This sounds kind of complicated, but it's really quite basic in principle. Consider a cloverleaf interchange, which has a full set of eight ramps, one for each of the eight possible movements at a generic interchange. Reduce it to a diamond, and there are only four ramps, but all eight movements are generally still doable. Reduce it to a half-diamond, and there are only two ramps, with four possible movements.
What are some interchanges that, due to one reason or another, don't fit evenly into this spectrum, and instead have an odd number of possible movements (namely one, three, five, or seven)?
Keep in mind that an odd number of ramps is different than an odd number of movements. I'm primarily looking for the the latter, since sometimes there are split entrance ramps but a single exit ramp, like this (https://www.google.com/maps/@42.905883,-77.6939826,16z). This nets an even amount of movements (all eight are still possible), and that's not as interesting.
This half-diamond (https://www.google.com/maps/@43.0429636,-77.4623111,16.96z) only has three movements, since you can turn either direction from the off ramp, but you can't turn left onto the on ramp.
This interchange (https://www.google.com/maps/@43.0171275,-77.4413734,15.73z) is a double-hit, since it has five ramps allowing seven possible movements - an odd number of both. The missing movement is from I-490 East to NY 96 North.
This interchange (https://www.google.com/maps/@43.1159055,-77.5525935,15.88z) is interesting in that there is some redundancy - multiple ways to make the exact same movement - yet there's still a missing movement. You cannot turn from NY 31 East onto NY 590 North, so the total number of allowable movements is only seven.
Perhaps this is more common than I previously thought, however, those are the only three examples I can find in my immediate area.
I-95 in Massachusetts between exit 11 and 12 (entrance only, so no number). 1 out of 8 allowed.
Arguably, I-495/US 3/Lowell Connector has 15 movements (20 minus the ones for continuing straight), assuming Lowell Connector → US 3 South is straight and therefore not a movement, but the US 3 North → Lowell Connector is a movement, as staying straight keeps you on US 3.
I-93 (MA), exit 36 allows 9: the typical 8 plus one more onto Maple St. east.
I-84 Exit 34 in CT has only 3 movements since the CT 72 interchange was rebuilt. You can get off and on EB, and get on WB, but to get off WB, you have to use CT 72 Exit 2.
The I-91/I-691/CT 66 interchange in Meriden has an odd number of movements. I-91N to CT 66E, I-91S to I-691W, I-691E to I-91N, CT 66W to I-91N, and CT 66W to I-91S are all direct connections. Movements from I-691E to I-91S and from I-91N to I-691W require the use of CT 15. However, there is no connection at all from I-91S to CT 66E unless one either exits at East Main St and either follows East Main to the end where it merges into CT 66 as the expressway ends, or gets back onto CT 15N, and gets off Exit 68 N-E to I-91N and immediately exits onto CT 66E.
I-79 exit 64 in Pennsylvania, for PA 51. Three movements; no exit from southbound I-79.
Quote from: 1 on September 11, 2018, 09:14:42 AM
I-95 in Massachusetts between exit 11 and 12 (entrance only, so no number). 1 out of 8 allowed.
IIRC, there are plans to add an exit ramp off I-95 northbound at the Dedham St. overpass. Not sure as towards
when.
I-285 exit 29: the usual eight movements, plus I-285 eastbound to Lake Hearn Dr westbound makes nine.
GA 400 exit 6: I count a total of 13 movements here.
- 400 NB → Northridge Rd WB
- 400 NB → Northridge Rd EB
- 400 NB → Roberts Dr SB
- 400 NB → Dunwoody Pl NB
- 400 SB → Northridge Rd WB
- 400 SB → Northridge Rd EB
- 400 SB → Dunwoody Pl NB
- Northridge Rd EB → 400 SB
- Northridge Rd EB → 400 NB
- Northridge Rd WB → 400 NB
- Northridge Rd WB → 400 SB
- Roberts Dr NB → 400 NB
- Dunwoody Pl SB → 400 SB
NJ's I-295 Exit 18 has an additonal movement exiting southbound without an equivalent entering movement.
