By Steve Plunkett
City officials want to put the brakes on the plan to build a “diverging diamond interchange” at Glades Road and Interstate 95 until the state assures them the design is safer and better than other approaches.
“Our concern obviously is safety No. 1, but also if they’re going to do a project that is going to be in place for 30 years, we want it to be successful and beneficiary, as [opposed] to detrimental and doesn’t work and causes a bigger problem long term,” City Manager Leif Ahnell said.
The Florida Department of Transportation’s original concept, presented to the city in March 2016, included a “flyover” ramp that would divert westbound traffic on Glades headed for the interstate away from the intersection with Airport Road.
That intersection has one of the highest traffic volumes in the city and one of the highest crash incidences, Zach Bihr, the city’s municipal services director, said at the March 9 City Council workshop.
With a flyover, “This traffic is separated from the rest of the vehicles traveling on Glades and removed from the intersection of Glades and Airport Road,” Bihr said.
Prince Contracting, the design-build firm spearheading the DDI design, was supposed to present its plan for final approval to the FDOT’s central office and the Federal Highway Administration on April 23 provided the coronavirus battle did not affect the schedule.
Bihr said he wanted to know that the DDI design is as safe as the flyover concept with the grade separation for the interchange. He also questioned the benefits touted by FDOT of the diamond design’s reducing left-hand turns and the number of traffic signal phases.
“The interchange in its existing configuration does not have left-turn movements in any direction onto the interchange,” Bihr said.
He also said a Federal Highway Administration report recommended no less than a 45-degree angle between opposing approach lanes but said the DDI plan uses approaches of 15, 17, 19 and 25 degrees.
“Staff is concerned that too flat an approach angle may lead to inadvertent maneuvers down the wrong way of an interchange,” Bihr said.
City traffic engineer Maria Tejera added that she does not understand how the diamond interchange’s level of service will be better than that of the original concept where the flyover took traffic out of the intersection.
She said the FDOT should provide traffic simulations for each peak period for the entire project corridor so she could see how Boca Raton would coordinate red lights.
Deputy Mayor Jeremy Rodgers wanted to skip to the bottom line.
“Where does that leave us?” he asked. “Can we put the stop on this? Where do we go from here?”
Mayor Scott Singer said Boca Raton should ask its state and federal lobbyists to help. Council member Andy Thomson agreed.
“I was under the impression, this is just the way it’s going to be. Yes, we’re going to come tell you, city of Boca Raton, and we hear you, but put your comment in the comment box,” Thomson said. “If that means calling in the government relations folks, we absolutely have to do that.”
In a diverging diamond interchange, drivers switch sides of the road at multi-lane X crossings guarded by traffic signals at either end of the diamond. The synchronized signals “facilitate the smooth flow of traffic, reducing delay times and minimizing conflict points,” the FDOT said. A DDI would decrease travel time, improve safety and mobility at the interchange and handle expected traffic increases through 2040, the agency said.
Its diamond interchange in Sarasota, the first in Florida and the largest in the nation, won the American Council of Engineering Companies’ National Recognition Award in April 2018.
The Glades Road interchange, part of a $148 million project to add express lanes to Interstate 95 through Boca Raton and into Delray Beach, is scheduled to open in late 2023.