Research On The Vehicle Routing Problem Of Intra-city Freight Instant Delivery Under Time-Varying Road Networks

With the rapid development of Internet information technology,more and more Internet companies are entering the logistics and distribution industry,which promotes the integration of the Internet and the traditional intra-city freight logistics and transportation industry.However,the influx of a large number of Internet information companies has also led to fierce competition between the intra-city freight information platforms.After the platform funding subsidies gradually end,freight information platforms will face greater competitive pressure.Therefore,the rational planning of instant delivery paths for intra-city freight has become an urgent issue for information platforms to address.In this context,and taking into account increasingly serious urban traffic congestion can seriously affect the normal movement of vehicles,making the vehicle lag in the delivery process to reach the customer.According to the time-varying nature of traffic congestion,the distribution time is divided into several time periods of consistent length.Then,the travel time between any two nodes under the time-varying road network is analyzed in detail.On the other hand,the fuel consumption and carbon emission of vehicles under the time-varying road network are determined from the perspective of energy saving and emission reduction.Finally,according to the process and characteristics of instant delivery of same-city freight,this paper establishes a mathematical model with minimization of delivery cost as the objective function from the perspective of logistics information platform.The total delivery cost in the mathematical model consists of four parts: cost of vehicle fuel consumption,cost of carbon emissions,cost of customer time window penalty,and fixed cost of vehicle.The constraints contain constraints such as pickup first and then delivery constraint,one-to-one correspondence constraint between pickup and delivery points,closed depot,and load capacity constraint.Then according to the objective function and constraints of the model,the corresponding genetic algorithm was designed to solve the model.In the genetic algorithm,the initial solution is generated by gradually assigning pickup and delivery nodes to vehicles and the corresponding repair strategy.The genetic manipulation is accomplished by using cross-swapping between individuals and two-point swapping on individual genetic segments.At the same time,to avoid the destruction of optimal individuals caused by genetic manipulation,the optimal individual retention strategy is used.Finally,in order to verify the validity of the model and the feasibility of the algorithm,a same-city freight information platform is used to obtain the same-city freight delivery orders that have been released in Zhengzhou City and its surrounding jurisdictions to build the case.A case study of instantaneous delivery of same-city freight under single-vehicle type in multiple yards is solved with the Matlab programming.Compared with particle swarm optimization algorithm,the feasibility and effectiveness of the algorithm are also verified.Then,through sensitivity analysis,we analyzed the effects of joint distribution in multiple depots and different levels of traffic congestion on the distribution results,and made reasonable suggestions for the distribution platform.