Some of the most pervasive sources of noise in the environment come from transportation systems. Highway traffic noise is a dominant noise source in urban and rural environments. In response to the problems associated with highway traffic noise, the United States Code of Federal Regulations Part 772 (23 CFR 772), "Procedures for Abatement of Highway Traffic Noise and Construction Noise," establishes standards for abatement of highway traffic noise. The purpose of this document is to provide Federal Highway Administration (FHWA) guidance for the applying 23 CFR 772 in the analysis and abatement of highway traffic noise. Following this guidance is strictly voluntary. It is based on lessons learned and best practices and does not constitute the establishment of an FHWA standard. Not all studies are the same; therefore this guidance is intended to be non-prescriptive, and its application flexible and scalable to the type and complexity of the analysis to be undertaken. -- Introduction.