Cooperative Intelligent Transportation Systems (C-ITS) are currently being widely deployed on the road network. However, the impact of such systems on traffic flow is still to be addressed, especially for advanced deployment phases (high number of connected and automated vehicles). In this context, the paper investigates the impacts assessment of Connected and Automated Vehicles (CAVs) on traffic efficiency, safety and environmental sustainability. The main contribution of the work is a multivariate assessment of the impacts CAVs subject to varying fractions of CAVs (representing successive C-ITS deployment phases). To illustrate the expected results of the proposed evaluation methodology, the authors design realistic scenarios in an agent-based simulation framework that integrate CAVs models. The wide range of indicators presented in this paper are calculated to assess the benefits of CAVs. The results highlight how the introduction of CAVs into traffic stream impacts the indicators' distributions. Multi-dimensional statistical analyses (Principal Component Analysis, Hierarchical Cluster Analysis) provide a synthetic insight on how these indicators are correlated to each other. The paper also investigates the quality of the selected indicators and derive some guidelines for the design of an assessment methodology of the potential benefits of CAVs from traffic efficiency, safety and environmental sustainability perspective.