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A U G U S T  1 9 9 7

Environment
Noisy Highways
Working with brass
Noise barriers give essential protection to people who live near crowded roads -- and a growing number of designers are showing that they needn't be eyesores.

by Philip Langdon

THERE is a troubling, and worsening, mismatch between Americans' love of personal transportation and the way the nation's highways are shaped. Even in 1916 -- the year Emily Post published By Motor to the Golden Gate, an account of her arduous car trip from New York to San Francisco, and Theodore Dreiser published A Hoosier Holiday, the story of his mud-splattered auto journey from New York to his boyhood home in Indiana -- it was plain that the future of transportation in the United States was the road, not rail. Motorists were starting to expect paved highways, and plenty of them.
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From the archives:

  • "The Back Road to Mars," by Charles W. Morton (February, 1956)
    "The stubble, beer cans, paper plates, along the sides.... Within the near future ... a man ought to be able to drive from New York to Los Angeles without having to look at anything at all."
  • Periodic bursts of improvement in highway design led to the creation of a number of beautiful naturalistic parkways before the Second World War and to the development in the 1950s and 1960s of interstate highways with gradual, easy curves, generous separation of opposing lanes, and much-needed restrictions on billboards. Since then the imagination of American highway builders has fallen into a long slumber, and it has been only minimally roused by a federal program of "transportation enhancements" enacted six years ago. Auto makers shoot car commercials in deserts and on mountaintops, while the highways traveled by millions become ever more prosaic.

    In 1968 California built what are believed to be the first noise barriers along modern federal highways. Walls were erected on Highway 101 in San Francisco and Interstate 680 north of San Jose to shield abutting residential neighborhoods from the sound of heavy traffic. Within four years the federal government followed California's lead, adopting regulations requiring that whenever a state builds, expands, or realigns a federally funded highway, an attempt be made to curtail excessive noise that would otherwise be inflicted on sensitive neighbors, such as schools, hospitals, and residential areas. Since then a total of forty-one states have built highway noise barriers, generally with 75 to 90 percent of the cost paid by the U.S. Department of Transportation. Nineteen of those states, including Colorado, Michigan, and Connecticut, have also voluntarily built noise barriers along existing highways where no widening or relocation of the roadway was taking place. In all, noise barriers have risen along some 1,300 miles of federal highway, and they are being added at the rate of ninety to a hundred miles a year. California still leads the nation, with 438 miles of barriers.

    Bruce Donohue, a landscape architect in Westport, Connecticut, is aware of the effects that prolonged exposure to highway noise can bring. "One summer when I was a student," he recalls, "I was painting a house along Interstate 95 in Stamford, and I noticed that I was tense. I noticed that the women in the neighborhood were irritated. They were screeching at the kids, and the kids were raucous. The whole neighborhood was irritable and irritated." Road noise does not damage the hearing of people who live close by, but it seems to cause physiological and psychological stress, with results that include nervousness, difficulty in sleeping, and elevated heart rates.

    The effects of stress vary so widely from person to person, however, that transportation departments have avoided basing noise-control programs on them. They have focused on something they can assess more objectively -- interference with hearing and speech. Federal regulations say that if a new or expanded road will produce noise approaching sixty-seven decibels (generally measured outdoors, near buildings), the state must try to bring about a "substantial" reduction in the sound level. Sixty-seven decibels is sound so loud that people have to be within three to five feet of each other to hold a conversation without raising their voices.

    The human ear usually cannot detect a change of three decibels or less, so transportation departments aim for improvements great enough to be easily noticed by the average person -- often eight to ten decibels. A ten-decibel reduction amounts to a 50 percent cut in loudness.

    Researchers for the federal Environmental Protection Agency have found that 20 percent of the population is "highly annoyed" if the sound level measures fifty-five decibels. This level, as it happens, is common outdoors in urban neighborhoods well away from major highways, and is one that transportation departments would often be glad to find in neighborhoods bordering expressways.

