Similarity of 3dis by first digit

[empirestate]

OK, got one more for you. I was going to tack this on to my last topic (Types of 3dis), but this seemed specific enough to warrant its own thread. I'll say straight away that any answers to this will clearly be based on coincidence and happenstance, not by design, but that's what makes it interesting to me (finding order amid disorder).

So: Can we find similarities between 3dis with the same first digit? Could we actually make loose categories of 3dis based on this aspect (not just odd or even, but all 3dis beginning with "1", with "2", etc.)?

For example, it strikes me that many 3xx Interstates tend to be the short little downtown spurs, often just "glorified exit ramps": I-375 MI, I-375 FL, I-395 MD...but then they also seem just as likely to be long-distance inter-city routes: I-380 IA, I-390 NY, I-395 CT/MA. Still, disparate as these categories are, it seems most 3xx's do fit into one of the two. (But maybe that's because most odd 3dis in general do so.)

And 6xx routes seem to be pretty short, highly localized alternate or bypass loops (cut-offs, even): I-670 KS/MO, I-670 OH, I-610 LA.

And is it just me, or are more full beltways 4xx's than 2xx's, while more half-loops seem to be 2xx? (Though there are some prominent 2xx beltways as well: I-285, I-275; and some pretty obvious 4xx half-loops: I-490 NY, I-405 CA.)

Finally, if you were to design the system from scratch and decided to intentionally categorize 3dis according to their specific first digit, how would you do it?

[Bickendan]

Hmm.
I-105 (CA) Long connector between LAX and I-605.
I-105 (OR) Spur into downtown Eugene, long enough to avoid glorified exit ramp. If ever extended east into Springfield...
I-205 (CA) Connector between I-580 and I-5. Hypotenuse of the southern I-5W(580)/5E interchange.
I-205 (OR/WA) Half-loop. Meets thread criteria.
I-305 (CA) Spears I-5, does not fall under the short downtown spur.
I-305 (cancelled) (OR) Spur into downtown Salem, long enough to stand as own freeway (if built) based on OR 99E BUS current spec.
I-405 (all three) Half-loops.
I-505 Formally I-5W. Falls under long-distance spur/connector? Trait of I-5xx?
I-605 No loop, connects I-210 and I-405, spears I-5. Black sheep of I-6xx?
I-705 Glorified ramp into Tacoma.
I-805 Half-loop.
I-905 Acts as a border crossing bypass/relief (once fully upgraded).

[hotdogPi]

I think the current even-odd system should be used, but with some additions.

1: Major, almost major enough to be a full 2di. The western I-86 would be in this category if it was a 3di.
2: Full beltways.
3: Current use. Ideally about 5-10 miles.
4: Partial beltways.
5: Short (but not "exit ramp") 3dis that are not loops.
7: "Exit ramps".

Add 2 if the desired number is already taken, with the exception that 2 becomes 6.

[roadman65]

If I am reading this correctly he is meaning the first number has a prominent meaning as well as just being odd or even based on some coincidences.

Yeah, pretty much most 2s and 4s are used as beltways only because those low numbers are the most popular.  Yeah that might set a precedent for future road numbering, however IF and I do say IF, the numbers are available I would say go for it.  Then leave the 6s and 8s for smaller inner city or urban loops.

As far as odd digits go spurs do vary.  Like you said I-395 in CT/MA is long while the I-395 in MD is relatively short.  Keep in mind that in CT/MA was a late addition to the system being CT/MA 52 for years before incorporated into the interstate highway network.  It was not intended to be a spur, but the number filled the quota so to speak.  However, back on subject, yes that one is not so coincidental, but worthy of using the 1,3,5,7, and 9 for specific purposes.  Use the low numbers for longer routes and the higher numbers like 7 and 9 for the glorified exit ramps like I-175 in St Pete.

[SSOWorld]

I think the current even-odd system should be used, but with some additions.

1: Major, almost major enough to be a full 2di. The western I-86 would be in this category if it was a 3di.
2: Full beltways.
3: Current use. Ideally about 5-10 miles.
4: Partial beltways.
5: Short (but not "exit ramp") 3dis that are not loops.
7: "Exit ramps".

