In this paper we aim at introducing Unmanned Aerial Vehicles (UAVs) to prevent accidents, considering a use case that is likely to happen in cities where vehicles are circulating and when approaching an intersection like a pedestrian crossing, a railway crossing or a crossroad. A first UAV observes from the top of the scene and will, in certain cases, notify a second UAV which will exchange information either with the car driver if its behavior is far from a reference profile, or with the infrastructure in the ultimate case. We highlight interactions between the two UAVs (U2U communication) as well as between the UAV and the car vehicle (U2V communication) and between the UAV and infrastructure (U2I communication). Hence, we emphasize the benefit of using UAVs to enhance safety and reduce accident gravity rate.