# The Environmental Impact of Inland Empty Container Movements Within Two-Depot Systems
## 2 Literature Review
[29] developed a model for determining the optimal locations of inland depots for both rail and road transportation. By considering both transportation modes in the movement of containers, the objective is to minimize overall transportation costs. Additionally, it has been demonstrated that the establishment of depots can reduce costs through the benefits of economies of scale. [PERSON] et al. [30] introduced a deterministic dynamic large-scale optimization model for managing company-owned containers from the perspective of a tank container operator. The model considered both inland and mar time distribution on a continental level. Only one container type was considered, which excluded substitution options, and rental opportunities were not incorporated. Several operational studies have focused on improving the day-to-day management of inland empty container movements across regional networks. [PERSON] et al. [31] introduced an operational model aimed at overseeing the management of inland empty containers across the Mediterranean basin, with a focus on optimizing empty container resources. Although the study took into account two types of container, substitution options were excluded. Storage was permitted only at ports, and leased containers were treated as if they were company owned. [PERSON] and [PERSON] [32] proposed an optimization model aimed at minimizing transportation costs between ports, inland depots, and customers. However, their model did not account for storage, substitution, or rental opportunities. Additionally, it was assumed that the number of requests and supplies at ports remained constant and unaffected by changes during each period. Another stream of research has focused on truck fleet operations and vehicle routing strategies to reduce the inland movement of empty containers and improve transportation efficiency. [PERSON] and [PERSON] [10] investigated the management of a truck fleet responsible for transporting containers to a port, where empty and full containers were not distinctly categorized, as both were generally considered part of the transportation service. In the same year, [PERSON] et al. [33] proposed the Inland Depots for Empty Containers (IDEC) system, analyzing its potential to reduce empty vehicle miles travelled and lower the costs associated with repositioning empty containers. Furthermore, [PERSON] et al. [34] examined four distinct container movement types--inbound full, outbound full, inbound empty, and outbound empty--while also considering the impact of time windows on truck operations. [PERSON] et al. [35] employed an enhanced particle swarm optimization method to tackle a heterogeneous vehicle routing problem (VRP) with a collection depot, aiming to minimize the inland movement of empty containers. Additionally, [PERSON] et al. [36] considered the issue commonly regarded as an extension of VRP. Considerable research has been performed on the issue of inland transportation of empty containers since it affects narrowing the potential operating costs. Beyond these operational studies, the environmental impact of empty container movements has become a critical focus in recent logistics and sustainability research. In 2018 alone, the movement of empty containers contributed approximately 58 million tons of CO\({}_{2}\) equivalent, representing around 1% of total global CO\({}_{2}\) emissions [6]. Furthermore, according to the International Maritime Organization's Fourth Greenhouse Gas Study [37], CO\({}_{2}\) emissions from the shipping industry could increase by up to 17% in the coming years [38]. Land transportation within the maritime field significantly contributes to CO\({}_{2}\) emissions, particularly during the movement of containers between ports and depots. [PERSON] et al. [39] focused on the pollution and congestion caused by empty container movements at ports, related to the truck traffic in the Southern California region. In a similar context, [PERSON] et al.