Add 2 if the desired number is already taken, with the exception that 2 becomes 6.

whatever.  a digit's a digit - even or odd meanings only.

[empirestate]

I think the current even-odd system should be used, but with some additions.

1: Major, almost major enough to be a full 2di. The western I-86 would be in this category if it was a 3di.
2: Full beltways.
3: Current use. Ideally about 5-10 miles.
4: Partial beltways.
5: Short (but not "exit ramp") 3dis that are not loops.
7: "Exit ramps".

Add 2 if the desired number is already taken, with the exception that 2 becomes 6.

Okay, so for 1xx, routes like I-135 already qualify; what else?

For 2xx and 6xx, full beltways; for 4xx and 6xx (again, by adding 2 to 4) partial beltways; what about 8xx?

For 3xx, what does "current use" seem to be? The downtown spurs? The intercity routes (but I think you want 1xx for that)? Something else?

Where would you put the big alternate/bypass routes (I-405 CA) that aren't beltways at all?

If I am reading this correctly he is meaning the first number has a prominent meaning as well as just being odd or even based on some coincidences.

That's right, but remember there are two parts to the question: 1) What patterns exist in the current, real-world system? and 2) What categories would you devise if you were intentionally grouping 3dis according to their first digit?

Yeah, pretty much most 2s and 4s are used as beltways only because those low numbers are the most popular.  Yeah that might set a precedent for future road numbering, however IF and I do say IF, the numbers are available I would say go for it.  Then leave the 6s and 8s for smaller inner city or urban loops.

Certainly, 2 and 4 are the most-assigned first digit because of sequence, and certainly beltways and half-loops are the most typical sort of even 3di, so it's not entirely coincidence that most routes with those first digits would tend to have those configurations.

Also, there seem to be more different types of odd 3dis overall, which is lucky since there are also more odd first digits available.

whatever.  a digit's a digit - even or odd meanings only.

Cool, so your answer to the thread topic is, succinctly, "no"? :-)

[GaryV]

Aren't they generally numbered in order of direction of the parent route in the state?  E.g.in Michigan: I-275, I-475 and I-675 in S to N; I-296, I-496, I-696 W to E.  And then if a new one is needed later, it becomes the next available number.

[empirestate]

Aren't they generally numbered in order of direction of the parent route in the state?  E.g.in Michigan: I-275, I-475 and I-675 in S to N; I-296, I-496, I-696 W to E.  And then if a new one is needed later, it becomes the next available number.

Yes, in many states they are. NY is another example with its x90s from west to east (then jumping back west when I-990 came along). But that's an intentional pattern; the patterns I'm looking at (to the extent they even exist) arise unintentionally from the "chaos" of the system.

Then in part 2 we take those unintentional patterns and devise an intentional system. For example, here's how I might classify the odd 3dis:

1xx–Spurs from a parent route that approach and sometimes enter a city to be served. Examples: I-110 FL, I-176 PA.
3xx–Short spurs or connectors serving a city center or highly localized area. Examples: I-375 MI, I-395 MD.
5xx–Routes that branch, bypass or cut off around a city. Examples: I-590 NY, I-526 SC.
7xx–Inter-city or prominent branch routes. Example: I-710 CA. (I'm really stretching for this category...)
9xx–Routes that branch away from a metro area. Examples: I-985 GA, I-990 NY.

Under this system, the following real-world routes might be re-classified:
1xx–I-395 VA/DC.
3xx–I-705 WA.
5xx–I-185 SC.
7xx–I-385 SC.
9xx–I-140 TN.

[Thing 342]

Here's how I tend to perceive 3dis:

1: Shorter spur that heads into town from a parent route, ends in the middle of an urban core, and is about 3-5 miles long. Examples include I-195 (FL, VA, and ME flavours), I-185 (SC, pre-Southern Connector),  I-165, I-126,  I-129, and I-180 (NE).

