Two-Echelon Dispatching Problem With Mobile Satellites in City Logistics

At present, city logistics mostly adopts a two-echelon dispatching model which combines distribution centers located in suburbs and fixed satellites located in urban areas for distribution. However, both expensive rental fees and daily changes of customer demand in metropolitan areas make dispatching route generated by fixed satellites inefficient. Moreover, the existing mobile depot model needs a large investment for facilities. In this paper, we propose a two-echelon city dispatching model with mobile satellites (2ECD-MS) which locations of mobile satellites change according to demands of customers to ensure the efficiency of delivery routes in every day. A cluster-based variable neighborhood search scheduling algorithm is proposed to determine locations of mobile satellites and dispatching routes of trucks and tricycles. Then, the 2ECD-MS is extended to 2ECD-MS-TDD to allow trucks dispatching directly (TDD) for further cost reduction. Experimental results show that the 2ECD-MS significantly reduces the total cost against the model using fixed satellites mode by 3.5% while the 2ECD-MS-TDD further reduces the total cost against the 2ECD-MS significantly by 3.25% in 54 cases with different customer scales, geographical scopes, and distribution types. These show the superiority of the proposed methods in cost reduction for city logistics in comparison to the traditional fixed model.

I. Introduction

The primary purpose of city logistics [1] is to transport goods in urban areas in an efficient way, taking into account traffic congestion, safety, and environments. With the rapid development of e-commerce and the increasing demand of consumers for the speed of delivery, city logistics faces enormous challenges. Major logistics companies have changed their urban warehousing and distribution strategies to meet the growing demand for distribution better. At present, a two-echelon distribution system is the most commonly used system for urban distribution by logistics enterprises such as JD.com and SF-express. The two-echelon distribution system [2] uses different types of vehicles on various echelons and satellites to consolidate and transship parcels. In the two-echelon dispatching, parcels 1) are loaded on the truck of the first-echelon transportation; 2) arrive the satellite located in the urban area; 3) are delivered to customers by the second-echelon distribution vehicles.