Understanding Emergency Vehicle Lighting Standards and Certifications

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The emergency vehicle lighting industry works with various regulating agencies to establish a certain level of product quality. These agencies collaborate with industry experts to define that level of quality through publication of emergency vehicle lighting standards, which can change over time as new information comes to light. These standards also define the testing requirements manufacturers must meet in order to claim compliance and receive certification for each product. Some of these certifications are required by law, but most are driven by the market (i.e., they are recognized and accepted by the industry based on accumulated experience, knowledge and testing). 

The documentation and steps involved in ensuring our products comply with all of these emergency vehicle lighting standards and specifications are long and complex–so much so that we have a full team dedicated to product compliance and testing, often working through an independent testing laboratory, to make sure our customers receive quality products. This article attempts to provide a brief run down of the standards to give you a basic understanding of what they mean. View the full list of emergency vehicle lighting standards we test our products to on our certifications page.

Emergency Vehicle Lighting Standards Overview

The main regulating agency for the emergency vehicle lighting industry in the United States is SAE International. Originally founded as the Society of Automotive Engineers, this global association of engineers and related technical experts in the aerospace, automotive and commercial vehicle industries publishes standards identifiable by the SAE prefix. These standards serve as recommended best practices, but are not required by law. Full publications may be purchased on SAE’s website for about $75 each.

The California Department of Transportation (a.k.a., Caltrans) publishes similar emergency vehicle lighting standards for products sold within the state of California, and, oddly, Minnesota as well. These standards fall under California Title 13 (CA Title 13), which is part of California’s Code of Regulations, and are enforceable by law. You can browse the code of regulations on govt.westlaw.com

The U.S. National Highway Traffic Safety Administration (NHTSA, pronounced “nit-sah”) publishes another set of standards for exterior vehicle lights other than warning lights. These are identified with the prefix, FMVSS (Federal Motor Vehicle Safety Standards), but only apply to products in our truck, trailer and bus divisions and will not be covered in this article.

European nations look to the United Nations Economic Commission for Europe (UNECE) for its emergency vehicle lighting standards, published in a document called ECE R65. In addition to ECE R65, we also test our products to ECE R10, which ensures that our products will not create electromagnetic interference with other systems and devices in the vehicle. ECE standards are required and enforceable by law for products sold within the European Union and other countries that recognize ECE standards, like Japan. You can download the ECE standards free of charge on their website.

Emergency Vehicle Lighting Standards Breakdown

The two main SAE standards recognized as recommended practice for emergency vehicle lighting products are SAE J595 and J845. There are many more SAE specifications that are referenced by these two standards, but we’ll get to those in a moment. 

SAE J595 applies to directional flashing optical warning light products, defined as those projecting a signal over a minimum horizontal area from 20 degrees right to 20 degrees left and vertical area from 10 degrees up to 10 degrees down. CA Title 13 gives requirements for this type of product in Table 1, Class B. In the EU, these products must be tested to ECE R65 Category X.

SAE J845 applies to omnidirectional flashing optical warning light products, defined as those projecting light horizontally in a 360 degree arc and vertically from 5 degrees up to 5 degrees down where a stationary observer sees flashes as it the light rotates through their sightline. A light does not have to be a full 360 degrees for J845; it can have what’s called a selective angle between 40 degrees up to 360 degrees. Table 1, Class B of CA Title 13 also applies to this type of product, but has some additional testing requirements. In the EU, this type of product is specified in ECE R65 Category T.

While each of these SAE specifications applies to a different type of product, SAE J845 and J595 both define and specify the following:

  1. Acceptable colors
  2. Definitions of colors
  3. Minimum brightness and distribution
  4. Acceptable flash patterns and frequencies
  5. Environmental testing
  6. Testing setup
  7. Acceptable materials
  8. Required lens markings

CA Title 13 and ECE R65 provide a similar list of specifications, but the exact requirements specified may vary. For example, SAE specifies minimum brightness, whereas ECE and CA both specify maximum brightness (although, CA only specifies maximum brightness for amber colored lights). Another difference is in flash rates–SAE allows 1-4 Hz, whereas CA allows 1-2 Hz and ECE allows 2-4 Hz.

Class Designations

Within SAE J845 and J595, our products fall under one of three classes. Class 1 specifies any primary optical warning device used by an authorized emergency vehicle responding to an emergency in order to warn surrounding motorists and pedestrians of a potentially hazardous situation. Class 2 is defined as a primary optical warning device used by authorized service and maintenance vehicles to caution people of traffic hazards. Class 3 is a primary optical warning device used by authorized vehicles to identify themselves as such (i.e., a volunteer firefighter, off-duty police officer, etc.).

Reference Specifications

There are several specifications that are referenced within SAE J595 and J845. These include SAE J575 which designates test methods and guidelines, SAE J576 which specifies acceptable use of plastics, and SAE J759 which stipulates the proper way to mark products that have been certified.

Color Specifications

SAE J578 is another standard referenced within SAE J845 and J595. This standard defines the range of color that can be used in external lighting products for motor vehicles and provides design guidelines and test procedures for obtaining certification. SAE specifies color based on the scientific representation of colors that are visible to the human eye, called the CIE 1931 Color Space Chromaticity Diagram (below). The outlined sections of the diagram show the range of colors allowed by SAE J578. 

SAE J578: Color Specification based on the CIE 1931 Color Space Chromatacity Diagram

As you can see from the chart, SAE allows specific ranges of red, yellow, white, blue and green. CA Title 13 and ECE R65, on the other hand, only allow red, blue, and amber.

How Our Eyes Perceive Color

To fully understand the Chromaticity Diagram, let’s recall our high school education on where color comes from and how our eyes perceive it.

Light, which is a form of electromagnetic energy, carries the full range of colors. Some objects emit light, such as the sun, stars, and LEDS, which travels in a pattern of waves varying in length (wavelengths) and frequency. Our eyes perceive color when light shines on an object that reflects a certain wavelength and absorbs all the rest. For example, green grass only reflects the green wavelength. The visible color spectrum, also called “visible light,” makes up a very small portion of the electromagnetic spectrum, as shown in the chart below. There are many wavelengths that our eyes do not see, such as radio waves, microwaves, ultraviolet light, and infrared light. 

Fun Fact: Scientists recently captured the first photographic evidence of light behaving both as a particle and a wave–a concept originally introduced by Einstein–using a super fast microscope. Learn more on Phys.org.

Electromagnetic spectrum, also known as visible light

The human eye has millions of receptors to interpret the wavelengths reflected by light, some of which are more sensitive to the color of light–called cones–and some more sensitive to the brightness of light–called rods. There are three types of cones–red, green and blue and when they are combined in different proportions, they create the full range of visible color. The CIE diagram forms a sort of triangle between the three cones and maps out exactly how much red, green and blue is needed to create each visible color on the spectrum.

There are three types of rods as well–blue, white and grey–which help us to interpret brightness and see in the dark. (The recommended minimum brightness of our products is specified by SAE within the aforementioned standards, J595 and J845.) Rods are so insensitive to color that they can’t see red, which is why dim red lights are often used by sailors and astronomers at nighttime. 

 touched on the debate over whether or not blue is more visible at night. The technical argument for this is that because the rods are less sensitive to red wavelengths and more sensitive to blue, then blue would be more jarring to the eye at night than red, and thus better for grabbing the eye’s attention. But would that also mean that blue light impairs our vision more at night than red? The answer is still up for debate.