Reported December 2005

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.

HOW WE SEE: We are able to see the world around us because light reflects off objects and radiates outward in all directions. Our eyes detect this light, which the brain then forms into recognizable images. The human eye works in much the same way as a camera captures images on film; its “film” is the retina, a thin layer of neural tissue lining the back of the eye, made of photoreceptor cells that receive light, and other cells that interpret this information and send the signal to the brain via the optic nerve. The retina contains two kinds of photoreceptor cells. Cone cells are sensitive to bright light and can perceive colors. In contrast, rod cells work best in low light and can perceive black and white images.

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.

If you would like more information, please contact:

See the new font on the web at:
http://www.clearviewhwy.com/

The American Society of Civil Engineers
1801 Alexander Bell Drive
Reston, Virginia 20191-4400
(800) 548-2723
http://www.asce.org

Human Factors and Ergonomics Society
PO Box 1369
Santa Monica, CA 90406
(310) 394-1811
http://www.hfes.org

FACTOID...

See the new font on the Web at