Redefining empty trips through occupancy and transferability of cross-modal strategies: A review

Source abstract

Empty trips, vehicle movements without payload, generate unsustainable externalities. This study addresses these challenges by identifying shortcomings in the literature on empty trip generation across all modes through a combined narrative and systematic review. The review revealed that the conventional definition of empty trips adopts a binary empty/non-empty perspective, which fails to capture the extent of the problem. In response, we propose a continuous measure based on the proportion of unused vehicle capacity. Our review also reveals that mitigation strategies are often case-specific, which limits their impact and transferability across modes. To address this limitation, we introduce a framework that facilitates the transferability of strategies by highlighting cross-modal similarities in generating empty trips. Finally, we reviewed these strategies, their methodologies, and the associated problems related to empty trips using the systematic review in driver-provided mobility, which includes public transportation, carpooling, taxi, and ride-hailing to support sustainable mobility through strategy generalization.