Residents have voiced their opposition to the proposal from the Expressway Authority of Thailand (Exat) to build an underground route as a replacement for a contentious section of the N1 Expressway development, following a 17-month preliminary feasibility study.
Exat recently conducted a third hearing regarding the project at a hotel located in Bangkok’s Chatuchak district, which was attended by more than 50 residents. During the meeting, concerns were raised by individuals such as Manawat Kamolsilp, who pointed out that constructing the underground route could cost approximately 50 billion baht compared to the 17 billion baht required for the elevated expressway.
Manawat argued that building an underpass would be more cost-effective and simpler to integrate with other projects. He mentioned that the maintenance expenses for the elevated expressway would be lower, resulting in cheaper toll fees for users.
Lt Gen Mahatthana Kamolsilp, another local resident, highlighted that residents had already experienced land expropriation for the expressway construction in previous years. The potential need for additional land expropriation for the proposed underground route could further disrupt the community, he explained.
Exat governor Surachet Laophulsuk indicated that the agency plans to finalize the project details for submission to the Transport Ministry for review before seeking cabinet approval. An environmental impact assessment is expected to be carried out early next year.
If the cabinet approves the project, the bidding process is tentatively scheduled for 2026, with construction slated to commence the following year. Surachet emphasized that after considering various factors such as engineering, costs, and environmental impact, the underpass was deemed the most viable option.
The 6.3-kilometer underpass, envisioned as the nation’s inaugural expressway tunnel, will traverse Ngarmwongwan Road through key intersections before linking up with the N2 Expressway. The design features a cut-and-cover structure with an entrance and exit spanning 1.75km and an elevated section of 2.49km to connect with the N2 Phase expressway.
Surachet disclosed that the tunnel would tower over 40 meters high, equivalent to a 10-story building. The project, including construction of the underpass and associated structures, is estimated to cost 49 billion baht. Construction costs will make up 44.5 billion baht, with additional funds allocated for land expropriation and construction supervision.
Exat intends to potentially self-fund the project due to its financial stability, considering the issuance of bonds to secure construction financing if necessary. The construction is anticipated to span roughly five years, with an estimated daily traffic volume of 70,000 vehicles in its initial year of operation, utilizing half of the route’s capacity.
Surachet expressed confidence that the proposed underpass would effectively address environmental concerns raised during the project’s development. He also mentioned the division of the expressway project in the northern region into two stages, with the N2 section covering a specific stretch and the N1 section being reevaluated with an underpass solution following discussions and consultations with stakeholders.
