WEST LAFAYETTE, Ind.—Purdue University has founded an institute to study the physics of tire and highway noise as the first step toward alleviating those problems. The Institute of Safe, Quiet and Durable Highways was dedicated at Purdue's Materials and Electrical Engineering building Aug. 27 with the unveiling of a life-sized sculpture of a tire rolling down a road.
Established by last year's passage of the Transportation Equity Act for the 21st Century, the institute is budgeted at $7 million for the next five years. About half of that—$3.6 million—is coming from a grant by the U.S. Department of Transportation, said Bob Bernhard, director of the institute and a mechanical engineering professor at Purdue.
``We're in the process of finding matching funds from government and private sources,'' Mr. Bernhard said.
Tire design, highway surfaces and their interaction will form the crux of the institute's research, Mr. Bernhard said. ``We have been working on tires for many years at Purdue,'' he said.
Engineers at the institute suspect several aspects of the tire/highway dynamic as being particular noise makers, including:
Compressed air bursting from the spaces between a tire's tread pattern and the road surface;
Block-like shapes in the tread pattern smacking against the road surface; and
Vibration of those tread blocks and the underlying belts, which produce sound much like the vibrating cones in stereo speakers.
Researchers at the institute already have some early insights into sound waves from tire/highway interaction that bear further study, according to Mr. Bernhard.
``Certain vibrating waves radiate sound, and some do not,'' he said. ``But waves that radiate are not necessarily those that dominate. This is revealing, and we want to isolate and focus on those waves that radiate sound.''
Although road surfaces—including the ``porous'' asphalt pavements used widely in Europe as a noise dampener—will be a major part of the institute's research, rubber-modified asphalt is ``back to the drawing board'' for the time being, Mr. Bernhard said.
``A proposal was put forward on rubber-modified asphalt,'' he said. ``It is a proposal that seems to have some interest, as far as rubberized binders and other new technologies are concerned.''
But officials of the Asphalt Paving Association and the American Association of State Highway and Transportation Officials, who sit on the institute's advisory board, discouraged rubber-modified asphalt research in general, saying their members had not had good experiences with the material, Mr. Bernhard said.
The Intermodal Surface Transportation Efficiency Act of 1993 required state highway departments to use rubber-modified asphalt as a condition for keeping their federal highway funding. The fallout from that abortive requirement is still affecting state officials' view of the product, said Doug Carlson, director of government relations for the Rubber Pavements Association.
Among other things, asphalt rubber—the major kind of rubber-modified asphalt—was still under patent then, making it double the cost of conventional asphalt, according to Mr. Carlson. To circumvent the patent, the market became ``a gold rush for...a lot of crazy processes'' that didn't work, he said.
``It's not unusual that a highway official would have some trepidation when rubber pavement is mentioned,'' he said. ``But all of the questions have been resolved, and the industry is far different from what it used to be.''