If this question has been answered/discussed in a previous thread, apologies in advance ...
In Atlanta, the Downtown Connector ("DC") is an I-75/I-85 duplex. The mileage markers on the DC reflect I-75 mileage, as do the exit numbers. Yesterday, when driving northward toward the end of the duplex, the yellow "Exit" tabs on a DC BGS for "I-85 Greenville" caught my attention. IOW I-85 "exits" from I-75 at that point (there is also a small exit sign at the split, either Exit 250 or 251 - I cannot remember exactly).
Is there any requirement to designate one 2di as exiting from another 2di at the end of a duplex? Could GDOT just as easily installed an "I-85/Greenville" BGS without an exit tab and simply have not installed an exit sign at the split? Equality among 2dis?
In this instance, using the I-75 mileage for the DC makes sense. IIRC I-85 is approximately 179 miles in Georgia; I-75's length in Georgia is much greater and the exits through Atlanta are generally in the 240s; motorist confusion avoided because no duplication of exit numbers on respective routes.
If this is simply a local practice by GDOT, I am curious as to how other states (maybe even state DOT districts?) handle this situation.
Well, I moved this thread before I saw there were two of them... Anyway, some states will and some states won't do it. You are supposed to designate one as the through route and have the other one exit, but to me there is one exception that should be added: when two routes start at MP 0 together. I'm thinking of I-20/59 entering Alabama when I say that, but there are many other cases. Otherwise, whichever route dominates the mileage and exit numbers, the other one should have the exit tab.
I'm sure the rationale is that the interchange needs to have some kind of exit number so it can be referred to by that number, and the sequence of exit numbers have to make some kind of sense for at least one of the routes.
I suppose they could give the exits on the duplex dual exit numbers, one reflecting I-75 mileage, one with I-85 mileage, but I think that would be needlessly confusing. Better to just pick one interstate as the through route and continue its exit numbers, as GDOT is doing here.
Anything's better than how Tennessee does it (or used to do it):
(https://www.aaroads.com/southeast/tennessee040/i-040_eb_exit_210c_03.jpg)
(This is on I-40, approaching the I-24 overlap.)
I'd love to tell you how NY does it, but we don't have any 2di multiplexes that would be considered normal. I-90 and I-87 is the only 2di multiplex in NY right now, and both routes have screwed up exit numbers thanks to the Thruway. Both have exit 1 following the Thruway exit; I-87 exits I-90, but this make sense as locals think of I-87 and the Northway as the same road (which they aren't, though they were planned to be).
In the case of I-86 and I-81, I-81 is the older route (naturally, as I-86 isn't designated on the multiplex yet; ironically, it can't, because I-81 isn't to interstate standards around NY 7). The multiplex has I-81's numbers because I-81 superceeds NY 17 (both in status on paper and importance in reality).
The only other possible multiplex is I-86 and I-99 (not confirmed, though the I-86/US 15 interchange is set up for it). In this case I would expect I-86 to have its numbers used, though it has seniority by miles as well (unlike I-86 and I-81).
What about I-29 in Kansas City? Its "0" mile marker is not at its true southern terminus, but where it meets I-35 for its short duplex to I-70. The road is actually 3 miles longer than the exits and mileposts.
Most likely it is so those on I-35 do not get confused as they could sign the short duplex I-29's numbers, but being that I-35 southern terminus in Missouri is nearby you may get duplicate exit numbers. However, some say that there is no official multiplex, but I think there is and the signs show it. It would be better to truncate I-29 and have the same situation between I-75 and I-59 in Chatanooga, TN with "TO" shields along I-24 to make the connection.
Quote from: roadman65 on January 28, 2012, 01:38:45 PM
What about I-29 in Kansas City? Its "0" mile marker is not at its true southern terminus, but where it meets I-35 for its short duplex to I-70. The road is actually 3 miles longer than the exits and mileposts.
Most likely it is so those on I-35 do not get confused as they could sign the short duplex I-29's numbers, but being that I-35 southern terminus in Missouri is nearby you may get duplicate exit numbers. However, some say that there is no official multiplex, but I think there is and the signs show it. It would be better to truncate I-29 and have the same situation between I-75 and I-59 in Chatanooga, TN with "TO" shields along I-24 to make the connection.
I do think it's a multiplex, a very strange case though. We're waiting for it to become part of I-49 (:
Quote from: Upside down frog in a triangle on January 28, 2012, 02:16:47 PM
Quote from: roadman65 on January 28, 2012, 01:38:45 PM
What about I-29 in Kansas City? Its "0" mile marker is not at its true southern terminus, but where it meets I-35 for its short duplex to I-70. The road is actually 3 miles longer than the exits and mileposts.
