Groundbreaking for a new, and unusual, type of highway interchange to be constructed at I-75 and S.R. 741 near Dayton, Ohio, will be April 20th. The new Continuous Flow Intersection (CFI) will be the fourth built within the United States.
The largest CFI built to date was completed near Baton Rouge, La., in 2006 to ease congestion in and out of the airport. Traffic had become increasingly snarled as more travelers used the Baton Rouge airport to get to and from New Orleans after Hurricane Katrina. Smaller CFI versions exist in Maryland and New York.
According to the design firm ABMB Engineers Inc., which served as technical consultants for the Ohio project, “the objective of CFI is to move the left-turn conflict out of the main intersection. In a typical CFI intersection, this is accomplished with a signalized left-turn bay placed several hundred feet before the intersection. The left turn leg feeds a special CFI leg, which in turn empties into the cross street near the main signalized intersection. The signals at the left-turn bay, CFI crossover, and main intersection are all operated by a single controller and coordinated to provide smooth continuous traffic flow.”
The $34.4 million project includes demolition of the existing overpass at Miamisburg-Springboro Pike and I-75, construction of the new two-leg CFI at Miamisburg-Springboro Pike/Austin Road, widening of Miamisburg-Springboro Pike between Wood Road and S.R. 741, and reconstruction of the intersection of S.R. 741 and Miamisburg-Springboro Pike. The CFI portion of the cost is estimated to be $22 million.
Sherry Wampler-Ley, ODOT district 7 project manager, said the CFI is being used based on traffic volumes at S.R. 741/Austin Pike because other dual lane designs didn’t work, based on the traffic volumes now, and those expected in the future. Construction is less expensive, less land is needed, it avoids traffic conflicts, and a lot of traffic can be moved without a lot of delay.
According to information provided on ABMB’s Web site, CFI’s are either under design or under construction in Utah and Mississippi, and are being considered in Arkansas and Texas. The prototype was built at Dowling College in New York, followed “by a full-scale project in Maryland, at the juncture of State Highway 228 and State Highway 210, approximately 15 miles south of Washington, D.C.” The site states that more than 40 CFIs have “proven their value in Mexico in the last decade, where they have reduced congestion and are well-accepted by motorists.”
The benefits of using the CFI as spelled out by the Ohio Department of Transportation include “improved access to and from I-75, congestion relief on adjacent state routes and existing interchanges on I-75, and support of existing and proposed economic development.”
Standard remedies for congested intersections have historically included additional turn lanes and signals, changing traffic patterns, eliminating traffic flow in one or more directions, or adding a grade-separated interchange. The CFI is seen as a lesser expensive solution than the grade-separation, and more long-term than additional lanes and signals.
A “CFI is an at-grade design that provides comparable levels of vehicular flow to grade-separated interchanges at a fraction of the cost — and dramatic, long-term improvements over conventional at-grade approaches,” according to ABMB’s Web site.
Miamisburg-Springboro Pike closed to traffic on March 30 to begin demolition of the existing bridge over I-75, according to Denise Heitkamp, ODOT’s district 7 public information officer. New ramps to and from I-75 are scheduled to be built between April and September 2009. Installing new bridge piers and the setting of beams for the new bridge will take place this summer, with the installation of a new noise wall in September. The new bridge is scheduled for completion in December. Completion of the entire project is expected in fall 2010.
ODOT’s Heitkamp doesn’t expect lane restrictions on I-75, but lanes may be shifted during construction. Detours will include Miamisburg-Springboro Road between Wood Road and SR 741, Pennyroyal Road, and Wood Road back to Miamisburg-Springboro Road. The southbound ramp from I-675 to I-75 will have one lane closed during construction and traffic on SR 741 will be shifted.
Simulations using specialized traffic modeling software “show that CFI outperforms conventional alternatives dramatically. In case after case, CFI produced extraordinary improvements in levels of service under existing traffic loads and reductions in average intersection delay of 90 percent or more,” according to ABMB.
Other advantages of CFI outlined by ABMB include:
• Achieves significantly more capacity than conventional at-grade intersection designs.
• Offers substantial savings over grade-separated alternatives while providing equal or better performance.
• Can be deployed in one-, two-, three-, and four-legged versions.
• Requires little more right-of-way than a conventional at-grade intersection.
• Provides clear lines of sight, avoiding the visual barriers created by overpasses.
• Helps reduce pollution by reducing congestion.
• Requires shorter construction time and less utility relocation.
The CFI built at Airline Highway and Siegen Lane/South Sherwood Forest Rouge in Baton Rouge saw a reduction of peak travel delays from three to four minutes per car or truck to less than half a minute.
For more information on CFI, visit www.abmb.com/cfi.html. CEG