DC-295 at Pennsylvania Avenue has seven possible movements on six ramps. The missing movement is from southbound 295 to inbound Pennsylvania Avenue.
Some freeway to freeway interchanges in CT with odd movements:
9/17, Middletown (3 out of 4)
8/15, Trumbull (5 out of 8 ... however 15/25 accommodates two movements, so it's functionally 7 of 8)
And 15/99 isn't technically odd, but it is strange: only 4 out of 8 movements allowed
Quote from: PHLBOS on September 11, 2018, 10:34:09 AM
Quote from: 1 on September 11, 2018, 09:14:42 AM
I-95 in Massachusetts between exit 11 and 12 (entrance only, so no number). 1 out of 8 allowed.
IIRC, there are plans to add an exit ramp off I-95 northbound at the Dedham St. overpass. Not sure as towards when.
MassDOT Project # 606146 - This is the project description:
CANTON- NORWOOD- WESTWOOD- DEDHAM STREET/I-95 INTERCHANGE RECONSTRUCTION INCLUDING REHABILITATION/REPLACEMENT OF 5 BRIDGES
QuoteThe Canton Street/Dedham Street project consists of the construction of an off-ramp from I-95 northbound to Dedham Street and improvements to the Dedham Street/Canton Street corridor. Within the approximately 4,000 linear feet between Kirby Drive and University Ave, the existing two lane Dedham Street/Canton St will be widened to provide two 11.5 foot travel lanes in each direction, 5 foot shoulders in each direction, and a 6 foot wide sidewalk will be constructed on the northern side of Dedham Street/Canton St, from Kirby Drive to the Canton St/University Ave intersection. This roadway reconstruction will require the bridges over AMTRAK and the Neponset River to be widened and the bridge over I-95 to be replaced. Traffic signal control will be installed at three locations: Dedham Street at the I-95 southbound on-ramp; Dedham Street at the proposed I-95 northbound off-ramp; and the Dedham Street/Shawmut Road intersection. These three intersections will operate as a coordinated signal system and will provide safe pedestrian crossing locations for the major potential sources of pedestrian trips.
Notice to proceed was issued in December of 2016, completion shown as Spring of 2022.
I-787 SB exit 3B (https://www.google.com/maps/@42.6439036,-73.7512524,18.11z) (the RIRO), due to a one-way street
I-787 SB exit 4A (https://www.google.com/maps/@42.658333,-73.7415241,17.66z) - one ramp, one movement, due to one-way streets
This ramp (https://www.google.com/maps/@43.0553991,-73.7668352,16.86z) is a former example; it has since been realigned to allow left turns onto it
NY 481 exit 11 (https://www.google.com/maps/@43.1602356,-76.1569774,16.99z)
Quote from: 1995hoo on September 11, 2018, 11:29:46 AM
DC-295 at Pennsylvania Avenue has seven possible movements on six ramps. The missing movement is from southbound 295 to inbound Pennsylvania Avenue.
Just up the road from the above, I'm pretty sure the DC-295/East Capitol Street interchange has three possible movements.
Quote from: hbelkins on September 11, 2018, 10:12:58 AM
I-79 exit 64 in Pennsylvania, for PA 51. Three movements; no exit from southbound I-79.
Yes, but all the other ramps are accessible from (or give access to) PA 51 in
both directions. So that's actually six out of eight, not three out of four.
Quote from: vdeane on September 11, 2018, 01:28:23 PM
NY 481 exit 11 (https://www.google.com/maps/@43.1602356,-76.1569774,16.99z)
I actually thought of that one, but decided against posting it since it actually allows two of eight theoretical movements.
I-94 in Detroit has 3 of them within a half mile or less: https://www.google.com/maps/@42.3295114,-83.1508426,15z?hl=en
One exit WB, 2 entrances EB.
