After a five-year study, a leading research group has concluded that loud, blaring sirens on fire trucks are ineffective at getting cars to clear a path.  In response to the study there is a new standard for apparatus sirens that replaces the familiar sirens with a soothing British aristocratic voice that nicely asks motorists to please move over. 

 http://www.firerescue1.com/fire-news/1424914-noisy-fire-truck-sirens-outlawed-as-kinder-gentler-sirens-sweep-country/