Constrained vehicle routing model for emergency relief supplies based on demand urgency
[Objective]Emergency relief supplies are crucial for dealing with disasters,and their reasonable and timely distribution relates to people's health and safety.Emergency relief supplies at rescue centers are limited and cannot meet the emergency needs of all affected areas simultaneously.Post-disaster emergency relief supplies face double challenges in this regard due to short supplies and limited transportation capability,resulting in the needs for medical rescue and materials of a disaster area in a short period.To develop a scientific and efficient post-disaster emergency response,we studied the constrained vehicle routing of emergency relief supplies based on demand urgency.Restrictions in traditional path planning,such as single objective,single depot,single distribution,undifferentiated supply,and closed scheduling,were considered.[Methods]The analytic hierarchical process was applied to measure the demand urgency index from personnel,facilities,and disaster resistance,considering the overall efficiency and key disposal.Furthermore,this study had multiple objectives,including the following:minimization of deprivation cost and response time,and maximization of demand satisfaction rate in the emergency rescue process.A constrained model of emergency vehicle routing was constructed,and a two-stage genetic algorithm was designed to deal with comprehensive distribution conditions,such as open scheduling,soft time windows,and demand splitting.The effectiveness and feasibility of the model and algorithm were verified using examples.[Results]The results revealed that the model effectively coped with the material distribution problem resulting from scarce transportation capacity and various degrees of disaster.The splitting strategy and open scheduling of vehicles guaranteed multiple services at disaster sites and optimal route combination.Moreover,relief progress in disaster sites(splitting demand,batch distribution,and service time)and vehicle dispatch schedules(distribution order,work duration,and resupply depot)were generated.During the planning period,the system loss was reduced by 40.3％,and a 99.4％material demand was obtained.When disaster derivation caused changes in road conditions,fluctuation parameters were inputted into the model.The model and algorithm adjusted the scheme with a low risk of service failure,and the adjusted scheme reduced the demand and supply by 1.5％in the decision period.[Conclusions]Constrained route planning is implemented for flexible distribution conditions,such as demand splitting,soft time windows,and open scheduling,based on the dynamic change characteristics of demand and supply during sudden natural disasters.This study considers the demand urgency of key disaster areas and the efficiency of global relief to accommodate unexpected road events and maximize resource availability.With the circulation of distribution vehicles,the needs of disaster sites are gradually met within the decision-making cycle,which provides full play to the time utility of emergency relief supplies and transportation resources.The proposed model can form scientific and reasonable material distribution and vehicle scheduling schemes and evaluate the workload of each rescue center and vehicle to deploy work in advance,providing a theoretical basis and a decision-making reference for vehicle route planning of emergency relief supplies.
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