Quick Answer
Fire trucks have blue lights for a few key reasons. The main reason is that blue lights are most visible at night compared to other colors. This allows firefighters responding to emergencies to be seen more clearly. Blue lights also stand out against other vehicle lights and environmental colors. Additionally, blue lights are associated with emergency services and allow fire trucks to be easily identified.
Blue Lights Are Highly Visible
The primary reason fire trucks have blue lights is that blue is one of the most visible colors, especially at night. The human eye is most sensitive to blue wavelengths of light. Blue light also scatters less compared to other colors when passing through particles in the atmosphere. This means blue lights maintain their intensity and are able to be seen from farther away.
Studies have shown that blue lights are perceived brighter than red and white lights of the same luminance. Blue also has a low threshold for detection, meaning the eye can detect dimmer blue lights than it can for other colors. This makes blue ideal for fire trucks that are often responding to emergencies at night when visibility is reduced.
Blue Contrasts Against Other Lights
Another reason for blue emergency lights is that blue contrasts well against other lights typically seen at night. Most vehicle headlights and street lights emit light that appears yellowish. Blue stands out distinctly against this yellow background. The complementary blue and yellow colors heighten the visibility of emergency vehicles.
Red lights could also work for visibility at night. However, red can blend in more with brake lights from other vehicles. Blue emergency lights are less likely to be confused with non-emergency vehicle lights. The contrast provided by blue makes fire trucks stand out more than red would.
Blue Is Distinct from Environmental Colors
Blue also contrasts well against typical environmental colors. During the day, blue pops against green vegetation and foliage. At night, it stands out against dark backgrounds. Blue has very different wavelengths compared to the warm oranges, reds, and yellows found in urban and natural landscapes.
Emergency vehicles need to be noticed both day and night. Blue is a versatile color that maintains visibility in both high light and low light conditions. It works well against the wide range of settings fire trucks operate in.
Blue Has an Emergency Services Association
The public associates the color blue with emergency services and urgent situations. Police typically use blue lights as well. The shared color helps identify fire trucks and police cars as emergency vehicles. It quickly communicates their purpose for responding rapidly with warning lights on.
Even when not consciously thinking about it, people instinctively feel alert when seeing blue lights approach. This association developed because blue has been the preferred color for emergency vehicles for decades. The strong link between blue and emergency helps make blue warning lights on fire trucks very effective.
History of Blue Emergency Lights
Blue emergency lights were first used in the 1930s for police cars. Early experiments by police departments found blue was the most attention-grabbing color for officers on patrol. This prompted switching patrol car lights from red to blue. The change was made first in Cincinnati in 1936 and adopted by other cities soon after.
Fire departments also transitioned warning lights to blue based on the increased visibility it provided. Minneapolis-Saint Paul was the first major city to use blue lights on fire vehicles beginning in 1937. In the 1950s and 1960s, standards were introduced recommending blue for emergency vehicle lights across the country.
How Blue Light Wavelengths Work
The specific wavelengths of light play a key role in making blue highly visible. Within the visible color spectrum, blue wavelengths range from around 450 to 495 nanometers. Shorter wavelengths are perceived as blue hues by the human eye. These short waves:
– Scatter less in the atmosphere, maintaining brightness of the light over distance
– Focus well due to minimal refraction effects
– Transmit through water droplets in rain and snow with minimal diffusion
This helps blue light maintain its alerting qualities under tough environmental conditions.
| Color | Wavelength Range |
|---|---|
| Blue | 450-495nm |
| Green | 495-570nm |
| Yellow | 570-590nm |
| Orange | 590-620nm |
| Red | 620-750nm |
Blue Light and the Human Eye
The eye’s biology also contributes to enhanced blue light visibility. The retina contains special photoreceptor cells called intrinsically photosensitive retinal ganglion cells (ipRGCs). These ganglion cells are most sensitive to light in the blue spectrum. Exposure to blue wavelengths triggers the ipRGCs to send signals to the brain that regulate functions like circadian rhythms.
While all photoreceptors in the eye allow us to see blue, the ipRGCs have a stronger response to these wavelengths. This amplifies the alerting nature of blue light. The ipRGCs act as a detector making the brain extra attentive to sources of blue light.
Blue Pigments for Emergency Lights
Producing blue warning lights on fire trucks begins with compounds that emit blue wavelengths. LED emergency lights use indium gallium nitride (InGaN) semiconductors. Adjusting the indium concentration in the InGaN alloy can tune the wavelength to blue hues. Blue emergency lights can also be produced by:
– Phosphors like divalent europium that emit blue wavelengths when excited
– Organic dyes and pigments with blue fluorescence
– Other inorganic pigments like cobalt blue
These substances provide the bright blue sources used in rotating beacons, flashers, headlights, and other emergency lighting on fire trucks.
