Aerial photo taken on May 21, 2019 shows the scenery of National Highway 212 at the boundary of Zhangxian County and Weiyuan County of Dingxi City, northwest China's Gansu Province. (Xinhua/Chen Bin)

　　Aerial photo taken on May 21, 2019 shows a running truck on National Highway 212 at the boundary of Zhangxian County and Weiyuan County of Dingxi City, northwest China's Gansu Province. (Xinhua/Chen Bin)

　　Aerial photo taken on May 21, 2019 shows the scenery of National Highway 212 at the boundary of Zhangxian County and Weiyuan County of Dingxi City, northwest China's Gansu Province. (Xinhua/Chen Bin)

　　Aerial photo taken on May 21, 2019 shows the summer view of National Highway 212 at the boundary of Zhangxian County and Weiyuan County of Dingxi City, northwest China's Gansu Province. (Xinhua/Chen Bin)

　　Aerial photo taken on May 21, 2019 shows running cars on National Highway 212 at the boundary of Zhangxian County and Weiyuan County of Dingxi City, northwest China's Gansu Province. (Xinhua/Chen Bin)