US 15 has this odd interchange (https://goo.gl/maps/HYoEQUhy8ps) with PA 973 north of Williamsport. Only one ramp–off–from southbound US 15. No offramp is provided northbound and no onramps in either direction. I know I've mentioned this interchange on another thread before, because there's another oddity there: The southbound US 15 overpass over PA 973 and the following bridge over Hoagland Run are wide enough for three standard lanes (plus a shoulder) (https://goo.gl/maps/MwdDHWAXEWQ2). In total, the pavement is wide enough for a third lane for approximately 1/3 mile (over 1,500 feet). It almost seems as if the grading and overpasses were built to accommodate an acceleration lane from PA 973 to southbound US 15, but one was never built. Further, the single offramp that was constructed doesn't swing wide enough for a loop to have been constructed inside it. Perhaps funds ran out or the plans were changed after overpasses were installed. I'd be interested to find out.
Also, about four miles north of this interchange, there's another one-ramp interchange (https://goo.gl/maps/e8UmdyWMDGp)–an onramp to northbound US 15 from the old alignment, Lycoming Creek Road.
Quote from: webny99 on September 11, 2018, 04:28:29 PM
Quote from: vdeane on September 11, 2018, 01:28:23 PM
NY 481 exit 11 (https://www.google.com/maps/@43.1602356,-76.1569774,16.99z)
I actually thought of that one, but decided against posting it since it actually allows two of eight theoretical movements.
I count three: left onto Maple, straight onto Caughdenoy, and right onto Caughdenoy.
I-80 at MacDonald Ave in Richmond, CA allows only 80 EB to MacDonald WB
I-90 Exit 3 in Seattle (https://www.google.com/maps/@47.5923654,-122.3127291,16z). No movement from Rainier to west I-90 to I-5. No big loss, because you can follow Dearborn there, but there is an exit from the west.
I-35 at US 2 East in Duluth: 5 of 8 possible movements
-no access from either direction of I-35 to 46th Ave W (aka the surface street that continues beyond the interchange)
-no access from 46th to northbound 35
Quote from: vdeane on September 11, 2018, 08:24:15 PM
Quote from: webny99 on September 11, 2018, 04:28:29 PM
Quote from: vdeane on September 11, 2018, 01:28:23 PM
NY 481 exit 11 (https://www.google.com/maps/@43.1602356,-76.1569774,16.99z)
I actually thought of that one, but decided against posting it since it actually allows two of eight theoretical movements.
I count three: left onto Maple, straight onto Caughdenoy, and right onto Caughdenoy.
By sheer chance, yes.
But since there's twelve available movements, one would expect three movements per ramp, in a theoretical full trumpet interchange. I guess technically, it does still count.
Quote from: vdeane on September 11, 2018, 08:24:15 PM
Quote from: webny99 on September 11, 2018, 04:28:29 PM
Quote from: vdeane on September 11, 2018, 01:28:23 PM
NY 481 exit 11 (https://www.google.com/maps/@43.1602356,-76.1569774,16.99z)
I actually thought of that one, but decided against posting it since it actually allows two of eight theoretical movements.
I count three: left onto Maple, straight onto Caughdenoy, and right onto Caughdenoy.
That interchange was my first thought when I first saw the OP, but after reading the post closer, I realized it wouldn't qualify, but I forgot about there being three options after exiting. Ever since I first saw the ramp as a kid, I thought it was weird that there was an exit there with just a single ramp.
Two that I can think of in CNY are State Fair Blvd at I-690 east (https://www.google.com/maps/@43.0631238,-76.1927891,19z), and Butternut St at I-81 (https://www.google.com/maps/@43.0569861,-76.1535926,17z). Depending on how you count the various ramps around Butternut St on I-81, there may be more. It's hard to tell since multiple exit numbers are mixed together because of where the ramps are.
On NY 17 west of Binghamton, the Airport Rd exit (https://www.google.com/maps/@42.1201656,-75.9460795,17z) is a folded diamond/parclo hybrid, and there's two ways to go from west to south, so there's 9 movements available.
