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Author Topic: Question for AHTD: SPUI / DDI  (Read 10565 times)

US71

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Question for AHTD: SPUI / DDI
« on: January 16, 2014, 09:43:52 AM »

I know AHTD has extensive experience with Roundabouts (Traffic Circles), but are there any plans to build Single Point Urban Interchanges (aka SPUI's) or Diverging Diamond Interchanges (DDI's) along any of the interstates?

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AHTD

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Re: Question for AHTD: SPUI / DDI
« Reply #1 on: January 16, 2014, 10:29:52 AM »

Sure!
 
The Bella Vista Bypass interchange with I-540 will be a SPUI - eventually.
 
We are also working through a determining whether a SPUI or a DD will be the best solution at a few of the other interchanges on I-540.
 
Stay tuned! We'll let you know what will go where once the determination has been made.
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Re: Question for AHTD: SPUI / DDI
« Reply #2 on: January 16, 2014, 04:38:20 PM »

The Bella Vista Bypass interchange with I-540 will be a SPUI - eventually.

I may be misunderstanding here, but isn't the Bella Vista Bypass supposed to eventually carry the I-49 designation south from Missouri to meet up with I-540? Wouldn't a freeway-to-freeway interchange be required here? If a SPUI were built, I would think it would have to be torn out and upgraded whenever Arkansas was ready to put I-49 on the bypass.
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Re: Question for AHTD: SPUI / DDI
« Reply #3 on: January 16, 2014, 07:55:49 PM »

I know AHTD has extensive experience with Roundabouts (Traffic Circles), but are there any plans to build Single Point Urban Interchanges (aka SPUI's) or Diverging Diamond Interchanges (DDI's) along any of the interstates?

God, I hope not.  The Death Diamond is a disaster waiting to happen.
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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #4 on: January 17, 2014, 12:22:52 AM »

I may be misunderstanding here, but isn't the Bella Vista Bypass supposed to eventually carry the I-49 designation south from Missouri to meet up with I-540? Wouldn't a freeway-to-freeway interchange be required here? If a SPUI were built, I would think it would have to be torn out and upgraded whenever Arkansas was ready to put I-49 on the bypass.
No, a freeway-to-freeway interchange isn't needed.

At the current interchange, US 71B (to the south) and US 71 (to the north) are not freeways.  US 71B is a 5 lane section, and US 71 to the north is 4 lanes divided by a raised median.

They are going to redo the interchange once I-49 will be constructed to that interchange.  (To my knowledge).
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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #5 on: January 17, 2014, 12:26:05 AM »

God, I hope not.  The Death Diamond is a disaster waiting to happen.

Why the hate for DDIs?  They definitely work when there is heavy left-turning traffic.  Signage is key with these and SPUIs.
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AHTD

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Re: Question for AHTD: SPUI / DDI
« Reply #6 on: January 17, 2014, 10:04:30 AM »

The Bella Vista Bypass interchange with I-540 will be a SPUI - eventually.

I may be misunderstanding here, but isn't the Bella Vista Bypass supposed to eventually carry the I-49 designation south from Missouri to meet up with I-540? Wouldn't a freeway-to-freeway interchange be required here? If a SPUI were built, I would think it would have to be torn out and upgraded whenever Arkansas was ready to put I-49 on the bypass.

The full SPUI won't be constructed until the last section of the Bella Vista Bypass is constructed - from Benton County Road 34 to the state line. This won't happen until Missouri is able to meet us at the line. So to continue moving forward and provide a usable section until this happens, the bypass will be open from CR 34 to U.S. Highway 71/I-540.
 
When the bypass is fully operational it will directly feed into I-540. If we were to proceed with the SPUI at this time, it would actually impede traffic on U.S. Highway 71 because of the way it will tie-into the intersection. This is counterproductive, so to provide access to the usable part of the bypass and to not impede flow on U.S. Highway 71, the traffic circle will suffice.
 
We'll see if we can get a drawing of the intersection and post it here to help illustrate the concept.
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US71

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Re: Question for AHTD: SPUI / DDI
« Reply #7 on: January 17, 2014, 10:09:47 AM »

God, I hope not.  The Death Diamond is a disaster waiting to happen.

Why the hate for DDIs?  They definitely work when there is heavy left-turning traffic.  Signage is key with these and SPUIs.

