Roundabouts could be the future of I-29 interchange north of Fargo

Published: May. 30, 2023 at 1:10 PM CDT
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FARGO, N.D. (Valley News Live) - The North Dakota Department of Transportation (NDDOT) has been studying an area north of Fargo, and preparing for future traffic needs as growth continues. Engineers are considering five options for the interchange at Interstate-29 and 40th Avenue North (County Road 20) in Fargo.

The options being studied for reconstruction at exit 69 include a standard interchange, dumbbell intersection with roundabouts, a diverging diamond with either traffic signals or roundabouts, and a partial cloverleaf. The cost estimates are below:

Interchange OptionCost Estimate
Standard interchange with traffic signals$31.7 million
Dumbbell interchange with roundabouts$28.1 million
Diverging Diamond interchange with traffic signals$34.1 million
Diverging Diamond interchange with roundabouts$27.8 million
Partial Cloverleaf with traffic signals$31.9 million

A study was done to determine potential interchange configurations, roadway alignments and bridge types. The current interchange is a two-lane, standard diamond interchange with stop control on the exit ramps and two bridges spanning the interstate and adjacent railroad. Officials are preparing for future demands for the I-29 and 40th Avenue North interchange and the 40th Avenue North corridor from 45th Street to 25th Street North.

Engineers with the NDDOT say the dumbbell option is the cheapest and the highest scoring. Scores are based on things like safety, traffic level, cost, flexibility with future improvements, environmental impacts, and how it could affect existing land use or new development.

According to a report being presented to the Fargo City Commission on Tuesday, May 30, the dumbbell interchange with roundabouts “will keep traffic moving without the use of traffic signals. It is a straightforward design and keeps costs the lowest.”

A dumbbell interchange is created by converting each ramp intersection into a roundabout. Circulating lanes are not necessary on the inside of each roundabout as the entire interchange effectively operates like one, large roundabout. Engineers say crashes are reduced by as much as 33% and injury/fatal crashes by as much as 65% with this configuration.

Disadvantages to this option are snow drifting and the fact that drivers are less familiar with the configuration.

The NDDOT has held two public input meetings on the reconstruction project. You can learn more about it here. The goal is to have plans complete by November 1, 2026, and a bid ready by January 1, 2028.