The Diverging Diamond Interchange (DDI) has emerged as one of the most effective and innovative interchange designs for improving traffic operations and enhancing roadway safety. TDOT Region 1 currently has four DDIs either in operation or under construction, including locations in Alcoa/Blount County, US-129, Alcoa Highway, at Bessemer Street, I‑40 at SR‑66 in Sevierville/Sevier County, and SR‑354 at I‑26 in Johnson City/Washington County, with an additional DDI under construction at I‑75/SR‑131 (Emory Road) in Knoxville/Knox County. These projects demonstrate TDOT’s commitment to implementing forward‑thinking solutions that address growing traffic demands across the region.

The DDI design improves traffic flow by eliminating traditional left‑turn conflicts and using a coordinated signal system that reduces stops, minimizes delay, and increases throughput. By shifting traffic to the opposite side of the roadway within the interchange, DDIs allow for free-flowing left-turn movements and shorter signal phases, resulting in significantly better operational performance compared to conventional interchange configurations. Safety is also enhanced through reduced conflict points, simplified driver decision‑making, and lower crash potential.

Collectively, TDOT Region 1’s DDI implementations highlight the benefits of innovative roadway design, including improved traffic operations, increased safety, and more efficient movement of people and goods. As traffic volumes continue to grow, these interchanges represent a vital investment in the region’s mobility and long‑term transportation network reliability.

*This session may not qualify for PDH/API certification