Improving aerodynamic performance of intermodal trains through optimisation of loading plans

This paper addresses the improvement of energy efficiency in intermodal freight trains by reducing aerodynamic drag through optimisation of container arrangement on railcars. In current terminal practice, loading plans are usually driven by local criteria such as minimising crane operating time or travel distance, which may result in non-compact cargo configurations and increased aerodynamic losses during train movement. A mathematical model of aerodynamic drag is formulated using position-dependent drag coefficients and a gap-penalty function that reflects the length and location of empty slots in the train consist. The loading problem is modelled as a constrained assignment task with the primary objective of minimising crane working time. Three approaches to generating the initial loading plan are analysed: a slot-priority heuristic, a greedy algorithm, and an ant colony optimisation algorithm. On this basis, a dedicated post-processing algorithm is applied, which iteratively relocates containers towards the front of the train, reduces gaps between units, and preserves all technical and operational constraints. The method is implemented by linking a FlexSim simulation model of an inland intermodal terminal with Python-based optimisation procedures. Nine scenarios with different shares of containers from the road zone and storage yard are evaluated using 16 replications each. The results show that the proposed procedure can reduce estimated aerodynamic drag by approximately 5–9%, at the cost of increased crane operating time. An energy balance comparison indicates that the additional terminal energy consumption is significantly lower than the traction energy savings, confirming that aerodynamic criteria should be explicitly incorporated into train loading strategies.