CHONGQING, Feb. 27 (Xinhua) -- The total length of operational rail transit in southwest China's "mountain city" of Chongqing has exceeded 500 km, as the new section of its Line 5 opened to traffic on Monday.

The opening of the new section brings the number of rail transit lines in operation to 12 in the city, according to the municipal commission of housing and urban-rural development.

Chongqing has made many breakthroughs in rail transit construction over the years. It has introduced train models specially developed to adapt to the terrain conditions of the mountainous city, and built many world-class rail transit bridges.

Chongqing will make more efforts to build a multi-layer rail transit system, said Yue Shun, director of the commission, adding that the city aimed to have a mileage of more than 1,000 km of rail transit, both in operation and under construction, by 2025.