Planning of Horizontal Transport is a significant problem with material impact on the development budget and productivity of a container terminal. This paper uses Queuing Theory, Petri Networks (PNs) and Discrete Event Simulation to address the fleet size determination problem for tactical planning. Considering the different information and modelling effort required for the three methods, it is recommended that queuing theory be applied in the preliminary planning stage as it is conservative, while discrete-event simulation which can yield significantly more cost-efficient results is applied for the detailed planning stage. Further development would be still required towards an easily applicable tool based on Petri Nets for practitioners to use in current planning problems, but the methodology itself can provide reasonable yet conservative results at a preliminary planning stage.