Fluo Green is the Most Visible Color for Swimmers, Triathletes, Cyclists and Runners for Road and Waterway Safety

Here is the full transcript of the video for those who don’t have time to sit thru the entire video:

If you work or play on or near the water; you are always at risk of accidental immersion. To be rescued, you must first be detected. To be detected visually, one must be conspicuous. Conspicuity is the characteristics of an object that influences the probability that it will be detected by coming to the attention of the observer. Color and luminance contrast effect conspicuity. Luminance contrast is considered the most important of these two mechanisms and is often the trigger for recognition. Luminance is the summed intensity of the visible light spectrum that is reflected back to the viewer from an object. It can be lightened to brightness and/or vividness. Luminance depends on the amount of incident light on the object. Color is defined by which wavelengths of light, from an incident light source are reflected back to an observer’s eye. These wavelengths describe the hue, or the shade of an object. This is due to the two types of photoreceptor cells in the eye known as cones and rods. Cones are more concentrated at the center of the eye and a responsible for color recognition. 

Rods dominate in the periphery. Since our central vision is only approximately 5% of our total field of vision, color alone will not assist in locating an object in the periphery. Peripheral vision responds to motion and visual stimuli at low light levels, and primarily detects contrast by differences in luminance. Highly fluorescent reds, oranges, and yellows appear unnatural and hence highly conspicuous. This effect is especially pronounced at twilight, or on overcast days when the ultraviolet light from the sky are present in greater proportions than normal sunlight. Using the science of how humans perceive colors, research can be done to select the most conspicuous or detectable colors for use on personal protective clothing and equipment.

There have been many recent studies on land concerning the conspicuity of road workers and the factors which can improve safety on work sites. The results of these studies have led to WorkSafeBC’s recent requirements for the use of modern fluorescent materials. WorkSafeBC adopted ANSI 107 standards and converted their mandatory safety color from bright orange to fluorescent green. Canadian regulations pertaining to the textiles and components used on life jackets, personal flotation devices, and immersion suits require the use of red, orange, or yellow. Both the WorkSafeBC requirements for work wear and the Canadian requirements for life jackets and personal flotation devices, intend to provide colors with maximum contrast against the dull background. Yet, each has regulated a different color. There is no known study that has compared which of these colors is the most detectable on the water.

In 2010, Mustang Survival proposed to WorkSafeBC that it would like to compare the performance of Canadian color requirements for life jackets and personal flotation devices, against the new fluorescent materials available today. Mustang Survival is a leading North American manufacturer of life support equipment and personal protective clothing. Their line of personal floatation devices, and anti-exposure coats and immersion suits is regulated by Transport Canada and Underwriters Laboratory. With the support of WorkSafeBC, Mustang Survival conducted a three-part research study on the visibility of four key colors.

In part one of the study, the color attributes of the four materials were quantified in the laboratory using the CEILAB scale. The CIELAB space describes the color coordinates and luminance factor. Testing found that the color coordinates for the four colors lie within close proximity to the European guidelines for lifejackets and immersion suits. Differences in luminance were found between the four fabrics, the highest luminance was found for the green at 0.93, the orange at 0.41, yellow at 0.32, and red at 0.18. Testing revealed there was five-fold differences in brightness between the green and red fabric. In part two of the study, an experiment was conducted using human subjects who viewed the colors against the simulated ocean environment. Using color metric analysis of photographs taken of the British Columbia coastline, a simulated image of a horizon was created. This image was projected onto a screen. Two holes were cut in the screen. Behind the screen were actual swatches of the four fabrics. This allowed pairs of the fabrics to be viewed simultaneously for comparison of conspicuity.

Facing the screen, 14 subjects were asked to evaluate the six possible color combinations. The subject pool consisted of non-boaters, recreational boaters, Coast Guard Auxiliary, private pilots, and commercial fishermen. Upon illumination of the screen and fabrics, the subjects were asked whether the target on the left or right was deemed the most conspicuous. Central vision testing determined that the yellow color, in comparison with the three other colors, had the lowest conspicuity. In the central vision test, green was found to be the most conspicuous, followed by orange, then red. The subjects were also asked to view the pairs of colors using their peripheral, or side vision. This experiment was done for both the right and left eyes. In the peripheral vision test, the pairs of colors were aligned vertically. Starting perpendicular to the image, the subjects rotated until the upper or lower color dominated their vision. Yellow was the color chosen to be the least conspicuous with both the left and the right eye. However, for the other colors there were dissimilarities between the right and left eye. In the left eye peripheral test, red and orange appeared to be the most conspicuous colors. In the right eye test however, red and green were found to be the most conspicuous colors in part three of the study.

An experiment was conducted at sea, where target buoys were placed out of view of an approaching observation vessel. On approach, when each subject detected the target buoys location, the vessel's longitude and latitude were recorded using a handheld GPS. Testing was conducted north of Jericho in English Bay, Vancouver, British Columbia during mid-December 2010. The targets were comprised of marker buoys, each of which covered with a snug fitting fabric cover. The targets were over ten inches in outer diameter; slightly larger than a human head. A small inflatable tender was used to exchange buoy colors. During the sea trials, several runs were conducted for each color, as the lake conditions varied. A data-logging light meter was used to record the light level next to the target throughout the experiment. By recording the longitude and latitude positions of the target, as well as that of the observing vessel, at any instant in time we were able to determine the distance between the observer and the target. Because the sun moves through the sky during the course of the day, it was imperative to change the orientation of the vessel with respect to the target to ensure that the sun was at the backs of the observers. This provides maximum illumination of the target.

Once each of the eight subjects had detected the target buoy, the observation vessel turned around and then began to leave the target. The latitude and longitude were recorded when the subject could no longer see the target. The majority of the test subjects had on water experience and had come from either commercial fishing search-and-rescue, Coast Guard Auxiliary, or were recreational boaters. None of the subjects had any color blindness, nor uncorrected vision defects. To account for varying light levels throughout the day, results were categorized into two groups low intensity and high-intensity illumination.

On approach, the average detection distance ranged from .035 to 1.08 kilometers. On leave, the average detection distance ranged from 0.5 to 1.4 kilometers. On water, testing found that the green and orange colors were the most conspicuous at larger distances under any illumination intensity. Experimental results from the simulated environment, and on water experiments, demonstrate that these particular shades of fluorescent green and orange, were the most conspicuous in comparison to yellow and red.

Thus, in conclusion, a floating green object will be detected visually from a greater distance than an orange, yellow, or red object. The order in which the fabrics were ranked in brightness from the laboratory testing agrees with the results from the simulated environment, which also agrees with the results from the on-water testing. Thus, we conclude, the most detectable colors were found to be in order: green, then orange, followed by yellow, and finally; red. The results of this study support the current recommendations for the use of high visibility green, and/or orange work wear. Wear green and be seen.