Pavement noise—U.S. and European recent developments
"The consumer has decided [noise is] a quality of life issue," began Larry Scofield of the Arizona DOT. He shared the findings of a scanning tour to Europe in spring 2004 that documented the continent's innovations in reducing pavement noise. The tour, sponsored by the FHWA, the American Association of State and Highway Transportation Officials, and the Transportation Research Board, found that "Europeans take a holistic approach," he said, particularly in terms of noise policies and mitigation strategies.
European Union members are required to map noise contours along all existing roadways by 2007 and then develop mitigation plans to address any problems identified. Permissible noise levels in Europe are already less than half of what's allowed in the United States. "That's how serious they are about it," Scofield said.
While approaches vary by country, the tour found that in general Europeans use both quieter pavements and noise barriers, implement policies that set noise level thresholds, and seek noise reductions from both vehicles and tires. Additional policies address the placement of new housing, for example.
The tour's experiences and findings are available in a draft report, Quiet Pavements (2.2 MB PDF). Recommendations include using porous mixes on high-speed roadways and thin-textured surfacings on urban or low-speed roadways. Scofield cautioned, however, that the highly porous asphalt mixes present winter maintenance problems: they typically use more chemical (25 to 50 percent more salt) and freeze earlier. And quieter pavements in Europe cost about 10 to 25 percent more than traditional pavements.
Scofield also reviewed a recent study by Caltrans that compared European pavements to those used in California and Arizona. This research showed that the asphalt rubber pavements used in the U.S. compared favorably with the quietest pavements tested in Europe. The European pavements were designed to be quiet, he noted, while ours were "off the shelf." The important point, he concluded, is that pavement can be used to mitigate noise.