The 30-kilometre long, 35.5-metre wide and six-lane highway section connects the Liem Tuyen intersection in Ha Nam province with National Highway 10 in Nam Dinh province and has a speed limit of 120 kilometres per hour.
It is a continuation of the 20-kilometre section between Cau Gie and National Highway 21, which was completed in November last year.
The completion of the Cau Gie - Ninh Binh highway will help ease traffic on National Highway 1A and halve the travelling time between Hanoi and provinces in the south of the Red River Delta.
The Cau Gie - Ninh Binh highway project was started in 2006 at total cost of VND9 trillion (US$432 million).
On the same day, the Thanh Xuan - North Linh Dam Lake section of Hanoi's third ring road also opened to traffic.
The 3,267-metre elevated road was completed after 24 months of construction at a total cost of VND1.376 trillion (US$66 million).