People drive the wrong way in DDI's., They also drive the wrong way in Roundabouts. :p
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Re: Question for AHTD: SPUI / DDI
« Reply #8 on: January 17, 2014, 11:38:44 AM »

I must be missing something. I don't know of one state-maintained roundabout anywhere in the Mid-South, much less Arkansas. I know at least one city-maintained one here in Prosper, which they put stop signs on at all ends to defeat the purpose. :crazy:
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US71

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Re: Question for AHTD: SPUI / DDI
« Reply #9 on: January 17, 2014, 12:16:34 PM »

I must be missing something. I don't know of one state-maintained roundabout anywhere in the Mid-South, much less Arkansas. I know at least one city-maintained one here in Prosper, which they put stop signs on at all ends to defeat the purpose. :crazy:

I don't know if it's state-maintained, but there are back to back Roundabouts in Conway, AR.
http://goo.gl/maps/Jw6MB
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Re: Question for AHTD: SPUI / DDI
« Reply #10 on: January 17, 2014, 08:08:37 PM »

I must be missing something. I don't know of one state-maintained roundabout anywhere in the Mid-South, much less Arkansas. I know at least one city-maintained one here in Prosper, which they put stop signs on at all ends to defeat the purpose. :crazy:

I don't know if it's state-maintained, but there are back to back Roundabouts in Conway, AR.
http://goo.gl/maps/Jw6MB

Sure enough, there are! Not particularly well-signed, but looks fully functional. Thanks.
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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #11 on: January 18, 2014, 01:39:14 AM »

Why the hate for DDIs?  They definitely work when there is heavy left-turning traffic.  Signage is key with these and SPUIs.
People drive the wrong way in DDI's., They also drive the wrong way in Roundabouts. :p

Meh, people are stupid.
This will happen at any newly introduced SPUI, DDI, etc. 
Think of the new Flashing Yellow Left Arrow traffic signal.  People will get used to it.

Look at Sioux Falls, SD (population 160,000-ish)... SDDOT introduced the SPUI at 10th & I-229 back in the late 90's/Early 2000's, I believe.  And now they have 3 SPUIs on I-29.

Point is, local traffic will adapt to it... Motorists from outside of the area will rely on signage.
« Last Edit: January 18, 2014, 01:44:59 AM by M86 »
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Re: Question for AHTD: SPUI / DDI
« Reply #12 on: January 18, 2014, 02:07:09 AM »

And now they have 3 SPUIs on I-29.

Point is, local traffic will adapt to it...
I attest. There are five SPUIs in my immediate area (counting the one on I-229 and the I-29 Tea exit). I have not found it hard to adapt, and now they're pretty much no problem.
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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #13 on: January 18, 2014, 02:34:45 AM »

A roundabout at the current US 71/US 71B interchange?  Oh. My. #*$)@.

Dang, if that won't clog up traffic even more, I don't know what will!

Is this for real?  Come on, AHTD... I know Northwest Arkansas isn't Little Rock, but jeez... Stop treating us like we don't exist.
« Last Edit: January 18, 2014, 02:46:47 AM by M86 »
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AHTD

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Re: Question for AHTD: SPUI / DDI
« Reply #14 on: January 18, 2014, 10:38:22 AM »

Hard not to get caught up on the term "roundabout," but once you see the design you will understand. Most important to understand is that this solution is TEMPORARY and design elements of this temporary solution will translate into the final solution, so its not like this temporary solution will have to be demolished before the SPUI is built.
 
It has not been officially announced (date & time not scheduled), but in February or March we will be hosting a public meeting in NWA - probably somewhere in Bentonville or Bella Vista to make ourselves available for questions about the Bella Vista Bypass project. We will announce the meeting in this forum too.
 
This meeting will include displays, drawings, and a team of subject matter experts that will be on-hand to help explain the intricacies of this project. In short, since Missouri cannot meet us at the line, that affects our ability at this time to construct the SPUI. The "roundabout" is a usable connector that will allow locals to use the section up to Benton County Road 34.
 
This meeting is NOT a pubic involvement meeting that is usually part of the environmental process.
 
Next month's bid letting is SCHEDULED to include the first half-cent sales tax-funded project - the stretch of the Bella Vista Bypass from the U.S. 71 area to the most southern end of what is currently under construction. Consult www.idrivearkansas.com for a look at what is currently under construction and where in this area.
 
 
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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #15 on: January 19, 2014, 03:10:25 AM »

I'm very familiar with roundabouts.

I just can't imagine the bottlenecks.

Does AHTD know the amount of trucks that travel along US 71/I-540?  And to introduce a roundabout? 

Holy. Crap.
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AHTD

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Re: Question for AHTD: SPUI / DDI
« Reply #16 on: January 19, 2014, 12:01:18 PM »

We sure do! See link below for ADT in and around Bella Vista:
 
http://www.arkansashighways.com/planning_research/technical_services/TrafficCountyMaps/2012ADT/TrafficCountMaps/BellaVista.pdf
 
Everyone can look at ADT counts for the entire state on our web site here: http://www.arkansashighways.com/planning_research/technical_services/2012_traffic.aspx
 
2012 is the latest information available. 2013 numbers will be available in the spring.
 
