MnDOT, What Were You Smoking?

[rte66man]

I don't think I've ever see anything quite like this:
http://goo.gl/maps/uilmU

Anyone know why MnDOT chose to do that rather than something like this:
http://goo.gl/maps/DMfBC

rte66man

[Brandon]

^^ No idea, but I like it.  The MnDOT one removes the interchange from the other intersections and minimizes the conflict points.  The MoDOT one along I-64 is a PITA to deal with, IMHO (I've been through there a few times, and it can be a bit confusing on the ground).

[The High Plains Traveler]

http://goo.gl/maps/tpXMh

[NE2]

It's a SPUI without the large intersection.

[pianocello]

Is it cheaper to build two extra bridges and leave the original intact than closing and rebuilding one bridge? I feel like it would be more convenient for drivers during construction.

[Big John]

Looks like there is a busy intersection just to the south of the interchange so the reason could be to get sufficient spacing from the interchange to that intersection with the traffic demand.

[getemngo]

It's a SPUI without the large intersection.

And I like it, especially because it removes all the weird angles that cause head-on collisions in SPUIs with poor lane striping. But if I were MnDOT, I'd give ramps to eastbound exiting traffic turning south and northbound traffic entering east, so they don't have to cross two bridges and double back.

[codyg1985]

I think this is a rather ingenious design. It provides a larger distance between the intersections than what would be offered with a SPUI. It was probably cheaper, too.

[Milwaukee, WY]

There's also one of these in Aurora, Colorado at 225 and Alameda. It works pretty well from my experience.
http://goo.gl/maps/Kc6l4

Edit- should have checked the whole thread. I see High Plains Traveler already beat me to it.

[midwesternroadguy]

I agree with the above comments.  There were queuing issues at County B just to the south of the existing EB ramp terminal.  I think it's a creative, and better-working solution too.  No more backups down the Trunk Highway 36 exit ramp.

[The High Plains Traveler]

Does this variant of SPUI have a name? I had thought "asymmetrical" until I noticed a plane of symmetry along the surface street.

[Milwaukee, WY]

Maybe offset?

[NE2]

Maybe offset?

Seems to have gotten some use:
http://www.google.com/search?q=%22offset+spui%22
http://www.google.com/search?q=%22offset+single+point%22

[The High Plains Traveler]

Maybe offset?

Seems to have gotten some use:
http://www.google.com/search?q=%22offset+spui%22
http://www.google.com/search?q=%22offset+single+point%22

Seems like someone has given the design a consistent name since there are at least two instances of it. Works for me. 

[Milepost61]

I called the I-225/Alameda interchange a "SPUI diamond hybrid". Doesn't roll off the tongue very well; offset SPUI works much better. Didn't realize there was another one.

Side note to the Alameda interchange: When I-225 was built CDOT didn't put in an interchange there, but Aurora really really wanted one, so ended up building it as a city-funded project in the early '00s. Funding came from a voter-approved temporary transportation tax.

[froggie]

Can't get to the google maps, but from the replies I'm guessing this is referring to MN 36 at Rice St.

I'd traded E-mails with MnDOT about it before construction began.  This design was chosen vice a more traditional SPUI or a DDI due to the spacing between the interchange and County Road B just to the south.  Also wound up being cheaper than a traditional SPUI.

But if I were MnDOT, I'd give ramps to eastbound exiting traffic turning south and northbound traffic entering east, so they don't have to cross two bridges and double back.

Same with above...lack of adequate spacing between the interchange and the County Road B intersection.  Your NB-to-EB idea might have been doable, but frankly there's not a lot of demand there.  EB-to-SB would've required a retaining wall just to get 200ft of spacing to the County B intersection...not enough.  Such a ramp would have required separate traffic control, which would both reduce efficiency and totally defeat the purpose.

[mgk920]

I like the simplicity of the MnDOT work.  'KISS'.

I wonder, had MnDOT done that now instead of when they did do it, would those intersections have been built as roundabouts?

BTW, the I-90 Wallace, ID east interchange is the same layout.

Mike

[froggie]

MGK:  I asked that too...they looked at roundabouts.  I do not remember the reason why, but they were ruled out.

[rte66man]

Can't get to the google maps, but from the replies I'm guessing this is referring to MN 36 at Rice St.

Correct.

I'd traded E-mails with MnDOT about it before construction began.  This design was chosen versus a more traditional SPUI or a DDI due to the spacing between the interchange and County Road B just to the south.  Also wound up being cheaper than a traditional SPUI.

It was hard for me to believe it was cheaper until you confirmed it.  2 small bridges are cheaper than a teardown and one SPUI bridge.

I wondered about the roundabout option, but I see that was answered in another post.  Thanks Froggie.

rte66man

[froggie]

Traditional SPUIs require a lot of bridge deck, plus multiple odd angles.  That adds a lot of cost to a SPUI.  Also, in this case, it would have required retaining walls on the south side of 36...retaining walls are also expensive.

[Mdcastle]

This seems like it would be friendlier to pedestrians than a SPUI or a diverging diamond, but one of the local message boards opposed this project, apparently just because we could spend the money on busses instead and anything that helps cars move is bad.

[Scott5114]

Kind of reminds me of the X interchanges on I-244 in Tulsa, which do something similar, but with left exits and entrances instead of bridges.

[froggie]

IIRC, there's an interchange on I-290 in Chicagoland that is the same way, a single intersection point but with left-side entrances and exits on the freeway.  US 41/IL 132 is also like that.  Both have the usual problems associated with left-side ramps.

[Brandon]

IIRC, there's an interchange on I-290 in Chicagoland that is the same way, a single intersection point but with left-side entrances and exits on the freeway.  US 41/IL 132 is also like that.  Both have the usual problems associated with left-side ramps.

Two of them on the Eisenhower Expressway (I-290), actually, and both in Oak Park.  One is at Harlem (IL-43) and the other is at Austin.

[I94RoadRunner]

I don't think I've ever see anything quite like this:
http://goo.gl/maps/uilmU

Anyone know why MnDOT chose to do that rather than something like this:
http://goo.gl/maps/DMfBC

rte66man

This design was chosen due to the close proximity of the MN 36 ramps to County Road B to the south. MnDOT basically wanted to build a SPUI at MN 36/Rice St. Despite the odd design, the new interchange does function reasonably well .....