时间阈值对公交不平等评价结果的影响

时间阈值对公交可达性计算结果的影响，是否进一步影响到公交不平等评价结果，尚不明 确。以浙江省海宁市为例，用一种改进的两步移动搜索法(E2SFCA)计算公交可达性，得到 10~90 min共9个时间阈值下研究区域的总体、市区和农村公交服务的基尼系数，比较了不同时间 阈值下的基尼系数差异；按市区和农村两个群组对总体基尼系数进行分解，分析在时间阈值下群 组内和群组间不平等对总体公交不平等的影响。结果发现：随时间阈值增大而基尼系数逐渐减 小，公交不平等评价由“差距悬殊”变为“相对合理”；总体公交不平等的主要来源为群组内不平等 且贡献率在10~40 min时逐渐下降，在50~90 min时逐渐上升。研究表明，不同时间阈值会使公交 不平等评价结果出现偏差甚至得到相反的结论，有必要进一步研究消除时间阈值影响的方法。

Impacts of Time Threshold on Public Transport Inequality Evaluation

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.