and Interstate numbers in a state.

[CobaltYoshi27]

Part of the rationale for I-45 staying in Texas (at least staying in the South) is that it enforces the separation of US and Interstate numbers in a state.

True, however due to I-45 being under 300 miles long, it would make sense for it to be I-47 instead. Also, I-78 connects New York City and Harrisburg, the former being the largest city in the US, being under 150 miles long. While 78 doesn't end in "0", it fits my reasoning for I-45 being I-47 instead.

[kkt]

Part of the rationale for I-45 staying in Texas (at least staying in the South) is that it enforces the separation of US and Interstate numbers in a state.

I-35 could have followed the route of I-29 north of Kansas City, and I-45 taken the route of US 75 and US 69 from Dallas to K.C. and then I-35 to Duluth.

[CobaltYoshi27]

Part of the rationale for I-45 staying in Texas (at least staying in the South) is that it enforces the separation of US and Interstate numbers in a state.

I-35 could have followed the route of I-29 north of Kansas City, and I-45 taken the route of US 75 and US 69 from Dallas to K.C. and then I-35 to Duluth.

Or I-45 could take over I-29 and I-49 and be one interstate entirely.

[Henry]

FWIW, I-85 is more east-west than north-south, but it works fine as a major route between Baltimore/Washington and Charlotte/Atlanta. Plus, a westward (or should I say southward?) extension is in the works, so there you go.

As for I-30, I never was fond of the number on a route that only connects Dallas and Little Rock, but an extension to the northeast is in the works, so that might make it more justifiable, though not much.

Finally, I-45 works well in TX, because it connects Dallas and Houston. I really don't see any problem with it.

[Lyon Wonder]

IMO the whole east/west grid north of I-40 is jacked up because the AASHTO thought motorists would confuse US 50/60 with an I-50/60.  But sparing that particular rant because it's probably worth another topic, basically the x0 routes should serve a major cross country traffic corridor and for what it's worth with I30 it seems to do just that connecting to I20 and I40 on both ends.  I would use I45 as a better example than I85 since 45 is only in Texas but still serves two of the biggest metro areas in the country. 

IMO, I-64 could have been numbered I-60, though US 60 from KY to VA would have to be renumbered or decommissioned, which would be easy to do with US 60 between Louisville and Virginia Beach since much of it parallels I-64.

[CobaltYoshi27]

IMO the whole east/west grid north of I-40 is jacked up because the AASHTO thought motorists would confuse US 50/60 with an I-50/60.  But sparing that particular rant because it's probably worth another topic, basically the x0 routes should serve a major cross country traffic corridor and for what it's worth with I30 it seems to do just that connecting to I20 and I40 on both ends.  I would use I45 as a better example than I85 since 45 is only in Texas but still serves two of the biggest metro areas in the country. 

IMO, I-64 could have been numbered I-60, though US 60 from KY to VA would have to be renumbered or decommissioned, which would be easy to do with US 60 between Louisville and Virginia Beach since much of it parallels I-64.

Yes, but people don't have common sense, so that wouldn't happen.

[lordsutch]

I think the designations of I-30 and I-45 can simply be explained by, at the time, there being no serious plans for longer corridors that needed numbers and fit the grid better. Had the I-10 to I-20 section of I-49 in Louisiana been seriously been considered for construction at the time, it might have gotten the I-45 number instead, but even then Dallas-Houston is a more important corridor that Shreveport-Lafayette.

I'm not sure what other corridor proposed then would have been more worthy of the number I-30; you could perhaps make an argument for I-85 getting the I-30 designation instead, given its more east-west than north-south orientation, although the US routes it "replaced" were also generally north-south routes.

[Revive 755]

I think the designations of I-30 and I-45 can simply be explained by, at the time, there being no serious plans for longer corridors that needed numbers and fit the grid better. Had the I-10 to I-20 section of I-49 in Louisiana been seriously been considered for construction at the time, it might have gotten the I-45 number instead, but even then Dallas-Houston is a more important corridor that Shreveport-Lafayette.

Perhaps if I-69, I-369, and I-49 from Texarkana to Kansas City had been under consideration back then . . .

I'm not sure what other corridor proposed then would have been more worthy of the number I-30; you could perhaps make an argument for I-85 getting the I-30 designation instead, given its more east-west than north-south orientation, although the US routes it "replaced" were also generally north-south routes.

Could have always had today's I-40 as I-30 and left I-40 reserved for a future addition to the system, such as the I-66 corridor across Missouri and Kentucky.  Given that much of US 40 is multiplexed across Missouri it would be less of a problem than a 2di duplicating US 50 or US 60.

[empirestate]

I think the designations of I-30 and I-45 can simply be explained by, at the time, there being no serious plans for longer corridors that needed numbers and fit the grid better.

