Future construction at Exit 8 interchange could help reduce traffic congestion

An example of how the proposed diverging diamond interchange may look. A final design has yet to be determined | Graphic courtesy of Utah Department of Transportation

ST. GEORGE – Commuters can expect to see road work begin on the Exit 8 interchange in St. George around July as the Utah Department of Transportation gives the green light for interchange improvements. If all goes as planned, construction will end early next year and traffic congestion at the interchange will be reduced.

Current projections by UDOT maintain that the interchange will experience “congestion failure” by 2040, so improvements are needed to meet future traffic demands.

During the 2013 Dixie Regional Transportation Expo, Kevin Kitchen, a spokesman for UDOT, said improvements to the Exit 8 interchange are a part of UDOT’s plans to improve traffic flow along Interstate 15 in Washington County.  He also said improvements made to the interchange would not only make travel on and off I-15 easier, but would benefit traffic in St. George as well.

Typically during peak travel times in St. George, traffic tends to back up on St. George Boulevard. Proposed improvements to the interchange, such as allowing motorists to make nonstop right-hand turns onto I-15, are projected to enhance traffic flow and help mitigate excessive traffic congestion.

Proposed areas of improvement also include the St. George Boulevard and 1000 East intersection, as well as the River Road intersection.

Diverging diamond interchange and design-build

Kitchen said the general design UDOT is shooting for is a “diverging diamond interchange,” or DDI.

According to UDOT, the DDI “allows for two-phase operation at all signalized intersections within the interchange instead of the six or more found in other interchange designs. This is a significant improvement in safety, since no left turns must clear opposing traffic and all movements are discrete, with most controlled by traffic signals.”

Pedestrian accommodations have also been factored into the design.

A diverging diamond interchange has already been constructed in American Fork. UDOT produced the following video to illustrate how the new interchange works:

 (Story continues below)

Note: This video details the DDI in American Fork, Utah, not the one to be built in St. George. | Video courtesy of the Utah Department of Transportation

The project is slated to begin in July, Kitchen said, and it would be a “design-build” affair. This means the contractors bidding on the project also propose their own designs for the interchange’s improvements using the diverging diamond interchange as a base.

According to UDOT, the design-build process helps cut down on project delivery time and the overall costs, as one company is handling the majority of the work involved.

During a St. George City Council meeting, UDOT project manager Kim Manwill also said the design-build process “provides innovation from the private sector.”

The running budget for the project is $16 million, Manwill said.

Whichever design-build team is picked will be working with the preexisting infrastructure of the interchange. Any elaborate designs proposed the project will not only add to the price, but add time to the project as well.

UDOT wants the interchange to be completed by spring 2014.

“We want to make this work as efficiently as possible with the dollars available,” said Dana Meier, UDOT planning engineer.

Kitchen said the winning design-build team should be picked sometime in May.

Traffic impact and pre-construction open house

With construction projected to take place sometime in July through to the end of the year, Marc Mortensen, assistant to the city manager of St. George, said UDOT would coordinate with the city on when to halt work for big events that already impact traffic like the St. George Marathon.

A pre-construction open house will also be held sometime in June or July where interested parties can attend to learn more about construction impacts, maintenance of traffic in the area during construction, and tips and suggestions for keeping businesses thriving during construction.

A hotline has also been set up to take questions and suggestions concerning the project. The hotline number is 435-216-9313.

Information can also be obtained on the project’s website.

An example of how the proposed diverging diamond interchange may look. A final design has yet to be determined | Graphic courtesy of Utah Department of Transportation
An example of how the proposed diverging diamond interchange may look. A final design has yet to be determined | Graphic courtesy of Utah Department of Transportation

Email: [email protected]

Twitter: @MoriKessler

Copyright St. George News, SaintGeorgeUtah.com LLC, 2013, all rights reserved.


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  • Ajsaloon March 25, 2013 at 1:26 pm

    This is a ridiculous idea. A Diverging Diamond Interchange is not the answer and will cause more confusion among the college students, snow birds, and tourist. I feel that a Single Point Urban interchange would be a better fit for the area. Much like exit 2 or the Orem university parkway intersection.

    • Bigger Bob March 25, 2013 at 4:10 pm

      I was thinking the same, but after watching the video, you’d have to be brain-dead to not be able to navigate the DDI. Besides, if they did another Dixie Drive or Southern Pky-type interchange (SPUI), then all the nice, the current maturing trees and landscaping would have to be cleared out and costs would be much higher.

      • Ajsaloon March 25, 2013 at 4:37 pm

        Generally speaking it would be a simple intersection, but we have all seen the drivers here. They wasted a bunch of money on Exit 5, why not waste some on an interchange that really needs some attention. BLVD to River Rd is always backed up to the interchange. It’s going to block the diverge and create more havoc.

        • Tyler March 25, 2013 at 6:36 pm

          Exit 5 or Dixie Dr. is only a waste if you don’t use it on your commute. If you use it like me and most west siders, it’s awesome, we don’t have to use Bluff to get to the 15. A waste would be to build another highway in the Red Cliffs Reserve parallel to Red Hills Parkway that’s supposedly being planed.

