In this aerial photo taken on June 23, 2018, workers make prefabricated building parts for the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour. (Photos: Xinhua)

A worker makes prefabricated building parts for the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region, June 23, 2018. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

This aerial photo taken on June 23, 2018 shows prefabricated building parts for the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

Workers make prefabricated building parts for the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region, June 23, 2018. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

A worker makes prefabricated building parts for the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region, June 23, 2018. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

In this aerial photo taken on June 23, 2018, workers construct a bridge in the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

In this aerial photo taken on June 23, 2018, workers construct a bridge in the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

In this aerial photo taken on June 23, 2018, workers construct a bridge in the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

In this aerial photo taken on June 23, 2018, workers construct a bridge in the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.

A worker makes prefabricated building parts for the Gansu-Ningxia section of the Yinchuan-Xi'an high-speed railway in northwest China's Ningxia Hui Autonomous Region, June 23, 2018. The 617-kilometer high-speed railway is scheduled to start operation by the end of 2020 with a design speed of 250 kilometers per hour.