Underground Road to Be Built Between Yangjae and Olympic-daero, a Chronic Traffic Bottleneck; Construction Targeted for 2028

[Financial News] A project to build an underground road between the Gyeongbu Urban Expressway in Yangjae-dong and Olympic-daero in Jamwon-dong, one of Seoul’s chronic traffic bottlenecks, is moving forward in earnest.
According to Seoul Metropolitan Government on the 13th, it released the draft strategic environmental impact assessment for the privately financed underground-road project between Yangjae and Olympic-daero on the 10th and will make it available for public inspection until the 16th of next month.
The project calls for constructing two underground roads—one for each direction—over a 7.65-kilometer section from the Gyeongbu Urban Expressway in Yangjae-dong, Seocho-gu, to Olympic-daero in Jamwon-dong. Seoul Metropolitan Government plans to begin construction as early as 2028.
According to the draft, each road would be 9.25 meters wide and consist of two lanes reserved for small vehicles, with traffic flowing in both directions. The northbound route would run beneath Gangnam-daero, to the right of the Gyeongbu Urban Expressway, before connecting to Olympic-daero near Hannam IC.
The southbound route would enter the underground section of Seochojungang-ro near Banpo Bridge on Olympic-daero, pass through the areas around Seoul National University of Education Station and Nambu Bus Terminal Station, and emerge near Sangchon Bridge to connect with the existing road network.
The plan includes 10 access facilities: two on the Gyeongbu Urban Expressway, four on Olympic-daero, and four on urban roads. It also calls for three vertical shafts, as well as one tunnel management office and one integrated operations management office. The total tunnel length, including the main underground roads and connecting routes, will be 18.888 kilometers.
After reviewing two options, Seoul Metropolitan Government concluded that the current plan, which uses underground sections beneath Gangnam-daero and Seochojungang-ro, is more suitable than the second option, which would pass beneath the existing Gyeongbu Expressway.
The project will be carried out under the build-transfer-operate (BTO) private investment model. Construction is scheduled to take 66 months after groundbreaking, followed by a 40-year private operating period after completion. The total project cost is KRW 1.1053 trillion, including an estimated KRW 949.1 billion in construction costs.
[email protected] Jung Kyung-soo Reporter