3DI numbering scheme—how it is, and how it should be

[PHLBOS]

In the case of the recent I-376 extension (onto PA 60 & the lower leg of I-279); another 3di number could've been selected for the highway portion of PA 60 and lower I-279 could've been left alone.

Though, that would have defeated part of the purpose of what they were trying to do. 
Part of it was business reasons; the belief that an I-designation will help development, and that Pittsburgh International Airport needed "to be served" by an interstate.  Just how important/beneficial it actually is, I think, can be debated....

To be clear, I wasn't disputing the redesignation of PA 60 into an Interstate (and the reasonings behind the move may be close to what you mentioned in your post).  I was commenting on the number choice and the fact that such a choice involved/required a complete renumbering of mile markers & interchange numbers for three different highways rather than one; especially a few years after a statewide revamp of interchange numbers (to mile-marker based) was already instituted.

But the rest of the reason was to unify a continuous highway that was a hodgepodge of numbers under one route designation, so they wouldn't want one number to just end, and other to just begin.

While I can relate to that reasoning; IMHO, PennDOT should've at least made an attempt to properly use the appropriate 3di prefix (in this case, even since it's clearly not a spur).  If one's going to change the designation of several roads in the process; why not do it properly?

The current changes not only have an odd 3di behave more like an even 3di; but the truncating of I-279 in Pittsburgh, now makes that road, in theory, a spur.

Fictional territory here; but IMHO the current I-376 should be I-276* (or I-280) and the current I-279 should be I-379.

*Current I-276 along the eastern end of the PA Turnpike could be redesignated as either I-876 or 695 (since it will be ending at I-95 in the foreseable future).  Most people in the Delaware Valley don't even refer to that stretch of Turnpike as I-276 (except when reciting signs) so a number change there isn't much of a big deal in their eyes.

[DTComposer]

In what way does I-605 CA function as a loop off I-5?

it falls in quite nicely with the "ends at another interstate" rule... on both ends, actually.  it connects 405 to 210.

I've always thought of I-605 as kind of a "double spur"-
A spur from I-5 northbound into the San Gabriel Valley;
and a spur from I-5 southbound to east Long Beach/coastal Orange County.

On an earlier thread I think we also talked about I-605 and I-405 making a loop/bypass from I-5 of Anaheim/Santa Ana.

[vdeane]

In the case of the recent I-376 extension (onto PA 60 & the lower leg of I-279); another 3di number could've been selected for the highway portion of PA 60 and lower I-279 could've been left alone.

Though, that would have defeated part of the purpose of what they were trying to do. 
Part of it was business reasons; the belief that an I-designation will help development, and that Pittsburgh International Airport needed "to be served" by an interstate.  Just how important/beneficial it actually is, I think, can be debated....

To be clear, I wasn't disputing the redesignation of PA 60 into an Interstate (and the reasonings behind the move may be close to what you mentioned in your post).  I was commenting on the number choice and the fact that such a choice involved/required a complete renumbering of mile markers & interchange numbers for three different highways rather than one; especially a few years after a statewide revamp of interchange numbers (to mile-marker based) was already instituted.

But the rest of the reason was to unify a continuous highway that was a hodgepodge of numbers under one route designation, so they wouldn't want one number to just end, and other to just begin.

While I can relate to that reasoning; IMHO, PennDOT should've at least made an attempt to properly use the appropriate 3di prefix (in this case, even since it's clearly not a spur).  If one's going to change the designation of several roads in the process; why not do it properly?

The current changes not only have an odd 3di behave more like an even 3di; but the truncating of I-279 in Pittsburgh, now makes that road, in theory, a spur.

Fictional territory here; but IMHO the current I-376 should be I-276* (or I-280) and the current I-279 should be I-379.

*Current I-276 along the eastern end of the PA Turnpike could be redesignated as either I-876 or 695 (since it will be ending at I-95 in the foreseable future).  Most people in the Delaware Valley don't even refer to that stretch of Turnpike as I-276 (except when reciting signs) so a number change there isn't much of a big deal in their eyes.

Does ANYONE follow the official 3di numbering rules?  I know NYSDOT doesn't care and never has.