Most likely it is so those on I-35 do not get confused as they could sign the short duplex I-29's numbers, but being that I-35 southern terminus in Missouri is nearby you may get duplicate exit numbers. However, some say that there is no official multiplex, but I think there is and the signs show it. It would be better to truncate I-29 and have the same situation between I-75 and I-59 in Chatanooga, TN with "TO" shields along I-24 to make the connection.
I do think it's a multiplex, a very strange case though. We're waiting for it to become part of I-49 (:
The State of Louisiana wants it badly. It will happen as they want New Orleans and Canada to have a direct route. Plus, I traveled the US 71 corridor and a freeway is needed. It take almost a whole day to go from Kansas City to Shrevport with the winding curves and 55 mph of Arkansas.
I've often wondered about I-29 too-why if it is multiplexed with I-35 down to I-70(as the signage indicates)-why doesn't its mileage reflect it? I've always wondered if the extension along I-35 was added later, and they didn't want to change the mileage of it on the rest of the route. I also wonder if there is any other interstate in the country that is marked past its 0 mile marker.
Quote from: Upside down frog in a triangle on January 28, 2012, 11:31:02 AM
Well, I moved this thread before I saw there were two of them... Anyway, some states will and some states won't do it. You are supposed to designate one as the through route and have the other one exit, but to me there is one exception that should be added: when two routes start at MP 0 together. I'm thinking of I-20/59 entering Alabama when I say that, but there are many other cases. Otherwise, whichever route dominates the mileage and exit numbers, the other one should have the exit tab.
I-70 and I-55 in Illinois have the same southern Terminus, but I-70 is counted as the exit when it splits at I-270.
At Effingham, I-57 is the "primary" route so all exits are numbered as I-57 exits. At the 57/70 split, 70 is signed as the exit.
At Bloomington, IL I-55 is the "primary" route, so I-74 is the exit.
At the risk of splitting the thread, in both cases the N-S is the "primary" route. Is this always true or are there exceptions?
Quote from: US71 on January 28, 2012, 02:31:05 PM
Quote from: Upside down frog in a triangle on January 28, 2012, 11:31:02 AM
Well, I moved this thread before I saw there were two of them... Anyway, some states will and some states won't do it. You are supposed to designate one as the through route and have the other one exit, but to me there is one exception that should be added: when two routes start at MP 0 together. I'm thinking of I-20/59 entering Alabama when I say that, but there are many other cases. Otherwise, whichever route dominates the mileage and exit numbers, the other one should have the exit tab.
I-70 and I-55 in Illinois have the same southern Terminus, but I-70 is counted as the exit when it splits at I-270.
At Effingham, I-57 is the "primary" route so all exits are numbered as I-57 exits. At the 57/70 split, 70 is signed as the exit.
At Bloomington, IL I-55 is the "primary" route, so I-74 is the exit.
At the risk of splitting the thread, in both cases the N-S is the "primary" route. Is this always true or are there exceptions?
In Iowa, with the two multiplexes of I-80/I-29 and I-80/I-35, I-80 gets the exit numbers on both. That makes sense as I-80 is the longest interstate in the state. On the western junction with I-35 at Des Moines, the exit is numbered with I-80, even though I-80 is actually the route that is exiting at that point.
Kentucky has two concurrencies (I have come to detest the terms "duplex" and "multiplex") and they are I-75/I-71 and I-75/I-64.
In both cases I-75 has its mile markers continue as the "host" and the exits are where its "guests" depart.
Although there is an error on a couple of the new Clearview advance signs for the I-75 north/I-64 west split near Lexington. The Exit 118 tab is placed on the right side of the sign, over the I-75 lanes on the diagrammatic sign, instead of on 64's side. Older signage at the split and at the exit gore are correct.
In my travels, I have seen one instance where mileposts for both routes of a concurrency are used -- the US 13/US 50 bypass of Salisbury, Md.
Quote from: roadman65 on January 28, 2012, 01:38:45 PM
What about I-29 in Kansas City? Its "0" mile marker is not at its true southern terminus, but where it meets I-35 for its short duplex to I-70. The road is actually 3 miles longer than the exits and mileposts.
Most likely it is so those on I-35 do not get confused as they could sign the short duplex I-29's numbers, but being that I-35 southern terminus in Missouri is nearby you may get duplicate exit numbers. However, some say that there is no official multiplex, but I think there is and the signs show it. It would be better to truncate I-29 and have the same situation between I-75 and I-59 in Chatanooga, TN with "TO" shields along I-24 to make the connection.
What's the difference? It's signed along with I-35 either way. The inclusion of the word "TO" doesn't alter the navigational usefulness one bit. In fact, it might be more reassuring for someone looking to get onto I-29 north to know they're already on it. And only us roadgeeks care about the mileage markers. I do agree, though, that I-29's "0" marker should be at it's actual beginning. Again, though, kind of an irrelevant issue.