    Attempts to provide relief from noise are complicated by the fact that walls work best at blocking short sound waves -- high-pitched sounds. Low-frequency sounds, such as the deep rumble of heavy trucks, may actually become more noticeable once the higher-frequency noise has been sharply reduced. "After a noise barrier has been installed," says Robert E. Armstrong, a senior highway-noise specialist for the Federal Highway Administration, "some people complain that they now hear every truck that goes by."

    To a limited extent designers of noise barriers take psychology into account. California determines heights for its noise barriers partly by calculating how high they must be to hide the sight of tractor-trailer exhaust stacks. "If there were no trucks on the road, the walls could be considerably lower," says Walter Whitnack, an engineer formerly with the California Department of Transportation. "When people can't see the source of the sound, they tend not to be as bothered by it."

    Highway engineers can seldom rely on trees and shrubs to buffer noise. A band of vegetation thick enough so that people could not see through it would provide much the same psychological relief as a solid wall, and most travelers would rather look at trees and bushes than at concrete. But an expanse of vegetation such as evergreen trees with dense undergrowth would have to be a hundred feet deep to reduce the sound level by five decibels, according to William Bowlby, a traffic-noise expert at Vanderbilt University. In most instances the expanse would have to be even deeper. "You almost never can find existing vegetation along a highway that could give you a significant sound reduction in a hundred feet," Armstrong says. "If we planted the right type of trees and ground cover-at considerable expense-it would take five to ten years for it to produce a five-decibel reduction."

    An alternative sometimes chosen by highway builders is to create a natural barrier by mounding up earth and planting grass or other vegetation on it. A planted earth berm seven or eight feet high can be as acoustically effective as a ten-foot-high wall. If the berm alone cannot provide all the sound reduction desired, a wall can be built atop it, and will look considerably less obtrusive than a ground-level wall.

    THE most common solution is walls, and nothing more than walls. In traveling around the country I've sometimes wondered whether highway engineers were competing to see who could build the wall with the bluntest, most macho appearance. Erie, Pennsylvania, has massive, zigzagging walls of concrete that look as if they were designed for military defense; all that is missing is an emplacement of howitzers behind them. Along I95 in Virginia are metal panels painted in alternating colors, inherently out of harmony with the landscape. In southern California walls have been mounted on highway overpasses, creating tight, viewless corridors. In Westchester County, New York, lengths of highway are lined with squalid walls of pre-cast concrete, every panel spray-painted by vandals. Along I-95 in Connecticut are startlingly crude walls of wood supported by lopped-off wooden posts that jab at the sky. An official of a neighboring state calls these the "Fort Apache design."

    Noise barriers typically reach a height of twelve feet above the road, though in the Northeast they often rise sixteen to twenty feet, and in Minnesota, which has been especially anxious to reduce highway noise, they climb as high as thirty feet. Among the tallest noise-barrier walls in the nation is a thirty-nine-foot-high, 2,000-foot-long concrete behemoth in Vienna, Virginia, built so that performers can give concerts in the open-air amphitheater of Wolf Trap Farm Park while traffic whizzes past on the Dulles Toll Road, 380 feet away.

    The harsh appearance of the walls is sometimes compounded by other elements, such as "Jersey barriers"-short walls with sloped bases to bounce straying vehicles back toward the traffic lanes. The longest bridge in the Florida Keys, spanning seven miles of brilliant blue-green water, is one of America's many bridges hemmed in by Jersey barriers so massive that a spectacular panorama is half hidden behind concrete.

    Transportation officials claim that in recent years they have increased their attention to roadside aesthetics. Years ago engineers often naively installed concrete with a smooth surface -- easy for anyone with a can of paint to turn into a message board. In residential areas some transportation departments erected metal walls that, they now admit, have a grimly industrial look. Elsewhere appeared economical wooden walls that soon warped and lost their effectiveness.

    Some neighborhoods complained about the unattractiveness of the initial noise barriers, so most transportation departments now consult the communities for which barriers are proposed. Today, if Pennsylvania wants to build a wall of pre-cast concrete, groups of neighbors get to choose the color and texture of the side that will be visible from their yards. With a mold known as a form liner, wet concrete can be cast to take on the look of wood or stone or to incorporate shapes such as silhouettes of trees.

