BACKGROUND: A new typeface for road signs, called Clearview, is much more legible than the existing typeface. The design is based on the results from six scientific studies and dozens of field reviews using drivers of all ages in both day and night driving conditions.
WHAT IT DOES: The Clearview typeface was developed by a team of perceptual psychologists, traffic engineers, type designers, graphic designers, vision experts, and optics engineers. It uses upper and lower case with initial capital letters, as well as spacing that takes into consideration how a driver will read the legend from an extended distance. It also eliminates nighttime overglow, also known as haloing. Overglow occurs when a car's headlights shine directly on a sign with letters formed from any highly reflective material. For a moment, the letters become so bright they simply resemble blobs. Clearview overcomes this by designing the letters to have more interior space, so that when haloing occurs, the overglow doesn't entirely fill them up.
ABOUT NIGHT VISION: There is very little visible light available to reflect off of objects at night, impeding human vision. A chemical called rhodopsin, found in the rod cells of the eye, is the key to good night vision. Whenever a rhodopsin molecule absorbs a photon, it splits into two secondary molecules -- retinal and opsin -- that later recombine back into rhodopsin. That's why most of us need a few minutes for our eyes to adjust to the dark when the lights go out. Exposure to bright light causes the rhodopsin to break down, impeding vision, until the two molecules combine back into rhodopsin. Unlike humans, cats have a special layer of cells lining the back of the feline retina, called the tapetum lucidum. It acts like a mirror, collecting and reflecting light back through the rods a second time to re-stimulate them. The result is a double exposure of light, permitting cats to see in near-darkness. When we see an eerie yellow glow in a cat's eyes in flash photographs, we are looking at light reflecting off the tapetum lucidum.
The Human Factors and Ergonomics Society and the American Society of Civil Engineers contributed to the information contained in the TV portion of this report.