Optical Filters Boost Blue Wavelengths
Lenses and filters are added to boost the intensity of blue wavelengths coming from emergency lights. Shortwave pass filters only allow short blue wavelengths to transmit while blocking longer green and red wavelengths. This enhances the coloration and brightness of the blue emergency lights.
Anti-reflective coatings on lenses also help more blue light pass through. By reducing reflective losses, more blue light reaches the eye of observers for maximum visibility. The optical design compliments the blue-producing LEDs or phosphors.
Blue Goes Hand-in-Hand with Red for Fire Trucks
While blue lights provide visibility for fire trucks, red lighting is also important. Red is traditionally associated with firefighting equipment. The red communicates the exact purpose of the emergency fire truck even before it fully arrives on scene.
Red and blue are frequently used together on fire trucks. Lower frequency red wavelengths partner with higher frequency blue for a bright mix of lights. The contrast makes both colors stand out more compared to using a single color. Red and blue complement each other for visibility and for quickly conveying the firefighting nature of the vehicle.
Alternating Red and Blue Creates a Flashing Effect
Many emergency lights alternate between red and blue. Some lights flash quickly between the two colors while others transition more slowly. This flashing and alternating pattern is extremely eye-catching.
The changing colors command attention as the wavelengths shift rapidly. Alternating red and blue provides color contrast but also generates a flashing alert. The human visual system is highly sensitive to flickering lights and movement. Combining these effects draws gaze toward the lights.
Brighter Than Steady Burning Lights
Flashing emergency lights appear significantly brighter than steady burning lights. A flashing light with the same peak intensity as a continuously burning light can appear up to 400% brighter to human observers. This flashing brightness boost allows emergency vehicles to use less powerful lights while maintaining visibility.
As the lights flash on and off, the eye’s photoreceptors briefly reset between pulses. This allows the receptors to maintain high sensitivity to the pulsing light. For steady lights, the eye adapts over time which reduces the perceived brightness. Flashing prevents this adaptation and takes advantage of the eye’s response to transient light.
Cameras Have Trouble Capturing Flashing Lights
While flashing lights are very noticeable in person, cameras often have difficulty accurately capturing them. The quick on-off cycles can confuse a camera’s autofocus and autoexposure systems. The camera tries to compensate for the flashing, which can cause the red and blue lights to appear less vivid or even white in photographs.
Specialized techniques are required to properly photograph emergency lights. The camera settings have to be manually configured to freeze the instant the light is pulsing on at peak brightness. This prevents the camera from trying to average out the brightness or producing motion blur. Photographing emergency lights well takes some technical photographic skill.
Strobing Lights for Maximum Visibility
Beyond just flashing, some emergency lights use an ultra-bright strobing pattern. Strobes create extremely fast pulses of light that amp up the visibility even more. Special xenon strobe tubes produce very short and intense flashes.
The strobe flash duration may only be a few millionths of a second. These fleeting but powerful light bursts reflect brightly down corridors between buildings and around objects. Strobes help emergency vehicles be seen from difficult angles and in challenging urban environments.
Drawbacks of Strobing Lights
The high intensity of strobes have some disadvantages however. The bright strobing effect can be disorienting for onlookers who are already under stress from an emergency. Photosensitive individuals may have a seizure triggered by the strobe flicker.
Strobes also create challenges for navigating and completing delicate emergency tasks. Flickering light makes it harder for firefighters to approach the emergency site. For these reasons, many departments employ strobes only when needed and turn them off on scene.
LEDs Offer Long Lifespans
Modern emergency lights use LED technology. LEDs offer some key advantages over the incandescent bulbs previously used:
– Long operational lifespan of thousands of hours
– Enhanced brightness with less power consumption
– Faster on/off transition times for strobing effects
– Compact size for increased mounting flexibility
The long lifespans of LEDs reduce maintenance needs. Fire trucks spend less time out of service for lighting repairs. And LEDs give designers more options for placing emergency lights in optimal visibility spots around the vehicle.
Blues Provide Safety for Firefighters
The blue emergency lights do more than just alert the surrounding public. The visibility the lights provide also improves situational awareness for the firefighters themselves.
Bright blue lights illuminate the full emergency scene as fire crews arrive. This helps identify hazards like downed power lines that could endanger the firefighters. The lights also indicate where fire truck access lanes exist so crews can work safely. Blue lighting continues keeping firefighters safe once out of the trucks at the emergency site.
Conclusion
In summary, fire trucks rely on blue lights because blue wavelengths:
– Are more easily detected by the human eye, especially at night
– Contrast strongly against other colors including those from vehicle lights
– Are strongly associated with emergency response services
– Can be produced through various technologies like LEDs and phosphors
– Can be combined with red lights for maximum visibility through color and flashing effects
The science of blue light’s visibility and psychological impact make it the ideal choice for fire trucks and other emergency vehicles. The iconic flashing blue lights provide critical safety for both firefighters rushing into danger and the surrounding public.