Rich Vehicle Routing Problem with diverse Vertices allowing Hierarchical and Multimodal Time-Dependant Transhipment of multiple Node- Vehicle- compatible Cargo with Cascaded Time-Minimization Objective for Emergency Decision Support Systems

A rich vehicle routing problem is considered allowing multiple trips of heterogeneous vehicles stationed at distributed vehicle depots spread across diverse geographies having access to different modes of transportation. The problem arises from the real world requirement of optimizing the disaster response/preparedness time and minimizes the route duration of the vehicles to achieve the solution with the minimum highest-vehicle-route-duration. Multiple diversely-functional vertices are considered including the concept of Transhipment Ports as inter-modal resource transfer stations. Both simultaneous and split pickup and transferring of different types of delivery and pickup cargo is considered, along with Vehicle-Cargo and Transhipment Port-Cargo Compatibility. The superiority of the proposed cascaded minimization approach is shown over existing makespan minimization approaches through the developed MILP formulation. To solve the problem quickly for practical implementation within Disaster Management-specific Decision Support Systems, an extensive Heuristic Algorithm is devised. The Heuristic utilizes Decision Tree based structuring of possible routes and is able to inherently consider the compatibility issues. Preferential generation of small route elements are performed, which are integrated into route clusters; we consider multiple different logical integration approaches, as well as shuffling the logics to simultaneously produce multiple independent solutions. Finally perturbation of the different solutions are done to find better neighbouring solutions. The computational performance of the PSR-GIP Heuristic, on our created novel datasets, indicate that it is able to give good solutions swiftly for practical problems involving large integer instances which the MILP is unable to solve.