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?


iPhone

[Max Rockatansky]

I think the designations of I-30 and I-45 can simply be explained by, at the time, there being no serious plans for longer corridors that needed numbers and fit the grid better.

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?


iPhone

Hence back to what I said about there being no Interstate 50 and 60.  Having those two not in the grid led to a ton of duplicate numbers being used in the 70s and 80s.  Back in 1957 the grid worked a lot better than it does now with half a century of growth and expansion.

[empirestate]

I think the designations of I-30 and I-45 can simply be explained by, at the time, there being no serious plans for longer corridors that needed numbers and fit the grid better.

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?


iPhone

Hence back to what I said about there being no Interstate 50 and 60.  Having those two not in the grid led to a ton of duplicate numbers being used in the 70s and 80s.  Back in 1957 the grid worked a lot better than it does now with half a century of growth and expansion.

That's sort of related, but you could still ask for better grid compliance even if you accept that 50 and 60 are omitted from the system. That works out OK because the U.S. isn't as tall as it is wide; if you had to leave out 55 and 65, you'd run into more problems.

To put it another way, the absence of 50 and 60 isn't the reason for, say, I-30. But putting I-30 in its proper place might mitigate the lack of 50 and 60: for example, it might allow I-94 to be I-90. (But 90 would still have to dip around the Great Lakes, or be discontinuous.)


iPhone

[Max Rockatansky]

I think the designations of I-30 and I-45 can simply be explained by, at the time, there being no serious plans for longer corridors that needed numbers and fit the grid better.

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?


iPhone

Hence back to what I said about there being no Interstate 50 and 60.  Having those two not in the grid led to a ton of duplicate numbers being used in the 70s and 80s.  Back in 1957 the grid worked a lot better than it does now with half a century of growth and expansion.

That's sort of related, but you could still ask for better grid compliance even if you accept that 50 and 60 are omitted from the system. That works out OK because the U.S. isn't as tall as it is wide; if you had to leave out 55 and 65, you'd run into more problems.

To put it another way, the absence of 50 and 60 isn't the reason for, say, I-30. But putting I-30 in its proper place might mitigate the lack of 50 and 60: for example, it might allow I-94 to be I-90. (But 90 would still have to dip around the Great Lakes, or be discontinuous.)


iPhone

How about this instead?

I-10:  Same as now.

I-20:  Same as now.

I-30:  Re-signed over current I-40

I-40:  Re-signed over current I-64 to St. Louis and I-70 west to I-15.

I-50:  Re-sign current I-70 to St. Louis.  This would avoid the duplication with US 50/I-50 out west.

I-60:  Re-sign current I-80.

I-70:  Re-sign current I-90.

I-80:  Re-sign current I-94, this can be to Chicago or the Canadian border.

There wouldn't necessarily need to be an I-90 in what I described above but it would open up a lot more non-duplicate route numbers being available through out the grid.  The change that i can really see as being practical in the east/west grid is reassigning I-45 to the planned full route of I-69 since it would terminate between I-35 and I-55 at the Mexican border. 

[kkt]

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?

I respectfully disagree.  SLC to Las Vegas to Los Angeles carries a whole lot more traffic than SLC to Yuma.  The powers that were at the time were right to make I-15 one number.  And it carries by far the most traffic of any N-S interstate between the Sierra Nevada and the Rockies, so it's also right for it to be a primary interstate number.  Most of I-15 is in the right place in the grid.  When direction of travel is not exactly N-S or E-W, the grid won't fit exactly, and that's okay.

[empirestate]

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?

I respectfully disagree.  SLC to Las Vegas to Los Angeles carries a whole lot more traffic than SLC to Yuma.  The powers that were at the time were right to make I-15 one number.  And it carries by far the most traffic of any N-S interstate between the Sierra Nevada and the Rockies, so it's also right for it to be a primary interstate number.  Most of I-15 is in the right place in the grid.  When direction of travel is not exactly N-S or E-W, the grid won't fit exactly, and that's okay.

Well, then that's simply your answer to my question; nothing to be disagreed with, respectfully or otherwise. :-)


iPhone

[Bickendan]

That raises the interesting question of whether, for better system purity, numbers might have been assigned more strictly according to their proper grid position without regard for whether there was actually a feasible project likely to be built at the time.

A good example is the I-15 corridor: grid-wise, it should really continue southerly through Arizona instead of diverting into California; thus, I-17 and I-19 would make up segments of the route. Of course, actual construction of the full corridor is precluded by some rather prominent physiography–but would the system as a whole work better if the numbers were closer to where we expect them?

I respectfully disagree.  SLC to Las Vegas to Los Angeles carries a whole lot more traffic than SLC to Yuma.  The powers that were at the time were right to make I-15 one number.  And it carries by far the most traffic of any N-S interstate between the Sierra Nevada and the Rockies, so it's also right for it to be a primary interstate number.  Most of I-15 is in the right place in the grid.  When direction of travel is not exactly N-S or E-W, the grid won't fit exactly, and that's okay.