[Alps]

In the case of the recent I-376 extension (onto PA 60 & the lower leg of I-279); another 3di number could've been selected for the highway portion of PA 60 and lower I-279 could've been left alone.

Though, that would have defeated part of the purpose of what they were trying to do. 
Part of it was business reasons; the belief that an I-designation will help development, and that Pittsburgh International Airport needed "to be served" by an interstate.  Just how important/beneficial it actually is, I think, can be debated....

To be clear, I wasn't disputing the redesignation of PA 60 into an Interstate (and the reasonings behind the move may be close to what you mentioned in your post).  I was commenting on the number choice and the fact that such a choice involved/required a complete renumbering of mile markers & interchange numbers for three different highways rather than one; especially a few years after a statewide revamp of interchange numbers (to mile-marker based) was already instituted.

But the rest of the reason was to unify a continuous highway that was a hodgepodge of numbers under one route designation, so they wouldn't want one number to just end, and other to just begin.

While I can relate to that reasoning; IMHO, PennDOT should've at least made an attempt to properly use the appropriate 3di prefix (in this case, even since it's clearly not a spur).  If one's going to change the designation of several roads in the process; why not do it properly?

The current changes not only have an odd 3di behave more like an even 3di; but the truncating of I-279 in Pittsburgh, now makes that road, in theory, a spur.

Fictional territory here; but IMHO the current I-376 should be I-276* (or I-280) and the current I-279 should be I-379.

*Current I-276 along the eastern end of the PA Turnpike could be redesignated as either I-876 or 695 (since it will be ending at I-95 in the foreseable future).  Most people in the Delaware Valley don't even refer to that stretch of Turnpike as I-276 (except when reciting signs) so a number change there isn't much of a big deal in their eyes.

Does ANYONE follow the official 3di numbering rules?  I know NYSDOT doesn't care and never has.

Florida looks pretty solid.

[cpzilliacus]

If PennDOT and PTC want to retain the abomination known as Breezewood, then FHWA should have I-70 re-routed by way of present-day I-68 and Pa. 43.

Current I-70 between California, Pennsylvania and New Stanton can be I-770; and Breezewood and Hancock, Maryland can become I-970.

Is this too far off-topic from 3DI routes?

[kkt]

In the case of the recent I-376 extension (onto PA 60 & the lower leg of I-279); another 3di number could've been selected for the highway portion of PA 60 and lower I-279 could've been left alone.

Though, that would have defeated part of the purpose of what they were trying to do. 
Part of it was business reasons; the belief that an I-designation will help development, and that Pittsburgh International Airport needed "to be served" by an interstate.  Just how important/beneficial it actually is, I think, can be debated....

To be clear, I wasn't disputing the redesignation of PA 60 into an Interstate (and the reasonings behind the move may be close to what you mentioned in your post).  I was commenting on the number choice and the fact that such a choice involved/required a complete renumbering of mile markers & interchange numbers for three different highways rather than one; especially a few years after a statewide revamp of interchange numbers (to mile-marker based) was already instituted.

But the rest of the reason was to unify a continuous highway that was a hodgepodge of numbers under one route designation, so they wouldn't want one number to just end, and other to just begin.

While I can relate to that reasoning; IMHO, PennDOT should've at least made an attempt to properly use the appropriate 3di prefix (in this case, even since it's clearly not a spur).  If one's going to change the designation of several roads in the process; why not do it properly?

The current changes not only have an odd 3di behave more like an even 3di; but the truncating of I-279 in Pittsburgh, now makes that road, in theory, a spur.

Fictional territory here; but IMHO the current I-376 should be I-276* (or I-280) and the current I-279 should be I-379.

*Current I-276 along the eastern end of the PA Turnpike could be redesignated as either I-876 or 695 (since it will be ending at I-95 in the foreseable future).  Most people in the Delaware Valley don't even refer to that stretch of Turnpike as I-276 (except when reciting signs) so a number change there isn't much of a big deal in their eyes.

Does ANYONE follow the official 3di numbering rules?  I know NYSDOT doesn't care and never has.