QuoteKentucky has two concurrencies (I have come to detest the terms "duplex" and "multiplex") and they are I-75/I-71 and I-75/I-64.
I agree, H.B. I'd rather use "concurrency." I think I've seen it more often in "official" usage, too.
If the Mt Hood Freeway had been built, then there would've been an Oregon concurrency (I-84/I-205) for me to compare to everyone's other examples, but alas, there are no Oregon concurrencies and I have nothing to offer!
Quote from: xonhulu on January 28, 2012, 02:52:49 PM
I agree, H.B. I'd rather use "concurrency." I think I've seen it more often in "official" usage, too.
Multiplex is almost never used officially (generally it's something written by a roadgeek who works there). I find overlap to be the most natural term, and it is used by a number of DOTs.
Quote from: NE2 on January 28, 2012, 03:02:44 PM
Multiplex is almost never used officially (generally it's something written by a roadgeek who works there). I find overlap to be the most natural term, and it is used by a number of DOTs.
"Overlap" is also better than "multiplex," but I dunno, somehow it doesn't seem like the most appropriate term to me. "Concurrency" still works best for me. However, if state DOT's prefer overlap, I'd rather use the term that's most official.
Personally, I guess it doesn't make that much of a difference.
Quote from: xonhulu on January 28, 2012, 03:18:15 PM
"Overlap" is also better than "multiplex," but I dunno, somehow it doesn't seem like the most appropriate term to me. "Concurrency" still works best for me. However, if state DOT's prefer overlap, I'd rather use the term that's most official.
Depends on the DOT. Some do use concurrency. Personally I find that a bit stilted, but that's just me.
Quote from: NE2 on January 28, 2012, 03:36:22 PM
Quote from: xonhulu on January 28, 2012, 03:18:15 PM
"Overlap" is also better than "multiplex," but I dunno, somehow it doesn't seem like the most appropriate term to me. "Concurrency" still works best for me. However, if state DOT's prefer overlap, I'd rather use the term that's most official.
Depends on the DOT. Some do use concurrency. Personally I find that a bit stilted, but that's just me.
Florida does use the term concurrency.
Quote from: roadman65 on January 28, 2012, 03:58:45 PM
Florida does use the term concurrency.
Really? Show me one page or document from FDOT that uses it in the sense of two routes sharing mileage.
I have to look, but back in the snail mail days, I think Fred Ferril was his name, used the term in his letters back to me about interesting findings regarding safety issues. Anyway, he used it and so I believe Steve Homan (the FDOT 5 Public Info officer) emailed me with something to that effect a few years back. My drive crashed since and lost all, but if I find the letter I will scan it and make it into a file and post it.
Quote from: roadman65 on January 28, 2012, 04:33:51 PM
Anyway, he used it and so I believe Steve Homan (the FDOT 5 Public Info officer) emailed me with something to that effect a few years back.
Hey, I believe you that one or two workers used it. No need to scan it.
A concurrency, overlap, or coincidence in a road network is an instance of one physical road bearing two or more different highway, motorway, or other route numbers.[1] When it is two freeways that share the same right-of-way, it is sometimes called a common section or commons.[2][3]
Road enthusiasts often use the term multiplex–as well as the more specific duplex and triplex–to refer to such instances although those type are the more common instances.
Concurrency is a relatively common phenomenon: where two routes must pass through a single geological feature, or crowded city streets, it is often both economically and practically advantageous for them both to be accommodated on one road.
Often when two routes with exit numbers overlap (concurrency), one of the routes has its exit numbers dominate over the other and can sometimes result in having two exits of the same number, albeit far from each other along the same highway. An example of this is from the concurrency of I-94 and US 127 near Jackson, Michigan. The concurrent section of freeway has an exit with M-106, which is numbered Exit 139 using I-94's mileage-based numbers. US 127 also has another Exit 139 with the southern end of the US 127 business loop in Mount Pleasant, Michigan. However, there are also instances where the dominant exit number range is far more than the secondary route's highest exit number, for example the concurrency of I-75 and I-85 in Atlanta where I-75 is dominant–the exit numbers range from 242 to 251 while I-85's highest mile marker in Georgia is 179. I-40 in Tennessee (a neighboring state of Georgia), which is also concurrent with I-75, has the instance of its exit numbers in the concurrency range being higher than I-75's highest exit number in the state.
Contents
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This was taken from Wikipedia.
California's only 2di concurrency (I-5 and I-10 along the southern tip of the Golden State Freeway - the portion that was never US 99), I'm not even sure if it has exit number signage up yet.
Not 2dis per se, but the Business 80/Route 99/US 50 concurrency through unsigned I-305 in Sacramento...contains NO exit number signage at all going east on US 50 through the junction! Also, no exit numbering at all for the I-80/Business 80 & US 50 split in West Sacramento. All the referenced signage was installed ca. 2008-2009, which makes this rather unusual.
