Abstract To meet the growing demands for yet more efficient and safer traffic, traffic control is deployed in all modes of transportation. In maritime transportation, traffic control is performed by Vessel Traffic Services (VTS). This paper describes research which is focused upon measurement of VTS operator performance. The concept of situation awareness is introduced as a means to describe and quantify VTS operator performance. Situation awareness is tested in a full scale interactive simulator. A scoring system for YTS operator performance accounts for the specific characteristics of YTS operator work, such as accuracy and relevance of information.