A new interchange connecting two of metro Atlanta’s busiest highways is on track to open by the end of the year. Here’s what you need to know about construction at I-285 and Ga. 400:

The project: The Georgia Department of Transportation is spending $800 million to rebuild the interchange, which handles 420,000 vehicles a day despite being designed for 100,000. The work will feature new “flyover” ramps and collector-distributor lanes that run adjacent to both highways. When it’s done, it will be almost as big as Spaghetti Junction, where I-285 meets I-85 northeast of Atlanta.

The project also includes a new diverging-diamond interchange at Ga. 400 and Abernathy Road, plus a new bridge at Mount Vernon Highway. Since major construction began in 2017, the project has expanded to include two new I-285 bridges at Glenridge Drive and Peachtree Dunwoody Road, bike and pedestrian trails, and design adjustments for future toll lanes along the top end of the Perimeter.

The timeline: Originally, the interchange was set to open last summer. But the additional work pushed back completion to late this year.

GDOT spokesperson Natalie Dale said the project will open to traffic by the end of the year. But she said some work — such as paving, which is dependent on the weather — could continue through next spring.

What’s happening: Over the next 60 days GDOT plans to open new ramps entering and exiting Ga. 400 from Abernathy Road and from the North Springs MARTA station, a new I-285 westbound ramp to Ga. 400 northbound, and new collector-distributor lanes and ramps along I-285 in both directions. As a result, motorists can expect a lot of traffic shifts in the area.

What’s next: When the new Ga. 400 ramps open, GDOT will continue construction of the new diverging-diamond interchange at Abernathy Road and new collector-distributor lanes on Ga. 400.

When the new collector-distributor lanes and ramps on I-285 open, GDOT can begin construction of I-285 bridges over Glenridge Drive, Ga. 400 and Peachtree Dunwoody Road. That construction will require I-285 to be reduced from five lanes to three in each direction from Roswell Road to Dunwoody Road.

That reduction in lanes is expected to continue through the end of the year, and GDOT says the public will experience “major impacts.”

“We know this is going to be tough for motorists, residents and the businesses in the area,” Dale said. “But these shifts mark a major milestone in the progression of this important project. We are in the homestretch.”

May 27, 2021 Sandy Springs - Aerial photo shows construction site of I-285 interchange at Ga. 400 in Sandy Springs on Tuesday, May 27, 2021. (Hyosub Shin / Hyosub.Shin@ajc.com)
May 27, 2021 Sandy Springs - Aerial photo shows construction site of I-285 interchange at Ga. 400 in Sandy Springs on Tuesday, May 27, 2021. (Hyosub Shin / Hyosub.Shin@ajc.com)

Credit: HYOSUB SHIN / AJC

Credit: HYOSUB SHIN / AJC

May 27, 2021 Sandy Springs - Aerial photo shows construction site of I-285 interchange at Ga. 400 in Sandy Springs on Tuesday, May 27, 2021. (Hyosub Shin / Hyosub.Shin@ajc.com)
May 27, 2021 Sandy Springs - Aerial photo shows construction site of I-285 interchange at Ga. 400 in Sandy Springs on Tuesday, May 27, 2021. (Hyosub Shin / Hyosub.Shin@ajc.com)

Credit: HYOSUB SHIN / AJC

Credit: HYOSUB SHIN / AJC

More information: You can find more details about the project at https://transform285400-gdot.hub.arcgis.com/.

CONTINUING COVERAGE

Aerial photos: How the project looked in 2019

From 2020: Updates on three major road projects in metro Atlanta

From 2019: Work at I-285 and Ga. 400 means traffic hassles in north metro Atlanta

From 2016: It begins. One of the first stories after I-285 and Georgia 400 project was under way

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