Quote from: US71 on January 28, 2012, 02:31:05 PM
At the risk of splitting the thread, in both cases the N-S is the "primary" route. Is this always true or are there exceptions?
I checked 3 other concurrencies of this type: the two along I-35 in OKC and 15/80 in SLC. The N-S exit numbers were used in all three examples.
I was looking through a lot of OreDOT pages, and they seem to use "overlap." However, it took forever to get back here as I started surfing a lot of other info on ODOT projects and got lost for awhile. Funny how that happens.
I-76/77 in Akron plays it both ways at the ends of the duplex. Eastbound on 76, 77 SB leaves as a one-lane exit which is signed as Exit 23A throughout. Westbound, 76 functions as the exit, with the two left lanes continuing as 77 NB, the #3 lane carrying 76 WB around the trumpet, and the #4 lane exit-only for East Ave, Exit 21A. 77 NB would be Exit 20, and is signed as such from 76 EB, but on the 76 WB/77 NB duplex as the signs begin for the breakup, 76 WB is signed with the EXIT ONLY signage despite the exits on the duplex having 76's exit numbers. You can see the interesting signage on street view. (http://g.co/maps/grrvx) Exit 21A is 76's exit number, and then 76 itself is shown as an exit without a number, with 77 displayed as the thru route. (These signs were 2003 carbon-copy replacements of older signs that had the same peculiarities, including advertising TO I-277 before I-76 WB, which makes no sense for two reasons--1. the actual route should be shown before the "TO" one, and 2. 277 goes the opposite direction and not too many people are looking for it at this point.)
It makes sense to sign the route which does not have its exit numbers used as an "exit".
The more interesting question is, which route do you use the exit numbers (and the mileposts) from? I would say use whichever route has a lower number but there doesn't seem to be a consistent policy.
Quote from: Duke87 on January 28, 2012, 08:52:20 PM
It makes sense to sign the route which does not have its exit numbers used as an "exit".
The more interesting question is, which route do you use the exit numbers (and the mileposts) from? I would say use whichever route has a lower number but there doesn't seem to be a consistent policy.
It seems that when the exit numbers are milepost based, the mileposts would have to correspond to the exit numbers for consistency. It seems common that the highway of higher classification (I over US, US over state) usually keeps milepost and exit number continuity, but in the case of a tie, it does seem that often the lower-numbered one wins, but not always. Sometimes the longer or more important one (in someone's judgement) wins out, or the one that was there first (e.g., I-90's mileposts and exit numbers win over I-39's, which would decrease where I-90's increase, and I-90 was there first and is much longer overall).
Quote from: PurdueBill on January 28, 2012, 09:56:13 PM
Quote from: Duke87 on January 28, 2012, 08:52:20 PM
It makes sense to sign the route which does not have its exit numbers used as an "exit".
The more interesting question is, which route do you use the exit numbers (and the mileposts) from? I would say use whichever route has a lower number but there doesn't seem to be a consistent policy.
It seems that when the exit numbers are milepost based, the mileposts would have to correspond to the exit numbers for consistency. It seems common that the highway of higher classification (I over US, US over state) usually keeps milepost and exit number continuity, but in the case of a tie, it does seem that often the lower-numbered one wins, but not always. Sometimes the longer or more important one (in someone's judgement) wins out, or the one that was there first (e.g., I-90's mileposts and exit numbers win over I-39's, which would decrease where I-90's increase, and I-90 was there first and is much longer overall).
I think the key here is "I-90 was there first". No way Wisconsin would renumber the exits along I-90 to accommodate the newly designated I-39. By strict application of the rule, though, you would. Much of this concurrency is also I-94. (Isn't this the only interstate "triplex"?)
To me, the worst misapplication of this rule is where I-94 is concurrent with I-694 in the northwest quadrant of the Minneapolis-St. Paul beltway. Here, I-94, which anyone would consider to be the obvious dominant route, is subordinate to I-694/494 mileage, and at the point eastbound where they split, I-94 is given an exit number for the 494/694 beltway.
Quote from: The High Plains Traveler on January 28, 2012, 11:15:14 PM
To me, the worst misapplication of this rule is where I-94 is concurrent with I-694 in the northwest quadrant of the Minneapolis-St. Paul beltway. Here, I-94, which anyone would consider to be the obvious dominant route, is subordinate to I-694/494 mileage, and at the point eastbound where they split, I-94 is given an exit number for the 494/694 beltway.
Same kind of thing happens with I-83 with I-695 (over a short distance) and I-74 joining I-465 (over a longer distance, including through where the exit numbers cross the zero point and the intervening exit numbers run against the grain, decreasing as I-74 travels EB on the duplex). Both times, the beltway takes precedence over the 2DI's mileage/exit numbers. Interestingly, when I-74 reaches I-275, 74's exit numbers take precedence over 275's for the length of the duplex. Seems to be a free for all situation when a 2DI overlaps a beltway. Wonder what will happen when I-69 joins 465 as well (forming another I-triplex).
