Big project may bring I-15 gridlock to Davis County
Traffic • UDOT says they need to move 20% of commuters onto Legacy or trains.
Published: March 27, 2014 07:19PM
Updated: March 27, 2014 09:16PM
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Trent Nelson | The Salt Lake Tribune Rush hour traffic northbound on I-15 in Farmington, Thursday, March 27, 2014.

A huge project to add express lanes to Interstate 15 through south Davis County and rebuild key interchanges there is about to begin, and officials warn it could bring gridlock unless 20 percent of daily commuters find other alternatives.

“We need to have a 20 percent reduction of traffic to avoid standstills,” said Utah Department of Transportation spokesman Vic Saunders.

“Legacy Parkway is an outstanding alternative to I-15, and we encourage people from the north to use it,” he said. Also, “We’ve also partnered with the Utah Transit Authority to offer a number of reduced-cost passes on FrontRunner” commuter rail.

Saunders said more information on those passes will be available later at udot.utah.gov/i15southdavis.

The $117 million project is scheduled to begin in mid-April to add new express lanes from North Salt Lake to Farmington, said Nathan Peterson, UDOT project manager. It is scheduled for completion in July 2015.

When finished, Utah will have the longest-in-the-nation stretch of continuous express lanes from Spanish Fork to Layton, about 80 miles. Those lanes are open to cars with at least two passengers, people who pay tolls through electronic transponders, motorcycles or motorists with clean-fuel vehicles.

Because of extra width needed for the express lanes, UDOT will replace bridges at 1500 South and 400 North in Bountiful. Crews will also replace bridges and rebuild intersections at 500 South and 2600 South. They’ll also add a pedestrian bridge at Parrish Lane in Centerville.

The biggest changes will come to the 2600 South Bountiful/Woods Cross interchange.

“It was built when the Interstate was first built in the Salt Lake City area,” Saunders said. “It was designed to serve traffic through maybe the early ‘90s. As the area has grown, we have a situation now where this intersection is overwhelmed with traffic.”

Peterson said the redesigned interchange will be unique in the United States, and essentially is a hybrid between innovative “diverging diamond” and “continuous flow” interchanges it recently has been using elsewhere, such as on Bangerter Highway in Salt Lake County.

Eastbound traffic toward the freeway on 2600 South will separate into lanes that will turn south onto the freeway, or proceed straight or turn north onto I-15. Designs will allow the southbound I-15 traffic to skip a usual traffic signal after passing under the freeway and allow entering I-15 without an additional stop.

“This design eliminates one signal” and should speed traffic, Peterson said, adding it was developed by the W.W. Clyde Co., which won a design-build contract for the project.

The design also moves signals now west of the freeway a bit further away and reconfigures streets and traffic flow. A drawing is available online here. The plan includes adding sidewalks and wider shoulders for bicyclists.

Peterson said it will also make it easier for oil-tanker trucks going to refineries in the area to navigate the area.

The 500 South interchange will also change significantly, with a “diverging diamond,” where cars temporarily drive on the “wrong” left-hand side of the road to eliminate left-turn signals and help speed traffic. A copy of the design is also available here.

Peterson said an innovation there will have pedestrian sidewalks in the middle of the diverging lanes beneath the freeway instead of on the shoulders. The project will also reconfigure the intersection of 500 South and 500 West (US-89), seeking to allow easier turns there.

Peterson said W.W. Clyde has designed construction so that some lanes will always be open, except for one night when one bridge is demolished. However, lanes will shift often because of construction.

The project is also using traditional bridge construction techniques, rather than building bridges to the side of the freeway and moving them into place — which UDOT has done on other projects recently. Peterson said traditional construction actually keeps more of the freeway open longer on this project. Most of the construction is scheduled for nighttime hours to help reduce impacts on traffic.

UDOT is able to build the new project without buying new land for the widening, Saunders said. That’s because the existing freeway has a wide footprint, with much of the land unused.

He said people seeking email updates may send a request to i15southdavis@utah.gov. UDOT also has a hotline for updates at 888-966-6624.

Follow the project

People seeking email updates may send a request to i15southdavis@utah.gov. UDOT also has a hotline for updates at 888-966-6624.