关键词: 城市交通, 公交不平等, 改进的两步移动搜索法, 时间阈值, 基尼系数, 可达性

Abstract: It is unclear whether the impact of time threshold on public transport accessibility will lead to errors of inequality evaluation. This study proposes an enhanced two-step floating catchment area (E2SFCA) method to calculate public transport accessibility. The public transport in Haining city of Zhejiang Province is taken as a case study for the proposed method. The Gini coefficients were calculated with nine different time thresholds from 10 min to 90 min for the overall public transport services, urban and rural area public transport services. The total Gini coefficient was decomposed into urban and rural subgroups, and the impacts of time threshold on the decompositions of total Gini coefficient were analyzed. The study found that the evaluation of public transport inequality changed from "wide disparity" to "relatively reasonable" when the public transport Gini coefficient decreases with the time threshold increases. The main component of total inequality was the inequality within the urban and rural subgroups. The contributions of inequality within subgroups to the total inequality decreased from the 10 min to 40 min but increased from the 50 min to 90 min. The result indicates that the time threshold should be carefully selected because it might cause unreliable or even opposite conclusions for public transport inequality evaluation. It is necessary to find an approach to reduce the impacts of time threshold on public transport inequality evaluation.

Key words: urban traffic, public transport inequality, an enhanced two- step floating catchment area, time threshold, Gini coefficient, accessibility