I-15 St. George Boulevard Bridge closure, switch to Diverging Diamond Interchange configuration

ST. GEORGE – More than a week ahead of schedule, the Interstate 15 – St. George Boulevard interchange will be switched over from a traditional diamond interchange to a diverging-diamond-interchange configuration beginning this Saturday. Crews will close St. George Boulevard between the freeway on- and off-ramps from Saturday at 11 p.m. until Tuesday at 6 a.m. in order to make the switch.

Originally, the new interchange was scheduled to be open before Black Friday on Nov. 29 to accommodate holiday shopping at area businesses. Now, Utah Department of Transportation is pleased to open the interchange more than a week ahead of schedule.

“It is important to UDOT and the City of St. George to make sure that the construction of this project doesn’t adversely affect area businesses,” UDOT Project Manager Kim Manwill said. “We want to make sure that the economy in the area stays strong throughout the project duration. I think, so far, we have met this goal.”

What is a diverging-diamond interchange, or DDI?

A DDI briefly swaps traffic to the opposite side of the road as it passes over the interstate, this allows left turns to be made on and off the freeway without the need for a signal. This provides more efficient signal operations, which significantly reduces delay; increases the capacity at the existing overpass by removing the need for turn lanes; increases the capacity of turning movements to and from the ramps; substantially reduces the number of conflict points, which improves safety; and improves pedestrian safety.

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Navigating the new St. George Boulevard Diverging Diamond Interchange

“There are several DDIs in operation in Utah and we are excited to have the first DDI in Southern Utah,” Manwill said. “This new interchange type will keep traffic flowing and allow for future growth in St. George.”

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Navigating the DDI WS
St. George Boulevard Diverging Diamond Interchange

Closure information

Making the switch to a DDI will require the closure of St. George Boulevard between 1000 East and River Road. Right turns will still be permitted at each ramp. The northbound off-ramp is scheduled to close the nights of Saturday, from 11 p.m. to 8 a.m., and Sunday, from 10 p.m. to 6 a.m., but will remain open during the day. There will be no east-west access on St. George Boulevard across the bridge throughout the duration of the closures. Motorists should use 100 South as an alternate east-west route. St. George Police Department will be present to assist motorists and protect the work zone.

During the two-day closure, crews will place new signal poles, excavate existing concrete islands, install new traffic signs, install sidewalk barrier and curbing, pave the bridge, and paint new striping. When the interchange re-opens Tuesday morning, traffic will be in the new DDI configuration. Minor construction activities will continue in the project corridor and on I-15 through December 2013.

Road closure and alternate route details

  • St. George Boulevard Bridge, between 1000 East and River Road | Saturday at 11 p.m. until Tuesday at 6 a.m.
  • Motorists should use 100 South as an alternate east-west route.
  • St. George Boulevard northbound off-ramp closure | Saturday from 11 p.m. to 8 a.m. | Sunday from 10 p.m. to 6 a.m.
  • Motorists who want to exit the northbound off-ramp should use Dixie Drive (Exit 5) or Bluff Street (Exit 6) as alternate exits.

Road restriction details

  • I-15-St. George Boulevard on- and off-ramps | Saturday at 11 p.m. until Tuesday at 6 a.m.
  • Only right-turn movements will be allowed.

Resources and contact information

  • Contact: Project Hotline – 435-216-9313 | Project email
  • Website: Visit UDOT for more information about the project, construction activities, and road closures.

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


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  • skippy November 12, 2013 at 4:14 pm

    Oh, my!! Please, please, for the love of Jupiter, offer free, mandatory training for all local residents (and free instructions for tourists at the border check, Chamber of Commerce, and up-Chuck-a-Rama)! No one wants to see any carnage from this obstacle course; that section of road was already frightening enough…

  • anonymous November 13, 2013 at 6:19 am

    Let the game of bumper cars begin.

  • utrefugee November 13, 2013 at 8:26 am

    Your idea of getting training for the ddi is great! I’ll be 1 of the first to sign up especially if it is free. The thought of driving on that “thing” terrifies me to death!!!
    I think I’ll just take river rd if I need to go on that side of town or the other side streets.

    • Gunther November 13, 2013 at 9:25 am

      Well, if you have any skill at operating a vehicle, driving through the DDI should be very simple. Just follow the lane striping on the road, as usual. Pay attention to the traffic signal and the three different colors of lights that will appear from time to time, as usual. Chances are you won’t find it too difficult to negotiate unless everyday driving is challenging already.

  • Boston Derby November 13, 2013 at 9:14 am

    people can’t do a simple rotary in this town….what makes city planners and UDOT think they can do a moving obstacle course?

    good thing there is a hospital just down the street !

  • skippy November 13, 2013 at 9:39 am

    “The DDI briefly swaps traffic to the opposite side of the road,” says the PM. Now that’s a model for the existing roads in town!! Weeeeeeeeee! Zig……Zag….. (Or a novel excuse for lane drift: “I’m just practicing for the double-D officer.”)

  • Gas It November 13, 2013 at 10:14 am

    useless highway interchange remodels is what passes for shovel-ready jobs in this state

    • Big Bob November 17, 2013 at 10:04 pm

      You won’t say useless in 5 years from now. It’s about time we have our interchanges upgraded to urban driving standards.

  • Melenie November 17, 2013 at 7:12 pm

    There is a similar intersection in American fork, and it works great. You’ll get used to it.

  • Jake November 17, 2013 at 9:22 pm

    I do suggest checking out the first map on this page:


    I shows what lanes will go where!

  • Dustin November 19, 2013 at 7:00 am

    The bad thing is the money they spent on this yet again remodel the could have build another needed over pass some where arround the mall. I just don’t understand the thinking going on here.

  • Jason November 28, 2013 at 8:20 pm

    16 million seems pretty steep for a figure 8. Someone got their pockets lined.

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