Most emergency lights-and-siren use saves no meaningful time — and measurably raises the risk of a crash.

What the evidence shows

The time saved is small — and rarely the deciding factor

The federal EMS literature review puts the time advantage of a lights-and-siren response at roughly 40 seconds to a few minutes, depending on setting.² But for most calls that margin does not change the clinical outcome. By the assessment of the EMS systems now reforming their own protocols, only about one call in five is genuinely time-critical,¹² and fewer than 7% of 911 EMS calls involve any potentially life-saving intervention at any point — including after arrival at the hospital.¹

The crash risk is not small

A national analysis of roughly 19 million responses found that crash rates rose sharply with lights-and-siren use, more than doubling during the transport phase.³ The 2024 national quality collaborative reached the same conclusion across five million calls and helped 50 agencies cut their L&S use by up to a third with no measurable effect on patient outcomes.¹ Fourteen national EMS associations now jointly recommend reducing it,⁴ and the U.S. Fire Administration has issued aligned guidance.⁵

The noise itself is a health cost

Beyond crashes, the warning sound is a chronic exposure for the neighborhoods it passes through. European public-health agencies now classify transportation noise as a driver of cardiovascular disease, attributing tens of thousands of premature deaths a year across Europe to noise exposure through stress-hormone and blood-pressure pathways.⁶⁷ Sirens are an acute, repeated form of exactly this exposure for residents near busy response corridors and stations.

And the warning often arrives too late to matter

A controlled audibility experiment by a New Jersey EMS cooperative found that an approaching siren first becomes audible to a driver in a closed, occupied car at about 280 feet — roughly seven seconds of warning at normal speeds.⁸ The intuition that "drivers hear sirens just fine" does not survive contact with modern, well-insulated vehicles. Much of the risk a siren creates is not offset by the warning it provides.

The reform runs through existing law — without putting the choice on the driver

In most US jurisdictions the traffic code permits emergency vehicles to use lights and siren; it does not require it. The decision is discretionary — which is what makes reform tractable, since tightening when the devices are used needs no new statute, no labor renegotiation, and in many cities no council action. But discretion exercised one call at a time, by an operator already driving under pressure, is the wrong place to locate it. It is a judgment most responders neither want nor should have to make in the moment. The durable reforms move the decision off the individual and into written policy and dispatch.

The most effective programs make the quiet response the default and the lights-and-siren response a defined exception, reserved by protocol for a narrow set of genuinely time-critical calls. Wake County, North Carolina, is implementing exactly this for 2026: its 911 center sorts calls by reported symptom and acuity, and lights-and-siren is held for the roughly one in five calls that are truly time-critical — cardiac arrest, severe collisions, shootings.¹² The crew's job does not change. The protocol, not the driver, decides how they roll.

Three levers do the work, and they reinforce each other:

• A default-quiet policy. Make non-lights-and-siren response the standard and reserve Code 3 for a defined list of critical situations — the St. Louis model. The decision lives in the policy, not in a split-second judgment call.
• Dispatch-side screening. Set the response mode at the 911 center, before a unit rolls, from the caller's reported symptoms — so the call type, not reflex, governs the response.
• Substitution for lower-acuity calls. Route the large share of non-emergency 911 volume — much of it medical and behavioral — to mobile-integrated-health or alternative-response teams that never needed a siren in the first place.

Framed this way, the reform reduces what it asks of front-line responders rather than adding to it, and it narrows the liability that lights-and-siren use creates for agencies and local governments.¹³ It does not ask a department to do less for the public — it reserves the warning devices for the calls where seconds genuinely change outcomes.