Seoul Mayor Oh Se-hoon inspects the site of the Gangbuk Crossing Underground Urban Expressway project near the Hawolgok Junction on the Northern Bypass Road in Seongbuk-gu, Seoul, on Dec. 22 last year. [Seoul Metropolitan Government]
Seoul Mayor Oh Se-hoon inspects the site of the Gangbuk Crossing Underground Urban Expressway project near the Hawolgok Junction on the Northern Bypass Road in Seongbuk-gu, Seoul, on Dec. 22 last year. [Seoul Metropolitan Government]

The Seoul Metropolitan Government is set to launch a planning study for the Gangbuk Crossing Underground Urban Expressway project using a supplementary budget. The project envisions demolishing the Inner Circular Road and the Northern Bypass Road in northern Seoul and routing traffic through a new underground highway.

The city is preparing to commission a study titled "Gangbuk Crossing Underground Urban Expressway Implementation Plan," with a total budget of 1 billion won ($675,000). Of that amount, 300 million won will be secured through a supplementary budget, allowing the city to issue the contract in September. The study is expected to run for one year, with the remaining 700 million won to be covered by next year's main budget. "We are currently going through additional procedures with the budget division," a Seoul city official said. "Since this is Mayor Oh's campaign pledge, we plan to move forward with a sense of urgency."

Seoul Mayor Oh Se-hoon personally announced the Gangbuk Crossing Underground Urban Expressway construction plan last December, saying the project "will serve as the core strategy of the 'Gangbuk Renaissance' initiative, dramatically enhancing the area's competitiveness." He added that he would "do his utmost to elevate Gangbuk's competitiveness and quality of life to the next level through seamless project execution."

The plan was also included as a key campaign pledge in the June 3 local elections. With the commissioning of this study, the project — which had previously existed only as a "recommendation" raised by National Assembly members and Seoul Metropolitan Council lawmakers — has now moved within sight of becoming reality.

Mayor Oh visited the Northern Bypass Road near Dolgoji Station on subway Line 6 last December, where he received a briefing on the project's implementation plan. He stressed that "the elevated expressway cuts through residential areas, degrading local development and living conditions, while aging infrastructure continues to generate maintenance and safety concerns — making it urgent to push ahead." He added that "the Gangbuk Crossing Underground Urban Expressway will resolve chronic traffic congestion, improve the urban landscape and enhance public safety."

The project calls for constructing a new six-lane underground road spanning approximately 20.5 kilometers beneath the Inner Circular Road and the Northern Bypass Road, which run across northern Seoul between Sungsan Interchange and Sinnae Interchange. The existing elevated structures would be demolished after the underground road opens. The goal is to eliminate the functional decline of aging overpasses and restructure the inefficient urban layout they have created, transforming the area into a future-oriented urban space where transportation, residential and natural environments coexist.

Opened in the 1990s, the roads have long served as key arteries for rapid movement through central Gangbuk, but their effectiveness has deteriorated significantly. About 4.54 million people — 47 percent of Seoul's total population — live in the Gangbuk area, yet the district accounts for only 96 kilometers, or 40 percent, of the city's 243-kilometer urban expressway network. Gangnam, by contrast, has 147 kilometers, or 60 percent of the total. The Sungsan-to-Hawolgok section handles about 130,000 vehicles a day, while the Hawolgok-to-Sinnae section sees roughly 90,000, with recurring congestion during rush hours. Average rush-hour speeds have fallen to 34.5 kilometers per hour, leading some experts to conclude the roads have already lost their function as arterial routes.

The elevated structures also occupy a large portion of the surface area, causing neighborhood fragmentation and hindering local development. The shade, noise and blighted conditions beneath the overpasses have weakened connectivity between surrounding commercial areas and residential neighborhoods, lowered pedestrian quality and long acted as a drag on local development. As the structures age, maintenance costs have also grown. Annual upkeep for the Inner Circular Road and the Northern Bypass Road is projected to more than double, rising from 39.1 billion won this year to 98.9 billion won by 2055.

The city has estimated the total project cost — covering underground highway construction, demolition of the existing elevated roads and surface road improvements — at 3.4 trillion won. That figure is a preliminary estimate at the planning stage. The city plans to refine the project's scope and implementation approach after a comprehensive review of traffic demand forecasts, congestion-relief effects and fiscal conditions.

In March, the city formed a public-private-academic policy consultative body for the project, bringing together community representatives, experts and city council members from the six most affected districts — Mapo-gu, Seodaemun-gu, Jongno-gu, Seongbuk-gu, Jungnang-gu and Nowon-gu. Two meetings have been held since the body's inaugural session in March. "Everyone welcomes the demolition of the overpasses, but concerns have also been raised about traffic congestion during construction and the placement of interchanges," a city official said. "We plan to incorporate the concerns and proposals from the consultative body into the study."


cook@heraldcorp.com