Abstract: The analysis of accessibility for urban public transit network can be used to reflect the level of transit convenience for urdan public different regions of the city．On the basis of presuming passengers’minds and their behaviour on their trip and confining the range that they can cover through the transit network and the road network.this paper proposes a formula for the accessibility and gives the process with the software TransCAD as wel1． Finally， this method is applied to evaluate the accessibility of the CBD of Changchun，reasonable conclusions are reached．

Key words: public transit network, accessibility, evaluating index, Trans CAD

摘要： 对城市公共交通进行可达性分析，可以反映城市间不同区域通过公交线网的交通便捷程度。本文通过对乘客出行心理、行为的假设和公交线路、道路可达性范围的界定，给出了一种简易的公共交通网络可达性指标计算公式，并基于TransCAD软件给出了指标计算方法步骤。最后，通过对长春市中心区的公交可达性进行了实证验算，得到了可信的结果。

关键词: 公共交通网络, 可达性, 评价指标, TransCAD