| The urban transportation system is an important component of urban infrastructure.Improving the feeling of comfort during the individual transportation process is importation for urban residents seeking high quality of life.In addition to the performance of transportation system,an enjoyable travel experience is also closely related to the urban environment.As a principal element of the urban landscape,urban street green vegetation can bring a pleasant experience to residents during transportation while improving the quality of the urban environment.Visual assessment of urban greenery has gradually become an important tool to improve passengers’ comfort levels during transportation.However,existing studies had not yet established the substantial connection between street greenery visibility and urban transportation process.How to objectively evaluate the urban green visibility and assist the urban transportation planning and greenery construction is a subject to be investigated.The free and open-source street view data had become an important data source for the assessment of the distribution of green vegetation on urban streets for its bulk information and perceptual intuitive reflection of the urban environment.However,it was urgent to explore how to mine effective information from the enormous street view images,and to associate the urban street green with transportation process,aiming at effectively estimate the green visibility during urban transportation.This paper aims at the evaluation of green visibility during urban transportation.To address the gap above,this paper proposed a new index,the Green View Index –Urban Transportation(GVI-UT),including Total Green View,Distance of green view,Duration of green view,Unit distance green view and Unit duration green view.With the street view data as support,employing the Internet data crawling,image processing,spatial analysis technologies to establish the substantial link between the visible green of the street and the urban transportation experience,and to explore the calculation method for the GVI-UT.The explicit research contents were as follows:(1)Definition and calculation method of the GVI-UT.The GVI-UT was defined by the ability of residents from different geographical locations in the city to see green vegetation along the street in their daily lives to different destinations,which was a street-level index.The GVI-UT calculation comprises four steps: obtaining street view panoramic photographs;calculating green views based on these photographs;route planning using Web application programing interfaces;and indicators calculation.(2)Analysis and verification of the GVI-UT on a city scale.From the city scale,the influencing factors of the GVI-UT index and the differences of different indicators were studied,and the validity and practicability of the GVI-UT index were discussed.Taking the downtown area of Kunming as the experimental area,selecting locations in different directions of the central area as the destination of the experiment,using different modes of transportation,comprehensively measuring and analyzing the green visibility of residents during urban transportation.Then studied the practical significance of the GVI-UT index for transportation planning and greenery construction,and introduced field survey data to verify that the index is used to evaluate the green visibility during transportation and residents’ comfortable experience.(3)Evaluation of green visibility during urban transportation of global urban cities based on the GVI-UT.From the global scale,the application of the GVI-UT was extended to the capital cities of the world.Selected 62 capital cities in the world as research areas,used the city center as the destination,and used different modes of transportation to measure the green visibility during urban transportation of urban residents.Then we evaluated and analyzed from three perspectives: global,continent and city levels,analyzed the green visibility during urban transportation in capital cities around the world and provided guidance for urban greening construction.The major research results indicate:(1)GVI-UT indicators were related to two important factors: destination and transportation modes.For individual dwellers,drivers,and travelers,in addition to the well-known travel costs,routes with higher GVI-UT values can be given priority selection to obtain a more comfortable travel experience.In addition,for travel without definite destinations,such as when running or walking for exercise,this study can be used as a guide for the selection of transportation route.(2)Kuala Lumpur,Vientiane,Jakarta,and Singapore are the cities with the best results measured by GVI-UT,while Sucre,Bishkek,Ulaanbaatar,and Copenhagen perform the worst.The green visibility of cities in Europe and Asia is significantly related to geographic location.The green visibility of cities in Europe is gradually increasing from west to east,while the Asian region is gradually increasing from north to south.Increasing the greening of the main roads of the city and the streets within a certain range around the residents’ transportation destinations is beneficial to improve the GVI-UT values.The analysis and verification of the evaluation results of the GVI-UT shown that the GVI-UT proposed in this study was centered on the "person’s perspective" and fully considered the transportation experience of people.Providing theory and a new framework for the status of green visual perception can be widely used in the evaluation of green visibility of urban travel in cities around the world.Based on free and easily accessible open-source street view data,this study proposed a green visibility index for urban travel.The quantitative calculation framework not only provided a new perspective for analyzing the urban greening situation during traffic travel but also expanded the practical application of street view images. |
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