I-25 & Fillmore Street Diverging Diamond Interchange
Owner: Colorado Dept. of Transportation Region 2
Lead Design Firm: HDR Inc.
General Contractor: SEMA Construction Inc.
Lead Owner’s Consultant: Wilson & Co.
Subcontractors: Martin Marietta Materials; A Higher Power Electric Inc.; Rocky Mountain Signing; Plum Creek Structures; Transit Mix Concrete Co.; Ideal Concrete Inc.; Kolbe Striping Inc.; Oldcastle Precast
The new freeway interchange at Interstate 25 and Fillmore Street in Colorado Springs has improved traffic flow and safety. The interchange had suffered from accidents and congestion for more than 15 years. High levels of truck traffic, lots of left turns and numerous conflict points contributed to more than 300 recorded accidents between 2009 and 2012. To correct the problems, the Colorado Dept. of Transportation considered building a single-point urban interchange. The innovative double-diamond configuration, however, saved $24 million while meeting the goals of reducing congestion and delays and improving safety.
The diverging diamond configuration eliminates the need for left-turn signals at on-ramps to the freeway. Diverging traffic separates gradually from the main flow, with improved safety and visibility. Diverging-diamond interchanges also increase traffic capacity and reduce potential conflicts at intersections. The project is only the third diverging-diamond interchange in Colorado.
The project also lengthened the southbound off-ramp and northbound on-ramps and added two new bridges, which replace an old bridge built in 1960. The two bridges are nearly 220 ft long, with a 14-ft-wide sidewalk on the eastbound side for pedestrians.
There are also 5-ft-wide bicycle lanes eastbound and westbound on both bridges. In addition, the southbound off-ramp and northbound on-ramp for I-25 were lengthened to accommodate current traffic volumes.
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