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Hanson’s study delivers fresh concept for Florida interchange

Are you prepared to drive on the left side of the road? An innovative design to relieve traffic congestion and improve safety is making a European experience possible in the United States. This design will help motorists spend less time in traffic and more time traveling safely to their destinations on time.

Hanson’s project development and environment (PD&E) study for Interstate 95 and 45th Street proposes the first diverging diamond interchange (DDI) for the Florida Department of Transportation’s (FDOT) five-county District 4. I-95 is the main interstate highway on the East Coast, stretching 1,920 miles from Miami to the Canada-U.S. border. 45th Street connects West Palm Beach to the town of Mangonia Park. The 18th busiest container port in the U.S., the Port of Palm Beach, is 4 miles from the interchange. Consequently, there is a lot of traffic on I-95’s 10 divided lanes and the six divided lanes on 45th Street. The interchange carries more than 41,000 heavy freight trucks daily. The site has frequent traffic jams, congestion and accidents. If implemented, the DDI — which causes traffic to briefly cross over to the opposite side of the road — would solve traffic problems that a conventional diamond interchange would not.

Hanson’s study tied for first in the Outstanding PD&E/Planning Project category in the American Council of Engineering Companies of Florida’s 2019 Outstanding Project Awards.

What is a PD&E study? According to FDOT, it’s an environmental and engineering process that the agency developed to identify the economic, natural and physical environmental impacts a proposed transportation improvement project will have on the project area if the project is implemented. It follows the National Environmental Policy Act of 1969, along with federal and state laws and regulations. It is similar in scope to an environmental impact statement, which is a process often used in other states.

A new concept

In March 2016, the project team began studying how to alleviate existing and future traffic congestion, identifying the short- and long-term needs of I-95 and improving safety at the interchange. Traffic backing up to the mainline of I-95 has to be prevented in the short-term; long-term, the interchange needs to accommodate future traffic demand.

Jeff Easley, P.E., a vice president and senior project manager at Hanson’s Miami office, led Hanson’s project team during the study, which included a comprehensive public involvement program.

This rendering shows the recommended diverging diamond interchange (DDI) at I-95 and 45th Street.

The program included kickoff meetings, alternatives workshops, hearings, a project website and coordination with local municipalities. Hanson met several times with the city of West Palm Beach, town of Mangonia Park, Palm Beach County and the Port of Palm Beach to gain approval for the study’s recommended alternatives. This collaboration resulted in Hanson’s DDI recommendation. Public input also fine-tuned this DDI.

A DDI is a specialized diamond interchange where through lanes of the non-freeway road cross over each other twice.

“While the DDI might be a new concept and a new experience for motorists, it’s actually fairly easy to navigate,” Jeff said. “Specially designed traffic signals help direct motorists through the interchange, alleviating confusion about the crossover of traffic.”

Thanks to this innovative design, the number of conflict points would be reduced to 14, compared to 26 for a conventional diamond interchange.

This DDI design would improve safety at the interchange, reduce congestion and eliminate traffic jams on I-95. The DDI would also provide additional continuous lanes, two free-flow left-turn lanes to I-95, 6-foot bike lanes, additional green space, new signage, a travel information system that updates drivers on current road conditions, and transportation systems management and operations enhancements. These enhancements include adaptive signal control technology at the interchange, a vehicle detection system and CCTV cameras.

A rendering of 45th Street shows the new improvements, such as continuous lanes, bike lanes, sidewalks and an on-ramp to I-95.

This interchange alternative would allow motorists to arrive at their destinations faster and safer. Two-phase traffic signal timing shortens the lights’ cycle length, meaning traffic jams and congestion would be reduced and red lights and pedestrian crossing times would be shorter. The two free-flow turn lanes would eliminate the need for left-turning vehicles to cross the paths of approaching through vehicles. 

The DDI would have minimal environmental impact, require less land acquisition and is the most acceptable to the community. It will provide more benefits at a lower cost, compared to a conventional interchange design.  

All renderings by Classen Graphics

To learn more about this project, contact Jeff Easley at or (305) 428-4350.

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