2: Medium-length loop route that curves into a city that the parent mostly bypasses. These tend to be anywhere from 5 to 30 miles long. Examples include I-264 (VA), I-295 (NC and DC), I-210 (LA), I-235 (IA), I-277 (NC), I-240 (NC), I-244, and I-280 (IL-IA)

3 (short definition): A very short spur carrying traffic from a parent route to downtown. These are often glorified exit ramps and are usually less than three miles long. Examples include I-395 (MD, FL, and ME), I-375 (FL and MI), I-315, I-345, I-381, and I-359.

3 (long definintion): A long, semi-rural connector that serves metro areas left off the mainline system. These are often as long as mainline routes, and are more than 30 miles long. Examples include I-390, I-369 (TX and KY), I-380 (IA), I-335, and I-385.

4: A longer loop route or beltway that serves an entire metro area. These are usually longer than 25 miles and tend to avoid urban cores and carry a large amount of bypass traffic. Examples include I-495 (Capitol Beltway, DE, MA), I-485, I-465, I-435, I-475 (OH), I-405 (WA), I-410, I-480 (OH) and I-494.

5: A suburban highway that travels radially from downtown and serves suburbs. These frequently run from some perimeter (like a beltway) and end in either a peripheral town or an exurban area. Examples include I-575, I-595 (MD), I-530, I-540 (AR, maybe NC), I-555, I-565, and I-580 (NV),

6 and 8: Medium-length roads that serve as connectors between roads in suburbs. Examples include I-664, I-605, I-610 (LA), I-630, I-635, I-895 (MD), the proposed I-885, I-865, I-890, and I-805.

7 and 9: Like 5xx routes, but shorter, tending to be from 4 to 12 miles long. Examples include I-795 (MD), I-781, I-985, I-910 and I-990.

[hotdogPi]

I think the current even-odd system should be used, but with some additions.

1: Major, almost major enough to be a full 2di. The western I-86 would be in this category if it was a 3di.
2: Full beltways.
3: Current use. Ideally about 5-10 miles.
4: Partial beltways.
5: Short (but not "exit ramp") 3dis that are not loops.
7: "Exit ramps".

Add 2 if the desired number is already taken, with the exception that 2 becomes 6.

Okay, so for 1xx, routes like I-135 already qualify; what else?

For 2xx and 6xx, full beltways; for 4xx and 6xx (again, by adding 2 to 4) partial beltways; what about 8xx?

For 3xx, what does "current use" seem to be? The downtown spurs? The intercity routes (but I think you want 1xx for that)? Something else?

Where would you put the big alternate/bypass routes (I-405 CA) that aren't beltways at all?

1xx would be the major non-beltway 3dis. If it could possibly be a 2di (even if no 2di number would fit), and it is not a 2di, it goes in the 1xx category. If it just barely misses the 2di "requirements", 1xx would also work.

3xx is medium-length: shorter than 1xx but longer than 5xx. It could also be used for semi-major 3dis that would otherwise be 1xx if the 1xx number is already taken.

If 2xx or 4xx is taken, then 6xx is used. If 6xx is also taken, that is the place for 8xx.

I-405 in California could be considered a partial beltway. It just isn't circular.

[DandyDan]

Here's how I tend to perceive 3dis:

1: Shorter spur that heads into town from a parent route, ends in the middle of an urban core, and is about 3-5 miles long. Examples include I-195 (FL, VA, and ME flavours), I-185 (SC, pre-Southern Connector),  I-165, I-126,  I-129, and I-180 (NE).

2: Medium-length loop route that curves into a city that the parent mostly bypasses. These tend to be anywhere from 5 to 30 miles long. Examples include I-264 (VA), I-295 (NC and DC), I-210 (LA), I-235 (IA), I-277 (NC), I-240 (NC), I-244, and I-280 (IL-IA)

3 (short definition): A very short spur carrying traffic from a parent route to downtown. These are often glorified exit ramps and are usually less than three miles long. Examples include I-395 (MD, FL, and ME), I-375 (FL and MI), I-315, I-345, I-381, and I-359.

