Vessel Traffic Service (VTS): a maritime information service or traffic control system?
Vessel Traffic Service (VTS) is a shore-side maritime assistance service that supports bridge teams in
their safe navigation of port approaches and other areas that present navigational difficulties. The VTS
is implemented in national waters and provides vessels with information through transmissions and
broadcasts on Very High Frequency (VHF) radio. With a continued growth in the number, size and
cargo volumes of merchant vessels, the role of the VTS has recently become a matter of discussion,
and it has been argued that changes, such as implementing an aviation-like control system, would be
of an enormous benefit for stakeholders and guarantee safe and efficient traffic movements in the
The complexity of processes in safety-critical domains, such as maritime traffic management, is
increasing due to continuing technical, organisational and environmental developments. The VTS is
currently undergoing drastic changes, primarily driven by strategies and projects focusing on
increasing the overall efficiency of the maritime transportation system through advanced technology.
To reduce the risk of unforeseen consequences, it is important to study and understand the service and
its contribution to traffic management before changes are implemented. The purpose of this thesis has
been to increase the overall understanding of everyday performance of the VTS system and identify
ways of modelling the performance of the service, as a contribution to the ongoing debate on the
future needs of maritime traffic management.
The VTS is described as socio-technical system that controls and manages maritime traffic in port
approaches and other areas that pose navigational difficulties for bridge teams. Field data collected
through semi-structured interviews, observations and focus groups have been analysed with the aid of
concepts derived from Cognitive Systems Engineering (CSE) and Resilience Engineering (RE) to
understand how the VTS actively contributes to safety through monitoring, responding to and
anticipating changes in traffic patterns in the VTS area. The data have also been used to model
performance variability in everyday operation with the aid of the Functional Resonance Analysis
Method (FRAM). Performance variability is necessary for a system to be adaptive, and is therefore
essential for the system’s functioning. By using the FRAM, a new angle of the VTS system has been
explored to understand how variability in its functional units affects the overall system performance.
The thesis demonstrates the importance of understanding how performance in a socio-technical system
can vary and the consequences this may have. The FRAM can be used to analyse the functional design
of a socio-technical system, and therefore help to identify and assess ways in which performance
variability can be monitored and managed. By understanding the functional design of the VTS system
and the complexity of everyday operation, stakeholders will be able to identify advantages and
disadvantages of current system design and use this to consider how future demands can best be met.
Cognitive Systems Engineering
Functional Resonance Analysis Method (FRAM)
Vessel Traffic Service