Officials say the DDIs will reduce wrong-way turns and rear-end collisions. Motorists should simply follow the road markings, signals and signs.

Officials say the DDIs will reduce wrong-way turns and rear-end collisions. Motorists should simply follow the road markings, signals and signs.

Photo by Deb Jacques


New interchange at 14 Mile and Big Beaver operational soon

By: Andy Kozlowski | Troy Times | Published December 21, 2020

 The new interchanges opening soon on Interstate 75 at 14 Mile and Big Beaver Roads in Troy are called diverging diamonds, and they promise to provide a safer and more orderly flow of traffic.

The new interchanges opening soon on Interstate 75 at 14 Mile and Big Beaver Roads in Troy are called diverging diamonds, and they promise to provide a safer and more orderly flow of traffic.

Photo by Deb Jacques

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TROY — Work is nearing completion on a new style of interchange on Interstate 75 at 14 Mile and Big Beaver roads, and officials are confident that motorists will come to appreciate the more orderly flow of traffic it creates.

The new system is called a diverging diamond interchange, or DDI. The one at Big Beaver Road is expected to fully open this month. The one at 14 Mile is looking to fully open in early 2021.

The first one in the state was implemented at I-75 and University Drive in Auburn Hills a couple of years ago. Others exist in Grand Rapids and Jackson.

In a DDI, both directions of traffic on the local road cross to the opposite side on both sides of the bridge, just for the duration of the interchange, guided by signs and signals.

This way, whether you wish to go north or south on I-75, your entrance ramp will always be on your side, without needing to cross traffic. When exiting the expressway, you can turn right or left, also without crossing opposing traffic.

“The idea behind the DDI is to make movements from the local road to the freeway and vice versa safer by eliminating conflict points, the main one being left turn movements in front of opposing traffic,” Rob Morosi, the spokesman for the Michigan Department of Transportation, said in an email. “The DDI design is much safer for non-motorized users, prevents vehicle queues that result in rear-end collisions, and helps prevent wrong-way driving on ramps.”

Prior to the DDI’s development, traffic on northbound and southbound I-75 looking to access Big Beaver Road used an access road adjacent to the freeway, while those looking to access 14 Mile Road used separate loop ramps. With the new interchange, those access roads are eliminated, and the separate exit ramps are combined into one exit for a direct connection to the east and west.

The interchanges are part of the larger project to modernize I-75. Currently, the segment between Coolidge Highway and 13 Mile Road has freeway lanes, shoulders and ramps paved out, with more remedial work to complete going into the spring, which includes completing sound walls, getting the DDIs fully operational, and some other minor items before that section is complete.

The segment between Eight Mile Road and 13 Mile Road started in earnest last year. In 2021, crews will focus on southbound I-75, rebuilding from Interstate 696 to Eight Mile. The northbound stretch there has already been completed. The sections between I-696 and 13 Mile Road will be completed in 2022 and 2023.

Bill Huotari, a city engineer and traffic engineer for Troy, said there are numerous benefits to the DDIs being set up in the city.

“First and foremost, a DDI improves safety. A DDI reduces the number of potential conflict points for both motorists and pedestrians. The DDI is also anticipated to improve mobility by reducing congestion and improving traffic flow,” Huotari said in an email. “The city of Troy is excited to see the new DDI in operation as part of the opening of Segment 2 of the I-75 project.”

Troy Mayor Ethan Baker said he sees the DDIs as a boon for the city’s infrastructure.

“The city of Troy is very fortunate to have I-75 literally run right through the middle of our city, essentially creating our Big Beaver Golden Corridor  ‘downtown’ at Exit 69.  I’m greatly looking forward to having this modernization project completed, so that our restaurants and businesses along Big Beaver can be given every opportunity to rebuild and thrive as we come out of COVID-19. We have some fantastic small businesses along Big Beaver that have been very patiently waiting for the modernization construction to end,” Baker said in an email.

“The new and improved I-75 and additional sound walls will serve our community very well for many years, and having Michigan’s first (high-occupancy vehicle) lanes in and through Troy will benefit all of metro Detroit,” he added. “As we shift from the construction to landscaping phase of this project, look for some aesthetic improvements in 2021 at our new Big Beaver DDI interchange, spearheaded by our Downtown Development Authority. A grand and new gateway to Troy is coming!”

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