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Flashing Lights and Flash Patterns

With the advent of LEDs, Police Emergency Lights are now designed with a multitude of flash options. Lights have brilliant luminosity seen over great distances, and come in a wide range of colors.  Emergency vehicle lights have evolved into sophisticated lighting mechanisms that warn approaching motorists and catch their attention, especially when sirens may not be heard. More importantly, they illuminate the specific location of an accident keeping officers well lit and safe. Rapid firing flashing lights today have reached a level of development that few could have predicted just 10 years ago, but with their phenomenal advancement have arisen some major health considerations.

Night TIme Flashing Police LightsFlashing Lights have 2 Primary Functions

Emergency Vehicle Lights (EVL) have two primary functions. First, they draw the attention of  motorists and pedestrians to the fact that something is going on ahead giving them time to slow down, change lanes, or even prepare to stop. The initial flash gets the attention and the additional ones direct the gaze. Flashing lights must be detected quickly and must be attention grabbing.  A major aspect of flashing colored lights is to be able to clearly identify the type of vehicle as belonging to either police, ambulance, fire, other emergency services, and, of course, school buses in order to make the relevant response quickly.  Flashing lights WARN motorist to slow down and to pay attention!

Driver Distraction

Driver Distraction is a major problem of so many who are behind the wheel. Cellphones, texting and accessing the Internet take the attention of the driver away from the road.  Flashing lights bring it back giving motorists the time they need for safe avoidance action.  A great many vehicles today are relatively sound proof so those inside don’t hear sirens; often drivers are listening to music on advanced sound systems like Sirius XM, or even talking on the phone through a hands-free option. Hopefully, they aren’t fiddling with their phones while driving, but, that, too, is often a common practice these days. No matter what the case may be, intensely flashing colored lights will catch their attention if they are configured properly.


Contrast with the surroundings (conspicuity) is paramount when choosing the most effective lights because the human eye is made to see ‘differences.’  The greater the contrast between the flashing/pulsating, colored lights and the surroundings the more the system will be noticed. Flash rate combinations and multiple patterns, intensity of the lights, and color combinations all add to conspicuity. Often fatal events occur if first responder vehicles parked at accidents or on the roadside are not clearly seen, or when people don’t notice stopped school buses.

Studies Regarding Flashing Lights

Many studies prove that the eye detects a flashing light quicker than a steady burn.  Peripheral detection of oncoming traffic is doubled by flashing lights. (Donne & Fulton, 1988) Investigations indicate that humans are ‘hardwired’ to pay attention to flashing lights from studying the gaze patterns of infants. (Teller, Movshon, & Jouen, 2011)  There are many variables, however.  Flashing lights in the city will be less noticed than in the countryside; therefore, selecting the right color combinations must be taken into consideration as well.

Research conducted on Emergency Vehicle Lights has been widespread by a variety of agencies, including fire and police departments, manufacturers, academic institutions, and governmental agencies. A Phoenix Fire Department ‘internal’ study in 1994, determined after a firefighter was killed by a motorists blinded by intense flashing white, red, and blue lights, that all fire trucks should flash amber when the parking brake was engaged. Today many departments nationwide employ this procedure.

Loughborough University in the U.K. conducted a study in 1999, proving that the faster lights flashed, the higher the sense of urgency experienced by those who saw them. The study also showed that red, blue, and amber lights produced about the same amount of glare, but amber lights were not as visible during the day as were the other 2.

A third study, the Arizona Blue Ribbon Panel Study and Report, was a joint investigation by the State of Arizona and the Ford Motor Company in response to 4 crashes of the Ford Crown Victoria Police car. Though the study was conducted in 2002, 4 key factors were identified as being the reasons that police vehicles stopped on the road side were run into by motorists. It was determined that not enough bright light emanated from the vehicle during daylight hours, that blue and red flashing lights were detected better than white, excessive flash rates caused glare, distraction, annoyance, and blending of colors, and that the Ramp Time, which is the time it takes for a light to go from fully OFF to fully ON was too slow. All of these findings are implemented on highway patrol vehicles today.

Other studies have also been conducted by reputable agencies. The Florida Highway Patrol Study is one, and the USFA sponsored research in conjunction with the SAE is another. The joint effort showed how warning lights affect driver vision and how those lights can be designed to provide the most benefit to all. Numerous positive and negative features of automotive emergency lighting have been investigated by experts in this field. Conclusions from these investigations have often made a huge impact on the implementation of guidelines and designs by manufacturers nationally and internationally.

Colored Lights and How They are Used

Popular Warning Light Colors


The most popular colors are red, blue, amber, white, and green; there are state regulations managing the use of these colors.  Any motorist knows that white lights go in front with perhaps the addition of amber fog lights, red lights on the back of their vehicles. These primary colors are also used on emergency vehicle lighting in specific zones for optical warning devices as shown in Figure 4.12 (Page 59) in the Fema Article cited below.  High intensity Blue/Red or Blue/White combination flashing lights are most common on police vehicles. Green has a special purpose.  It is only used to designate the location of the commander post of any operation and is totally restricted for that purpose.

Flashing Red/Amber is authorized on school buses when children are entering or exiting the bus, and mean mandatory STOP.  Amber lights are most often employed in ‘cautionary’ service situations having the widest uses in construction and utility vehicles, tow trucks, funeral processions, and security patrols.  There are specific rules that govern the use of colored lights and their placement on any vehicle used by first responders, government and state vehicles, or for the general public.  ETD has compiled a comprehensive list of State Rules and Regulations in the Knowledge Base section.