    Some states have switched from smooth gray concrete to concrete with a rough-textured ribbed surface or an aggregate (pebbly) surface, for a richer appearance that is harder to deface. A number have decided to pay an extra dollar or two a square foot to coat walls with an anti-graffiti compound. (Noise barriers cost an average of a million dollars a mile, and elaborate ones cost considerably more.

    The effort to please people living close by has made some highways uglier for motorists. Virginia allowed neighborhoods in Fairfax County to select so many different kinds of barriers and retaining walls along I-66 that the road, despite skillful planting, "looks like a showroom of barrier technology" in the opinion of William Rieley, a Charlottesville landscape architect who teaches road design at the University of Virginia. The potential to shape the road into a visually coherent experience was lost in the politics of overcoming community opposition.

    The aesthetic progress of highway departments has been agonizingly slow. The Florida Department of Transportation, for example, expresses pride at having molded the city of Hollywood's seal into local sound walls on I-95 and at having let community groups elsewhere select decorations for stretches of that densely traveled road. But there has been little coordination of the road's growing accumulation of concrete silhouettes: municipal logos, lighthouses, laughing gulls, snowy egrets, pelicans, flamingos, and sailboats. Moreover, a symbol like Hollywood's municipal seal, as it was rendered, is out of proportion to the wall -- neither big nor bold enough to make much impact on a surface stretching 2,000 feet long and as much as eighteen feet high.

    NOT all sound walls are aesthetic disasters. Michigan has built good-looking walls of red brick trimmed with concrete beside I-696 outside Detroit. California has built sound barriers topped by a continuous line of masonry caps with a continuous recess running just beneath the caps. The unbroken horizontal lines lead the eye smoothly forward. I-680 in Walnut Creek, California, has sound walls made of blocks in a combination of colors, textures, and sizes. The walls start uniformly dark gray at either end and progress to a lighter tone of gray interspersed at random with dark-reddish blocks; then the reddish blocks form two horizontal bands. The pattern changes from one end to the other, giving rhythm to the drive.

    Upgrading the character of a highway does not necessarily push costs to outrageous levels. "Because of all the gray block, these walls were less expensive than the usual earth-tone walls we build," Arthur Yee, of the California Department of Transportation, says of Walnut Creek's patterned walls.

    One of the most ambitious efforts to improve the character of roads is a public-arts program that has been operating in Phoenix since 1987. Under the guidance of the Phoenix Arts Commission, the city planning department, and the street-transportation department, artists have been hired to design new sound walls and improve existing ones, retaining walls, bridges, and overpasses. For example, Marilyn Zwak, of Cochise, Arizona, and two assistants applied 150 tons of adobe to the Thomas Road overpass on Phoenix's Squaw Peak Parkway, shaping the twenty-four-foot-high support columns into evocative profiles inspired by Hohokam Indian zoological forms. On the retaining walls of the overpass Zwak installed thirty-four relief panels based on human, animal, and abstract images found on Hohokam artifacts. Then she invited neighborhood residents to imprint into the adobe their own designs or objects, ranging from tools to clothing remnants to the key to one of the houses that was demolished to make way for the freeway. Completed in 1990, the overpass has since been voted Phoenix's most popular work of public art.

    On another stretch of the same highway the artist Mags Harries, with Harries/Heder Collaborative, of Cambridge, Massachusetts, and the Planning Center, of Phoenix, installed thirty-five whimsical sculptural pieces of cast concrete and steel that were finished in paint, tile, metallic leaf, and other graffiti-resistant polychrome materials. Among them were giant teapots, bowls, vases, and pots, the biggest of them fifteen feet tall, placed mainly on the residential side of the noise barriers. Here, it was hoped, the artworks would make the six-lane road and its ten miles of beige concrete barrier more acceptable to neighborhoods that had regarded the road as a monstrous imposition. After the installation, in 1992, motorists noticed tops of pots and handles and spouts of oversized teapots rising above the sound walls. The seeming frivolity of the project, together with its cost of $474,000 at a time when Phoenix was suffering a recession, at first aroused public condemnation, but now it is well liked.

