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October 20, 2021

Ambulance sirens: Do they save lives—or put them at risk?

Daily Briefing
    Editor's note: This popular story from the Daily Briefing's archives was republished on Apr. 7, 2022.

    Some public health experts argue that the overuse of sirens on emergency vehicles, along with lights and high speeds, pose a significant risk to emergency responders and civilians, causing a "public health dilemma"—but newer low-frequency models could help make sirens safer and more effective during patient transport, Christopher Mele writes for the New York Times.

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    Risks vs. benefits

    According to Mele, experts believe that emergency sirens can be useful when responders need to navigate through traffic in urgent situations—but for the majority of situations, many experts say that sirens can often do more harm than good.

    For example, experts told Mele that emergency responders are more likely to engage in high-risk behavior during "hot" responses, when ambulances deploy their flashing lights and wailing sirens. In addition, during lights-and-sirens responses, other drivers sometimes respond in unpredictable ways, such as stopping in front of an emergency vehicle instead of moving out of its path.

    Experts also told Mele that sirens have the potential to harm emergency responders, who sometimes experience premature hearing loss, as well as patients, who could become distressed by the blaring noise. Further, a study by the National Highway Traffic Safety Administration estimated that an average of 4,500 ambulance accidents occurred annually from 1992 to 2011, resulting in an average of 33 deaths and injuries to 2,600 people each year, Mele writes.

    Research has also been mixed on whether hot responses provide a medical benefit over "cold" responses, when ambulances don't use their lights or sirens, Mele writes.

    Ultimately, over a dozen studies have estimated that responses using lights and sirens can reduce travel time to a scene by anywhere from 42 seconds to three minutes—a response time that typically has little to no effect on the majority of patient outcomes.

    In fact, many medical services try to meet response times based on studies from the 1970s, a time when life-saving devices such as automatic defibrillators were not widely available in public settings, Mele writes. In addition, some municipal contracts require private ambulance services to meet outdated response times, which incentivizes the use of lights and sirens, according to experts.

    "Most of the things that are time-dependent are a very tiny minority of the E.M.S. calls," said Douglas Kupas, E.M.S. medical director for Geisinger E.M.S., acknowledging that these responses are usually only necessary in cardiac arrest calls. Despite that, however, a report Kupas wrote found that "the average overall use of lights and sirens in E.M.S. calls nationally from 2010 through 2015 was as high as 77.5 percent," Mele writes.  

    According to Jeff Clawson, founder of the International Academies of Emergency Dispatch, this overuse of lights and sirens in emergency situations poses a "public health dilemma." He said, "Killing nuns and children at crosswalks because you are running lights and sirens on a mouse bite doesn't make any sense."

    Sirens compete with improved insulation and sound systems in cars

    Making the problem more complex, Mele writes, is the bolstered insulation and improved sound systems of modern-day cars.

    For example, in an experiment conducted on a closed road by the former Monmouth Ocean Hospital Service Corporation, an ambulance starting 1,500 feet from an idling car had its siren set to "wail" mode—and with the window open, the driver heard the siren. However, with the window closed, the radio on, and the driver talking on the phone, the driver heard the siren when it was less than 283 feet away. Under those conditions, with the ambulance going 25 miles per hour, the warning time for the driver decreased to seven seconds—and when the ambulance was going 45 mph, the warning time decreased to less than four seconds.

    "High-frequency sounds get blocked easiest, and that includes sirens," said Keith Stevenson, a captain with the Newfoundland Area Ambulance Association. "Add a killer sound system to that car and the latest Beyoncé track, and it erases the last bit of siren that could reach the driver. "

    But newer siren models now rely on sound waves that can be both heard and physically felt. Referred to as the Growler, Howler, and Rumbler, these sirens emit low-frequency sounds that penetrate and shake solid materials, such as car mirrors, Mele writes.

    "I don't know the mechanism by which they work, but it is pretty effective," Stevenson said. "You'll be coming up behind someone with the sirens blaring and then as soon as you flip the switch for the Growler, you get brake lights. In combination with an air horn, you can usually grab the driver's attention." (Mele, New York Times, 10/19)

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