Last-mile mail delivery using multimodal green transportation modes

With the continued reduction in mail volume, existing delivery strategies are becoming increasingly inefficient and unsustainable. These pressures are exacerbated in regional areas with complex terrain and road layouts, where mail delivery is mainly conducted using conventional vans or motorbikes, increasing sustainability and safety concerns. To address these challenges in Australian regional areas, an adaptive multimodal delivery decision support framework has been developed. This study aims to develop and evaluate a flexible multimodal decision-support system for optimizing vehicle routing, mode selection, and customer allocation in regional areas with declining letter delivery volumes. This expert optimization system integrates mail demand and GIS data, a robust adaptive large neighborhood search optimization engine, and a visualization module. The optimizer intelligently coordinates van delivery with green and sustainable modes, walking and cycling, and dynamically determines suitable customer clusters for walk or bike delivery, while the remaining customers are serviced by vans within the same route. The optimizer system is tested on a real-world case study, and its performance and adaptability are subsequently validated through a second case study, demonstrating its practical applicability and scalability across heterogeneous geographic contexts. The sustainable multimodal system achieved reductions of up to 21.67% in delivery time and 11.36% in CO 2 emissions, respectively, compared with van-only operations. The findings emphasize the effectiveness of the developed adaptive expert system for supporting complex multimodal routing decisions in improving the efficiency and sustainability of last-mile mail operations.