Simulation Study On Traffic Flow Evacuation Under The Urban Major Emergency Incidents

The urban system becomes more complicated because of the expansion of urban, and the major emergency incident occurs frequently. It is undeniable that many emergency incidents cannot predict accurately. Because of its occasionality and dangerousness, the decrease of casualties and property loss become the primary goal to meet the emergency. In fact, the emergency itself is not the main factor to cause casualties, the main reason is that people cannot be transferred outside in time because they are trapped in dangerous zone for long time. In general case, the impact range of emergency can be divided into three parts: dangerous zone, buffer zone and safety zone. As the direct impacting zone of emergency, the evacuation effect of dangerous zone decides the strengths and weaknesses of the whole evacuating process. Therefore, the paper mainly investigates the evacuation problem of emergency in direct impacting zone.Compared with the normal traffic, the evacuation of traffic stream has higher request for time in an emergency case. On this basis, the urban traffic traits are summarized in emergency case, including urban traffic equipment, traffic stream and traffic network. Then the emergency evacuation is further analyzed on above basis, and the starting point of research is established.In order to improve the efficiency of evacuation, it’s feasible to take some strategy. Therefore, the one-way evacuation measure and its principle is analyzed and elaborated according to the traffic characteristics of emergency. The total evacuation time charge primarily related to road travel time, including a section of the passage of time and the intersection delays, coupled with unexpected events directly affecting the degree of emergency and road traffic density in the region and the relatively high volatility, the road dynamic impedance model is established. Subsequently, an emergency evacuation model is established by using the road barrier formula. And the solution of the model is got according to the characteristics of the model and the ant colony algorithm. Finally, we make a simulation analysis for its primary network condition through an assumption case, and obtain a setting plan for one-way street network in above case condition. Then the evacuation condition is stimulated in above plan. And the result shows that it can obviously improve the evacuation efficiency.