Abstract Summary
This study investigates an integrated water- and land-transportation (IWLT) system for a delivery service in Amsterdam, the Netherlands, where inland waterways cover 25% of the city's land area. Meeting the demands of the growing population and tourist population has become challenging under regulations limiting the reach of freight vehicles in cities. The use of inland waterways for various freight activities worldwide motivates service providers, policymakers, and researchers to explore IWLT systems and reduce the costs caused by limited access and vehicle idle times during congestion in cities. However, the cost efficiency of an IWLT system depends heavily on the design of transshipment facilities, or satellites, where goods are transferred from the water network to the road network. These facilities offer limited resources, such as space, storage, equipment, or labor, shared by vehicles on both networks. Instead of investing in resources at the satellites, public spaces can also be utilized as transshipment points, such as parking spots and public transportation stops, among others. However, this requires exact synchronization between city freighters and vessels to ensure they are present at the satellites for transshipment and forces all vehicles to wait if necessary. The trade-off between infrastructure investments and logistics costs plays an important role in transitioning towards more flexible, integrated, and sustainable systems. The challenge is to optimize the integrated routing problems connected via transshipment facilities to achieve the global optimum. In this study, we decompose the integrated problem into several optimization problems: multi-trip vehicle routing problem (VRP) on the streets, job scheduling problems at the transshipment facilities, and VRP over waterways. The decomposition method lets us model and test different variants of such systems considering various fleet specifications, direct/indirect services, and storage options at transshipment facilities. Different synchronization degrees are analyzed regarding the capacity of the transshipment facilities: i) asynchronous, ii) semi-synchronized, and iii) fully synchronized systems. Then, these systems are assessed on the case study along with various discussions on network service design and efficiency. Acknowledgments: This research is supported by the project “Sustainable Transportation and Logistics over Water: Electrification, Automation and Optimization (TRiLOGy)” of the Netherlands Organization for Scientific Research(NWO). The case study in Amsterdam is conducted in collaboration with the Municipality of Amsterdam and we are especially thankful to Marcel Ludema, Thomas Vernooij, and Thomas Meindertsma for the discussions and inputs.
