The cause and evolution of urban street vitality under the time dimension: Nine cases of streets in Nanjing City, China

Street vitality is associated with a comfortable human-based public environment and urban sustainability. In most current studies, street vitality is assessed considering single or multi factors; however, the impact of time dimension is ignored. This study selects nine different year-built streets in old, main, and new urban areas, in Nanjing, China, proposes a framework to assess street vitality considering the different time dimensions and selects the following factors: street form, including building density, continuity, and height-width; street business type, including store density, function density, and permeation rate; and street accessibility, including location, the number of entrances/exits, transportation, and walkability. After calculating the values of the subfactors, a ranking method was applied to assign the ranking of impact of all factors for a comprehensive analysis. The results showed that Pipa Street, Wufu Street in a main urban area, and Hongmiao Street had the highest street vitality and the highest rankings of almost all the factors. Street vitality in different periods demonstrated that street vitality in new urban areas is lower compared with old and main urban areas.