Study On Evaluation Index System Of Road Traffic State Under Abnormal Events

In recent years, congestion becomes a global problem and the focus of attention.Especially in our country, urban population and motor vehicle quantities constantlyincrease greatly year by year, attracts the world attention by the rapid development ofprivate cars particularly. But the construction of basic tranffic facilities is relatively slow,and it is relatively backward in traffic management level, the contradiction betweentraffic upply and demand is more and more sharp and the problem of traffic congestionbecomes serious, thus traffic pressure is unprecedented. When traffic conestion has beena very knotty problem under normal conditions, what is more, the frequent abnormalevents all over the world which includes earthquake, blizzard, explosion, traffic accidentsand so on effect the traffic directly or indirectly, which leads to the traffic congestion orincreases its severity.At present it has been very difficult to solve traffic congestion in big cities byincreasing transportation infrastructure, to fully exploit the potential of existing trafficfacilities and to improve its own use efficiency can be more effective to meet the trafficdemand. Especially in conditions of abnormal events, all kinds of factors involves withtraffic have changed greatly compared to normal circumstances. If accurate real-timenetwork traffic state information can be got, traffic managers can make effective controlmeasures and travelers are able to choose reasonable travel plans, as a result, the time andspace resources of traffic system can be used fully, avoiding traffic’s further deteriorationor even paralysis.Based on this, it becomes the key of easeing and solving traffic congestion to holdroad traffic state accurately. In this kind of situation, by analysing the type of abnormalevents and their influence of traffic state, and with full consideration of the needs ofdifferent users, this paper studies on evaluation index system of road traffic state underabnormal events. This research mainly relies on the subject “Research and Developmentof Road Traffic Abnormal Information Acquisition Technology under Abnormal Events”,which includes a total of six parts and main contents are as follows: Abnormal events and their influences on traffic state. Firstly the paper comparativeanalyses several related concepts which include incident, crisis, emergency, disaster andcatastrophe. Determine to definite abnormal events based on emergency, and divide itinto four categories: natural disasters, accident disasters, public events and socialsecurity incidents; Then a systematic analysis of abnormal events’ effects on traffic stateis carried out including the following five aspects.: bring out physical or functionaldamage of traffic facilities, influencing travellers’ behavior, leading to abnormalchanges of traffic demand shown in traffic flow, and reducing the reliability of trafficnetwork.User requirement analysis under abnormal events. Evaluation index system of trafficstate under abnormal events must be in service for its users. Based on the definition ofusers in " Framework of Intelligent Transportation Systems in China " and according toeach one’s important degree under abnormal events, this paper divides the users intoseven categories: government departments, public security departments, trafficmanagers, road users, operation managers, road builders and academic institutions. Thena detailed analysis of each user’s needs of traffic state under abnormal events is carriedout, so as to provide the reference to establishing the evaluation index system of trafficstate under abnormal events.Study on evaluation index system of traffic state under abnormal events. Accordingto the analysis of users’ demand under abnormal events, define the meaning of trafficstate as following: use basic traffic parameters to characterize the state in microscopicscales, traffic condition comprehensive level of sections and intersections for mediumscales, and congestion degree of network or local network for macroscopic scacles.Then determine the design principle of evaluation index system. With the analysis onthe role of basic traffic parameters representing traffic state, the statistical investigationof traffic parameters used in traffic state evaluation and classic automatic traffic stateidentification algorithms, and the accessibility of traffic parameters under abnormalevents, finally establish the three-layers traffic state evaluation index system, whichcontains six microscopic traffic parameters (3for sections and3for intersections),medium traffic state of sections and intersections (smooth, slightly congested, congested,serious congested) and macroscopic network traffic congestion index.Quantization of evaluation index of traffic state. According to the influencemechanism of different kinds abnormal events on road traffic state, two sets of indexthreshold value system are used in micro level. And based on the research of service level, the practical survey data and related researches, determine each level threshold ofthe6microscopic traffic parameters index with statistical menthod and regression fitting.After the unification and dimensionless processing of the microcosmic index, we canget the traffic state of section and intersection in middle scale level by multi-indexcomprehensive evaluation. Macro network traffic state uses the concept of trafficcongestion index which can be got by weighted computation of the medium level index,in which the wight is caculated based on VHT. Finally, by simulating the network trafficstate of large activities in Changchun in vissim4.3, test the evaluation index system oftraffic state presented by this paper. And the results show that the index system has goodpracticability and accuracy.