The Research Of Urban Expressway Automatic Incident Detection Method

Currently, urban expressway networks have been established in many aboard and civil metropolitan cities, e.g. New York, Paris, Tokyo, Beijing and Shanghai. As the skeleton, urban expressway networks are playing a significant role in urban road transportation systems. The principal influence of traffic incident on urban expressway is that incident leads to the appearance of traffic bottleneck which dramatically reduces the capacity and efficiency of urban expressway system and the occurrence of traffic congestion, at the same time it threatens the safety of people and vehicles. To reduce the negative effect of incident on urban expressway, the crucial procedure is to discover incident quickly and exactly.Automatic Incident Detection (AID), is the method to detect and discover incident automatically, based on the real-time field traffic data, which automatically identifies the change of traffic condition caused by incident. But, most of the current research work related to AID is directed towards highway, not urban expressway. So, according to the actual situation in our country, this paper makes a systematic study on AID for urban expressway, puts forward the combined theory, method and technique, and addresses the following topics;(1) Study of incident influence mechanics: based on the traffic wave theory and macroscopic traffic flow theory, according to the different background traffic condition and severity of incident, it analyzes the influence mechanics of incident on background traffic, discusses the time-space changing characteristics of several traffic coefficients under incident condition, and puts forward the common basic principle of AID methods, which are based on sectional field traffic data, and several alternative AID indexes;(2) Study of AID basic traffic data: it proposes the concepts of "Original Traffic Data (OTD)" and "Basic Traffic Data (BTD)" for AID, and two essential requirements of BTD; based on the error analysis method of data sequence and data sequence difference, it analyzes the characteristics of nine traffic data sequences in incident and non-incident traffic background; integrating the advantages of two outstanding traffic data sequences, it constructs the Un-Continuous Moving One Minute Occupancy Sequence (UCMOMOS) which is used as BTD for AID in this paper;(3) Study of AID indexes: it fixes four ultimate AID indexes; based on large quantities of historical incident data of Shanghai urban expressway, it discusses the changing characteristics of the four AID indexes in low-occupancy, high-occupancy and complicate traffic background, the actual relationships between AID indexes and background traffic condition, and the differences of AID indexes between different urban expressway segments and lanes;(4) Multiple indexes detection method, fixing threshold method and detection performance evaluation: it puts forward the incident judgment method of multiple co-operating AID indexes, and the threshold calibration and self-modification method of AID indexes; according to actual incident data, based on the parallel test method, it evaluates the incident detection performance of this paper's Multiple Indexes AID algorithm and several existed AID algorithms;(5) AID program development: integrating the aformentioned research achievements, it develops the urban expressway AID program, which is composed ofsix modules------analyzing OTD, calculating BTD, calculating AID indexes, settingAID index thresholds, incident judgment and incident alarm;Based on the comprehensive research, this paper proposes a complete technical framework of AID for urban expressway transportation management. Finally, several topics of further studies are discussed.