EDIT: It looks like exit 9 on I-390 (https://www.google.com/maps/@43.1088606,-77.6160463,17z) counts too since there's two ways to get to NY 15A south from I-390 west, but it's hard to tell for sure since the aerial and Street View imagery were both captured during construction.
Quote from: Michael on September 12, 2018, 04:26:38 PM
EDIT: It looks like exit 9 on I-390 (https://www.google.com/maps/@43.1088606,-77.6160463,17z) counts too since there's two ways to get to NY 15A south from I-390 west, but it's hard to tell for sure since the aerial and Street View imagery were both captured during construction.
If by Exit 9 you mean Exit 16 ;-)
As of now, there is only one route from I-390 West (actually North) to NY 15A South*; via the loop ramp. This BGS (https://www.google.com/maps/@43.1083949,-77.6118967,3a,75y,243.97h,84.51t/data=!3m6!1e1!3m4!1srbknK-WNhWDAZQ_eVc0VKg!2e0!7i13312!8i6656!5m1!1e1) accurately reflects the situation here; the first ramp to NY 15A North permits right turns only, while traffic to NY 15A South must take the second exit and use the loop ramp.
*Not counting this ramp (https://www.google.com/maps/@43.0834583,-77.6084466,3a,75y,74.67h,88.02t/data=!3m6!1e1!3m4!1s9z-Nd0Sgoc1J4Zrdsex2Kg!2e0!7i13312!8i6656!5m1!1e1), which DOES allow access from I-390 North to NY 15A South, but it's part of a separate interchange 14 several miles south of the one in question.
As far as the actual thread goes, I-390 Exit 16 is very challenging, since you can't very easily calculate the total number of movements that a) should be available, and b) actually
are available. There's at least 16 movements (8 for NY 15A and 8 for NY 15), but then East River Road and Kendrick Road are involved too, and some movements require using East River Rd to get to I-390 and vice versa, so whether to double-count them is questionable. Overall, the redesign was well-done and there are no glaring omissions.. I can't think of a single movement that is completely missing.
Quote from: jeffandnicole on September 11, 2018, 11:14:14 AM
NJ's I-295 Exit 18 has an additonal movement exiting southbound without an equivalent entering movement.
There is also Exit 36A-B which has 7 or 9 movements depending on how you count (there is no direct access from I-295 South to NJ 73 North, but the indirect access is to and from all directions of NJ 73 to and from I-295 South:
https://www.google.com/maps/@39.9367516,-74.9643261,17z/data=!5m1!1e1
I'm not sure of the point of this thread. So many interchanges do not have complete interconnectivity, e.g., CA 60/71 has full movement from WB CA 60 to both NB and SB CA 71. However, EB CA 60 only connects to SB 71, NB CA 71 only connects to WB CA 60, and SB CA 71 only connects to EB CA 60 for a total of five ramps.
My favorites are those with extra connectivity.
I-70/I-170 NW of St Louis has an extra NB I-170 to WB I-70 ramp making nine total ramps
I-64/I-264 in Norfolk has two extra flyover ramps and one reversing flyover ramp for 11 total ramps
Quote from: skluth on September 13, 2018, 06:14:13 PM
I'm not sure of the point of this thread. So many interchanges do not have complete interconnectivity, e.g., CA 60/71 has full movement from WB CA 60 to both NB and SB CA 71. However, EB CA 60 only connects to SB 71, NB CA 71 only connects to WB CA 60, and SB CA 71 only connects to EB CA 60 for a total of five ramps.
My favorites are those with extra connectivity.
I-70/I-170 NW of St Louis has an extra NB I-170 to WB I-70 ramp making nine total ramps
I-64/I-264 in Norfolk has two extra flyover ramps and one reversing flyover ramp for 11 total ramps
I'm pretty sure the extra I-170 to I-70 ramp in STL is because of the Airport...
