Fluorescent yellow-green is the new black in Pittsburgh.

With road construction almost everywhere, schools back in session and more bicyclists on the road, it's arguably the most visible color in our urban and suburban landscape. The yellow-green that pops off the color chart like a firecracker first appeared on school safety signs, and has spread to construction cones, safety worker vests, fire trucks and even the runningwear that was seen in Pittsburgh's Great Race on Sunday.

Whether the neon yellow-green is an innovative traffic stopper or an assault on your eyeballs depends on your sense of color.

"It really pops. It looks really bright. That's the deal," said Dave Burns, a 3M senior research specialist who helped design the technology to make it a roadside color. The human eye is especially sensitive to this safety color, he said, and motorists slow down.

Critics say there is bright, and then there is garish overkill.

"It's like having Paris Hilton to lunch every day," said Nick Hale, a psycho-physicist and color consultant who lives in Florida. "It's too much."

The crosswalk color was the reason an angry New York woman called up Leatrice Eiseman, executive director of the Pantone Color Institute, a few years ago.

"I have a problem with you," the woman screamed into the phone.

"What can it be?" replied Ms. Eiseman, whose company provides professional color standards for the design industry.

"I understand that you are the guru of color in the United States and you allowed those people to use that disgusting, obnoxious yellow green at crosswalks. It makes me angry."

Ms. Eiseman had to talk the woman down and explain that she had nothing to do with the selection of color by the Federal Highway Administration.

And you are likely to see even more of fluorescent yellow-green because the Federal Highway Administration has proposed a new standard that would require it for school zones and school bus warnings. The government agency recommends, but doesn't require, the color for pedestrian crossings, school zones and bike areas.

The Pennsylvania Department of Transportation sometimes uses the yellow-green for some construction sites, a spokesman said, because it does not blend into the foliage and show the dirt as did the old orange cones.

Though you won't find the color in many high-end boutiques, it suits crossing guard Elaine Kelly just fine. She dons a fluorescent yellow-green vest as she faces down traffic hurtling down Washington Road in Mt. Lebanon, stopping commuters at the crosswalk in front of Washington Elementary School. "I don't care, if it's orange or green, as long as they see me on the street and don't run me over."

In fact, she prefers the fluorescent green, saying it stands out better than orange.

Crossing guards wouldn't be wearing such traffic-stopping garments if there had not been an innovation in fluorescent paint coverings at 3M in the late 1990s.

The same quality that makes fluorescent yellow-green so bright also makes it so fragile. Ultraviolet rays -- invisible rays found in sunlight -- excite the fluorescent colors, making them more visible than traditional orange, especially at dawn and twilight. But the ultraviolet light used to destroy the colorant after just a few months.

Mr. Burns and a few other 3M scientists solved that problem in the mid 1990s by developing a way to stabilize fluorescent colorants so it no longer degrades in the sunlight, Mr. Burns said. Now fluorescent yellow-green colorants can withstand the elements for up to 10 years.

And in 1998, the Federal Highway Administration tested out the fluorescent yellow-green on school crossings instead of the traditional bright yellow. "The motorists do behave differently," Mr. Burns said. "They slowed more when they came up to the pedestrian crossing. There are fewer conflicts with drivers slamming on their breaks. They could differentiate the pedestrians."

In 2000, the fluorescent yellow-green was designated the official color for pedestrian traffic. Reflective yellow-green replaced bright yellow at school crosswalks.

Of critics who call it too vivid, Mr. Burns said, "There is always a fine line between providing the driver roadway information and being aesthetically pleasing."

Ms. Eiseman of Pantene says the color -- the hottest of the greens -- has so much pop because it is such a saturated hue. Maybe too saturated in her view. "I get it, but of all the greens available to choose from, my choice would be a little more subtle, not so in-your-face, knock-your-socks-off green."

Other color experts found it more inspiring.

"I think it's great," said Kathleen J. Dutka, owner of Color My Space, an interior decorating firm in Upper St. Clair. "Your eyes go directly toward it. Maybe it is just because it is so different than orange and red colors. If you go down the turnpike and see all those red flashing lights, you can hardly drive. But the green doesn't seem to affect your eyes so much. It doesn't blind you, but you notice it."

Ms. Dutka uses a muted version -- an apple green -- in decorating and loves it. But she is not sure if the color would cross over to fashion. "I don't care what color your hair is, fluorescent lime green is not going to do much for anybody."

Ms. Eiseman thinks the color is tricky for fashion because the fluorescent green reflects onto the face. "It would be good for a kid for Halloween if the Hulk was one of his favorite characters."

It's definitely hard to look chic in screaming green neon, says Allison Casey of Ben Avon and her three other sister fashion stylists. Collectively, they are known as the Style Sisters.

"Usually when we are asked what constitutes 'traffic-stopping style,' " they wrote in an e-mail, "neon anything is not on our list. Would a Style Sister be caught dead in such a color? Well, if we were working a construction site, it definitely serves its purpose, and is certainly preferable to actually being caught dead."