How green are the streets? An analysis for central areas of Chinese cities using Tencent Street View.

Ying Long,Liu Liu,Xiaolei Ma

doi:10.1371/journal.pone.0171110

Ying Long, Liu Liu + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0171110

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Abstract

Extensive evidence has revealed that street greenery, as a quality-of-life component, is important for oxygen production, pollutant absorption, and urban heat island effect mitigation. Determining how green our streets are has always been difficult given the time and money consumed using conventional methods. This study proposes an automatic method using an emerging online street-view service to address this issue. This method was used to analyze street greenery in the central areas (28.3 km2 each) of 245 major Chinese cities; this differs from previous studies, which have investigated small areas in a given city. Such a city-system-level study enabled us to detect potential universal laws governing street greenery as well as the impact factors. We collected over one million Tencent Street View pictures and calculated the green view index for each picture. We found the following rules: (1) longer streets in more economically developed and highly administrated cities tended to be greener; (2) cities in western China tend to have greener streets; and (3) the aggregated green view indices at the municipal level match with the approved National Garden Cities of China. These findings can prove useful for drafting more appropriate policies regarding planning and engineering practices for street greenery.

Highlights

As one of the most prominent colors in nature, green has been an everlasting beloved color of humans, and the “garden city” advocated by [1] is among the most famous planning theories
Considering the crawling, processing, and computation load of street-view pictures (SVPs), we only focused on the downtown areas of each city
We noticed that some cities with less green were associated with street views taken in autumn or winter

Summary

Introduction

As one of the most prominent colors in nature, green has been an everlasting beloved color of humans, and the “garden city” advocated by [1] is among the most famous planning theories. As an essential aspect of green-city implementation, green coverage at various scales—at the block level (green land area divided by block area), for example, or citywide (total green land area divided by the city’s urban land area)—is a mandatory element of spatial plans for promoting a high quality of life. Green coverage in planning drawings does not directly correspond to the total greenery in reality. This is one reason why visual greenery has been extensively discussed in the research community and is suggested for use in practice. Not required in spatial plans, street greenery—as the focus of this study and a key indicator for evaluating urban form at the citydesign level—is important for citizens’ quality of life (especially for pedestrians in daily life); this has not been sufficiently studied due to a lack of fine-scale data

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