There is a ramp that enters I-70 West on the left side, for Thru Traffic, and the ramp that enters I-70 on the right side becomes C/D lanes for I-170 entering I-70 and Airport traffic exiting I-70. This also gives I-170 a semi-direct ramp to the Airport
In terms of odd ramp movements, I need a pen and paper to count the movements possible at the Chicagoland I-55, I-294, and Joliet Rd/Old Rt 66 Interchange. Don't know if it will come out odd, but the fact that the Interchange is missing the Direct I-55 South to I-294 South movement, it makes me curious... (that movement is filled in by I-55 South to US 12/20/45/La Grange Rd South to I-294 South. La Grange Rd is free flowing between the two interstates). Heck, might as well count the movements from La Grange Rd, Archer Ave, and the Southbound Entrance Ramps to I-294 at that interchange
Quote from: webny99 on September 13, 2018, 10:32:29 AM
Quote from: Michael on September 12, 2018, 04:26:38 PM
EDIT: It looks like exit 9 on I-390 (https://www.google.com/maps/@43.1088606,-77.6160463,17z) counts too since there's two ways to get to NY 15A south from I-390 west, but it's hard to tell for sure since the aerial and Street View imagery were both captured during construction.
If by Exit 9 you mean Exit 16 ;-)
As of now, there is only one route from I-390 West (actually North) to NY 15A South*; via the loop ramp. This BGS (https://www.google.com/maps/@43.1083949,-77.6118967,3a,75y,243.97h,84.51t/data=!3m6!1e1!3m4!1srbknK-WNhWDAZQ_eVc0VKg!2e0!7i13312!8i6656!5m1!1e1) accurately reflects the situation here; the first ramp to NY 15A North permits right turns only, while traffic to NY 15A South must take the second exit and use the loop ramp.
*Not counting this ramp (https://www.google.com/maps/@43.0834583,-77.6084466,3a,75y,74.67h,88.02t/data=!3m6!1e1!3m4!1s9z-Nd0Sgoc1J4Zrdsex2Kg!2e0!7i13312!8i6656!5m1!1e1), which DOES allow access from I-390 North to NY 15A South, but it's part of a separate interchange 14 several miles south of the one in question.
As far as the actual thread goes, I-390 Exit 16 is very challenging, since you can't very easily calculate the total number of movements that a) should be available, and b) actually are available. There's at least 16 movements (8 for NY 15A and 8 for NY 15), but then East River Road and Kendrick Road are involved too, and some movements require using East River Rd to get to I-390 and vice versa, so whether to double-count them is questionable. Overall, the redesign was well-done and there are no glaring omissions.. I can't think of a single movement that is completely missing.
Yes, I meant exit 16, 16B to be precise. I guess I didn't proofread close enough. I'd consider exits 16A and 16B a pair of braided parclo/diamond hybrids.
Quote from: webny99 on September 13, 2018, 10:32:29 AM
Quote from: Michael on September 12, 2018, 04:26:38 PM
EDIT: It looks like exit 9 on I-390 (https://www.google.com/maps/@43.1088606,-77.6160463,17z) counts too since there's two ways to get to NY 15A south from I-390 west, but it's hard to tell for sure since the aerial and Street View imagery were both captured during construction.
If by Exit 9 you mean Exit 16 ;-)
As of now, there is only one route from I-390 West (actually North) to NY 15A South*; via the loop ramp. This BGS (https://www.google.com/maps/@43.1083949,-77.6118967,3a,75y,243.97h,84.51t/data=!3m6!1e1!3m4!1srbknK-WNhWDAZQ_eVc0VKg!2e0!7i13312!8i6656!5m1!1e1) accurately reflects the situation here; the first ramp to NY 15A North permits right turns only, while traffic to NY 15A South must take the second exit and use the loop ramp.
*Not counting this ramp (https://www.google.com/maps/@43.0834583,-77.6084466,3a,75y,74.67h,88.02t/data=!3m6!1e1!3m4!1s9z-Nd0Sgoc1J4Zrdsex2Kg!2e0!7i13312!8i6656!5m1!1e1), which DOES allow access from I-390 North to NY 15A South, but it's part of a separate interchange 14 several miles south of the one in question.