As far as two Interstates, Ohio seems to strictly follow the lower-number-rules rule. 74/275, 70/71, 76/77 all follow the rule of mileposting by the lower-numbered route in those cases--the "exit" to stay on 76 WB notwithstanding.
The short duplex of 65 and 70 in Indy uses 65's exit numbers, applying exit numbers to 70 with none for 65. Coincidentally, the duplex section does physically run north-south.
Virginia currently has two instances of this: I-64 and I-95 in Richmond, and I-64 and I-81 between Staunton (the U is silent) and Lexington. In both cases the odd-numbered interstate's exit number is used and the exits on both ends are for I-64 (this is more obvious with I-81, but I-95 also makes a turn at both ends of the concurrency/duplex/overlap)
Quote from: US71 on January 28, 2012, 02:31:05 PM
Quote from: Upside down frog in a triangle on January 28, 2012, 11:31:02 AM
Well, I moved this thread before I saw there were two of them... Anyway, some states will and some states won't do it. You are supposed to designate one as the through route and have the other one exit, but to me there is one exception that should be added: when two routes start at MP 0 together. I'm thinking of I-20/59 entering Alabama when I say that, but there are many other cases. Otherwise, whichever route dominates the mileage and exit numbers, the other one should have the exit tab.
I-70 and I-55 in Illinois have the same southern Terminus, but I-70 is counted as the exit when it splits at I-270.
At Effingham, I-57 is the "primary" route so all exits are numbered as I-57 exits. At the 57/70 split, 70 is signed as the exit.
At Bloomington, IL I-55 is the "primary" route, so I-74 is the exit.
At the risk of splitting the thread, in both cases the N-S is the "primary" route. Is this always true or are there exceptions?
Further north, I-94 is the primary route on the Ryan and Kennedy Expressways, and I-90 is the exit at both the Skyway (Exit 59A) and at the Junction.
When I-294 gets exit numbers (already has mileposts), I-80 will be an exit off I-294 (most likely Exit 5).
I-94 is an exit off I-80 (Exit 160).
I-495 in Virginia exits off of I-95 spite that in reality I-95 exits while I-495 takes all through Capital Beltway travel lanes.
In the old days of the Richmond- Petersburg Turnpike in Virginia, I-95 exited the turnpike at Exit 2, but I-85 was made to exit from the lanes of the Turnpike when this interchange was made into a trumpet after I-95 was constructed. The ramp toll for SB Exit 2 and NB entrance from Exit 2 was made a mainline type of plaza between the current NB exit for I-85 on I-95 and the NB I-85 merge onto I-95 NB. This way motorist that entered the SB Richmond- Petersburg Turnpike from I-95 NB would not pass through the Exit 2 toll gate as they were tolled at the mainline plaza on I-85 a few miles south of I-95. Those going NB from I-85 to NB I-95 would be tolled already and therefore did not need to pay toll on the Exit 2 ramp toll so it worked out well where it could merge with I-95 north of this tollbooth.
I know these aren't two digit route concurrences, but while we are talking about numbering schemes from dominating roads this fits in.
Here's an interesting one:
In Greensboro, I-40 used to terminate at I-85...with a stub of it running through the RTP and Raleigh areas. Back then, it was extended to Hillsboroough. It took exit #'s from I-85 at that time, from Exit 123 in Greensboro to Exit 163 in Hillsborough.
Eventually I-85 got rerouted along a bypass route, so Business I-85 took over from Exit 36A to Exit 44, then from Exit 131 to Exit 163 along regular I-85. The reason was that I-40 through this area was going to go along the bypass I-85.
I-40 then took over the corridor with I-85 business and took over the numbering scheme, from Exit 219/220 to Exit 227, on it's concurrency with I-85 Business, then along the original I-85 from Exit 131/227 to Exit 163/259.
I think in the case of a tie, it's the longer route or the original designation on the multiplex. Certainly the case with I-40/75 in Knoxville, I-40/24 in Nashville.
Not sure why that's not the case with I-95/64, though.
Quote from: OracleUsr on January 29, 2012, 01:39:37 AM
Here's an interesting one:
In Greensboro, I-40 used to terminate at I-85...with a stub of it running through the RTP and Raleigh areas. Back then, it was extended to Hillsboroough. It took exit #'s from I-85 at that time, from Exit 123 in Greensboro to Exit 163 in Hillsborough.
Eventually I-85 got rerouted along a bypass route, so Business I-85 took over from Exit 36A to Exit 44, then from Exit 131 to Exit 163 along regular I-85. The reason was that I-40 through this area was going to go along the bypass I-85.