Flash Pattern Options

Flash patterns on light bars have names reflecting their functions, often having as many as 30 different patterns that are made to catch the attention and to direct traffic. LED vehicle lights are controlled by electronics. This allows them to be programmed in an almost endless variety of operating patterns.  Flash patterns have options that split colors, move in and out, flash all or side by side, and have Chaser Flashes at slow, medium, and fast speeds. There is a Cycle Flash option and Steady-On as well. All of the flash patterns perform at ever-increasing rates from single flash, Quad and Quint flash modes, to Super Extreme Accelerator. The advanced flash patterns are purposely created to catch the attention of motorists and to control their performance at the wheel.  The wide range of patterns are easily selected by the vehicle operator. An officer determines which function facilitates the movement of traffic and the control of conditions in which the vehicle is being operated.

Most emergency lights have pattern memory, a feature that ‘remembers’ the last flash pattern produced in the sequence when a light in turned on again.    A high intensity, pulsating lights on a full size light bar, mounted to the roof of a vehicle, provides maximum visibility to all around, advancing motorists and pedestrians.  Extreme Tactical Dynamics has 4 high-end light bars with the maximum length of 48” that meet ALL the criteria for a SUPERIOR, multi-task, high-intensity light bar.  They get the job done!

Types of EVLs

Rotating Lights, Fixed Flashers, Strobe Lights, and Light-Emitting Diodes (LEDs) all fall into the category of flashing lights, though some LEDs, especially in small appliances and electronics remain only steady on.  Most often today, fire trucks and other fire vehicles use red rotating beacons to signal their presence; construction machinery, utility trucks, and security vehicles use amber. These are the oldest type of warning lights and originally used mirrors to create the appearance of flashing.

Fixed flashing emergency lights, known as ‘fixed flashers’ that simply flash ON/OFF, are common to all vehicles, and referred to as ‘hazard lights’ on POVs. Flashers are a standard addition to  manufacturer lighting. Red fixed flashing lights are governed by placement regulations as are other emergency lights. Often on newer ambulances, today, only fixed flashing lights are mounted around the perimeter of the vehicle.

Strobe lights are Xenon gas flash lamps that put out a very quick, but very bright, flash of light. They cannot be ‘programed’ as LEDs can be because the flashing light is created by ionizing and then discharging an electrical current through the Xenon gas. They are strong, intense whitish lights that are mounted and well hidden in the head and tail light reflectors, so make perfect undercover lights.

LED lights can be used in the same applications discussed above, but they are much more flexible than those of conventional flashing light systems.  Because they have solid-state design, there is no filament to burn out. LEDs emit a powerful beam, use a minimal electrical energy, and won’t overload electrical systems as older styles of lighting does. LED lights themselves are colored, so use clear domes, instead of the the more traditional colored dome over a clear light.  Most are made to last 100,000 hours. ETD uses LEDs in almost all of the lights we sell because they are the most efficient and have a multitude of programmable flash patterns.

Major Concerns Regarding Flashing Emergency Lights

Intensely flashing lights have some drawbacks, for often overly intensive flashing lights produce discomfort and disability glare, in addition to more serious problems. There is a limit at which lights should flash because if it’s too fast the human eye will not be able to detect it and it will appear as a steady beam. At 20 Hertz (Hz) or above the light will appear constant if only one light is flashing, thus alternating 2 or even 3 colors in intricate flash patterns will ensure notice.  Parents must be vigilant and not allow children to become mesmerized by the lights on an emergency vehicle.

Reports show that 10-20 Hz, could trigger an epileptogenic response in them, or with possibly any adult, as well, who stares at them. Phototaxis also known as the “moth-to-flame” effect is yet another physiological condition brought on by flashing lights.  Drivers, especially under the influence of drugs or alcohol, may be so distracted by the beacons that they are “drawn” to them causing them to drive towards the flashing lights endangering all those at the scene!  There is even increased eye strain associated with looking at even low-level 5Hz flashing lights.  High frequency flashing lights increase glare and annoyance, as well.


Several factors must be considered when selecting the right emergency lights for a vehicle.  What color lights are best? How many lights are needed and the configuration of them, must be determined. What weather conditions limit their efficacy and how the light performs in daylight?  In order to choose the best flashing lights for the job, it’s not a matter of choosing the ones that look ‘cool’ on the vehicle, but for the ones that get the job done best.

Safety factors are associated with exceedingly bright, super accelerated flashing light, some positive, but some negative. They create a safe, well-lit zone for police officers and other first responders at accident scenes, as well, as alerting motorists well in advance of an emergency situation they are coming up on. They provide an early warning to motorist who aren’t paying full attention to the driving environment. Flashing lights catch and keep the attention and prepare drivers to adjust their speeds to a pending dangerous situation.  And while there are huge benefits of giving heed to flashing lights, caution must be exercised when looking at them too long.

The LED emergency light industry is awash with high intensity flashing light systems that can be mounted just about anywhere on a vehicle. When purchasing lights from Extreme Tactical Dynamics, our customers can expect well made products with high-tech materials that meet or exceed industry standards. ETD guarantees the highest quality lights at the lowest prices.  Our customers can depend on it!


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Emergency Vehicle LED Lighting: Friend or Foe?

Emergency Vehicle Lighting Wikipedia

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The Safety and Effectiveness of Emergency Vehicles

Tips for Buying LED Strobe Light Bars

Inferences About Infants’ Visual Brain Mechanism

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