At 8:38 am on Friday, a train with about 350 passengers departed Chongqing Caiyuanba Railway Station, marking the Lanzhou-Chongqing line's official opening.

After the 886-kilometer railway line passes through Sichuan province, it dips into Shaanxi province before passing through Gansu to reach Lanzhou, the province's capital. The project, started in 2008, is the country's third main north-south rail line after the Beijing-Shanghai and Beijing-Guangzhou lines.

This significant part of the country's railway network speeds up travel between the western regions and the rest of the country.

Chongqing, the only provincial-level municipality in western China, is a gateway to the vast inland area. Gansu province is rich in natural resources but has long been poverty-stricken because of poor transportation.

The new rail line cuts the distance between the two cities by about 650 kilometers and travel time from 20 to 13 hours.

It is expected to greatly boost the economy in less developed inland China in combination with the Belt and Road Initiative and the Yangtze River Economic Belt plan.

The line's design speed is 160 kilometers per hour with some sections at 200 km/h.

As early as about 100 years ago, Sun Yat-sen (1866-1926), the first provisional president of the Republic of China, wrote in his book General Plan of China that the country should build a railway linking Lanzhou and Chongqing.

But complicated geographic conditions mean the project is considered the most difficult one in China's railway construction history.

Thanks to advanced technologies, workers have built 226 tunnels and 396 bridges to pass through the mountains and rivers, especially the Qinling Mountains, a major east-west mountain range in southern Shaanxi province.

Because more than 72 percent of the line is bridges and tunnels, safety has been the most important issue, according to train crew supervisor Tian Yu, a longtime railway worker.

"When passing through the tunnels, the negative wind pressure can easily hurt people who stand at the junction of two rail cars," he said.

"Our staff needs to pay more attention to educating passengers about safety issues."

Also Friday, a freight train loaded with 290 automobiles made in Chongqing departed from Tuanjiecun Railway Station for Lanzhou.

The rail line is eventually expected to transport 50 million tons of cargo every year and operate 50 passenger round-trips every day.