I-40 then took over the corridor with I-85 business and took over the numbering scheme, from Exit 219/220 to Exit 227, on it's concurrency with I-85 Business, then along the original I-85 from Exit 131/227 to Exit 163/259.
I think in the case of a tie, it's the longer route or the original designation on the multiplex. Certainly the case with I-40/75 in Knoxville, I-40/24 in Nashville.
Not sure why that's not the case with I-95/64, though.
In Richmond it has to do with the Richmond- Petersburg Turnpike having its own sequential exit numbers along this duplex. I-64 WB from the original NB Turnpike (now I-95 and I-64) was Exit 15A and the exit then for I-64 EB from former Turnpike SB was Exit 11.
The Richmond-Petersburg Turnpike had numbers 1 from the US 1 interchange on I-85 in Petersburg to 17 for the US 301 & VA 2 interchange north of Richmond. The turnpike ran along I-85 into I-95, then along I-95 and terminated at a former directional interchange with US 301 & VA 2 that has now been modified just north of the Richmond City Limits.
Quote from: hbelkins on January 28, 2012, 02:41:17 PM
In my travels, I have seen one instance where mileposts for both routes of a concurrency are used -- the US 13/US 50 bypass of Salisbury, Md.
The MUTCD frowns upon this now, but NJDOT used to do this. There are two examples still around: US 9 on NJ 35 and US 202 on NJ 23.
What it even more confusing is that the western terminus of I-195 in New Jersey, and the western terminus of I-24 in Illinois both use the other routes exit numbers instead of its own. Being it is a terminus, it could very well be not numbered at all as this throws confusion to the mix especially on I-195 in NJ being it becomes NJ 29 with its own set of numbers.
I-4 has it eastern terminus split into three ramps with only one being numbered and that one for FL 400. I-95 North and South do not get any exit ramp numbers. On the west terminus in Tampa the exit for Downtown East/ Jefferson Street gets I-275's exit number of 45A when you do not even get onto I-275 at all from I-4 to exit here. It is split from the ramp to I-4 WB to I-275 SB. The actual Exit 45A on I-275 is with in the confines of the I-4 and I-275 Interchange where I-4 WB has to have ramp of its own to access what is missed because its merge is afterwards.
Quote from: roadman65 on January 29, 2012, 02:48:20 PM
What it even more confusing is that the western terminus of I-195 in New Jersey, and the western terminus of I-24 in Illinois both use the other routes exit numbers instead of its own. Being it is a terminus, it could very well be not numbered at all as this throws confusion to the mix especially on I-195 in NJ being it becomes NJ 29 with its own set of numbers.
Western I-76 does it one better even; it has only one numbered exit in Nebraska, its end at I-80, and the exit for I-80 WB is numbered with 80's exit number (Exit 102), only 3 miles into Nebraska. The thru movement to I-80 EB is not numbered. (This does at least manage to maintain continuity as those who are continuing through "eastbound" on 76 to 80; the next number they see will be the next higher exit number from 102. I say "eastbound" in quotes because Nebraska's signage on 80 WB refers to 76 as heading SOUTH to Denver, not West.)
I think that of all the cases cited here, the I-40 one makes the most sense, as I-85 was the solo route to Hillsborough in the days that I-40 ended in Greensboro. When I-40 was eventually extended to Wilmington, the I-85 exit numbers stayed in place, so as to avoid confusion. And although the Atlanta example also makes a lot of sense, I-85's mileage could have been used to determine exit numbering instead of I-75's (which is a better fit anyway, as it's the far more dominant route there), especially when you take into account the fact that I-85 exits to the left of their split on the north end.
Well, in Nashville, the 24-40 duplex uses 40's exit numbers.
The 24-65 duplex uses I-65 numbers (N-S thing again).
The 40-65 duplex uses the I-40 numbers. (E-W) Of course, this is likely because the current duplex was created by the moving of I-65 onto the old I-265, so the current duplex was previously just I-40.
http://maps.google.com/maps?q=Nashville,+TN&hl=en&ll=36.165666,-86.774139&spn=0.055157,0.090895&sll=37.0625,-95.677068&sspn=37.871902,93.076172&oq=nas&hnear=Nashville,+Davidson,+Tennessee&t=h&z=14
With the triple-plex of I-39/90/94 between Madison and Portage, the duplex of 90/94 to Tomah, and the duplex of 39/90 to the IL state line, WI uses I-90 exit numbers over the entire length. Although one can argue that at Tomah heading WB, I-90 should be the exit and not I-94.
Quote from: NE2 on January 28, 2012, 03:02:44 PM
Quote from: xonhulu on January 28, 2012, 02:52:49 PM
I agree, H.B. I'd rather use "concurrency." I think I've seen it more often in "official" usage, too.
