| In recent years,the accelerating process of urbanization and motorization have promoted the continuous gathering of urban population and the rapid expansion of urban areas.However,the process of urban sprawl also brings a series of problems,such as lagging industrialization of suburbs,single land use function and lagging public transportation facilities,which not only causes the increase of commuting distance and commuting cost,but also aggravates the burden of existing transportation facilities,and aggragates the congestion in the city center.Urban commuting congestion seriously affects the social and economic development of cities and gradually becomes a common social problem faced by most countries in the world.According to Inrex,the top 10 most congested cities in 2019 are located in Latin America and Europe.Bogota,Colombia's capital,is the most congested city in the world,with an average commute of 191 hours.According to the Census report,traffic congestion in 2019 in the United States caused an average of 99 hours of extra commuting time,resulting in a direct and indirect economic loss of $88 billion.China is also facing particularly severe urban congestion,with residents on the Chinese mainland taking 40 minutes to one-way commute in 2014,exceeding the world average of 32 minutes.According to IBM's survey of major cities around the world,Beijing and Shenzhen ranked second and third respectively on the commuter misery index.Therefore,how to better understand the mechanism of congestion and control the growth of commuting time has become a challenge for researchers in economics and transportation.The current researches focus on the short-term socio-economic factors,but ignore the basic geographical structure that affects the long-term development of cities.Therefore,there is a lack of consistent conclusions,and the reference value for urban transport policies is also limited.According to U.S.Census data,8 of the top 10 cities with the longest average commute times are located near the east and west coasts —with large geographic barriers.The geography of these cities is generally more complex because of barriers.However,the relationship between urban geographical structure and commuting has not been discussed in previous studies,and the impact of geographical barriers on urban geographical structure has not been well described.Commuting research urgently needs to explore the impact of urban basic geographical factors,especially geographical barriers,on individual traffic behavior and macro traffic congestion from the perspective of geography.Therefore,in order to fill this gap in urban commuter traffic research,this paper uses traffic data from the United States to verify the impact of geographical barriers on individual commuter behavior,local congestion and urban commuter efficiency from three levels,including micro,meso and macro,and further explores the mechanism of geographical barriers on commuting.The main work of this paper are as follows:(1)This paper studies the impact of geographical barriers on individual commuting activities,and finds the mechanism of geographical barriers on individual commuting behavior from the micro level.Through the implementation of spatial division and representative point strategy,and the establishment of geographical barrier rate describing index and the correlation model between track and geographical barrier,this paper verified that the existence of geographical barrier will have an impact on the basic commuting indexes of morning rush hour residents — commuting distance,commuting speed and commuting time.At the individual level,the effect mechanism of geographical barriers on individual traffic behavior is preliminarily found,which lays a foundation for establishing the relationship between urban geographical structure and urban congestion.(2)This paper studies the impact of geographical barriers on local congestion in cities,and finds that geographical barriers can increase the traffic trajectory in the central area of the city,and reduce the congestion evacuation capacity of areas near geographical barriers.In this paper,a calculation model of effective commuter and effective commuter flow was constructed based on the urban transit rate index,the shortest path near the coastline,and the job-housing distribution data of Boston residents.It was found that the impact of geographical barriers on individual commuter trajectories would increase the total number of commuter trajectories within 5km of downtown by 13.8%.By introducing the physical heat conduction equation,it is found that the existence of geographical barriers will force commuters in coastal areas to choose fewer routes,thus reducing the capacity of congestion evacuation in coastal areas,resulting in long-term traffic jams.It is found that the urban geographical structure has an impact on the local commuter flow,and the presence of every 1%geographical barrier in the traffic direction will result in a 0.21% decrease of the commuter flow.The above conclusions further found the mechanism of geographical barriers on local urban congestion,and established the relationship between individual commuting behavior and local urban congestion from the meso-scale.(3)This paper studies the impact of geographical barriers on the overall commuting efficiency at the city-level.Based on the geographic and social economic data of 868 U.S.CBSA,we design two description indexes of geographical barrires,from the perspective of geography and urban economics,respectively,and establish the regression between the indexes and the urban commuting efficiency.We find that high proportion of geographical barriers can increase the average urban residents commuting time and advance the departure time of the commuters.The above impacts can be intensified by he complexity of geographical barriers.The above conclusions finally verify that the existence of geographical barriers will have a negative impact on the overall commuting efficiency of the city,which has a strong universal reference for the formulation of urban traffic layout optimization scheme. |
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