Highway beauty: major roadways all over the state of Illinois are getting a much-needed facelift.(COMMUNITIES)

We don't often consider how much time we spend staring down the highways, perhaps because we don't wish to remember it. Highways are functional but ugly, miles of blank asphalt threading the landscape. But what can be done? These days, most of us spend a fair portion of our lives commuting to and from work, visiting friends and relatives who live ever more distant, or meeting the basic needs of a suburban lifestyle. The average American spends over an hour in the car each day. The stark ugliness of highways is an unfortunate cost of modern mobility.

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But just as cities and trees aren't mutually exclusive--just ask your local urban forester--neither are trees and highways. Maybe you've never noticed the strips of trees lining certain portions of highway, or dismissed them with a disdainful "that isn't real nature." And it's true, of course, that driving among those trees is not like being enveloped in the stillness of a forest, where one of the attractions is the distance from such things as trucks, cars, and highways. But highway-side trees should not be dismissed so easily. They are a reminder that, beyond the concrete and asphalt, the lush green of the natural world still exists, something that can be forgotten in lives full of synthetic goods and buildings. Further, studies suggest that the presence of trees along highways can mitigate some of the lesser-known health impacts of busy roads.

The United States has the largest network of highways in the world. The Interstate Highway System covers nearly 48,000 miles, which is about twice the length of the earth's circumference. It's fairly common knowledge that highways enable more car emissions and particulates to pollute the air, but fewer people know that living near highways and other busy roads can be harmful to human health because of the high levels of noise. Automobiles are one of the greatest and loudest sources of noise, and over 17 million people are daily exposed to noise levels of traffic that exceed 70 and even 80 decibels. Exposure to high and constant levels of noise causes hearing loss, accelerated heartbeat, high blood pressure, gastro-intestinal problems, sleep problems, and heart disease. Psychological effects such as anxiety and depression only compound other health problems caused by noise pollution.

No one noticed the effects of noise until the early 1970s, decades after serious highway work had already begun. Past planners routinely built communities--houses, hospitals, schools, libraries--around roads, and both the number of cars and the noise have increased in ways the original planners could never have predicted. Beginning in 2004, major cities began passing stronger noise codes, citing noise as a quality-of-life issue, but these ordinances can only control certain human-produced aspects of noise pollution like street performers or outdoor speakers.

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Though many highways were built without buffers, trees are an excellent way to screen communities from the noise and pollution of nearby highways. The U.S. Department of Energy reported that a large enough area of trees can cut traffic noise levels in half. In the area of Chicago, AMERICAN FORESTS has partnered with local organization Trees Across the Miles in an unconventional Global ReLeaf project to plant trees along the highways of Illinois. For three years, our two groups have planted thousands of saplings along portions of Route 53 and I-290, Stevenson Expressway I-55 and Kennedy Expressway I-90, and the Elgin/O'Hare Expressway. The US Department of Transportation reported that in 2006, some 9.9 million vehicles--privately, commercially, and publicly owned--were registered in the state of Illinois. Thousands of motorists come by these functional forests, or green belts, each day.