Multiplex is almost never used officially (generally it's something written by a roadgeek who works there). I find overlap to be the most natural term, and it is used by a number of DOTs.
Correct ... 'overlap' is the usual term used by DOTs.
Quote from: Takumi on January 29, 2012, 12:45:45 AM
Virginia currently has two instances of this: I-64 and I-95 in Richmond, and I-64 and I-81 between Staunton (the U is silent) and Lexington. In both cases the odd-numbered interstate's exit number is used and the exits on both ends are for I-64 (this is more obvious with I-81, but I-95 also makes a turn at both ends of the concurrency/duplex/overlap)
Virginia also has the I-81 / I-77 overlap, and the I-95 / I-495 overlap.
It will be interesting to see which route in the FL 414 and FL 429 overlap will dominate over the exit numbers? The FL 414 already has exit numbers on it are mileage based from the future point of its permanent west terminus that has not yet been built. Then you have FL 429 that will be the western beltway for the Orlando area which in its own right should be consistent its whole length. Right now FL 414 goes from FL 429 to US 17 & 92, with it east of US 441 as a surface arterial with no freeway exits (although Fl 434, I-4, and Sandspur Road do have interchanges along with its eastern terminus having a trumpet interchange), but it having all its toll road section numbered completely.
Quote from: deanej on January 28, 2012, 01:02:41 PM
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In the case of I-86 and I-81, I-81 is the older route (naturally, as I-86 isn't designated on the multiplex yet; ironically, it can't, because I-81 isn't to interstate standards around NY 7). The multiplex has I-81's numbers because I-81 superceeds NY 17 (both in status on paper and importance in reality).
When NY 17 was first routed along I-81 in Binghamton, the exit numbers for both I-81 and NY 17 were posted on guide signs. Where I-81 and NY 17 split from each other, no exit numbers were used, like many Interstate to Interstate interchanges in the Empire State (at least in Upstate and not including the Thruway), though I-81 NB has exit 2E for I-86/NY 17 East, though that's the odd interchange out.
In Columbus, I-70 is the dominant route, even though I-71 was there first*. There are two exits EB, and one exit WB which is only legally accessible from I-70; those and the ramps splitting off with I-71 get exit numbers based on I-70's mileage.
When the overlap is rebuilt, the two Interstates won't share exits at all, but I-71 will probably still exit from I-70.
Personally, I don't like the mainline of an Interstate being signed as an "exit", particularly when it's beefier than a single-lane ramp or when there's no significant direction change involved. Then again, I think I would like to see both sides of the split signed as exits from each other – for example, eastbound on the South Innerbelt, your choices would be Exit 101A / I-71 North / Cleveland, or Exit 107 / I-70 East / Wheeling. What works for one should work for both. Let's say someone is in Springfield and they have directions that say "take I-70 east to exit 142": they "know" not to turn north on I-71 because it's signed as an exit, right? What if that someone is in Grove City and has directions that say "take I-71 north to exit 176": with the current signage, they might wind up in Cambridge because they "knew" not to take exit 101B, since they were looking for exit 176. And I know people who would make that mistake. This is why I say, at the split, sign both or neither as exits, and make the driver think about which Interstate they're trying to follow.
*It's actually a little complicated, but to the best of my understanding, the South Innerbelt was first I-71, then I-70, then both.
The US 6/24 overlap is messed up because ODOT District 2 got anal about putting exit numbers everywhere, even in places that don't look like exits. This overlap follows US 6's mileage because it's the lower number, even though US 24 is the continuous expressway and 6 only has exits on its overlap with 24.
The US 33/50 overlap is also messed up. The exits are numbered based on US 33's mileage, but at the ends of the overlap, it's the US 33 through movements that are signed as exits. The worst is on 33 EB approaching 50: the ramp carrying 33 EB is signed as an exit, while the ramp to 50 EB (a ramp which doesn't carry the mainline of anything) is not signed as an exit. I have other complaints about the signage on that stretch...
Quote from: Henry on January 29, 2012, 06:43:31 PM
I think that of all the cases cited here, the I-40 one makes the most sense, as I-85 was the solo route to Hillsborough in the days that I-40 ended in Greensboro. When I-40 was eventually extended to Wilmington, the I-85 exit numbers stayed in place, so as to avoid confusion...
Well, since the first NC example I thought of was mentioned already, I will add one more NC example...
I-73/74 overlap from Randleman to south of Candor towards Rockingham will use I-73's mileage and exit numbers when complete...
http://i1147.photobucket.com/albums/o552/jcarte29/9a61fff4.jpg (Fictional I-73 Exit 5, South side of Rockingham NC, where I-73/74 depart from each other just north of the SC state line)
This is what it might eventually look like, when I-74 breaks from I-73 near Rockingham, NC...
