High vessel traffic densities, restricted water areas, and low manoeuvrability are common factors that form constraints for the navigating vessels in port areas. While navigating through these areas, vessels get assisted by the Vessel Traffic Service (VTS). VTS operators (VTSO) are monitoring the vessels in ports and provide the navigating skippers with the required information to ensure the safety and efficiency of the vessel traffic in the port. Information is communicated using very high frequency (VHF) radios on the corresponding VHF-channels of the sectors. In busy sectors in the port, these VHF-channels are very crowded, which results in unclear situations and high workloads for the VTSOs. The Rotterdam Port Authority is currently investigating measures to reduce VHF-traffic. To define effective measures, it is required to understand by which factors the VHF-communications are triggered. In this thesis, a quantitative method has been developed to investigate whether VHF-communications are caused by certain properties of a fairway system. The method is based on analysing VHF-traffic and identify factors that lead to an increase in these communications. The main component is digitizing the VHF-communications, which is achieved by converting spoken VHF-audio bands to text, then dividing this text into different conversations and finally classifying each phrase according to place, time and content. Subsequently, the spatial and temporal characteristics of the VHF-communications are linked to spatial and temporal characteristics of a property of the fairway system, to analyse whether the occurrence of a particular form of VHF-communication is related to the occurrence of that particular property of the waterway system. The method can be applied to investigate the individual influence of several fairway properties, but in this research the focus is on analysing to what extent the fairway property “blocked view” leads to the development of VHF-communications. To investigate whether VHF-communications are related to the occurrence of visual obstructions, a method is developed to estimate the visibility for varying locations and vessel parameters.