Diverging Diamond in St. Louis Missouri
Hwy 15 Diverging Diamond Interchange
Stearns County Road 120 in Sartell and St. Cloud
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Click on layout to see larger detailed layout.Work on the Hwy 15/Stearns CR 120 Diverging Diamond Interchange (DDI) began Monday, July 16, 2012.


The $10 million project is being constructed by the Minnesota Department of Transportation (MnDOT), in partnership with Stearns County and the cities of Sartell and St. Cloud.


The area around this intersection has been rapidly developed over the years. New healthcare facilities and retail businesses have increased the amount of traffic, which warranted the development of this project. Construction of the future interchange is to be completed by late Fall 2013.



Motorists Driving a DDI in Missouri

Traffic crisscrosses at either end of the bridge, so instead
of making hard left turns, drivers veer to the left for access.



Highway 15 St. Cloud/Sartell
Location: Intersection of Hwy 15 and Stearns County Rd 120 in Sartell/St. Cloud
Description: Construct a diverging diamond interchange
Construct: 2012-2013
Communities: Sartell, St. Cloud, Stearns County, Le Sauk Township
Detour: TBD
Cost: $10 million



A Diverging Diamond Interchange (DDI) allows two directions of traffic to temporarily cross to the left side of the road. A DDI moves high volumes of traffic through an intersection without increasing the number of lanes. This movement provides easier access to a busy divided highway.


A DDI reduces congestion by allowing traffic to keep moving through an intersection. It also improves safety by allowing free flowing turns when entering or exiting the roadway, eliminating left turns against oncoming traffic and reducing the number of traffic signal phases.


The DDI provides better sight distance at turns and fewer chances to conflict with other vehicles, resulting in fewer crashes.





In 2007, the district completed a corridor study of Hwy 15 from I-94 to Hwy 10 in St. Cloud.  Future traffic volumes showed the need to convert the current expressway design (at-grade signalized intersections) to a freeway design.  The cost for the whole corridor was over $300 million, but some of the interchange locations were isolated enough (like this project) that they could be built separately as need arose and funding became available.


Why a Diverging Diamond


The Greater Minnesota Interchange project selection criteria was weighted towards business development and increased employment (75%), safety (15%), and congestion relief (10%). 


Neighborhood Noise Impacts


Three of the interchange quadrants are filled with office and commercial uses.  The area southeast of the existing intersection includes residential neighborhoods. Limiting noise impacts to the neighborhoods was a primary objective. Early in the process it was decided to depress Hwy 15 under Stearns County Hwy 120, taking the highway noise below the existing ground line.  A screening berm along the southeast ramp may be constructed to separate the interchange from the neighborhood.




In 2009, the legislature (through Chapter 36 and Chapter 152 bond funds) made a limited amount of funding available for interchange construction in greater Minnesota.  The district applied for Greater Minnesota Interchange Funding and was awarded $10 million in bond funds towards the project. 


In 2010, a separate application was made for Destination Innovation Program (DIP) funding, recognizing the district’s preferred alternative was a new concept called a Diverging Diamond Interchange.  The project was awarded an additional $4.5 million in DIP funding. Stearns County, Sartell and St. Cloud will be responsible for the remainder of the funding.


Did you know?


The DDI roadway design originated in France and may reduce traffic delays up to 60 percent!



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