CDOT marks completion of department’s first continuous flow intersection

Durango, Colo. — Colorado Department of Transportation (CDOT) and contractor, Concrete Works of Colorado held a grand opening event to mark the on-schedule completion of work for the US 160/US 550 Continuous Flow Intersection, a first for the department.

The work began on March 17 with the contractor, Concrete Works of Colorado, completing work on the urban section’s through lanes prior to the Memorial Day holiday weekend. The project wrapped up August 15, meeting the projected “mid-August” completion date. The total project cost, from design through construction, is $6.69 million, a third of which came from federal safety funds.

A CFI effectively removes a left-turn movement from an intersection by re-configuring the highway to allow vehicles to cross to the left side of the highway in advance of the intersection. Removing this turn phase from the main intersection allows for additional concurrent traffic movements that are not possible at a conventional signalized intersection. These additional concurrent movements increase signal efficiency and provide the opportunity for longer green times for southbound and eastbound movements at US 160/US 550.

“While there is an additional signal to accommodate CFI cross-over traffic, there are still more green phases occurring at the same time,” CDOT Project Engineer Tommy Humphrey said. “This results in more time given to continuous traffic flow for all users, which in turn leads to increased intersection safety and decreased congestion.”

The US 160/US 550 intersection currently sees 28,000 to 36,000 vehicles per day, depending upon season and future traffic volumes are expected to continue to increase. It is the most heavily traveled intersection on the Western Slope. As with every major intersection, CDOT conducts ongoing intersection and corridor analyses (data on collisions, traffic counts, traffic patterns, signal wait times, etc.) Prior to the project, this intersection was functioning at a “Level of Service D,” with traffic back-ups particularly heavy for westbound left turns.

“This project meets one of CDOT’s top priorities, which is to ‘get more out of the existing highway system — improving mobility through better operations, management and innovation without adding capacity,” CDOT COO/Deputy Executive Director Scot Cuthbertson said.

Improving traffic flow by making operational changes at the US 160/US 550 intersection meant also making highway and intersection improvements to the north and west. The CDOT project team had three main goals: increase safety and efficiency of US 160/US 550 intersection and enable it to handle increasing multimodal traffic volumes well into the future; provide enhanced traffic flow and improved safety at the congested US 550 (Camino del Rio)/College Drive intersection to the north; and work in coordination with the City of Durango’s Multimodal Unit to improve bicyclist and pedestrian transportation features.

“We looked to the Utah Department of Transportation (UDOT) when we envisioned these intersection improvements, as they’ve constructed numerous CFIs,” CDOT Region 5 Traffic and Safety Engineer Mike McVaugh said. “Now UDOT is looking to us on how to incorporate bike and pedestrian mobility into their CFIs. This project has been a great example of implementing multimodal forms of transportation and partnerships.”

CDOT worked in coordination with the City of Durango when designing, gathering public input and installing the many multimodal features on this project (see features listed below.)

The CFI is a proven approach to reducing congestion and increasing safety at high-traffic intersections, based on other CFIs constructed nationwide and worldwide.

“With CDOT’s traffic modeling, a CFI proves to be the right fix,” Humphrey said, “and with much of the infrastructure needed for a CFI already in place prior to the project, it is an economical fix for this urban intersection.”

The project team determined that a higher-cost interchange would provide minimal additional benefits due to its close proximity to the College Drive signal and future signalized intersections on US 160 West. A roundabout could neither handle the amount nor directional distribution of traffic at US 160/550. According to the Federal Highway Administration, a CFI “provides additional advantages over conventional designs under a wide spectrum of traffic conditions including the following: 1) increased intersection capacity that could postpone or even eliminate the need for future grade-separated interchanges and 2) potential safety measures to reduce crashes at high crash sites.”

CFIs in Other areas: The first CFI in Colorado was constructed in 2010 by the City of Loveland (see article on results at www.reporterherald.com/ci_18831980). As cities, counties and states work to solve traffic congestion challenges across the nation, more and more are turning to the CFI. CFIs have been in operation around the world for over 20 years. The first CFI in the U.S. was built in 1996 in Shirley, N.Y., and Other CFIs can be found in places such as West Valley City, Utah; Fenton, Mo.; and Lafayette, La.

Additional project features include the following:

Improvements at Camino del Rio (US 550) and College Drive to the North – The traffic signal and College Drive lanes approaching US 550 (Camino del Rio) are reconfigured for more efficient signal operation for all approaches. The busiest stretch of College is westbound between US 550 and Main Street, which daily sees 600-vehicles per hour during the summer evening peak hours. The improved WB lane configuration accommodates this majority by providing additional lanes and turn movements at the signal; bike lanes heighten awareness and accommodate the increasing number of cyclists.

Improvements for Bicyclists – There are cycling features on Camino del Rio, College and 9th streets. Improvements include: bike lanes, green bike boxes (designated spaces in front of stopped motorized traffic, green sharrows (bike symbols with arrows), signing and bicycle capable signal detection.

Improvements for Pedestrians (adhering to federal ADA law and state statute on pedestrian safety and mobility) — Raised curbed medians and islands, raised crosswalks to increase pedestrian visibility, Rectangular Rapid Flash Beacons and added/reconstructed sidewalks.

Transit Mobility – A “DO NOT BLOCK” intersection box (large white box with X) is painted in the intersection at Camino del Rio (US 550) and 8th Street, accompanied by a sign, to help keep the intersection clear for buses turning into the city’s transit center.


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