EXAT, the Expressway Authority of Thailand, said bidding could start in 2026 with construction starting in 2027 and opening in 2030.

A tunnel as part of the N1 Expressway might alleviate congestion in the Thai capital Bangkok (image © Siiixth/Dreamstime)
Laophulsuk also said an environmental impact assessment would be completed in May and then be submitted to the government for approval.
A report in The Nation newspaper noted that the 6.7km double-deck tunnel, which will be the country's first expressway tunnel, would bypass the heavily congested Kaset-Nawamin intersection in Bangkok’s Bueng Kum district. Traffic volume is estimated at 70,000 vehicles per day.