Seoul to Build Underground Expressway Across Gangbuk for 3.4 Trillion Won

The Seoul Metropolitan Government announced plans to construct an underground expressway across Gangbuk by relocating the Inner Ring Road and Northern Arterial Road underground, investing approximately 3.4 trillion won ($2.4 billion) in the project.

The Inner Ring Road and Northern Arterial Road, which opened in the mid-1990s, are major vehicle routes in northern Seoul. The city determined that the massive elevated highway structures have caused regional fragmentation and hindered development, while also creating chronic traffic congestion and increasing safety risks and maintenance burdens due to aging infrastructure.

The city unveiled the Gangbuk Cross Underground Urban Expressway construction plan on Sunday, which includes expanding lanes through underground relocation and improving surrounding areas. The plan aims to enhance transportation functions in the Gangbuk area and reorganize urban structure in harmony with living and natural environments.

A six-lane underground road spanning approximately 20.5 kilometers will be constructed from Seongsan Interchange, where the Inner Ring Road begins, to Sinnae Interchange at the end of the Northern Arterial Road. After the underground road opens, the existing elevated highways will be demolished. Once demolition is complete, additional surface roads will be secured using the space previously occupied by the structures, which is expected to increase overall vehicle capacity beyond current levels.

The city plans to create waterfront leisure spaces along Hongje Stream and Mukdong Stream, which have been affected by obstructed views from existing elevated structures, and restore the fragmented urban structure to improve cityscape and residential environment across the Gangbuk area.

Considering traffic conditions, regional circumstances, and fiscal situation, the city will proceed with the Seongsan-Hawolgok-Sinnae section as Phase 1, followed by the remaining Hawolgok-Seongdong section of the Inner Ring Road as Phase 2.

The city expects the project to improve living conditions for approximately 2.8 million residents across 134 administrative districts in eight autonomous districts in Gangbuk, with significant effects on restoring regional competitiveness and urban vitality.

The total project cost for underground expressway construction, existing elevated road demolition, and surface road improvement is estimated at approximately 3.4 trillion won. This is a provisional figure at the planning stage, and the city will determine specific project scale and implementation methods through comprehensive review of traffic demand forecasts, congestion relief effects, and fiscal conditions.

Starting next year, the city will establish and operate the "Gangbuk Golden Era Planning Group," a joint task force of relevant departments, to ensure smooth project implementation. A public-private-academic consultative body involving the city, autonomous districts, local residents, and experts will be formed to develop detailed plans. The city will gather diverse opinions through working meetings, public hearings, and forums to create surface space plans tailored to project direction and regional characteristics. Following these preparations, the project aims to break ground in 2030 and complete construction by 2037.

"Gangbuk's leap forward is the starting point of a major transformation that rewrites Seoul's future, going beyond simple regional balance," Seoul Mayor Oh Se-hoon said. "The Gangbuk Cross Underground Urban Expressway construction project will be the core strategy of 'Gangbuk Golden Era, Again' that dramatically enhances regional competitiveness."

He added, "We will do our best to elevate Gangbuk's competitiveness and quality of life through seamless project execution."