Which Green Space Are Easily Accessible for Pedestrians in a City?

Kee Moon Jang, Hyeyeong Lee, Hyemin Cho, Jaeman Kim, Youngchul Kim (KAIST)

This study aims to develop an automation method that measures people’s accessibility to green space and locations dispersed throughout the city as well as represents either citywide or local characteristics. The proposed method comprises an index formulated to integrate the amount of green space with the significance of the street near green space and radii of pedestrian’s catchment area in a city. By using Normalized Difference Vegetation Index, a widely-used index that measures the greenness from an aerial image by reflecting biological characteristics of a green plants, we developed the Urban Green Accessibility defined as the total sum of pedestrian’s accessibility to vegetation point in a city. The significance of street in the proposed method adopts the integration and choice values of angular segment analysis. By integrating the street index with the greenness index, we seek to evaluate pedestrian’s accessibility to green space in a city. In San Francisco, CA, eight satellite images are collected. In total, 42,230,594 counts as vegetation points among points in the eight satellite images. 34,961 road segments are collected using open source road centerline data. The values of the Urban Green Accessibility are calculated in different metric radii within the city boundaries. As a result, this study successfully reveals differences in accessibility to green spaces based on the significance of the street. When the analysis distances are a neighborhood scale, i.e. 1,600 meters’ radius, a couple of hot-spots appear in famous green areas on commonly accessible streets and local neighborhood parks in residential areas. The appearance of high-accessibility points in low-NDIV areas implies the potential of efficient and good distribution of green spaces for the pedestrians. The proposed measure to efficiently evaluate the accessibility of green spaces is expected to help plan and manage green areas in a city for people’s accessibility and spatial relationship.