Abstract: Aimed to solve the deficiency of determining car-following state，based on He’s method which uses the varying rule between the absolute value of relative speed difference and time headway，this paper presents a new method. This proposed method employs the varying rule between time headway and the relative coefficient of both leading and lag vehicles on the basis of analyzing the surveyed data. Compared with former methods，the improved Method considers more information and links with the fact closer. This research may have an important role in heightening the precision and reliability of microscopic traffic simulation.

Key words: car-following state, time headway, relative coefficient, speed

摘要： 针对现行交通仿真研究中跟驰状态判定的不足之处，本文基于何民等人利用相对速度绝对差随车头时距变化的规律来判定跟驰状态的基础上，通过实测数据深入分析前后车速度的相关系数与车头时距的关系，提出了利用前后车速度的相关系数随车头时距变化的规律来确定车辆跟驰状态的临界值，与以前的方法相比，这一方法考虑的信息更为全面，与现实结合更为紧密，本研究期望能对提高交通微观仿真的精确度、可信度取到一些有益的作用.

关键词: 跟驰状态, 车头时距, 相关系数, 速度