Hybrid optimization procedures applying for two-echelon urban underground logistics network planning: A case study of Beijing

Abstract

Motivated by urban land scarcity and surging demand, the underground space has become a frontier domain for future city logistics industry. The Underground Logistics System (ULS) is a sustainable option to overcome traffic congestion while improving freight transport efficiency. This study presents a comprehensive layout design and facility planning method for the two-echelon urban ULS network with hub-and-spoke structure. The underground network is organized by the primary and secondary ULS nodes and tunnels which have strong alignment with existing logistics nodes such as distribution centers and major demand terminals. A bi-objective mixed-integer linear programming model considering minimal costs and maximal system utilization was established to formulate the location-allocation of ULS nodes, tunnel layout and flow routing in the network. Given the inherent problem complexity, a series of simplification techniques and hybrid optimization procedures integrating both exact and meta-heuristic algorithms were developed to obtain high quality solutions. Finally, a real-world simulation was carried out in Beijing, China to demonstrate the applicability of proposed method. Results show that our procedures can effectively obtain the best configurations of ULS network under various scenarios and has better convergence efficiency and optimality performance. Moreover, a group of horizontal tests and sensitivity analysis reveals further insights regarding ULS network decision-making and layout strategies.