From NEMSQA....

It is believed that using lights and siren helps patients receive life-saving emergency care more quickly, leading to better patient outcomes. The use of emergency vehicles’ lights and siren does not, however, save clinically significant amounts of time, according to numerous studies, systematic reviews, and position papers.

The fortunate fact is that few patients actually require critically time-sensitive, life-saving interventions in virtually all EMS systems. As a result, using lights and siren fails to accomplish the desired goal and significantly raises (by more than 50%) the chance of an ambulance crash. The judicious use of lights and siren, only when necessary, should be standard practice in order to increase the safety of patients, healthcare clinicians, and the general public.