Ambulances & Vehicle Ops

Lights and Sirens Improve Safety of Emergency Calls

As the bay doors open and we pull into traffic, I know this is going to be a challenging emergency run. It’s 5 p.m. on a hot summer night and there’s bumper-to-bumper traffic. The incident we were just dispatched to sounds very serious, so I know time is of the essence. Someone’s life depends on our unit getting to them quickly and safely in the chaos of Friday night rush hour.

When we hit Prince and Main Street I can see we aren’t going anywhere quickly: Gridlock! I change the siren tone and lay on the air horn, but no one’s moving. Why? Are they distracted by texting, loud stereos, telephone calls or crying children? Maybe their air conditioning is running and their windows are sealed tightly.

“What’s going on with these people, don’t they see or hear us?” I think to myself. “No one’s moving and I’m in a hurry to save a life.”

Then slowly, like Moses parting the Red Sea, a path begins to open and we carefully maneuver through. Will we be there in time to make a difference?

Ambulance lights and sirens
These individual surface-mounted lights above the cab are mounted directly on the body. The clear lenses on each light allow them to perform multiple functions and flash different colors in different patterns.
Photo courtesy Wayne Zygowicz

Risky Business

We live in a mobile society that’s always in a hurry to get somewhere fast. Each year traffic increases and our roadways and interstates become clogged with drivers who are often impaired by fatigue, alcohol, drugs or distractions.

Driving an emergency vehicle is a risky business that can have grave consequences around each turn. Each time we get behind the wheel of our ambulance and turn on our lights and sirens, there’s risk involved. Therefore, it’s imperative to crew safety that motorists can quickly hear, see and identify our ambulance, or other emergency vehicle, and react fast enough to get out of our way and avoid a collision.

A number of variables affect emergency vehicle identification: the vehicle size, color scheme, conspicuous markings and retroreflective striping, as well as environmental factors. Properly positioned emergency lighting and the use of audible sirens and horns, however, may be the most important elements for avoiding a deadly collision.

Ambulance lights and sirens
Mount grill lights near the center of the grill and away from the front headlights. Photo A.J. Heightman

Lighting Specifications

Your ambulance chassis comes with the minimum lights required by law: headlamps, tail lights, signal lights, marker lights and brake lights. However, this original manufacturer’s equipment (OEM) provides only a limited outline of your vehicle. A wealth of industry standards has been developed to guide agencies on the selection and placement of additional emergency lighting. (See sidebar “Industry Standards,” below.)

Lighting placement is important. Emergency lighting should capture the attention of motorists, bicyclists and pedestrians, and alert them to the presence of your ambulance. This is especially important when entering intersections—where many accidents occur. Adding emergency lighting increases the conspicuity of your ambulance by defining the upper and lower clearance lines of your vehicle from all sides, making it easier to spot day or night.

Emergency lights should be mounted high on the ambulance box and as close to the corner points on all sides. Lower-level lights should be added to the front and rear corners, forward and aft of the vehicle’s two axles. LED strip lights work great for this application, plus they use minimal power.

Lighting should be installed above the cab and in the grill/bumper area to outline the front of the ambulance. These lights make your ambulance visible to low-profile vehicles as you approach them from the rear.

Ambulance lights and sirens
Patient loading lights at the rear of the ambulance and on the interior of the door can help increase the visibility around your vehicle and improve safety for personnel working at night. Photo courtesy Wayne Zygowicz

New roof-mounted LED light bars are a good option for over-the-cab lighting since they use little amperage compared to older technology. Look for a light bar that provides 360-degree lighting and can be easily reprogrammed with a laptop computer. Changing the lighting configuration and flash pattern is easy and can be accomplished with a few keystrokes. Current light bar technology is brighter, more aerodynamic and more user-friendly than what was on the market in the past.

Another effective and economical front lighting system design, popular on European ambulances, builds the lights into the ambulance box, which makes the light bar aerodynamic with the roof line.

A third option uses individual surface-mounted lights installed above the cab and mounted directly to the body. Installing clear lenses on each light allows them to perform multiple functions and flash different colors in different patterns. A single surface-mounted light is also easy to repair when it burns out vs. dissecting a whole light bar.

Front grill lights come in several configurations and sizes. They should be mounted near the center of the grill and away from the front headlights.

Ambulance lights and sirens
Siren speakers and air horns should be mounted as low and as far forward on the chassis as possible to protect the hearing of the crew. Photo A.J. Heightman

Scene lighting, loading lights and ground lighting increase the visibility around your vehicle and improve safety for personnel working at night. Two bright scene lights, individually activated from the cab or from the patient compartment, should be mounted to each side of the body.

Patient loading lights should brightly illuminate the working area in the rear of the ambulance and activate automatically when the back doors are opened. They should also be designed to be operated manually from the cab and/or patient compartment with the doors closed.