But again... the modified connector (similar to a roundabout) is designed in such a way to ALLOW traffic on U.S. 71/I-540 to flow unimpeded as it does now (except for backups during peak times). The modiifed connector simply allows access to usable parts of the Bella Vista Bypass so that folks in Hiwassee, Gravette and those that live in west Bella Vista can use it.
 
 
« Last Edit: January 19, 2014, 12:03:23 PM by AHTD »
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Re: Question for AHTD: SPUI / DDI
« Reply #17 on: January 20, 2014, 04:01:30 AM »

There's going to be a ROUNDABOUT at I-49 and US 71/71B?  Are you shitting me? 
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Re: Question for AHTD: SPUI / DDI
« Reply #18 on: January 21, 2014, 07:22:29 AM »

Thanks for your replies, AHTD!

I think a schematic is definitely in order here.
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Re: Question for AHTD: SPUI / DDI
« Reply #19 on: January 21, 2014, 09:05:17 AM »

A schematic would be good.

A roundabout should cope theoretically with the traffic. However it is at the upper limits of large, multi-lane roundabouts. And I doubt that NW AR people are used to such roundabouts in the way that Brits are.

You might want to look at this scheme, which is massively upgrading a roundabout that hasn't got much more traffic:
http://www.highways.gov.uk/roads/road-projects/a1-black-cat-roundabout-part-time-signals-chawston/
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US71

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Re: Question for AHTD: SPUI / DDI
« Reply #20 on: January 21, 2014, 10:07:37 AM »

A schematic would be good.

A roundabout should cope theoretically with the traffic. However it is at the upper limits of large, multi-lane roundabouts. And I doubt that NW AR people are used to such roundabouts in the way that Brits are.


Conway seems a little more adept now that they have had an opportunity to get used to them.  Fayetteville at the North Hills Medical Park, no so much, but it may just be a learning curve.


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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #21 on: January 22, 2014, 01:07:04 AM »

We sure do! See link below for ADT in and around Bella Vista:
 
http://www.arkansashighways.com/planning_research/technical_services/TrafficCountyMaps/2012ADT/TrafficCountMaps/BellaVista.pdf
 
Everyone can look at ADT counts for the entire state on our web site here: http://www.arkansashighways.com/planning_research/technical_services/2012_traffic.aspx
 
2012 is the latest information available. 2013 numbers will be available in the spring.
 
But again... the modified connector (similar to a roundabout) is designed in such a way to ALLOW traffic on U.S. 71/I-540 to flow unimpeded as it does now (except for backups during peak times). The modiifed connector simply allows access to usable parts of the Bella Vista Bypass so that folks in Hiwassee, Gravette and those that live in west Bella Vista can use it.
 
 

I can see how this would be appropriate, as ridiculous as it sounds.  Thank you, AHTD.

I would love to see the plans, as others have stated.
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Re: Question for AHTD: SPUI / DDI
« Reply #22 on: January 22, 2014, 05:18:38 PM »

Here is the original SPUI design. This is still planned for construction:
http://www.arkansashighways.com/forums/Bella_Vista_SPUI.pdf
 
Here is the modified connector design:
http://www.arkansashighways.com/forums/Bella_Vista_Modified_Connector.pdf
 
We are working on a traffic model video that we will post here once it's ready for public consumption. It will show how the modified connector will work.
 
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Re: Question for AHTD: SPUI / DDI
« Reply #23 on: January 22, 2014, 07:37:49 PM »

If Missouri Petitions for a tax bill to finish there part of the Bella vista Bypass, will AHTD put the Interchange on hold to see if they pass it in November. Also it would help if the Federal Government would Pass a new Highway Bill soon so States would know that the money want run out in October.
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M86

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Re: Question for AHTD: SPUI / DDI
« Reply #24 on: January 23, 2014, 02:49:00 AM »

Here is the original SPUI design. This is still planned for construction:
http://www.arkansashighways.com/forums/Bella_Vista_SPUI.pdf
 
Here is the modified connector design:
http://www.arkansashighways.com/forums/Bella_Vista_Modified_Connector.pdf
 
We are working on a traffic model video that we will post here once it's ready for public consumption. It will show how the modified connector will work.
 
I'm reversing my opinion that this roundabout is a good idea.

How is AHTD going to introduce this roundabout? 

Good luck to the truckers that have to deal with Bella Vista... Considering the amount of trucks/semis will have to go through that roundabout...



« Last Edit: January 23, 2014, 04:18:01 AM by M86 »
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