| Metropolitan area was the trend of regional economic development,which could not only relieve the pressure of central cities,but also strengthen the relationship between core cities and surrounding small and medium-sized cities,so as to achieve the common development goal of social regional economy.The service ability of traffic system directly affected the comprehensive development of metropolitan area.Although China had made great achievements in the development of transport,there were still problems of unbalanced and inadequate development.The layout of transport networks needed to be improved,and connectivity and network resilience needed to be enhanced.Therefore,the state put forward the comprehensive three-dimensional transportation network planning outline,in order to solve the problem of traffic congestion,improved transportation efficiency,reduced traffic environmental pollution and other problems.In order to establish and improve the comprehensive three-dimensional traffic network in the metropolitan area,it was necessary to study the three-dimensional traffic carrying capacity.Only by clarifying the evolution and development of the three-dimensional traffic carrying capacity,could we provide reasonable countermeasures and directions for the construction and improvement of the traffic system.In this paper,based on the analysis of domestic and foreign research theories and methods on traffic carrying capacity,first of all,the definition of three-dimensional traffic was defined,the metropolitan area three-dimensional traffic was divided into two aspects of the synthesis: one was the synthesis of different transportation mode.The second was the synthesis of different subsystems,namely the three-dimensional transportation infrastructure subsystem,the three-dimensional transportation economic development subsystem,and the three-dimensional traffic environment subsystem.The relevant theories of each system and the correlation and constraint of the development of the metropolitan area were analyzed and expounded.Secondly,from the level of index interaction,it described the impact of multiple factors on the measurement of three-dimensional traffic carrying capacity,and constructs the measurement index system and model of three-dimensional traffic carrying capacity.Considering the weight difference of the corresponding index system of different cities,a three-dimensional traffic carrying capacity measurement model of the metropolitan area was constructed considering the environmental impact,which provided a scheme for the measurement of three-dimensional traffic carrying capacity of the metropolitan area.At the same time,according to the classification of hierarchical types of metropolitan areas,this paper selected Nanjing metropolitan area,Chengdu metropolitan area,and Changzhutan Metropolitan area as research objects,used entropy weight method to calculate the panel data of the three metropolitan areas from 2011 to 2021,and obtained the weight of each subsystem of three-dimensional traffic carrying capacity and the weight of each index.The weights of three-dimensional transportation infrastructure system,three-dimensional transportation environment system,and three-dimensional transportation economic development system were 0.3578,0.2758,and 0.3664,respectively.It could be seen that the contribution of three-dimensional transportation economy and three-dimensional transportation infrastructure to three-dimensional traffic carrying capacity was greater than that of three-dimensional transportation environment subsystem.This paper calculated the three-dimensional traffic carrying capacity of each city in the three metropolitan areas,calculated the carrying capacity of each metropolitan area,compared and analyzed the three-dimensional traffic carrying capacity of different metropolitan areas in the same period and the same metropolitan area in different periods.The results showed that: The three-dimensional transport carrying capacity of the Nanjing metropolitan area,Chengdu Metropolitan area,and Changzhutan Metropolitan area continued to improve from 2011 to 2021,but the development level of three-dimensional transport carrying capacity between core cities and surrounding cities in the three metropolitan areas was significantly different.By comparing and analyzing the spatial structure of the three-dimensional traffic carrying capacity system in different metropolitan areas,the results showed that the development of the three-dimensional traffic carrying capacity system in the Nanjing metropolitan area was more balanced.To further studied the spatial evolution characteristics of the three-dimensional traffic carrying capacity of different metropolitan areas from the spatio-temporal dimension and analyzed the spatial structure of the three-dimensional traffic carrying capacity system of the three metropolitan areas,Arcgis software was used to draw the spatio-temporal evolution trend of the carrying capacity of three-dimensional transportation infrastructure subsystem,three-dimensional transportation economic development subsystem,and three-dimensional transportation environmental subsystem in different metropolitan areas in different periods for visualization processing.The results showed that: The three-dimensional transport economic development carrying capacity was positively correlated with the three-dimensional transport infrastructure carrying capacity,while the three-dimensional transport environment carrying capacity was negatively correlated with the three-dimensional transport infrastructure carrying capacity before2015,and the negative correlation between the two gradually decreased from 2016 to 2021.Finally,to study the development level and restrictive factors of the three-dimensional traffic carrying capacity in each metropolitan area,the coupled coordination degree model and the grey relational degree model were introduced in this paper to study the spatio-temporal pattern of the coupled coordinated development of the three-dimensional traffic carrying capacity system and the factors affecting the coupled coordinated development level,and to reveal the spatio-temporal distribution characteristics of the coupled coordination of the three-dimensional traffic carrying capacity in different types of metropolitan areas.The results showed that the development level of three-dimensional traffic carrying capacity in Nanjing metropolitan area was higher than that in Chengdu metropolitan area and Changzhutan metropolitan area.By 2021,the coupling coordination degree of the three-dimensional traffic carrying capacity system of Nanjing metropolitan area was 0.776,that of Chengdu metropolitan area was 0.556,and that of Changzhutan Metropolitan area was0.592.All the three-dimensional traffic carrying capacity systems of the three metropolitan areas had not reached the extreme coordination stage.It showed that the development of the three-dimensional traffic carrying capacity system in the metropolitan area still had great room for improvement. |