3 (long definintion): A long, semi-rural connector that serves metro areas left off the mainline system. These are often as long as mainline routes, and are more than 30 miles long. Examples include I-390, I-369 (TX and KY), I-380 (IA), I-335, and I-385.

4: A longer loop route or beltway that serves an entire metro area. These are usually longer than 25 miles and tend to avoid urban cores and carry a large amount of bypass traffic. Examples include I-495 (Capitol Beltway, DE, MA), I-485, I-465, I-435, I-475 (OH), I-405 (WA), I-410, I-480 (OH) and I-494.

5: A suburban highway that travels radially from downtown and serves suburbs. These frequently run from some perimeter (like a beltway) and end in either a peripheral town or an exurban area. Examples include I-575, I-595 (MD), I-530, I-540 (AR, maybe NC), I-555, I-565, and I-580 (NV),

6 and 8: Medium-length roads that serve as connectors between roads in suburbs. Examples include I-664, I-605, I-610 (LA), I-630, I-635, I-895 (MD), the proposed I-885, I-865, I-890, and I-805.

7 and 9: Like 5xx routes, but shorter, tending to be from 4 to 12 miles long. Examples include I-795 (MD), I-781, I-985, I-910 and I-990.

I like your definitions, but here in the Omaha area, they got I-480 and I-680 backwards, at least when you consider that I-680 was planned as I-280, before they realized it was going into Iowa, which already had I-280.  And multistate 3di's are where defining a 3di goes bad.

[empirestate]

And multistate 3di's are where defining a 3di goes bad.

That, and multiple cases of the same type within a state. If I now try to categorize even 3dis...

2xx–Half-loop; loop to and through a city from a parent that bypasses it. Examples: I-240 OK, I-205 OR/WA
4xx–Beltways, full or reasonably projected to become full. Examples: I-485 SC, I-410 TX
6xx–Very localized bypasses or cut-offs. Examples: I-610 LA, I-670 KS/MO.
8xx–Sub-level or secondary loops; a loop from a loop or a concentric beltway. Examples: Can't think of a real-world example, but I-840 TN, if it had come to pass.

...then that mean in NYS, I-490, I-890 and arguably I-690 would all deserve to be 2xx's. But it's an imaginary exercise, so I won't lose sleep over it.

[mrpablue]

CalTrans doesn't care about this stuff. I would keep California out of this.

[empirestate]

CalTrans doesn't care about this stuff. I would keep California out of this.

Well, CalTrans isn't involved; it's a mental exercise. Besides, probably no state DOT cares about this stuff–but it's not much fun to think about if we leave every state out of this!

[triplemultiplex]

I think it's more important to pick a 3di based on what will 'stand out' better against the mainline interstate(s) it junctions.  That is to say, I would favor numbers that aren't 'alliterative' (like 880 or 555) or maybe don't 'clash' with some other interstate nearby.  Unless that's the only option available because it's, say, California.  Your divisible by 11 interstates; this is not as big a deal because the 'alteration' is on the end of the number, not the front.

Example:  If I want to slap a 3di on the WI 30 freeway spur into Madison, there are literally a dozen options.  The east end would be the Badger Interchange where interstates 39, 90 and 94 all meet.  So theoretically, I could use an odd spur of any of those three (except 794 of course).   Right away, I would eliminate 390 from consideration.  Why?  Because with I-39 in the mix, I think that's potentially confusing to see the numbers 39 and 390 next to each other on an overhead BGS.  394 is also out for the same reason.  A 9xx can also be scratched because that junction doesn't need more 9's.  And because I feel like 9xx's are for places where that's the last option for a state, but that's just my preference.  (Hello, 985! :poke )

The flip side of this are the palindrome numbers like 535, 464 or 393.  Those I rather like.  They roll off the tongue and because they do, they stand out well from the parent.  So I have a tendency to want to use them as I fictionalize.

I tend to defer to what number 'sounds' better when picking 3di numbers if I have a blank slate to work with.

[ilpt4u]

I don't think IDOT follows any on these guidelines...

