Cooperative Intelligent Transport Systems (C-ITS) promises to bring societal benefits. The lack of large-scale implementations and real traffic conditions, however, present a challenge in quantifying the impact of C-ITS services. Road authorities are in need of information about the necessary conditions and options required to achieve a successful implementation of C-ITS This guide serves as a tool for road authorities and cities to support investment decisions regarding C-ITS on signalized intersections. It provides a step-by-step process for the assessment of the (potential) effectiveness of C-ITS applications in its own specific setting. Next to obtaining realistic expectations on the benefits from implementing C-ITS on various types of signalized intersections, this document guides in the process on how to investigate the impact of C-ITS on signalized intersections.