| Large-scale area evacuation is an effective method to transfer affected population and their property in response to predictable natural disasters.Regarded as a systematic work,regional evacuation involves a wide range of management departments and many influencing factors.It is difficult to coordinate the relationships between these factors and departments.As the carrier of regional evacuation,the evacuation road network undertakes the responsibility of ensuring the smooth operation of evacuation.To study on its characteristic is obviously beneficial to the evacuation manager to handle the evacuation state and formulate a reasonable plan.The purpose of the regional evacuation coordination management and control strategy,which is the key work of evacuation plan,is to transit evacuees to safe areas as far as possible by integrating the evacuation resources and using traffic management and control strategies.This paper focuses on the traffic characteristics and coordinated management of road network for regional evacuation,including: 1)the traffic bottlenecks identification method of evacuation network and the spatial-temporal distribution characteristics of traffic bottlenecks;2)vulnerability evaluation for the evacuation network considering the role and function of evacuation managers;3)joint optimization of pedestrian-bus evacuation route;4)application prospects,existing problems,and personalized service modeling and algorithm design for shared vehicles in evacuation.The specific research contents are as follows:First,the existence of traffic bottlenecks limits the network capacity and leads to massive recurring and nonrecurring congestions during daily traffic peaks and in the critical event of an emergency evacuation.It is important to identify possible network bottlenecks to improve evacuation efficiency.Based on Newell's simplified kinematic wave model,this paper presents a methodology to identify the network bottleneck links under hurricane evacuation.The methodology mainly includes three parts: 1)achieve traffic flow state updating and propagation based on the kinematic wave model;2)estimate the evacuation demand using a hurricane evacuation response curve;and 3)identify the bottleneck links according to the mean and variance of the measurement of the degree of congestion.Hence,the proposed methodology is elaborated with a sample network,and the travel time distribution of identified bottleneck is analyzed.Furthermore,the method is applied to the bottleneck identification of a realistic network and results are obtained based on simulations using the methodology.Second,good understanding of the network vulnerability can improve the preparedness for an emergency evacuation.This paper presents a game theory based approach to the analysis of the network vulnerability under a hurricane evacuation.A zero-sum game is constructed between a router,who is to seek the minimum-cost paths for the evacuation trips,and a tester,who is to maximize the travel cost by disturbing the links.The distribution of evacuation demand is elastic because the probability of selecting an evacuation destination is determined by the path risk and travel cost.In addition,the congestion effect is also considered.A solution strategy based on the method of successive averages(MSA)is adopted.Over a sample network,the proposed method is compared with three other methods for the network vulnerability analyses.Third,planning for a bus-based regional evacuation is essential for emergency preparedness,especially for hurricane or flood prone urban environments with large numbers of transit-dependent or transit-captive populations.This paper develops an optimization based decision-support model for pedestrian-bus evacuation planning under bus fleet,pedestrian and bus routes,and network constraints.Aiming to minimize the evacuation duration time,an optimization model is proposed to determine the optimal pickup points for evacuees to assemble using existing pedestrian routes,and to allocate available bus fleet via bus routes and urban road network to transport the assembled evacuees between the pickup points and designated public shelters.The numerical examples with two scenarios based on the Sioux Falls urban network demonstrates that this model can be used to optimize the evacuation duration time,the location of pickup points and bus assignment simultaneously.Fourth,optimization of on-demand transportation provisions and ride-sharing services in evacuations may provide increased network capacity and enhanced evacuation performance to transportation systems and improve equity and disaster preparedness for community and society.This paper proposes a two-phase model for optimizing trip planning and operations by integrating a ride-sharing process in shortnotice evacuations,to allow a joint optimization of driver-rider matching and necessary transfer connections among shared vehicle trips.In the first phase,following network topology information and personal requests,a vehicle-space-time hyper dimensional network is developed by constructing vehicle-space-time vertexes and arcs.In the second phase,based on the constructed vehicle-space-time network,a new timediscretized multi-rider multi-driver network flow model is built to formulate ridesharing with connecting transfers.A Lagrangian relaxation solution approach is designed to solve the model in a real-world network scenario.Numerical analyses are conducted with considerations given to the three operating parameters(detour tolerance of driver,penalty factor for transfer time,and maximum allowable parking time)in the method,and the analysis results show that the proposed model can not only meet the evacuation trip needs of the participating parties but it also supports personalized requests and on-demand accesses.A small sample network is used to theoretically test the whole model and the underlying concepts and solution strategy to show each step implemented in details,and finally the applicability of the method is demonstrated using the Chicago city network. |
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