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Publication Number: FHWA-HRT-13-018
Date: April 2013

 

Daytime Color Appearance of Retroreflective Traffic Control Sign Materials

APPENDIX A. PARTICIPANT MATERIALS

This appendix contains instructions and materials provided to study participants during training and data collection. In some cases, representative samples have been provided instead of the full set of materials.

INSTRUCTIONS FOR SCALING HUE, SATURATION, AND BRIGHTNESS

As each color sample panel is mounted in the tripod, describe your sensation of the light reflected from this particular color sample. First, divide your sensation into three parts. The first part consists of hue. You must divide your sensation of hue into red, yellow, green, or blue. These are the only words you may use to describe the hue. If you wish, you may use pairs of names to describe a hue. When you are describing your sensations of hue, please state them in percentages. If there is any hue at all, the percentages you assign to these words must add up to 100 percent. For instance, your sensation might be 40 percent red and 60 percent yellow or 86 percent green and 14 percent yellow or 95 percent blue and 5 percent red, and so on. It can also be 100 percent of one of the hues. The only limitation is that you may not pair red with green, nor pair yellow with blue; all other combinations are allowed. If there is no hue at all and the color is either black or white or some shade of gray between black and white, then the percentages you assign to the words will be 0 percent and they will add up to 0 percent.

Think carefully about your answer and try to be as precise as possible. Remember that the term hue refers to your own sensation elicited by the light reflected off the material. You are not being asked how you might create the particular hue you saw. You are being asked to describe your sensation. Please note that there are no right or wrong answers; you are simply describing your sensation.

The second part of your sensation is not hue but is related to hue. After describing the hue of your sensation, you must consider what percentage it formed of your entire sensation; that is, what is the percentage of chromatic versus achromatic-plus-chromatic sensations? This value is called apparent saturation. It refers to the strength or concentration of hue in your total sensation. A total absence of hue would be represented by 0 percent saturation, in which case a color would be white or gray or black. At the other extreme, a fully saturated color with 100 percent saturation would be as far away as possible from white or gray or black. Think of your total sensation when you see a color sample as something contained in a bucket. Now pour a little bit of a hue into the bucket and stir. What has happened to the saturation? Now add a little bit more and stir. Again, how has saturation changed?

The third part of your sensation is neither hue nor saturation. This part is achromatic; it is not sensitive to color. In this case we want you to rate the brightness of the light reflected off the material. Brightness is the sensation of the amount of light. Brightness is expressed on a scale from bright to dark, with 100 percent being the brightness of the sky on a clear day, and 0 percent being the brightness of a completely dark surface that does not appear to reflect any light at all. Zero percent brightness is what you would perceive in a completely dark room with no light whatsoever.

First, you will scale some color patches printed in a training booklet in order to get used to the task. Next, you will scale a few actual color sample panels as practice trials. This training is designed to familiarize you with the procedure. We will tell you when they end and the experimental trials begin. Do not leave any blanks on your answer sheet. It is always better to guess. The first data collection period after the practice trials will last about 30 min. Then you will have a break. Do you have any questions?

INSTRUCTIONS FOR BRIGHTNESS RANKINGS

In this part of the experiment you will rank order the brightness of five color sample panels lined up in a row with the letters A–E under each panel. All of the panels will be of a similar color. On your answer sheet, please rank the five panels for their sensation of brightness only. Place the letter of the brightest sample under the number 1 on the answer sheet, and the letter of the next brightest sample under the number 2, and so on, until you have ranked all five samples. When you are done, the letter corresponding to the brightest sample will be under the number 1, the letter corresponding to the darkest sample will be under the number 5, and the other letters will be arranged in between according to their perceived brightness.

SATURATION SUPPLEMENT

If this is still confusing, consider pink and red. Red is a highly saturated color; it would be given a high saturation score. However, if red becomes more white or gray, it becomes pink and would be given a lower saturation score. With even less saturation, it becomes a pastel pink. If the color continued changing in this manner, at some point it would turn white or gray and would get a saturation score of 0 percent. Remember that black would also have a saturation score of 0 percent.

TRAINING EXAMPLES AND PARTICIPANT PRACTICE

This diagram shows examples of saturation differences provided to participants during training. There are three rows each containing five color blocks. At the top of the figure, the left- and right-most blocks are marked “Lower,” and the center block is marked “Highest.” Each row shows five shades of a single color starting with a very dark shade on the left and fading to a pastel shade on the right. The top row is blue, the middle row is red, and the bottom row is green.
Figure 24. Illustration. Training examples for saturation.

 

This diagram shows examples of brightness differences provided to participants during training. There are three rows each containing five color blocks. At the top of the figure, the left-most block is marked “Darkest,” and the right-most block is marked “Brightest.” Each row shows five shades of a single color starting with a very clear, dark shade on the left and fading to a light, pastel shade on the right. The top row is black fading to white, the middle row is shades of yellow, and the bottom row is shades of green.
Figure 25. Illustration. Training examples for brightness.

 

Twenty-four color samples were provided to participants for practice in assigning percentages for the red, green, yellow, and blue in the sample as well as for saturation and brightness. An example from the participant practice is provided in figure 26.

This figure shows a small pink color block that is representative of the color examples used for participant training. Beneath the block are spaces in which the participant can write the perceived percentage of red, green, yellow, and blue in the sample as well as the perceived saturation and brightness percentage.
Figure 26. Illustration. Example participant practice sample.

 

EXPLANATION OF THREE COLOR SCALES

Hue = What color or colors are present in the sample, even in small amounts?

Saturation = How concentrated or strong is that color or color combination?

Brightness = If all color were to disappear, how bright or dark would the sample be?

This diagram is a three-dimensional figure representing brightness and saturation. At the center is a vertical post that is white at the top and transitions to black at the bottom. The white top of the post is labeled “Brightness = 100,” and the black bottom is labeled “Brightness = 0.” Two axes cut through the post perpendicularly at right angles to each other, making an “X” into and out of the plane of the page. The center of the X, near the vertical post, is labeled “Saturation = 0,” and the far end of one axis is labeled “Saturation = 100.” Each part of the X fades from color to gray from the far end to the center. One axis is labeled “-a” and “+a,” with green at the -a end and red at the +a end. The other axis is labeled “-b” and “+b,” with blue at the -b end and yellow at the +b end. Figure 27 was intended to help participants understand the color scales used in the experiment.
Figure 27. Illustration. Color dimensions.

 

PARTICIPANT RESPONSE SHEETS

The response sheets provided to participants were in a tabular format with space to enter data for red, green, yellow, blue, saturation, and brightness percentages for each sample. Space was also provided for numbers assigned during the brightness ranking task. Figure 28 shows a representative portion of the response sheets.

This figure shows a representative portion of the response sheet provided to participants during data collection. The figure shows a table with column headers of red, green, yellow, blue, saturation, and brightness. There are two levels of row headers, one for block (denoted by the letter A in this sample) and one for trial (ranging from 1 to 10 in this sample). The data cells of the table are empty so the participant can record data. At the bottom of the table is a section for brightness ranking, with blank cells for samples 1 through 5 and a key that indicates 1 equals brightest and 5 equals dimmest.
Figure 28. Illustration. Response sheet sample.

 

 

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