I think it would be interesting to have interstates bouncing off each other on the map -- if not in practice. For instance, if I-15 began in Nogales and followed the proposed I-11 corridor to Las Vegas then rebounds northeasterly to Utah and SLC, and I-11 starting in San Diego to Las Vegas then northwest toward Reno. I-15 could then be an extension of MX 15...
Likewise, supplanting I-45 onto I-49 and I-35 north of KC, with I-35 taking I-29.

Corridor wise, however, I agree with you in keeping the overarching corridor unified under one number. San Diego-San Bernardino [Los Angeles]-Las Vegas-Salt Lake functions as a single entity at this point, same with San Antonio-Dallas/Ft Worth-OKC-KC-Minneapolis/St Paul.

[empirestate]

Perhaps my question is best expressed this way: if the numbering system is based entirely on the geometric arrangement of the corridors (running north-to-south, increasing from west to east, etc.), why is it better to take a number off of its geometrically-appropriate course and have it follow some other parameter such as where traffic actually wants to flow or where a road is actually built? Mind you, I'm not saying that isn't better, I'm just asking why it's better–because if it's better, one would think the numbering system would have been devised based around those parameters rather than the ones that were actually chosen.

[hotdogPi]

Perhaps my question is best expressed this way: if the numbering system is based entirely on the geometric arrangement of the corridors (running north-to-south, increasing from west to east, etc.), why is it better to take a number off of its geometrically-appropriate course and have it follow some other parameter such as where traffic actually wants to flow or where a road is actually built? Mind you, I'm not saying that isn't better, I'm just asking why it's better–because if it's better, one would think the numbering system would have been devised based around those parameters rather than the ones that were actually chosen.

As an example, I-89 and I-91 cross. The current way that it is done (where no turns are required to stay on the route) is much better than if the routes "bumped", with I-89 staying on the west side and I-91 staying on the east side.

[Sykotyk]

Perhaps my question is best expressed this way: if the numbering system is based entirely on the geometric arrangement of the corridors (running north-to-south, increasing from west to east, etc.), why is it better to take a number off of its geometrically-appropriate course and have it follow some other parameter such as where traffic actually wants to flow or where a road is actually built? Mind you, I'm not saying that isn't better, I'm just asking why it's better–because if it's better, one would think the numbering system would have been devised based around those parameters rather than the ones that were actually chosen.

As an example, I-89 and I-91 cross. The current way that it is done (where no turns are required to stay on the route) is much better than if the routes "bumped", with I-89 staying on the west side and I-91 staying on the east side.

Exactly. I-80/I-74 in Illinois and I-80/I-76 in Ohio are two places that really annoys me the numbers change. Especially Illinois as I-74 ends not far from there. It would've made sense to continue I-80 WB across I-280 to end at the current I-80 just east of the World's Largest Truck Stop. Then, I-74 could've continued straight north on old I-80 and turned west, also ending where old I-280 butted into I-80 right near the WLTS. And then the small stretch of poorly built I-74 between I-80 and I-280 could've been a 3di connector.

Two groups of people could've headed west without having to intermingle (74 staying on 74 while 80 staying on 80, without having to exit) and 'through traffic' wouldn't need to be reminded to stay on I-280 to avoid going straight through town.

[pianocello]

Exactly. I-80/I-74 in Illinois and I-80/I-76 in Ohio are two places that really annoys me the numbers change. Especially Illinois as I-74 ends not far from there. It would've made sense to continue I-80 WB across I-280 to end at the current I-80 just east of the World's Largest Truck Stop. Then, I-74 could've continued straight north on old I-80 and turned west, also ending where old I-280 butted into I-80 right near the WLTS. And then the small stretch of poorly built I-74 between I-80 and I-280 could've been a 3di connector.

Two groups of people could've headed west without having to intermingle (74 staying on 74 while 80 staying on 80, without having to exit) and 'through traffic' wouldn't need to be reminded to stay on I-280 to avoid going straight through town.

That was originally the intent, it's just that they signed I-80 over the bridge that was completed first. And then (I think) Iowa found they liked the commerce they got from cross-country traffic along the northern edge of the Quad Cities, so they opposed switching them around.

[RobbieL2415]

When it existed, the original I-86 from East Hartford, CT to Sturbridge, MA was only ~45 miles.  Not sure if it should count though since it was multiplexed with CT/MA 15 until the re-desiganation to I-84.

[Zzonkmiles]

I would like to see I-85 be renumbered as I-30 since it's more east-west than north-south.

Then I-81 could become the new I-85.

Then I-99 could become the new I-81.

[Pink Jazz]

Then I-81 could become the new I-85.

A significant portion of I-81 is also more east-west than north-south, particularly in Tennessee and Virginia.