Powerful electric locomotives with high traction performance are foreseen to be used to boost the overall performanceof freight transport. However, they would exert extra burden on the power supply system, so the power peak demandwould be a bottleneck for future freight transport. To avoid large-scale modifications to the existing systems but ensureoperational reliability, this study investigates the formation of power peaks and explores power peak shaving concepts tolet the existing systems be more reliable and accommodate more freight traffic. Different from many previous studieswhich focus on energy saving, this study aims at lowering the power peak demand by “smart train operation”, i.e.altering the train speed profile without compromising running time. This study is mainly performed by simulation basedon a standardized freight operation with full regenerative braking used. But this study also shows a real case study basedon measurement data of power history from an onboard energy meter. The study shows the formation of power peaksin different conditions and suggests some possible measures to shave the power peak demand. The study also showsthat there is a compromise between power peak shaving and energy saving, to which more attention is needed in futurestudies