Interchanges with an odd number of movements allowed

[Michael]

EDIT: It looks like exit 9 on I-390 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 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, 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.

[vdeane]

EDIT: It looks like exit 9 on I-390 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 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, 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).

[TheHighwayMan3561]

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. 

[Eth]

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.

[GaryV]

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.

[webny99]

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.

[bzakharin]

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

[hbelkins]

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.

[webny99]

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.

[hbelkins]

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.

[roadman65]

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?

[jp the roadgeek]

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.