For a few decades now, dozens of municipalities around the country have adopted an intersection design commonly known as the continuous flow intersection (CFI).
The CFI is designed to allow vehicles attempting to turn across the opposing direction of traffic to cross before they enter the intersection. This makes left turn signals in the intersection unnecessary, as vehicles traveling in both directions can proceed when a generic traffic signal or stop permits.
The Florida DOT (FDOT) adopted this design with the help of its engineer of record, Dewberry, at the intersection of S.R. 82 and Daniels Parkway/Gunnery Road as part of the S.R. 82 from Lee Boulevard to 40th Street widening and reconstruction project. Initially, the designer looked into several preliminary designs, including an overpass option, to address the notorious backups at this intersection. “It was determined that with the space we had available and the right of way that we had available, that while innovative, [the CFI] would also meet the peak traffic volumes that we were encountering in the morning and afternoon,” Tom Deer, P.E., senior project engineer for Kinard Stone Inc. (KSI)—which provided construction, engineering and inspection for FDOT—told Roads & Bridges. “So mainly it was, without having to do bridge construction, we were able to still achieve the objective of getting the number of cars through the intersection.”
While CFIs are becoming more common in the U.S., the Daniels Parkway/Gunnery Road CFI is the first to be constructed in the state of Florida. For this intersection, motorists are able to make a left turn from S.R. 82 onto Daniels or Gunnery before they reach the main intersection. Three sets of signals, one at each of the crossover points as well as at the main intersection, are all interconnected using a single traffic controller.
For FDOT, the CFI became a solution to solve the issue of major traffic backups at the intersection, which was an important corridor for an area seeing high growth and heavier truck traffic. Additionally, along a nearly 5.5-mile stretch of S.R. 82, the roadway was widened from two lanes to six lanes to accommodate growing traffic demands. “When it was on two lanes of traffic, you had a lot of people trying to speed and pass trucks, or were just not using the roadway as intended,” Deer said. “The department had done multiple projects to try and enhance safety—including rumble strips. Ultimately, they advanced the funding to widen the section so that we’re on to six lanes.”
Over the course of the project, the team had to implement an aggressive public outreach campaign to educate drivers on the benefits of the CFI and how to navigate it. “We had to educate the public on how to use the left turns because the opening is approximately 600 ft prior to the intersection,” Deer explained. “But you’ve got a long left-turn lane to even get over there, and then there’s a signal there. You wait until availability, and then you cross over it. It’s not a natural feeling at first, but then once you start using it, it’s pretty normal.” The extensive six-week public outreach program included TV commercials as well as information on the FDOT website, which included videos, to explain how drivers would make left turns from S.R. 82 to Daniels/Gunnery Road.
The CFI contained 10 in. of concrete paving, correlating to 53,095 sq yd or 164 truckloads of concrete. For the contractor, some of the challenging aspects of placing 10-in.-thick concrete pavement included nailing the grades through the crown of the intersection, which split into two directions at the heart of the configuration and shed stormwater past the feeder ramps and turn lanes. This was accomplished by matching the longitudinal and transverse joints at each adjacent pour and keeping individual grades to the plan.
Another challenge for the contractor and FDOT was keeping traffic moving while placing an entire intersection. “That part was difficult because we ended up breaking the intersection into four separate cycles—north, south, east, west,” Deer said. “They were all given about two minutes of green time, and you were allowed to make left turns, go straight, and right turns. And it did cause an impact, even then—it would take longer for peak hours to get through, because you could only have ‘X’ number of traffic, and there were only really two lanes.” For one of the traffic shifts, the team closed down the intersection over an extended weekend to build up the CFI.
The work on this stretch of S.R. 82 was the first of seven segments to be completed by FDOT. While the first segment initially only stretched from Lee Boulevard to Shawnee Road, FDOT decided to accelerate the second segment, and extended the contract for an additional $1.4 million to complete work up through 40th Street. As of this writing, six lanes of the project from the CFI to Lee Boulevard are now open to traffic, and the last touches on the project are expected to finish up this month.
