Terminal operating systems (TOS) play a major role in today's terminal performance. A TOS is used to create operational plans in order to ensure timely handling of vessels, trucks and trains at minimal operational cost. Creating appropriate operational plans forms a challenge for the planners, as plans should take into account a variety of aspects, such as grounding decisions and equipment dispatching. In addition, several decisions have to be made within a limited time frame, couple of hours before starting the operation. Wrong decisions in the plan can have major impact on the operation and implies financial and safety consequences. Planners face these problems only when the plans are actually executed in live operation. In this article, we propose to use a fast yet accurate simulation of both the operation and the TOS in order to support planners to investigate and adapt plans before they are applied in live operations.