As far as the actual thread goes, I-390 Exit 16 is very challenging, since you can't very easily calculate the total number of movements that a) should be available, and b) actually are available. There's at least 16 movements (8 for NY 15A and 8 for NY 15), but then East River Road and Kendrick Road are involved too, and some movements require using East River Rd to get to I-390 and vice versa, so whether to double-count them is questionable. Overall, the redesign was well-done and there are no glaring omissions.. I can't think of a single movement that is completely missing.
Well, technically NY 15A to NY 15 is missing, but Westfall and Crittenden are both very close to the interchange and handle that perfectly well (if not better - in fact, NY 15A to Crittenden was and is Dad's preferred route to NY 15 south over taking the additional distance through the interchange, and doing the reverse to I-390 south may be more efficient than using the ramp from River Road).
It'll be gone later this year, but for about a decade the I-494/Bush Lake Road interchange in Bloomington was missing a connection to westbound 494 largely due to a rail line paralleling Bush Lake Road. The missing westbound on-ramp is now under construction, likely questionable both in necessity and the ridiculous costs being spent to build that westbound on-ramp as it will have to loop all the way across mainline 494 and curve around.
Quote from: skluth on September 13, 2018, 06:14:13 PM
My favorites are those with extra connectivity.
I-70/I-170 NW of St Louis has an extra NB I-170 to WB I-70 ramp making nine total ramps
I-64/I-264 in Norfolk has two extra flyover ramps and one reversing flyover ramp for 11 total ramps
I'd be here all night trying to count all the movements associated with the I-75/I-285 interchange in Cobb County, since some of the ramps also interact with three adjacent interchanges, but relevant to that is that there are two ramps from I-75 southbound to I-285 eastbound: one flyover and one old cloverleaf ramp. I suppose if you really wanted to, you could use the cloverleaf ramp to turn around and go back north on I-75 (not technically allowed, as it requires a multi-lane weave across solid lines, but physically possible); otherwise there doesn't seem to be a clear reason for it to still be there.
How about the I-96/I-696/I-275/M-5 interchange? All 20 (yes 20!) movements are possible. But at least one of them requires using 2 different ramps. And some of the movements are more like mainline than ramps. So depending on how you look at it and how you count, there might be an odd total number of ramps.
Quote from: vdeane on September 13, 2018, 07:45:16 PM
and doing the reverse to I-390 south may be more efficient than using the ramp from River Road.
Yeah, that ramp from River Rd to I-390 South is really only worth using if you're originating from NY 15
north of the interchange (or River Rd itself).
Whenever we're heading north on NY 15 (coming from the south) we'll usually turn right, take the service road, and wait it out at the light at NY 15A. Either that, or using Crittenden Road, probably ends up faster than doing the left turn + backtracking to get to the new ramp.
Another one is I-295/I-76/NJ 42 interchange
From I-295 North there are two ways to I-76, but no movement for NJ 42
From I-295 South there are movements onto both I-76 and NJ 42
From I-76 there are movements to both directions of I-295
From NJ 42, it's just I-295 North
That's 7 movements
This one is on its way out eventually as construction is under way. The current project will eventually eliminate the second 295 North to 76 movement bringing it down to 6, and an upcoming project will eventually result in 8
Quote from: webny99 on September 11, 2018, 04:28:29 PM
Quote from: hbelkins on September 11, 2018, 10:12:58 AM
I-79 exit 64 in Pennsylvania, for PA 51. Three movements; no exit from southbound I-79.
Yes, but all the other ramps are accessible from (or give access to) PA 51 in both directions. So that's actually six out of eight, not three out of four.
Since PA 51 is a surface two-lane route here, I dispute your math.
