McCalla, Ala. — Construction has officially started on a $22 million Diverging Diamond Interchange (DDI) project at Exit 104 on Interstate 59/20 in McCalla, south of Birmingham, the Alabama Department of Transportation (ALDOT) confirmed. The project is designed to improve traffic flow, reduce crashes, and provide easier access to surrounding communities and industrial areas.
The DDI design, first installed in Springfield, Missouri, in 2009, allows vehicles to cross to the left side of the road at one end of the interchange and then return to the right side at the other end. This eliminates traditional left-turn conflicts and increases traffic efficiency.
“As drivers approach one side of the bridge, the DDI design allows traffic to gently transition from the right side to the left and then back again at the other end of the bridge,” ALDOT officials wrote. “Drivers will make all left turns without crossing opposing traffic since it travels on the left side of the bridge.”
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The project, expected to be completed by fall 2026, will transform the interchange at McAshan Drive, offering access to the Rock Mountain Lakes community and Jefferson Metropolitan Park. The corridor serves several industrial campuses, including the recently opened $1.1 billion JM Smucker Uncrustables plant.
Funding comes primarily from Jefferson County, which is contributing $14 million. The remainder is provided through a mix of federal and state sources, including $2 million from the Rebuild Alabama Act and $6 million from the Federal Interstate Maintenance Fund.
ALDOT highlighted that DDIs are not only safer but cost-effective. Research by the Federal Highway Administration shows that DDIs reduce costs by 75%, cut vehicle conflict points by 50%, and increase traffic efficiency by 30% compared with conventional intersections. Alabama’s first DDI opened in Baldwin County in 2020, and as of June 2024, 150 similar interchanges exist across the country.
Motorists should anticipate temporary lane closures and traffic shifts throughout the project. Additional improvements include planned interchanges at I-65 and Lakeshore Drive in Homewood and the future Exit 9 on I-459 in Hoover, enhancing regional connectivity.
The DDI project represents a forward-looking approach to roadway design in Alabama, balancing safety, efficiency, and economic development. Officials say local residents, commuters, and industrial traffic will all benefit from reduced congestion and smoother travel once construction is complete.
Originally reported by Kayode Crown in Alabama. Com
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