Relations Between Objectives in Additional Train Scheduling

Scheduling additional trains is an essential task of railway systems. Under the pressure of increasing demand for railway networks, academia has worked in recent decades on the modeling and solving of this task. To be truthful to reality, models must consider the involved stakeholders and account for technical conditions. Satisfying these different interests leads to several objectives, often modeled by a weighted sum. However, extensive studies on objective relations are lacking in the literature, especially for more than four objectives, while practitioners need to deal with larger numbers. As a first step to fill this gap, we study the correlation between pairs of eight objectives. To do so, we generate over a hundred instances from three corridors of the Swiss Federal Railways. To focus on the relations between objectives, we fix the objective function's weights. The results obtained show that some linear correlations are observable. However, they are not generalizable across the different corridors.