The National Academies

NCHRP Synthesis 20-05/Topic 12-07 [Final (Synthesis)]

Highway Noise Barriers
[ NCHRP 20-05 (Synthesis of Information Related to Highway Practices) ]

  Project Data

This summary of progress on highway noise barriers gives quantitative and qualitative perspectives of the design, construction, maintenance, and impacts of the barriers that have been built to mitigate excessive highway noise. The Federal Highway Administration (FHWA) design noise levels are the principal criterion used to determine height and length of a barrier. Most states will not install a barrier unless it will result in a noise reduction of at least 10 dBA (some use 5 dBA as a minimum). Most states use the FHWA model for highway noise prediction, and two thirds of the states design for the most critical receptor. Systematic procedures to obtain data on impacts on residents and motorists are discussed. The perceived effectiveness is often influenced by aesthetics and landscaping of a barrier rather than by acoustical performance. Maintenance problems of barriers include difficulty with mowing close to barriers, litter accumulation, graffiti, and vandalism. Several states have developed priority rating systems for installing noise barriers on existing highways. Design details as well as construction and maintenance aspects are covered in this report. It is recommended that states seek innovative ways to reduce mass of barriers while maintaining noise reduction capability.  The report for this topic can be purchased at http://www.trb.org/news/blurb_detail.asp?id=3470

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