Well a mission where the emergency units are already on the scene but that they need back up like police to organizing the traffic and hold people on a distance or you send more units because the fire is out of control? Or you recevied a 911 call that a biker falt of his bike and that you need to treat him but when the ambulance/fire department arrived that the croud crowd will turns again the ambulance and ambulance crew, and that you need to send police to assist the paramedics and fire fighters on the scene or something like that But this are just ideas