Pricing, mandates, and tipping points in port–hinterland decarbonization

Reaching net-zero greenhouse gas emissions in maritime logistics requires coordinated action across ports and their hinterland corridors. Policymakers debate whether to prioritize market-based mechanisms (MBMs, such as carbon pricing) or command-and-control (CAC) regulations (such as rail-share mandates and shore-power requirements), but evidence on the relative performance of these instruments at the corridor scale remains limited. This paper develops a calibrated mixed-integer optimization model of a stylized but data-informed port–hinterland corridor that co-optimizes truck and rail flows, discrete rail capacity expansion, and at-berth electrification. We use the model to construct cost–emissions frontiers and to evaluate MBM, CAC, and hybrid policy mixes against this benchmark. The analysis yields three main policy insights. First, the corridor exhibits “lumpy” marginal abatement costs driven by discrete rail investments, which implies that tightening emission targets in small steps is more cost-effective than relying on a single aggressive instrument. Second, we derive closed-form tipping thresholds for rail modal shift and shore-power adoption, and map them over observable parameters such as grid carbon intensity, berth utilization, and rail handling cost; these maps identify regimes in which pricing alone, mandates alone, or hybrid instruments deliver the highest emissions reduction per dollar. Third, sensitivity analysis shows that operational improvements that reduce rail intensity or terminal handling costs both compress the cost–emissions frontier and lower the carbon-price thresholds required to unlock modal shift. Together, these results provide a transparent tool for designing corridor-specific policy mixes and for interpreting carbon prices, modal-share targets, and electrification mandates in terms of observable corridor characteristics rather than model-specific assumptions.