I-255/I-270 form the STL Beltway, which includes IL and MO

I-294 isn't a full Beltway, due to that Lake Michigan thing...

I-280 forms a full beltway in combination with Parent I-80 of the Quad Cities in IL/IA. On its own, its a half-belt

I-474 is a half-belt for Peoria. Making it a Full Belt has been studied, but probably not happening any time soon

I-180 – ugh

I-190 – ORD Airport Access Road

I-155 - Shortcut route for traffic between Springfield and Peoria

I-355 - Probably should be an Even, as it functions as an outer partial Belt. Will function moreso if the IL 53 North extension ever comes to pass

There isn't really a pattern in IL that I can discern

[hotdogPi]

I don't think IDOT follows any on these guidelines...

I-255/I-270 form the STL Beltway, which includes IL and MO

I-294 isn't a full Beltway, due to that Lake Michigan thing...

I-280 forms a full beltway in combination with Parent I-80 of the Quad Cities in IL/IA. On its own, its a half-belt

I-474 is a half-belt for Peoria. Making it a Full Belt has been studied, but probably not happening any time soon

I-180 – ugh

I-190 – ORD Airport Access Road

I-155 - Shortcut route for traffic between Springfield and Peoria

I-355 - Probably should be an Even, as it functions as an outer partial Belt. Will function moreso if the IL 53 North extension ever comes to pass

There isn't really a pattern in IL that I can discern

The only official rules are that an even first digit is a loop, and an odd first digit is a spur. In practice, routes that connect two different Interstates can have either an even or odd first digit. There is also a general guideline to avoid using 7xx, 8xx, and 9xx if lower numbers are available, but this isn't universally followed.

Functionally, there is no difference between 2xx and 4xx; everything in this thread indicating that there is a difference is either a proposal or an attempt to see a pattern that isn't there.

[ilpt4u]

I forgot I-290 on my IDOT list

I guess, by rule, I-290 should be an Even, as it touches its Parent on both ends. Really, its moreso an Alternate Spur to reach Downtown Chicago via the Western Suburbs and West Side vs the Northwest Suburbs, ORD, and Northwest Side. It certainly does not function as a Bypass or Beltway

I think I-290 is a good candidate for redesignation, but that is not the discussion here.

[empirestate]

I don't think IDOT follows any on these guidelines...

I-255/I-270 form the STL Beltway, which includes IL and MO

I-294 isn't a full Beltway, due to that Lake Michigan thing...

I-280 forms a full beltway in combination with Parent I-80 of the Quad Cities in IL/IA. On its own, its a half-belt

I-474 is a half-belt for Peoria. Making it a Full Belt has been studied, but probably not happening any time soon

I-180 – ugh

I-190 – ORD Airport Access Road

I-155 - Shortcut route for traffic between Springfield and Peoria

I-355 - Probably should be an Even, as it functions as an outer partial Belt. Will function moreso if the IL 53 North extension ever comes to pass

There isn't really a pattern in IL that I can discern

Well, your 2xx's all fit right in with my classification as half-loops, as does 474. The odd routes are more all over the place, as they are nationwide (although 155 actually fits in with some other 1xx's that function like branch routes: 135 (KS), 190 (NY), 185 (SC).

Functionally, there is no difference between 2xx and 4xx; everything in this thread indicating that there is a difference is either a proposal or an attempt to see a pattern that isn't there.

Well, a pattern that isn't intentionally there. Whether it's actually there depends on where you look and what classification you select. But yes, this thread isn't about actual rules, it's about finding order in (relative) chaos.

