Optimising Vehicle Routing for Skip Containers
A Waste Collection Case Study with Container Reuse and Stacking using LNS
C.M.W. Aalders (TU Delft - Civil Engineering & Geosciences)
B. Atasoy – Graduation committee member (TU Delft - Mechanical Engineering)
S. Fazi – Graduation committee member (TU Delft - Technology, Policy and Management)
J. Duran Micco – Graduation committee member (TU Delft - Mechanical Engineering)
K.M. Hauge – Mentor (AMCS)
K. Van Duurling – Mentor (AMCS)
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Abstract
Growing volumes of construction and demolition waste create increasing pressure on waste logistics systems. Skip containers are one of the main container types used for this type of waste, yet existing routing research still focuses mainly on large rollon-rolloff (RoRo) containers. As a result, the operational characteristics of smaller chain-lift skip containers remain underexplored. In particular, the possibility of stacking empty containers on a vehicle and directly reusing an empty container between customers has received limited attention in the literature. This thesis addresses this gap by studying how vehicle routing for skip container waste collection can be optimised under container reuse and stacking feasibility constraints.
First, a mixed-integer linear programming (MILP) benchmark model is developed to represent standard skip container operations under simplified assumptions. Second, an extended Large Neighbourhood Search (LNS) metaheuristic algorithm is proposed to incorporate more detailed stacking rules, direct container reuse, and multiple storage and disposal location options. The benchmark and metaheuristic models are evaluated using operational and algorithmic key performance indicators.
The validation experiments showed that the LNS algorithm generated solutions within an average deviation below 3% from the benchmark while requiring substantially shorter runtimes. Furthermore, the results show that exact optimisation becomes less practical as the number of customers increases. Across the larger experiments, vehicle configurations with limited full container capacity consistently performed worst, indicating that a primary operational bottleneck lies in the number of available positions for transporting full containers rather than in stacking height alone. In addition, reuse reduced total operational time and improved productivity mainly through reduced handling time, although the number of vehicles required remained unchanged. These findings show that detailed stacking constraints and direct container reuse can be incorporated successfully into skip container routing models and that these extensions improve the practical relevance of optimisation for chain-lift skip operations.