Abstract
More than 450 mi of noise barriers have been constructed in the United States at a cost of more than $300 million (in 1986 dollars). About one third of these were constructed after the highway had originally been built, and about one third are adjacent to interstate highways. The average barrier is about 12 ft high and costs about $12/sq ft in 1986 dollars. More than 30 percent of all highway noise barriers are in California, and about 10 percent are in Mminnesota. It is reasonable to expect that in the future, noise barrier construction will be of the order of tens of miles annually.