[jp the roadgeek]

Let's go ahead and take a look at the x-95's.  I've omitted the decommissioned ones, including newly demoted I-895 in NYC

I-195 (FL): Short spur from I-95 to Key Biscayne
I-195 (VA): Short spur into Richmond that becomes a state route
I-195 (MD): Former MD 46.  Short spur from I-95 to BWI
I-195 (NJ): 40 mile cross-state route that crosses its parent in favor of ending at a related 3di
I-195 (RI/MA): Originally planned as I-95E.  Significant connector from Providence to Cape Cod
I-195 (ME): Very short spur serving Saco and Old Orchard Beach.  Only sees traffic in summer months.
I-295 (FL): Jacksonville Beltway
I-295 (NC): Fayetteville partial belt.  Will be extended in the future.
I-295 (VA): Partial Richmond beltway.
I-295 (MD): Short freeway that downgrades to a state route but becomes a useful alternate to I-95 for passenger vehicles.
I-295 (DE-NJ-soon to be PA): Significant alternative to the NJTP and the most important Delaware River crossing outside of Philly.
I-295 (NY): Short freeway.  Only important part is the Throgs Neck Bridge
I-295: (RI/MA): Providence half belt. Useful Providence bypass for long distance traffic
I-295 (ME): Became much longer and more important when I-95 was rerouted onto the METP.
I-395 (FL): A glorified extension of FL 836 to Key Biscayne
I-395 (VA/DC): The built portion of I-95's planned route through DC
I-395 (MD): Glorified exit ramp
I-395 (CT/MA): Mostly a middle of nowhere promoted state route. Made more important by Mohegan Sun.
I-395 (ME): Short spur into Bangor.  Screams out for extension to NB 1.
I-495 (VA/MD): The Beltway
I-495 (DE): Wilmington bypass for long distance I-95 traffic.  Should really be I-95 proper.
I-495 (NY): The LIE.  Could have become a 2di if the Mid-Manhattan Expressway were built.
I-495 (MA): 30-mile half belt of Boston.  Serves as a gateway to the Cape and Northeastern New England from points west.
I-495 (ME): So emasculated from its Maine Turnpike heyday that it's not even signed anymore.
I-595 (FL): An eastern extension of Alligator Alley to the airport
I-595 (MD): The interstate 99% of non-roadgeeks know nothing about with its US 50 façade.
I-695 (MD): The other Beltway
I-695 (NY): Blink and you're ether on the New England Thruway or the Throgs Neck
I-795 (FL): FL 9B still waiting for promotion
I-795 (NC): Essentially a bypass of US 117
I-795 (MD): Spur off the Baltimore Belt serving Reisterstown and Gettysburg area bound traffic.
I-895 (MD): Once the de-facto I-95 through Baltimore until the Fort Mac Tunnel was built.  Now a useful alternate.

[CtrlAltDel]

I think it's more important to pick a 3di based on what will 'stand out' better against the mainline interstate(s) it junctions.

I agree.

This is why I never liked that I-290 and I-294 have numbers that are so similar, given that there is a stretch where they run side by side. I would have named 294 as 494.

[ilpt4u]

I think it's more important to pick a 3di based on what will 'stand out' better against the mainline interstate(s) it junctions.

I agree.

This is why I never liked that I-290 and I-294 have numbers that are so similar, given that there is a stretch where they run side by side. I would have named 294 as 494.

Na, just rename 294 back to Toll 41, tho this time with an Interstate Shield

[Flint1979]

They go in order in Michigan. I-275 starts at exit 20, I-375 starts at exit 51, I-475 starts at exit 111 and ends at exit 125, I-675 starts at exit 150 and ends at exit 155.

[Henry]

Guess I'll take a crack at this, with examples of such:

1 and 3--Major spur route into a city (I-195 NJ, I-380 IA)
2 and 4--Major loop/bypass route (I-290 IL, I-405 CA)
5--Medium spur route (I-595 FL)
6--Medium bypass/connector route (I-675 GA)
7--Minor urban spur route (I-794 WI)
8--Minor bypass/connector route (I-895 MD)
9--Minor suburban spur route (I-985 GA)

[Flint1979]

Another Michigan Interstate I-96 goes in order as well.
There is a I-296 in Grand Rapids that is unsigned.
I-196 though starts at Exit 37.
I-496 starts at Exit 95 and ends at Exit 106.
I-696 starts at Exit 164.

I-94 only has one child in the state of Michigan. I-194 which runs multiplexed with M-66 for it's entire route starts at Exit 98 and runs into downtown Battle Creek.