May 7, 1996 Vol. 25 No. 32

Transportation engineers helping
to improve road sign readability

By Barbara Hale
Public Information

Feminine folklore holds that men get lost because they won't stop driving to ask for directions. Don't worry. Soon asking for directions may no longer be necessary.

Transportation researchers are helping to make it harder to get lost by improving road sign readability at night, especially for the older driver.

Martin T. Pietrucha, research associate, and Philip Garvey, research assistant, in the University's Pennsylvania Transportation Institute, joined forces with graphic designers Donald Meeker, Harriet Spear and Christopher O'Hara of Larchmont, N.Y., to design and test a new typeface or alphabet style for the signs. The Penn State researchers have shown the typeface results in nighttime legibility distances 16 percent greater than Standard Highway Series E(M), the 50-year-old typeface now used in the U.S. and Canada.

"With a 15-inch letter height, this could increase legibility distance by 150 feet, allowing drivers almost two seconds longer to read highway guide signs," Pietrucha, who is also an assistant professor of civil engineering, said.

The new typeface is called Clearview. It achieves its greater nighttime clarity by avoiding the effects of a phenomena called "blooming" or "halo-ing."

Garvey said blooming occurs when a car's headlights shine directly on a sign on which letters have been formed from highly reflective material. The letters become, momentarily, so bright that they lose their familiar shape and look instead like blobs.

Pietrucha said blooming is especially troublesome for those over age 65.

Clearview retains its readability despite blooming because the letters have been designed to have more interior space. The "B," "e," "g" and "a," for example, have more space inside the letters so that when blooming occurs, the overglow doesn't entirely fill them up.

The researchers conducted both laboratory and road tests on Clearview. Eighty people ranging in age from 20 to 50 were recruited from the PTI staff to be the first subjects in the laboratory tests, which involved reading signs simulated on a computer screen.

"Since standard lettering works OK in the daytime, and we wanted to fix a nighttime problem, we eventually had to conduct field testing at night," Pietrucha said.

In addition, because older drivers are more sensitive to high contrast problems, all field testing was conducted with subjects age 65 and older.

"We figured that if it worked for them, we could be pretty certain that it would work for everybody," Pietrucha said.

Pietrucha said that daytime field tests found no difference between the legibility of Clearview and that of Highway Standard Series E(M) font.

However, at night, with headlamps shining on the highly reflective materials, field tests with older subjects showed that Clearview words could be read from greater distances than words in the standard font on the same size sign panel.

"Part of the reason for this improvement is the fact that the Clearview font requires smaller between-lettering spacing," Pietrucha said. "Clearview letters can actually be made larger than those in Series E(M) without increasing the sign's overall size."

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This page was created by Annemarie Mountz.
Last updated May 3, 1996.