Two high-speed railway lines opened in Central and Northeast China on Monday, showcasing the country's ability to build railways in different climates and geographic conditions.

The lines will boost regional social and economic development, improve people's travel experiences, enhance local tourism and assist rural vitalization, the national railway operator, China State Railway Group, said.

The new line in Central China's Hunan province is located in the west of the province, an area with multiple scenic spots. The 245-kilometer line, with a designed speed of 350 km per hour, links Zhangjiajie and Huaihua with a journey of 1 hour and 10 minutes.

With seven stations, the line passes Furong town and Fenghuang ancient town, popular tourism spots that gained fame from works written by late 20th century scholar and writer Shen Congwen.

The region is known for its remarkable natural views with mountains, rivers and scattered natural reserves. But the breathtaking views challenged railway designers because of complicated geographic conditions.

Construction began in December 2016, and engineers built 162 bridges and 118 tunnels stretching 223.9 km. More than 90 percent of the railway is bridges and tunnels.

In Northeastern China, the new high-speed railway linking Mudanjiang and Jiamusi in Heilongjiang province also opened on Monday, when temperatures dropped to about-10 C.

The 372-km line, with a designed speed of 250 km/h, is China's easternmost high-speed railway. The railway, which passes by Changbai Mountains, is located in a region where temperatures can drop to as low as-40 C.

Frozen earth and heavy blizzards challenged construction crews and design engineers. Thirty-four tunnels and 173 bridges were built along the line, accounting for 56 percent of its length.

Niu Yongping, the project's chief engineer at China Railway Design, said the line represents China's top technology and management expertise in building high-speed railways in extremely cold areas.

Engineers adopted new materials and designed intricate structures to combat the cold, including rail beds, bridges, tunnels, tracks and houses along the line.

Dealing with frozen soil was essential to designing adequate rail beds, as ultralow temperatures can distort tracks. Freeze-resistant materials and new structures were adopted to prevent rail beds from changing shape, Niu added.

The line, linking two major cities in the province, reduces travel time between them from seven to two hours. It has seven regular stops and forms a high-speed railway circle linking Harbin, the provincial capital, with Mudanjiang and Jiamusi.

The new line has greatly improved the traditional heavy industry hub's connectivity with other parts of the country and will boost the socioeconomic development of northeastern China.

Track-laying work was completed in November last year. Since June, different types of bullet trains have been put into operation for test runs, with full-line trial runs beginning in August.

The line was scheduled to open to traffic in late September but experienced several delays because of the emergence of scattered COVID-19 cases in the region.