TULSA, Okla. — It may look a little daunting to navigate at first glance, but experts—and data—say the Diverging Diamond Interchange design coming to Memorial Drive and the Creek Turnpike is not only safe and easy to navigate, but also reduces time spent in traffic.
Crews began work on converting the existing traditional diamond interchange at South Memorial Drive and the Creek Turnpike/US-169 in south Tulsa into a state-of the-art Diverging Diamond Interchange (DDI) Monday morning.
Work is expected to last until Spring 2024.
When complete, traffic on Memorial will flow in an unusual pattern.
As each direction of Memorial traffic passes under the Turnpike, it will go through a light, where it will crisscross drivers onto the left side of the road, before crossing back to the right side at another light after it finishes passing under the highway.
The design allows traffic exiting the turnpike to make a left turn or a right turn onto Memorial without having to worry about crossing two directions of traffic.
Need a visual? In the video above, a highway department in Florida released a visual simulation of a very similar DDI it recently built to give a better idea of how traffic moves on a completed DDI.
“They reduce the number of conflict points, which is where you could have a collision,” said TJ Gerlach, a spokesperson for the Oklahoma Department of Transportation. “They reduce that number from 26 down to about 14.”
With a DDI, you can make a left turn on red the same you can make a right turn on red now.
“The people getting off the highway don’t technically have to wait for a light,” Gerlach said. “They just mostly have to wait for yields.”
Gerlach said concrete walls and clear markings make will it easy to know where you need to go, and very unlikely—even virtually impossible—for drivers to accidentally go the wrong way.
He also said the design makes it virtually impossible for drivers to mix up an entrance ramp for an exit ramp, without driving over several concrete barriers. In turn, he says Diverging Diamonds reduce wrong-way driver incidents on highways.
“A lot of people may ask… you modeled this on the computer, is that really how traffic’s going to react to it,” said Stacey Reese, Assistant Head Engineer for the Missouri Department of Transportation’s Southeastern District. “And absolutely. We saw the improved capacity, the improved safety.”
Reese oversaw construction of the country’s first diverging diamond in Springfield, Missouri in 2009.
Since it was built, she said traffic has flown faster, and crashes went way down.
“We saw a significant drop in the number of crashes after it opened, and the rest is history,” Reese said.
She said, almost immediately, highway engineers from other states paid Springfield visits, took notes and began building diverging diamonds of their own.
“We were giving tours on almost a weekly basis,” she said.
Missouri built more Diverging Diamonds too—a lot more. And as traffic improved, they gained a cult like-following.
“Now the public will be like, why can’t we have a diverging diamond at this interchange or that interchange,” she said. “It is a pride point.”
In Oklahoma, Gerlach said ODOT looked to Missouri’s success with Diverging Diamond Interchanges when the state built its first one in 2020 in Elk City.
“Studies from those first Missouri DDIs showed about a 40 percent reduction in overall crashes,” Gerlach said.
He said drivers need to be patient as construction goes on. Memorial will be reduced to two lanes until work is done. It will briefly be down to one lane each way at times.
Gerlach said it will take a little bit of getting used to once complete, but expects—based on other states’ experiences with DDIs—drivers will get used to it fairly quickly.
“There can be a bit of an adjustment cycle as drivers get used to it. But within the first week or two it should even out,” Gerlach said.
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