"Exit" From Two 2di Duplex

[Duke87]

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.

[PurdueBill]

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).

[The High Plains Traveler]

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.

[PurdueBill]

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.

[Takumi]

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)

[Brandon]

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).

[roadman65]

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.

[OracleUsr]

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.

[roadman65]

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.

[Alps]

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.

[roadman65]

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.

[PurdueBill]

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.)

[Henry]

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.

[mightyace]

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

[hobsini2]

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.

[Beltway]

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.

[Beltway]

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.

[roadman65]

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.

[machias]

.

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.

[vtk]

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...

[jcarte29]

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...

[jcarte29]

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...

[dfilpus]

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.

[thenetwork]

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???

[1995hoo]

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.