A brownfield container terminal aims to realize a zero-emission vehicle fleet by 2040. To prepare for the fleet investments, the terminal wants to ascertain the consequences for its costs and operational performance of implementing a new generation of zero-emission equipment for the horizontal transportation of the containers at the terminal. To address this issue, a literature research is carried out to formulate the technological criteria for energy carriers and to identify possible energy sources that could facilitate the transition from a fossil fuel-based vehicle fleet toward a zero-emission vehicle fleet. The list of possible energy carriers is reduced by an assessment. The outcome of the assessment results in two best options, namely, the lithium-ion battery and hydrogen, for the vehicle fleet. Consequently, a discrete event simulation is carried out to assess the operational performances of these two energy carriers. This approach can be applied for many other terminals that are exploring ways to achieve a zero-emission fleet.@en