Ground lights provide an extra margin of safety for those entering and exiting the ambulance. Mounting ground lights under the driver and crew door that activate automatically when the doors are opened and closed is recommended.

The Science of Color

The most effective color for emergency vehicle lighting has been the subject of debate for years. What’s been adopted over time has been based partly on science and partly on tradition.

The literature tells us that the sensitivity of human vision peaks in the yellow-green portion of the color spectrum.1–3 The most visible color is white, followed by green, yellow and red. Although white emergency lights are easily seen, they fail to adequately identify that an emergency vehicle is approaching since all other vehicles on the road have white headlights.

Ambulance lights and sirens
If you drive an emergency vehicle, it’s crucial to understand the laws that regulate their use and the responsibility and liability that go with utlizing them. Photo courtesy Braun Industries

Green, also visually effective, isn’t recommended for emergency lighting since our culture associates green with “go” and would likely cause confusion for motorists and also for other providers when at an emergency scene.Yellow and red, on the other hand, are associated with “danger” and have traditionally been used for warning lights or caution signs.

Current standards recommend using a combination of red, blue and yellow (amber) lights and limiting the use of any white lights to the front of the vehicle.4–7

Builders often recommend installing amber lights on all sides of the vehicle that activate when the ambulance is parked in or along the roadway. Some people theorize that red and blue lights actually distract other drivers, drawing their attention to the side of the road long enough to potentially cause a crash.

All current standards recommend that your lighting system operate in two separate signaling modes.4–6 Each mode activates different lighting combinations and colors.

The primary mode, “calling for the right of way,” signals drivers and pedestrians that your ambulance is responding to an emergency. This display activates when the lighting master switch is on, parking brake is off and the transmission is in drive. Primary mode incorporates mostly red and blue lights used for emergency response.

The secondary mode, “blocking the right of way,” activates amber lights and reduces red and blue lights. This mode activates automatically when the ambulance is stopped and the transmission is in park with the master lighting control on.

Can You Hear Me Now?

Our hearing is one of our most acute and primary senses. Just try shouting loudly or blowing a whistle in a crowded venue and you see how effective you are in getting people’s attention. Loud auditory sounds exert an immediate response and draw attention to the sound’s location.

The use of sirens and audible warning devices on emergency vehicles dates back hundreds of years. Barking Dalmatian dogs used to run ahead of horse-drawn fire brigades not just to rally and motivate the horses, but to warn pedestrians to get out of the way.

Today, many state laws require that the ambulance siren is always activated when responding with emergency lights on.

To be effective, your siren has to compete and overpower surrounding urban environmental noises and penetrate the sound-proofing insulation found in modern automobiles. This can be difficult even with a very loud siren, and will reduce the effective distance at which your siren can be heard. This was very well demonstrated in an award-winning EMS10 Innovator of the Year public service announcement produced by the MONOC EMS System in New Jersey.8

The traditional motor-driven wind-up mechanical sirens like the Federal Q siren has been used on fire apparatus for decades. These sirens were very effective because of their decibel level and penetration power, but they’ve been replaced by electronic sirens with new technology and less expense. I recommend purchasing an electronic siren with ample power that produces a wide spectrum of frequencies and has multiple signaling modes.

Current recommendations are that the siren speakers should be mounted as low and as far forward on the chassis as possible to reduce the potential for hearing damage to the vehicle occupants. Recessed bumper-mounted speakers are perfect for this application.

A new siren concept utilizes sound waves that not only can be heard but physically felt by motorists. Recommended for urban environments with heavy vehicle and pedestrian traffic, these sirens emit low frequency sounds that can penetrate and shake solid materials with their sound waves. Not only do drivers hear and feel the sounds, they may experience their rear-view mirror shaking from the penetrating sound waves.

The manufacturers suggests that these sound waves can be heard and felt from at least 200 feet away with these highly effective sirens. Two examples of this technology are the Whelen Howler Low Frequency Emergency Siren and Federal Signal Rumbler Siren. Current standards specify a traffic horn should be used in conjunction with the electronic siren. Air-powered horns, typically used on larger trucks, are now common on most ambulances. Although little research has been done on air horns, ambulance builders suggest a dual-trumpet air horn that produces two different tones. Air horns should be mounted low on the chassis or in the bumper, not on the cab roof, to reduce noise exposure to the crew.

Hearing loss due to loud sirens and air horns is well documented in first responders.9–11 A concerted effort should be made to prevent noise levels in the cab from exceeding safe occupational standards. Simple measures like adding extra sound-dampening insulation to the cab, closing the windows while responding and mounting audible devices low will help reduce unwanted noise exposure.

