- Name of the project: Tam Diep Tunnel
- Location: Thanh Hoa
- Year of commencement: 2021
- Year of completion: 2023
Tam Diep Tunnel is part of Package 10 XL – North – South Expressway Project, section Mai Son (Ninh Binh) – National Highway 45 (Thanh Hoa). Tam Diep Tunnel connects the expressway between Ninh Binh and Thanh Hoa provinces on the journey from Hanoi to the South. Tam Diep Tunnel has 2 independent tunnels, running parallel, about 50 meters apart, each tunnel is 245 meters long, with a cross-section width of 14 meters – equivalent to 3 car lanes.