Quote from: jcarte29 on February 24, 2012, 10:25:24 PM
Quote from: Henry on January 29, 2012, 06:43:31 PM
I think that of all the cases cited here, the I-40 one makes the most sense, as I-85 was the solo route to Hillsborough in the days that I-40 ended in Greensboro. When I-40 was eventually extended to Wilmington, the I-85 exit numbers stayed in place, so as to avoid confusion...
Well, since the first NC example I thought of was mentioned already, I will add one more NC example...
I-73/74 overlap from Randleman to south of Candor towards Rockingham will use I-73's mileage and exit numbers when complete...
Currently, the I-73/74 overlap from Asheboro south to Ellerbe is signed I 73/I 74/US 220 and uses US 220 mileage and exit numbers, instead of either interstate. Part of the upgrade around Ashebore will change the signage to use I 73 mileage.
Quote from: PurdueBill on January 28, 2012, 06:32:04 PM
Exit 21A is 76's exit number, and then 76 itself is shown as an exit without a number, with 77 displayed as the thru route. (These signs were 2003 carbon-copy replacements of older signs that had the same peculiarities, including advertising TO I-277 before I-76 WB, which makes no sense for two reasons--1. the actual route should be shown before the "TO" one, and 2. 277 goes the opposite direction and not too many people are looking for it at this point.)
Was I-277 ever routed and/or signed on the Kenmore Leg (I-76 between I-77 & US-224) as a duplex with I-76 -- or it's I-80S predecessor?
I would think it would make more sense for ODOT to completely recognize the downtown bypass of the 76/77 multiplex as I-277. It's not like Akron is a stranger to multiplexes (what with I-76/I-77, I-76/US-224, I-77/SR-21, SR-8/SR-59 already in the books and somewhat signed properly), so why not an I-76/I-277 multiplex???
Quote from: roadman65 on January 29, 2012, 01:26:38 AM
I-495 in Virginia exits off of I-95 spite that in reality I-95 exits while I-495 takes all through Capital Beltway travel lanes.
....
VDOT is somewhat inconsistent about the signage in that respect. On the Outer Loop the "exit" tabs for the Beltway thru lanes have been removed; on the Inner Loop some remain and some are absent. I rather like the way Maryland handles it, recognizing of course that their situation is a little bit different from Virginia's because the exit numbering for both I-95 and I-495 starts at the same point (where the road crosses the state line on the Wilson Bridge). At the College Park Interchange where I-95 splits off to go north to Baltimore, when you approach on the concurrency portion of the Beltway (Outer Loop) there is no exit number posted for either the I-95 to Baltimore lanes or the Beltway thru lanes, and at the gore point instead of "Exit" or "Exit xx" the sign says "North I-95" with an arrow. Coming the other way on the Inner Loop (I-495 only), the exit for I-95 to Baltimore is numbered as Exit 27 and the thru lanes bear no exit number. I've always thought this system makes eminent sense.
I suppose there are two arguments in favor of posting the thru Beltway lanes in Virginia as "exits"–(1) the I-95/I-495 concurrency is a "paper concurrency" and the I-495 route number is unofficial, such that you are genuinely exiting I-95 if you stay on the Beltway; (2) since I-95 exit numbers were used on the concurrency it would be illogical to have the exit numbers jump from 57 to 173 (Outer Loop) or 170 to 54 (Inner Loop) unless you had to "exit" in between. While I see the "logic" in those points (and I use the term "logic" with distaste here), I think it's one that makes little sense to the average motorist out on the road. Put differently–who cares what the MUTCD may say. There's an exception to just about every rule, and this is a prime example of a place where an exception is logical when it comes to posting the roads in the manner the average driver expects. As "roadman65" notes, just about everyone in Northern Virginia, except VDOT employees and some roadgeeks, views I-95 as the route that "exits" in Springfield (both from the Beltway and from Shirley Highway), and there's some serious validity in that thought process given that it's weird, at best, to have four thru lanes as the "exit" instead of two flyover-ramp lanes. (To be sure, I wouldn't sign I-95 as an "exit" from the Inner Loop either, as that would confuse the out-of-towners who expect to stay on I-95. I'd do it the way Maryland does.)
I never really understood why it was so confusing to people when Virginia and Maryland had their own separate exit numbers on the Beltway anyway. Most people are used to exit numbers resetting at the state line.
I-4 eastern terminus has no exit numbers for I-95, but has one for straight through FL 400. It would make sense not to label both I-95 and I-495 as 1995hoo mentions it for its other end in MD. If it could be done almost 900 miles to the south on another interstate, it would work here.
I-93 in Dedham, MD from I-95 SB has EXIT 12 assigned to it, even though I-95 exits there with the through lanes going from SB I-95 to NB I-93. Also it is US 1 Northbound straight through what used to be MA 128 all the way through. 128 is like 495 as they both are beltways and you have I-95 on both of them.