Effectiveness of Audible Warning Devices on Emergency Vehicles.

3576287PDFTech ReportDOT-TSC-OST-77-38PB-274 567DOT-TSC-868Auditory perceptionEmergency vehiclesGrade crossing protection systemsSirensWarning systemsLoudnessSound levelHuman factorsNoiseJohn A. Volpe National Transportation Systems Center (U.S.)Potter, R. C.Fidell, S. A.Myles, M. M.Keast, D. N.Bolt, Beranek, and Newman, inc.NTL-SAFETY AND SECURITY-Human FactorsNTL-SAFETY AND SECURITY-Highway SafetyVolpe National Transportation Systems Center, Technical Reference CenterThe purpose of the study was to examine the effectiveness of audible warning devices (AWD's) on emergency vehicles in terms of aural detectability. Community noise intrusion and opportunities for AWD optimization were also investigated. Measurements were made of sirens, automobile insertion loss, and human detection performance in real-life and simulated situations. Warning effectiveness distances were calculated for three representative situations: (1) Rural environment with vehicle windows closed and radio on; (2) urban environment with vehicle windows open and radio off; and (3) suburban environment with vehicle windows open and radio off. It was concluded that reliance on present audible warning devices to warn drivers in traffic is not justified. To be loud enough to warn in all ordinary circumstances, the sound level of audible warning devices would have to be increased greatly -- producing intolerable community noise. Present audible warning devices can be improved; more uniform horizontal forward radiation and higher frequency sounds would increase detectability. The analysis procedure can provide the basis for an objective measure of audible warning device performance