Do you know the colors of the road?

By Peter DeMarco  |  July 5, 2009

We learn the colors of Independence Day about as soon as we can talk. The colors of the road are just as familiar - what could possibly be confusing about red, yellow, and green? Well, let me tell you.

I’ll start with a simple question: What does a flashing green light mean? Don’t bother checking the Registry of Motor Vehicles’ driver’s manual: It is not in there.

Now for a tougher question: What does a yellow curb signify? Or a curb painted blue or green? Is there a state law that delineates curb coloring, or do local communities just do what they please?

Or try this one. In 2004, a section of Pennsylvania Avenue in front of the White House became a pedestrian path. But instead of using standard asphalt, the Federal Highway Administration got creative, laying down a rustic brown binder to mimic dirt.

“They wanted to make it look like it used to before the days of asphalt. Like it did in the days of Ulysses S. Grant,’’ said Doug Hecox, highway administration spokesman. “But it’s better than dirt. It doesn’t get muddy or dusty and it looks very natural.’’

The road is reserved for pedestrians, but could a public street be the same color? Or any color other than black or gray? Could Cambridge lay down crimson asphalt in Harvard Square? Could Peabody pour yellow asphalt in front of Kodak’s Eastman Gelatine company? Might Lexington pave red, white, and blue around its Revolutionary town common?

Prepare yourself for some colorful answers.

The RMV’s driver’s manual covers the basics. Treat a flashing red like a stop sign. A flashing yellow warns you to proceed with caution. You can make a right-hand turn on a steady red arrow, unless a sign is posted that says you can’t.

Ah but there are trickier lights out there. On a solid yellow we’re actually supposed to stop (unless it’s unsafe to do so), not speed up to beat the light, though I can’t remember the last time I saw anyone stop for a yellow.

A flashing green is the same as solid green, but you should be aware that a pedestrian can push a crosswalk button to turn the light red. If you ever encounter one you should slow down.

Signals that flash red and yellow simultaneously are also nearly extinct, and if you’re under 50, you probably have no idea what the combination means. Before the advent of “Walk’’ signs, the two colors signaled drivers to stop for pedestrians to cross.

On a recent trip to California I was stumped by the multitude of curbstone colors I saw along a single block - green, red, white, and yellow. My friend, Dan, said they stood for various things, such as commercial loading zones, bus stops, and no-standing areas.

We have painted curbs in Massachusetts, too, but I can’t give you an accurate rundown of what they signify. Curbstone colors aren’t regulated by federal or state laws, so it’s up to local officials to decide, which means that a yellow curb in one city might mean something completely different than a yellow curb in another.

I live in Somerville, so I asked one of the clerks in the Traffic and Parking Department what the yellow curb on my home street means. She told me that property owners sometimes paint curbs to make people aware of their driveways. “And you can’t park within two feet of either side of a driveway,’’ she said.

“So,’’ I countered, “if someone painted 10 feet of curbing yellow in front of his house, I can actually park alongside most of it?’’ Yes, she said.

John Gillon, Quincy’s traffic engineer, doesn’t believe in painted curbs because they’re not part of the Manual on Uniform Traffic Control Devices, the federal bible of street signs and pavement markings.

“You’re not going to find any colored curbstones in Quincy because it’s not in the MUTCD,’’ he said. “It’s not an approved traffic control device.’’

That got me wondering whether painted curbstones were, in fact, illegal. But Hecox, whose department oversees the MUTCD, nixed the thought. Since curbs are “technically not part of the street,’’ municipalities can paint them, he said.

“There is no law that says thou shalt have black asphalt,’’ said Hecox. “But at the same time, most of the rules of the road are based on common sense. Imagine if you painted your black pavement white. In the wintertime you’d never know where the road is. Some people might say, ‘Why don’t you make it blaze orange, like the color hunters use [for better visibility.]’ That’s fine, but how do you distinguish the lane markings?’’

The other practical matter is price. While paving companies have a number of new technologies at their disposal far better than mere paint, taxpayers would certainly have to pay more, perhaps as much as double, for a tan, chocolate-brown, or yellow brick road.

But John McNulty, vice president of McNulty Construction Corp. of Framingham, said colored roads might not be as far-fetched as they seem.

His company recently applied a green epoxy to a 500-foot stretch of Commonwealth Avenue bike lane and is bidding on coloring Boston bus lanes - in both cases, the colors are supposed to increase awareness of the lanes.

Perhaps more intriguing, colored pavement is better for the environment, McNulty said.

“If the color coat we put on a road has a solar reflectance index greater than 29, it reflects more light than it absorbs, so the ground will be cooler,’’ he said.

Cooler ground means cooler cities - and less money spent on air conditioning and fans. New York and Chicago are among those cities experimenting with the concept, McNulty said. It’s also the reason you might see light-colored parking lots associated with “green’’ buildings.

“It’s all exciting to me,’’ McNulty said. “But I think a whole road green would be obnoxious.’’

True enough. But you have to admit, a Monster-green Yawkey Way would look pretty cool.

Peter DeMarco can be reached at demarco@globe.com