Washington follows it completely, as far as I can see.  It's easy if you only have a few routes...

[kkt]

There is, effectively, already a 4di: I-H201, if you consider the 'H' as part of the number.

I'm looking at I-H201, and I'm only seeing three digits, two letters, and punctuation mark.

[kkt]

So–multi-part question–what is your interpretation of the existing rule (for odd/even numbering), and in either a pragmatic or perfect world, what do you think it should be?

The odd/even first digit rule has been broken so many times it might as well not be a rule.  It doesn't help anyone navigate.

There's only four first digits available for loop or link routes.  It would have helped a little to use odd first digits for loops and links, and evens for spurs, so that there'd be five first digits available for the loops and links.

The lack of 3dis in California (at least) could have been avoided if California got more 2dis that they've asked for several times.   

[Bickendan]

There is, effectively, already a 4di: I-H201, if you consider the 'H' as part of the number.

I'm looking at I-H201, and I'm only seeing three digits, two letters, and punctuation mark.

So a 6di then?

[mrose]

I'd kind of like to see all permutations of a 3di exhausted before they start to repeat. For example, there are three I-210s and two I-610s, but there are no I-810s.

Maybe it's somewhat impractical since some 2dis have enough 3dis to make repeats inevitable, but it always bugged me, especially when you get a number that shows up several times in close proximity like some of the x95s do.

[Roadsguy]

We all know the numbering rules for Interstates, including at least a vague notion of the rules for 3DIs–first digit odd: spur, first digit even: loop/beltway.

Should 4DIs be allowed in states that "need" more 3DIs?

There is, effectively, already a 4di: I-H201, if you consider the 'H' as part of the number.

Isn't it really I-H-201, with the second hyphen removed so it can fit on shields?

[NE2]

The D stands for digit. Dumbasses.

[Brandon]

We all know the numbering rules for Interstates, including at least a vague notion of the rules for 3DIs–first digit odd: spur, first digit even: loop/beltway.

Should 4DIs be allowed in states that "need" more 3DIs?

There is, effectively, already a 4di: I-H201, if you consider the 'H' as part of the number.

Isn't it really I-H-201, with the second hyphen removed so it can fit on shields?

How is it set up for the Hawai'i interstates anyway?  I believe the "H" is a part of the number of the route, IIRC.  The hyphen seems to appear on older signs, but not on newer ones.

[Rover_0]

I'd kind of like to see all permutations of a 3di exhausted before they start to repeat. For example, there are three I-210s and two I-610s, but there are no I-810s.

Maybe it's somewhat impractical since some 2dis have enough 3dis to make repeats inevitable, but it always bugged me, especially when you get a number that shows up several times in close proximity like some of the x95s do.

One example here out west is I-580. I always felt that I-580 (NV) and I-580 (CA) were too close together for repeating 3DIs. Now IIRC, Nevada using I-5xx for its 2 3DIs fits is numbering for urban routes (NV-5xx), which does make sense. However, I feel that I-180 would fit better--despite being used 4 times already--as, unless California suddenly gets the itch to renumber CA-180, won't ever have an I-180.

However, I'd prefer to spread out 3DI numbers as much as possible, so I'd be inclined to use either I-780 or I-980, neither of which are terribly long, for Nevada's I-580.

[briantroutman]

If PennDOT and PTC want to retain the abomination known as Breezewood, then FHWA should have I-70 re-routed by way of present-day I-68 and Pa. 43.

Considering that the Mon-Fayette Expressway was one of those cart-before-the-horse plans to stimulate economic development by building a freeway, adding a well-known cross-country Interstate designation might be a way to get a few cars on the road. So far, according to the Post-Gazette, the traffic hasn't materialized. http://bit.ly/ZgVT3q

One example here out west is I-580. I always felt that I-580 (NV) and I-580 (CA) were too close together for repeating 3DIs. Now IIRC, Nevada using I-5xx for its 2 3DIs fits is numbering for urban routes (NV-5xx), which does make sense. However, I feel that I-180 would fit better--despite being used 4 times already--as, unless California suddenly gets the itch to renumber CA-180, won't ever have an I-180.