Wireless noise-canceling headsets, integrated with the ambulance’s primary radio, also help eliminate siren noise while enabling effective communication with dispatchers and crew members throughout the vehicle. In addition, the use of available wireless devices allows you to exit the cab or patient compartment and stay in communication with the driver while you’re backing the ambulance.

Risk vs. Benefit

If you drive an emergency vehicle, it’s important to know how your emergency signaling devices are designed, installed and activated. It’s also crucial to understand the laws that regulate their use and the responsibility and liability that go with utilizing them.

Remember one important point: emergency lights and sirens are extremely limited warning devices. Even when designed and installed correctly, active warning devices can’t overcome preoccupied drivers. Emergency vehicle operators must drive with caution and adopt a defensive posture while driving with lights and sirens. There are countless lawsuits that have occurred following emergency vehicle crashes that resulted in injury or death.

And, let’s not forget the patient. Most EMS veterans will tell you that driving emergent usually doesn’t improve patient outcomes or significantly reduce scene or hospital arrival times. Rarely does a minute or two make the difference between life and death on most of the calls we run. Some authors actually believe lights and sirens may cause more injuries than they prevent.12

Your agency should develop standard operating procedures that address emergency driving and each member should be trained when to activate warning systems and risk associated with them. The life you save may be your own.


References

1. De Lorenzo RA, Eilers MA. Lights and sirens: A review of emergency vehicle warning systems. Ann Emerg Med. 1991;20(12):1331–1335.

2. Emergency Vehicle Safety Initiative. (February 2014.) United States Fire Administration. Retrieved June 1, 2016, from www.usfa.fema.gov/downloads/pdf/publications/fa_336.pdf.

3. Emergency Vehicle Visibility and Conspicuity Study. (August 2009.) United States Fire Administration. Retrieved June 3, 2016, from www.usfa.fema.gov/downloads/pdf/publications/fa_323.pdf.

4. Commission on Accreditation of Ambulance Services. (March 28, 2016.) Ground vehicle standards for ambulances. Ground Vehicle Standard. Retrieved June 1, 2016, from www.groundvehiclestandard.org/wp-content/uploads/2016/03/CAAS_GVS_v_1_0_FinalwDates.pdf

5. NFPA 1917: Standard for Automotive Ambulances. (2016.) National Fire Protection Agency. Retrieved June 1, 2016, from www.nfpa.org/codes-and-standards/all-codes-and- standards/ list-of-codes- and- standards?mode=code&code=1917.

6. NFPA 1901: Standard for Automotive Fire Apparatus Ambulances. (2016.) National Fire Protection Agency. Retrieved June 1, 2016, from www.nfpa.org/codes-and-standards/all-codes- and-standards/list-of-codes-and-standards?mode=code&code=1901.

7. Federal Specifications for the Star-of-Life Ambulance. (August 1, 2007.) United States General Services Administration. Retrieved June 1, 2016, from www.ok.gov/health2/documents/ KKK-A-1822F%20%2007.01.2007.pdf.

8. Siren public service announcement. (n.d.) MONOC. Retrieved Aug. 17, 2016, from www.monoc.org/newPub/sirenPSA2.cfm.

9. Hong O1, Samo DG. Hazardous decibels: Hearing health of firefighters. AAOHN J. 2007;55(8):313–319.

10. Fernandez AR, Crawford JM, Studnek JR, et al. Hearing problems among a cohort of nationally certified EMS professionals. Am J Ind Med. 2010;53(3):264–275.

11. Clark WW, Bohl CD. Hearing levels of firefighters: Risk of occupational noise-induced hearing loss assessed by cross-sectional and longitudinal data. Ear Hear. 2005;26(3):327–340.

12. Wolfberg D. Lights, sirens and liability. JEMS. 1996;21(2):38–40.


Industry Standards

Emergency warning devices should be incorporated into all ambulance specifications. In addition, buyers should review current industry standards and examine international best practices before developing their design specifications. The internet makes this very easy to do. After doing your homework, consult with your ambulance builder, who’s the expert in industry standards, lighting design and audible warning devices. Also network with other industry leaders to see what they’re building and what works and what doesn’t. This is helpful to avoid making mistakes others have already made.

Industry standards will help guide your lighting and siren purchasing choices. The federal Star of Life specifications, which for years were used to set minimum ambulance standards, are being replaced by new and improved guidelines.

Current industry standards include:

>> National Fire Protection Agency (NFPA) 1901 Standard for Automotive Fire Apparatus;

>> NFPA 1917 Standard for Automotive Ambulances; and

>> the Commission on Accreditation of Ambulance Services Ground Vehicle Standards (GVS) for Ambulances.

Buyers should also consult their own state and local requirements governing emergency lighting. Most states have statutes that outline what type of vehicles can use emergency lighting, color schemes and rules for their use.