## 2 Literature Review  
Urban or city logistics has been investigated for many years but evolved over time due to environmental changes [5]. The problem is associated with freight transportation including logistics movements that allow freight to arrive at markets for producing other products and movements that are made by end-consumers [6]. Factors involving urban logistics include the growth of city population, e-commerce, sharing economy and sustainability [7]. Planning urban logistics has been supported by advanced technology such as automation, big data, digital connectivity and automotive technology. There were also concerns about the rapid growth of urban logistics which increased city air pollution levels [8]. Emission reductions and sustainability were discussed in many publications such as [PERSON] et al. [9] who studied profits and CO\({}_{2}\) emission in collaborative city logistics. Last-mile delivery, which is the last leg of the supply chain, accounts for 28% of the total delivery cost [10]. There have been some attempts to improve the efficiency of the last-mile delivery, such as Modular BentoBox System [11] where commodities were deposited to the bento box locations for an end-consumer to pick them up. This practice was adopted by logistics operators such as Post.24 (Austria), and SmartPOST (Estonia). Furthermore, shipment efficiency can be improved by consolidating and synchronizing shipment resources between logistics companies such as those in Singapore logistics collaboration [11], an interactive freight-pooling service [12], or the use of third party consolidation centers [13]. Recently, [PERSON] et al. [10] proposed to increase the last-mile delivery effectiveness by applying a crowdsourced delivery model, utilizing a large pool of citizen workers to reduce infrastructure expenses. The last-mile logistics can be considered as a vehicle routing problem. Route balancing problems are usually introduced in order to find fair job distributions amongst all vehicles. Majority of researches in the literature tackle the routing balance problem as a vehicle routing problem with two objectives. Generally, the bi-objective function includes (1) minimizing the total route length and (2) balancing other variables between routes. Examples of balancing variables can be classified into two types: load-related variables and length-related variables. For the load-related variables, there were several solution methods proposed such as an integer programming model [14], and a mixed integer programming model [15]. To balance length-related variables, such as total distances, the method of [PERSON] et al. [16] applied the min-max formulation as one of the objective functions and was solved with the non-dominated sorting genetic algorithm II (NSGA-II). The length-related variable involving a route cost was also solved by a multi-startstrategy on Path-Relinking [17]. [PERSON] et al. [18] implemented evolutionary algorithms to find solutions to vehicle routes with seven balanced objective functions. A real case study on distribution of orders across Hong Kong was studied in [PERSON] et al. [19] by applying multi-objective large neighborhood search to create delivery routes with profit balanced. Clustering algorithms such as \(k\)-means have also been applied to partition areas for a vehicle routing problem [20]. The two-stage approach starts by applying \(k\)-means to partition the entire problem into several areas, and the borders are subsequently adjusted to balance the number of visiting locations within clusters. While the original \(k\)-means algorithm can partition the whole region into areas based on the visiting location distribution, the algorithm does not produce equally sized groups for the number of visiting locations. Thus, the second stage, which is a method for adjusting borders, is applied to move points from a large cluster to a smaller adjacent cluster. While most solution methods presented above were mainly introduced for a single time period vehicle routing problem (e.g., [PERSON] et al.