  • Keep Our Freedom March 25, 2013 at 2:06 pm

    The problem isn’t the intersections or interchanges. It’s the drivers and the city messing up the programming of the stop lights.
    If a St. George city intersection flows smoothly for all lanes of traffic, the city workers will come in and mess up the programming and make east/west bound traffic green for 5 seconds and north/south bound traffic 2 minutes.

    • Bigger Bob March 25, 2013 at 4:13 pm

      Usually I’d agree with you, but this interchange has become comparable to any SLC or Vegas interchange in way of congestion – almost all hours of the day. The article stated that UDOT saidd it would be at failure status by 2040, it’s already there at rush hours if you ask me.

  • Dave Whipple March 25, 2013 at 2:11 pm

    UDOT should go to California and look at real traffic. The simple and inexpensive clover leaf design has worked perfect on freeways for years. But then again, what incentive is there do to the cost efficient most proficient method? We only need to look at I-15 from Payson to Brigham City to see they build to tear it up and build all over again. Why expect anything else.

  • Alvin March 25, 2013 at 2:33 pm

    If you are the operator of a vehicle and you cannot figure out how to maneuver through an interchange or roadway with signs and paint stripes telling how to do so, “turn in your drivers license now”!! We don’t want you on the road. Quit complaining and deal with it!

  • Big Don March 25, 2013 at 2:52 pm

    Oh I’m sure this will work at least as well as their much touted and loved round-a-bouts. Wonder what they are smoking. . .

  • Joanna March 25, 2013 at 3:04 pm

    If you need a 5 minute video to explain how a Diverging Diamond works, it’s probably not a good idea.

    • Tyler March 25, 2013 at 3:56 pm

      Right? ESPECIALLY in this town!! I swear UDOT has fun introducing new road designs for STG’s infamous dumb and old drivers!

  • Suddenly Suzan March 25, 2013 at 4:22 pm

    I think a clover leaf needs to be introduced here, and would work well into the future. Btw, why didn’t they widen SG Blvd to 3 lanes each direction during the big reconstruction project? 7 lanes should be standard arterial street width from now on in this ever-growing city where traffic volumes are only rising.
    Wasn’t there talk of North Bluff being widened to 7 lanes a while back, what’s the status on that project? And River Road from SG Blvd to Riverside should be widened as well.

    • Zeke March 25, 2013 at 6:49 pm

      Really? 3 lanes each way on the Blvd. So I guess UDOT could pay off ALL the property owners to tear down all the buildings to make room for the expansion. They already thought through that one. Bluff has the room for the most part but these other roads would be too costly to pay off property owners. This town has some geographic problems that hinder a simple traffic flow system. Also, with all the events and being a destination city, it’s just going to be crowded and traffic flow will be difficult at times.

    • Big Don March 26, 2013 at 1:33 pm

      The problem with a clover leaf interchange there, is the same one as Zeke mentions on Boulevard. It would take up so much room, and it would cost so much to buy out the businesses, that it may not be worth it. However, there certainly are alternatives to The Boulevard. My belief, is that rather than the massive project that was done, what should have been done, was to make Boulevard one way, and either Tab or 100 S one way the other way. The fact is, that there would be some traffic relief now, if they would leave Boulevard alone, and make Tab one way, and 100 S. one way the other way. They love to spend our money, so let them cut Tab through under the freeway, so it runs from Bluff to River Road.
      Widen 700 S. and put an interchange in there. That would take a lot of the pressure off Exit 8.
      Bring SR 9 from where it terminates at I-15 on through to SR 18. Finish the Southern Parkway.
      There are so many different things they can do to improve traffic here! All it takes is money. Our money. (sigh)

      • STG Dood March 27, 2013 at 10:57 am

        Excellent idea, I have wondered why they haven’t made Tab and 100 South one-ways, they would alleviate so much downtown traffic from college traffic to major annual events in the city.

  • STG Dood March 27, 2013 at 10:51 am

    I think the City needs to start utilzing one way streets rather than wideneing, much cheaper and less reconstruction. An easy fix for narrow and crowded 1000 East would be to make it, and parallel 900 East one ways. (1000 East one way traffic going north to Red Hills only, 900 East, southbound only from Red Hills to blvd?

  • Luke July 20, 2013 at 9:00 pm

    what is needed is an interchange under the freeway just north of formaster ridge, oh wait st George filled in the hole that would have made this possible when the dorks had to widen red hills parkway there was a perfect south bound off north bound on run and a perfect place to under cut the freeway. That way everyone getting off to go to Santa Clara could have.

  • Jimney December 3, 2013 at 9:55 am

    Don’t really care what they do, but if you need to produce an explanatory video animation explaining the plan, you don’t have the best solution. Combined with the European influence, one is right to be suspect of the design.

    It will work just fine once people get used to it, and since it is so controlled, people will likely adapt more quickly than with roundabouts, but the truth is engineers get bored and it’s fun to try new things. Much ado about nothing.

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