The underpass will run 475 metres along the streets of Le Van Luong and To Huu, including a 95-metre long tunnel and 380 metres of access roads, each direction featuring two lanes across a width of 7.75 metres.
Parts of the pavement along the above two streets will be cropped to expand their width.
The total cost of the project is VND698 billion (US$30 million) and it is expected to be complete after 18 months.
Head of Hanoi’s transport projects management Pham Hoang Tuan said the structure is highly complex because they have to ensure normal traffic during construction.
The city also needs to build an electrical substation to power the tunnel’s water pumping system and relocate telecommunications cables, water pipes and other structures in the area.
Speaking at the ground-breaking ceremony, Hanoi Chairman Chu Ngoc Anh stated that the underpass is a key project to deal with congestion at the junction and help to complete the capital city’s transport infrastructure.
To Huu Street, which joins Le Van Luong Street at the third ring road, has been a major congestion hotspot for years as the two sides of the street are lined with dozens of apartment buildings.
