中文摘要：

为了估计城市道路在随机和模糊条件下的行程时间可靠度,提出了基于云理论的三时估计法.修正了无确定度逆向云算法,假定路段行程时间服从单峰点在m,端点在a和b的Beta分布,对形状参数进行了估计.运用基于云理论的三时估计法求出路段行程时间的期望值、方差和超熵,进而得到路径的行程时间正态云数字特征,根据数字特征对路径进行了排序,并求出了路径、OD和路网的行程时间可靠度.最后,通过一个算例验证了该方法的有效性,说明三时估计法结合云理论可以有效解决不确定条件下的行程时间可靠度问题,为城市交通规划和管理提供技术参考和支持.

英文摘要：

A three-time estimation method based on cloud theory was presented to assess travel time reliability of urban road network under random and fuzzy conditions. The backward cloud algorithm without certain degree information was amended. Link travel time was assumed to follow the Beta distribution, and its unimodal point was m and the endpoints were a and b. Based on the assumption, shape parameters were estimated. Expected value, variance, and hyper entropy of link travel time were then computed through the proposed method. In addition, digital characters of route travel time were obtained, and according to that, the routes were ranked, and route, OD and road network travel time reliabilities were provided. At last, a numerical example suggests the effectiveness of the proposed method. Therefore, the three-time estimation method combining the cloud theory can effectively solve the problem of travel time reliability under uncertainty conditions and provide reference and technical support for the urban traffic planning and management.