## 5 Evolution of Passenger and Freight Transportation Network
Meanwhile, the State Council has further refined and improved the policies for the large-scale development of the western region, with emphasis on infrastructure construction, the development of characteristic and advantageous industries, the construction of ecological civilization, the improvement of people's livelihood, and deepening the reform and opening up. In 2016, the State Council approved the development plan of Chengdu Chongqing urban agglomeration, which proposed to cultivate and develop Chengdu Chongqing urban agglomeration with Chongqing and Chengdu as the center, and integrate into the \"Belt and Road\", the development of the Yangtze River economic belt and the new round of western development. With the continuous expansion of the cooperation scope of the \"southbound channel\", the new land and sea channel in the western region was officially put forward in 2019, which greatly saved the international transportation time and cost, greatly released the vitality of internal and external opening, and further promoted the leap forward in the development of the western region. The evolution of the urban freight network in each year is shown in Figure 4. In 2000, the overall correlation strength of freight network was comparatively weak, and the spatial structure was formed with Chengdu and Chongqing as the centers and Xi'an as the sub-center gradually became prominent. In 2006, the entire network connection strength increased, mainly reflected in Chengdu-Chongqing urban agglomeration, Baotou, Ordos, Kunming, Qujing, Qianxinan, Liuzhou, Hezhou, Laibin, and other regions, treat Chengdu-Chongqing urban agglomeration as the center and formed the spatial pattern with Tongchuan, Xi'an, Weinan, Baotou, ordos, Kunming--Qujing--Qianxinan, and Liuzhou-Hezhou-Laibin as vice centers. In 2012, the network connection was further strengthened; higher values were mainly distributed in Chengdu, Chongqing, Xi'an, Deyang, Meishan, Nanning, Qinzhou, Fangchenggang, Baotou and Ordos; higher values were allocated in Dazhou, Nanchong, Luzhou, Neijiang, Kunming, Qujing, and Yuxi; and it shaped Chengdu-Chongqing urban agglomeration as the center and the network spatial pattern of Xi'an, Nanning, Kunming, and Ordos as sub-centers. In 2018, the correlation strength of Chongqing, Guiyang, Zunyi, Luzhou, Nanchong, Kunming, and Yulin was further reinforced; the high-value areas shifted to Chongqing, Zunyi and Guiyang; and the sub high-value areas spread to Luzhou, Nanchong, Anshun, Qiannan, Guigang, Yulin, Kunming, and Yuxi. The high-value areas were mainly concentrated in Sichuan province, Guizhou province, Guangqi province, and Inner Mongolia, and they form a network space pattern with Chengdu-Chongqing urban agglomeration as the center and Guiyang, Xi'an, Kunming, Nanning, and Ordos as the sub-centers. From 2000 to 2018, the logistics network has realized the spatial pattern evolution of \"two masters and one deputy\" to \"one master and multiple deputy\". In addition to the factors affecting the evolution of the passenger flow network, the evolution of the logistics network is inseparable from the construction of the traffic network. In 2000, the density of the transport network in the western region was low at only 834.91 km/10,000 km\({}^{2}\), which was only 53% of the national average and 18% of the eastern region. It has affected the optimization of resource allocation and seriously delayed the development of the western region. In 2006, the Qinghai-Tibet Railway was officially completed and opened to traffic. The construction of national trunk lines and inter provincial channels for the development of the western region was basically completed. The total length of highways in the western region exceeded 940,000 km, and substantial progress was made in the construction of a comprehensive transportation system. In 2012, the rapid development of China's railway construction accelerated the implementation of passenger and freight line transport, which greatly improved the freight capacity of the railway.