Sound (noise) occurs when an ear senses pressure variations or vibrations in the air. Noise is unwanted sound.  A person’s brain relates a subjective element to a sound, and an individual reaction is formed.  Studies indicate that the most pervasive sources of noise in our environment today are those associated with transportation. Highway traffic noise tends to be a dominant noise source in both the urban and rural environment.

Public concern about noise led to federal legislation in 1970 that authorized the use of federal-aid highway funds for measures to abate and control highway traffic noise.  The guidelines in the MoDOT Noise Policy are used to determine the need, feasibility, and reasonableness of noise abatement measures and provide the basis for statewide uniformity in traffic noise analysis.

The Federal Highway Administation regulations require MoDOT to:

identify traffic noise impacts and examine potential mitigation measures; incorporate reasonable and feasible noise mitigation measures into its highway projects; and coordinate with local officials to provide helpful information on compatible land use planning and control during the planning and design of a highway project.

The regulation makes a distinction between projects for which noise abatement is considered as a feature in a new or expanded highway and those for which noise abatement is considered as a retrofit feature on an existing highway.