    One lesson of the Phoenix experience, says James Matteson, the city's director of street transportation, is that artists and designers should be invited to work with highway engineers while a road is being designed, rather than being asked to relieve existing highway structures of their starkness. He points out that Zwak was asked to collaborate with the engineering team for the Thomas Road overpass from the very beginning -- a principal reason the project achieved such wide appreciation and yet cost less than the plain overpass the engineers would have produced.

    Another lesson, says Deborah Whitehurst, the founding director of the Phoenix Arts Commission and currently a consultant on public art, is that "the wall is not the problem: it's what we put in front of the wall that's critical." She now favors generous plantings to make man-made sound barriers recede into the background. Living matter -- whether saguaro cactuses and desert flowers in Arizona or lush green growth in the East -- exerts a tremendous effect on travelers, as evidenced by the continuing pleasure people derive from the country's surviving if antiquated pre-Second World War parkways.

    William Rieley, in Charlottesville, advocates such relatively simple steps as planting Boston ivy where it will cover sound walls. Along a portion of I-476, or the "Blue Route," in the western suburbs of Philadelphia, the Pennsylvania Department of Transportation has built concrete walls in which pockets allow vines, shrubs, or ground cover to take root.

    The stumbling block is that transportation departments, even where they have room for deluxe landscaping, usually either resist spending enough money to create it or neglect its maintenance. A saying popular with transportation analysts goes, "There are no ribbon-cuttings for maintenance."

    Edward Beimborn, the co-author with Julie Farnham of noise-barrier-design guidelines published by the National Academy of Sciences' Transportation Research Board, says that northern Europe treats sound walls more skillfully than the United States does. Though Europe has less room for highway landscaping, European noise barriers more frequently take into account people's desire for an enjoyable experience, including views of the areas being traversed. In the Netherlands, Beimborn says, a sound wall may be built to shield a town from noise, but at certain intervals the opaque surface will incorporate stripes of glass or transparent plastic, "just enough so you can see the town." The see-through sections are in stripes, he says, to prevent birds from smashing into them.

    Rieley argues that cities fare best when highways are "suppressed" -- sunk into the ground. This cuts noise dissemination, reduces or eliminates the need for freestanding walls, and makes it possible for the city to be knit back together. "The caveat," he says, "is that it is expensive. It involves earth-moving."

    Can state and federal governments afford to spend more on highway design and maintenance? Perhaps a better question is whether they can afford not to. In some states, Virginia among them, tourism is a leading industry; highway improvements that make traveling more appealing stand a good chance of bolstering the economy. In Radnor, Pennsylvania, where $3 million was spent on corridor beautification for U.S. 30 and I-476, the stockbroker who chaired the township's design-review commission calculated that the beautification effort helped property values to rise, rather than be depressed, by the new interstate.

    Ugly or unwelcome highways dampen people's enthusiasm and hasten the deterioration of adjacent neighborhoods. William Morrish, the director of the Design Center for American Urban Landscape, at the University of Minnesota, cites as an example of a decision that adds value to an area the construction in St. Paul in the mid-1980s of a 45-mph, truck-free, well-landscaped thoroughfare for I-35 East instead of a standard expressway. "It costs more than a standard highway," he says, "but it's going to be cheaper than bailing out a failing neighborhood."

    Transportation departments need to see their task as both enriching motorists' experiences and enhancing neighborhoods' well-being in addition to simply providing for traffic movement. Only when transportation planners take a more balanced approach will Americans' time on the road become decidedly more enjoyable.

    Illustration by Gretchen Dow Simpson
    Copyright © 1997 by The Atlantic Monthly Company. All rights reserved.
    The Atlantic Monthly; August 1997; Noisy Highways; Volume 280, No. 2; pages 26- 35.

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