After May last year,there was another wave of rapid development in urban rail transit.According to incomplete statistics,there are currently over 70 subway lines under construction in China,with a total investment of over 800 billion yuan.If approved projects are added,the investment amount exceeds 1.5 trillion yuan.It is not difficult to find a positive correlation between the total economic output of these cities and their subway mileage.Generally speaking,the larger the total economic output,the more subways are built.

  After the implementation of the national"stable growth"policy in May last year,urban rail transit ushered in a wave of enthusiasm.Recent subway plans or adjustment plans for 14 cities including Changzhou,Xiamen,and Shenyang were approved,involving a total mileage of 993 kilometers and a total investment of 728.3 billion yuan.Currently,35 cities across the country are connected to the subway system.

  It is not difficult to notice the close relationship between the mileage of urban subway construction and its total economic output.For example,Beijing,with the second largest economic output,ranks first in the national rail transit mileage with a distance of 443 kilometers,while Shanghai,with the largest economic output,only ranks second on the Curie mileage list with a difference of 3 kilometers.The mileage ranking of the two first tier cities,Guangzhou and Shenzhen,closely follows their economic aggregate ranking.The economic output of other cities also ranks among the top 20 in the country.

  Kong Lingbin,a senior engineer at the China Urban Planning and Design Institute,told reporters that the construction and operation of rail transit require huge investment and a certain amount of economic support.On the other hand,the construction of rail transit can promote the overall growth of urban economy.

  Hu Xiaodeng,director of the Urban Economy Research Institute of Guizhou Academy of Social Sciences,told reporters that there is a certain coefficient relationship between rail transit and urban population and area,and rail transit is only needed when there is a certain demand for transportation.In his opinion,for a city to build rail transit,the main urban area should be over 300 square kilometers and the population should reach several million or more.

  However,the relationship between total economic output and urban rail mileage is only an approximate reference value,and the two are not absolutely equivalent.For example,Suzhou,despite ranking sixth in terms of total economic output,is mainly composed of contributions from its subordinate counties and cities,and its central urban area is not very large,so its mileage only ranks 14th in the country.But some provincial capitals in the central and western regions,such as Guiyang and Lanzhou,although their economic output did not enter the top 50 in the country,due to their large central urban areas and large populations,they have also been approved to build rail transit.

  This is a relative coefficient,an approximate reference value,"said Hu Xiaodeng.In addition to the total economic output,it is related to the city's planning,future development positioning,scale,and the city's position in regional development.For example,provincial capitals such as Guiyang and Lanzhou are the only unipolar core cities in western provinces,with strong attraction and radiation to the surrounding areas.The main resources are concentrated here,so the demand for rail transit is relatively high.

  In big cities like Beijing and Hangzhou,it is indeed possible to rely on land to support railways,but in some third tier cities,the income obtained from relying on land to support railways is far from enough.Ding Changfa,an associate professor in the Department of Economics at Xiamen University,believes that in the current situation where the population turning point is looming,the future population expansion of some third tier cities is relatively limited,so the construction of rail transit should be more cautious.(First Financial Daily)