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Erik Burgess, Published January 16 2014

MnDOT looks to improve congested south Moorhead I-94 ramps with 'diverging diamond'

MOORHEAD – State traffic officials are planning a big renovation of the busy Interstate 94 interchange at Eighth Street here, and their preferred option is one that might have drivers scratching their heads.

It’s called the “diverging diamond,” and it throws to the curb the eternal American driving rule of “stay right.” In the diamond format, drivers temporarily cross to the other side of the road and then back to their original lanes.

The Minnesota Department of Transportation has been planning an I-94 interchange renovation for years. Construction would likely start and be completed in 2016.

The oft-congested interchange needs to be redone to improve efficiency and ultimately safety, said project manager Seth Yliniemi.

MnDOT estimates about 76,200 vehicles travel through the interchange every day, making it the fourth-busiest intersection in the Fargo-Moorhead metro, according to the F-M Metropolitan Council of Governments.

As construction is happening, Yliniemi said crews should be able to get the work done without shutting down the busy interchange.

“There’s going to be pretty major delays through there, but at this time we haven’t really taken a hard look at the (construction) staging,” he said.

The diamond option, while strange, is MnDOT’s preferred plan. At a cost of roughly $4 million, it’s the cheapest of the three alternatives that will be presented during a public meeting from 5 to 7 p.m. Jan. 23 at the Courtyard by Marriott in south Moorhead.

If the diverging diamond is selected, it would be the fourth such interchange in the state. Others are in Elk Run, St. Cloud and Bloomington.

The design was first built in 2009 and is becoming more popular because it allows cars to turn left without crossing oncoming traffic, Yliniemi said.

With a diamond layout, cars traveling northbound on Eighth Street would hit a traffic light just before the bridge that crosses over I-94. They could turn right before the light to head east on I-94, or they could continue through the light, crossing over to the left side of the bridge.

Once on the left side of the bridge, drivers could make an unencumbered left turn to go westbound on I-94, much like making a left turn from a one-way onto another one-way.

“It makes it more efficient and safer because you eliminate those left-hand turn conflicts,” Yliniemi said.

Those who don’t want to enter I-94 would hit another light on the other side of the bridge, and then cross back over to the right side of the road to continue going north.

The diamond model is also efficient, Yliniemi said, because traffic leaving I-94 to come into Moorhead would be faced with a fork and could go left or right without facing oncoming traffic.

“It doesn’t look as crazy (in real life) as it looks from above,” MnDOT spokesman Jerimiah Moerke said, referring to the schematic.

If it all sounds too confusing, breathe easy. MnDOT will have some instructional simulations at the public meeting Thursday. There are also two other options on the table that, while more expensive, are more traditional.

One is called the “northeast loop,” which would allow northbound traffic on Eighth Street to turn right after the bridge and enter a cloverleaf-style on-ramp to head west on I-94. Drivers now have to turn left across traffic to do this. That option costs an estimated $5.8 million.

The final option is a $7.5 million “partial cloverleaf,” which would have the same on-ramp as the northeast loop plan but would add another ramp for southbound traffic on Eighth Street to turn right and loop into eastbound I-94.

The project’s cost will be split 80/20 between federal and state dollars, respectively, Yliniemi said. All plans are preliminary.

No matter the option chosen, Yliniemi said I-94 will gain a third lane in each direction between the Eighth Street and 20th Street interchanges.

City Engineer Bob Zimmerman said the four-lane stretch of I-94 inside city limits is problematic because if there’s an accident and one lane has to be closed, traffic can be clogged for miles.

“It functions fine with two lanes, but it’s that close to capacity where if you lose one of those lanes, it just kind of all blows up,” Zimmerman said.

A final plan will be chosen and further developed after Thursday’s open house. Another open house will likely be scheduled in late spring or early summer to go over more details of the final plan, Yliniemi said.

The project will likely be bid out for construction in fall 2015.

If you go

What: Minnesota Department of Transportation public meeting

When: 5-7 p.m. Jan. 23

Where: Courtyard by Marriott, 1080 28th Ave. S., Moorhead

Info: MnDOT discuss and take comments on three proposed plans for renovating the Interstate 94 and Eighth Street interchange.

Readers can reach Forum reporter Erik Burgess at (701) 241-5518