Among the strategies of the fifth and beyond generations of communications (B5G/6G) to manage massive connected objects and their increased experience requirements, using relays is gaining much interest. Particularly, the infrastructure supporting applications such as Rescue Operations can beneficially use relay-empowered approaches for efficient disaster management in a city. Several works propose analytical models providing a big picture of the performance expected in large scale deployments. Conversely, real-world testings at a lower scale show performance for more concrete but very limited scenarios. This paper proposes a simulation based approach to evaluation of such applications. It uses an event-based urban traffic modelling that accelerates large-scale simulation, even at the level of a city. It also uses propagation models designed from real-world measurements performed on mobile operator 5G infrastructure to obtain performance results close to reality. The evaluations over a relay-empowered 5G network including one base station, 180 relays and up to 350 vehicles in an urban city, show the gain on metrics such as end-to-end delay and communication speed when using relays.