Cooperative Intelligent Transport Systems (C-ITS) promise to bring large benefits in terms of increased transport safety. While some communication technologies used in C-ITS, such as Dedicated Short-Range Communications, have been already available for a long time, they were never adopted on a mass scale in consumer electronics, severely limiting the options for Vulnerable Road Users (VRUs) to foster the benefits of C-ITS. This situation might change with the advent of 5G-enabled smartphones. However, thorough testing of the available 5G networks is necessary before the deployment of C-ITS services to ensure their reliable operation. In this paper, we present a methodology for measuring and evaluating the selected performance parameters of V2P and Pedestrian-to-Infrastructure (P2I) communication based on 5G Uu communication interface using off-the-shelf hardware likely to be used by VRUs. We present a set of mobile applications that emulate V2P and P2I message transmissions and measure the increase in communication delay and message loss. Furthermore, we demonstrate the methodology of data collection and evaluation on a real case study conducted in the city of Zilina, Slovakia. The results suggest that the currently deployed commercial 5G networks can support V2P communication over Uu interface reliably if the generation frequency of the communication messages remains low.