Urged on by residents tired of excessive highway noise, Arizona Dept. of Transportation engineers are progressing with landmark efforts of quiet-pavement designs.
After public complaints peaked in 2001, ADOT in 2002 topped 13 miles of the 12-in.-thick concrete surface of U.S. 60 in Phoenix with a 1-in.-thick, open-graded friction course (OGFC). The hot-mix asphalt was modified at the plant with a 20% crumb-rubber binder made from recycled tires. The publics response was unexpected, says George Way, ADOTs chief pavement-design engineer. "They started calling in and saying, This is incredibly quiet. Why dont you pave the whole freeway this way?"