Sound Barriers Guidelines - Type I Sound Barrier Program

PROGRAM OVERVIEW


This program covers highways on new locations and the alteration of existing highways that significantly change the horizontal or vertical alignment or increases the number of through-traffic lanes. Federal regulations require the Maryland Department of Transportation State Highway Administration (MDOT SHA) evaluate highway traffic noise impacts and consider abatement where reasonable and feasible. 

MDOT SHA performs a traffic noise analysis when planning a noise-sensitive land use (near residences, schools, houses of worship, and historic sites). Noise levels are projected for the design year and twenty years into the future utilizing the latest approved FHWA noise prediction model. MDOT SHA furnishes the results of highway traffic noise analysis to local government officials and encourages communities and developers to practice noise-compatible development.

To check for any ongoing Type I projects in your county, click here.



CRITERIA FOR COMMUNITY ELIGIBILITY




Type I Criteria

For Type I approval, a project must meet the following criteria:

IMPACT CRITERIA

  • Predicted future noise levels equal or exceed 66 decibels OR will be greater than existing noise levels by at least 10 decibels and exceed 57 decibels.

    66 decibels is the impact threshold because research shows that conversation between two people speaking in a normal voice and standing three feet apart is impaired above 66 decibels.


FEASIBLE CRITERIA

  • The sound barrier must yield a significant noise reduction for impacted residents.
  • Sound barrier construction should have no significant impacts on existing drainage and utility, and should not restrict pedestrian or vehicular access.
  • The construction of a sound barrier should not impact publicly owned recreation areas, parks, wildlife areas, conservation areas, and historic sites.


REASONABLE CRITERIA

  • A barrier system is considered reasonable if the area of wall provided per benefited residence is 2,700 square feet or less.
  • A majority of the homeowners impacted must favor the barrier.







PROJECT EXAMPLES


The following examples illustrate applications of the Type I eligibility criteria.



EXAMPLE 1



The proposed project will widen an existing four-lane freeway to eight lanes. Ten single-family homes are located in a residential neighborhood in the vicinity of the proposed project. The existing noise level in the area is 66 dBA. A future "build" noise level of 72 dBA and a future "no-build" noise level of 68 dBA are predicted for the design year. A sound barrier approximately 1,385 feet in length and 18 feet in height is required to significantly reduce the noise level.


EVALUATION PROCESS

Type I Criteria

DECISION: The construction of a sound barrier will be considered.

REASON: The predicted noise level in the area exceeds the impact threshold of 66 dBA. The proposed sound barrier would equal 2,493 square feet, within the 2,700 square feet maximum allowed.




EXAMPLE 2



The proposed project is a two-lane highway. Twelve single-family homes are located in a residential area near the proposed project. The existing noise level in the area is 50 dBA. A future build noise level of 58 dBA and a future no-build noise level of 50 dBA are predicted for the design year.


EVALUATION PROCESS

Type I Criteria

DECISION: The construction of a barrier will not be considered.

REASON: The predicted noise level does not exceed the impact threshold of 66 dBA and does not exceed the existing noise level by 10 dBA.






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Additional questions? Contact the Office of Highway Development(OHD) at 1-888-228-5003.