However, I'd prefer to spread out 3DI numbers as much as possible, so I'd be inclined to use either I-780 or I-980, neither of which are terribly long, for Nevada's I-580.

Apparently, the entire concept of 3DIs is so foreign to the people of Reno that a local newscast ran a story explaining what a 3DI is and why a section of US 395 was being designated as one. http://bit.ly/11wmgSD

Down in the comments below the video, one person said "Hey, I thought 580 was in California..." Probably a sign of how the Interstate numbering system (sadly) is meaningless to anyone except DOT officials and roadgeeks.

[kkt]

Apparently, the entire concept of 3DIs is so foreign to the people of Reno that a local newscast ran a story explaining what a 3DI is and why a section of US 395 was being designated as one. http://bit.ly/11wmgSD

Down in the comments below the video, one person said "Hey, I thought 580 was in California..." Probably a sign of how the Interstate numbering system (sadly) is meaningless to anyone except DOT officials and roadgeeks.

I'm not surprised.  Interstates are supposed to be a national system, and yet there may be many different routes with the same number?  How can this not confuse people?

[kphoger]

I've said it before, but I would be in favor of completely abandoning any parent/child relationships in route numbering.  For all I care, a spur of I-55 can be numbered I-923; in fact, that would be less confusing to me than encountering I-155, I-255, I-355, et seq, and trying to figure out which is which.  My only real beef with 3-digit routes is that I think they should be shorter than two-digit routes; there are several two-digit Interstates that are shorter than I-135 in Kansas (yes, I know it wasn't always numbered that).

[roadfro]

One example here out west is I-580. I always felt that I-580 (NV) and I-580 (CA) were too close together for repeating 3DIs. Now IIRC, Nevada using I-5xx for its 2 3DIs fits is numbering for urban routes (NV-5xx), which does make sense. However, I feel that I-180 would fit better--despite being used 4 times already--as, unless California suddenly gets the itch to renumber CA-180, won't ever have an I-180.

However, I'd prefer to spread out 3DI numbers as much as possible, so I'd be inclined to use either I-780 or I-980, neither of which are terribly long, for Nevada's I-580.

It's tough for me to think two I-580s, in two different states, whose exits are about 200 miles apart, would be a cause of confusion... Perhaps that is my roadgeek knowledge factoring in.  Aren't there some same-number 3DIs that are much closer?

Apparently, the entire concept of 3DIs is so foreign to the people of Reno that a local newscast ran a story explaining what a 3DI is and why a section of US 395 was being designated as one. http://bit.ly/11wmgSD

Down in the comments below the video, one person said "Hey, I thought 580 was in California..." Probably a sign of how the Interstate numbering system (sadly) is meaningless to anyone except DOT officials and roadgeeks.

I don't think it was the concept of a 3DI that was foreign to Reno. It was the fact that the I-580 designation was newly signed, and was being signed in place of (not alongside) US 395 shields. The community has known the highway as US 395 for a long time, so to see US 395 shields disappear (as was especially the case on 'freeway entrance' and related signs on the cross streets) prompted some confusion--I'm still not sure why NDOT did that.

[hobsini2]

I always looked at the even/odd 3dis in how they relate to the city that they serve and not so much how they interact with other interstates.  Granted, there are always going to be exceptions to this (I-355 comes to mind) but you can reasonably expect an even number to be at least a bypass or beltway of the city.  The first digit should reflect what the traffic is expected to do whether the highway will feed traffic in/out of an area or bypass the area all together.

Let me give you an example of what I mean. Take Milwaukee. There is I-794 and I-894. I-794 acts more of as a feeder between I-94/43 and the Lakefront so an odd number makes sense.  I-894 is a certainly bypass for traffic going say from Kenosha to Madison or Fond du Lac. If the northern part of the bypass was ever built to meet back with I-43 in the north suburbs, it would still be reasonable to call that extension I-894 because it completes the bypass.  Some would argue that you need a new number for that if it ever happened but IMO that would be a complete waste of a number, just like what happened in Minneapolis does with I-494 and I-694. That should have been one number.