There are three movements -- I-81 northbound to PA 51, PA 51 to northbound I-81, and PA 51 to southbound I-81. If PA 51 was a full freeway that required separate ramps for each direction of travel, I'd agree with you. The ramps to PA 51 aren't separate movements; you come to the end of the ramp and then turn onto PA 51 in either direction you wish. So three of four movements, not six of eight.
I know this because I was on Neville Island and wanted to get to PA 51, but was not able to get on I-81 and go a short distance south on the interstate. I had to backtrack to reach PA 51, and then ended up traveling under I-81.
Quote from: hbelkins on September 14, 2018, 01:23:18 PM
Quote from: webny99 on September 11, 2018, 04:28:29 PM
Quote from: hbelkins on September 11, 2018, 10:12:58 AM
I-79 exit 64 in Pennsylvania, for PA 51. Three movements; no exit from southbound I-79.
Yes, but all the other ramps are accessible from (or give access to) PA 51 in both directions. So that's actually six out of eight, not three out of four.
Since PA 51 is a surface two-lane route here, I dispute your math.
There are three movements -- I-81 northbound to PA 51, PA 51 to northbound I-81, and PA 51 to southbound I-81. If PA 51 was a full freeway that required separate ramps for each direction of travel, I'd agree with you. The ramps to PA 51 aren't separate movements; you come to the end of the ramp and then turn onto PA 51 in either direction you wish. So three of four movements, not six of eight.
You're saying I-81, but I think you mean I-79.
In any case, this entire thread is based on the assumption that one movement
does not necessarily equal one ramp. If you can use a single ramp to make two (or even three) movements, as you can at most diamond interchanges, then so be it. I am not discouraging mentions of interchanges with an odd number of ramps, and they often fit, but an odd number of ramps
alone is not exactly what I was looking for, as this particular interchange illustrates.
However, I-79/PA 51 is definitely a unique interchange, and therefore worth mentioning; it fits in spirit, if not according to the exact letter of the OP.
Quote from: webny99 on September 14, 2018, 03:45:37 PM
Quote from: hbelkins on September 14, 2018, 01:23:18 PM
Quote from: webny99 on September 11, 2018, 04:28:29 PM
Quote from: hbelkins on September 11, 2018, 10:12:58 AM
I-79 exit 64 in Pennsylvania, for PA 51. Three movements; no exit from southbound I-79.
Yes, but all the other ramps are accessible from (or give access to) PA 51 in both directions. So that's actually six out of eight, not three out of four.
Since PA 51 is a surface two-lane route here, I dispute your math.
There are three movements -- I-81 northbound to PA 51, PA 51 to northbound I-81, and PA 51 to southbound I-81. If PA 51 was a full freeway that required separate ramps for each direction of travel, I'd agree with you. The ramps to PA 51 aren't separate movements; you come to the end of the ramp and then turn onto PA 51 in either direction you wish. So three of four movements, not six of eight.
You're saying I-81, but I think you mean I-79.
In any case, this entire thread is based on the assumption that one movement does not necessarily equal one ramp. If you can use a single ramp to make two (or even three) movements, as you can at most diamond interchanges, then so be it. I am not discouraging mentions of interchanges with an odd number of ramps, and they often fit, but an odd number of ramps alone is not exactly what I was looking for, as this particular interchange illustrates.
However, I-79/PA 51 is definitely a unique interchange, and therefore worth mentioning; it fits in spirit, if not according to the exact letter of the OP.
Yes, I meant 79 in my response. I had 81 on the mind because I'd seen a picture from I-81 not long before.
Would the US 22 at US 202 & 206 in Somerville, NJ count missing one movement from EB to SB as it would leave 7 left plus the extra 4 movements from Mountain Avenue then being 12?
CT 8 and the Merritt Parkway (CT 15) has only 5 direct connections (8N/15N, 8S/15S, 15N/8N, and 15S to 8 in both directions. 2 of thevremaining 3 (8N/15S and 15N/8S) are freeway to freeway but require the use of CT 25. The 8th (8S/15N) requires exiting onto CT 108 and passing a couple of turns and traffic lights to make the connection.