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Sound Barriers Guidelines - Type I Sound Barrier Program

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Home | Highway Traffic Noise | Noise Analysis | Type I Program | Type II Program | FAQs



PROGRAM OVERVIEW


This program is associated with the construction of a highway on a new location or the physical alteration of an existing highway which significantly changes either the horizontal or vertical alignment or increases the number of through-traffic lanes. Federal regulations require the evaluation of highway traffic noise impacts and consideration for abatement where reasonable and feasible.

For a proposed highway project, a traffic noise analysis will be performed, where a noise sensitive land use (i.e. residences, schools, places of worship, historic sites) or where one is planned. Future noise levels will be projected for the design year, usually twenty years in the future, utilizing the latest approved FHWA noise prediction model. The Maryland State Highway Administration will furnish the results of all highway traffic noise analysis to local government officials and will encourage local communities and developers to practice noise compatible development.

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



CRITERIA FOR COMMUNITY ELIGIBILITY




Type I Criteria

For a project to be approved as a Type I project, it has to meet the following criteria:

IMPACT CRITERIA

  • Predicted future noise levels equal or exceed 66 decibels OR exceed existing noise levels by at least 10 decibels and also exceed 57 decibels.

    66 decibels was set as the impact threshold because research has shown that conversation between two people standing 3 feet apart and speaking in a normal voice is impaired above a noise level of 66 decibels.


FEASIBLE CRITERIA

  • The sound barrier should be able to 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 and parks, wildlife areas, conservation areas, and historic sites.


REASONABLE CRITERIA

  • A barrier system will be considered reasonable if the area of wall provided per benefited residence is equal to, or less than, 2,700 square feet.
  • A majority of the homeowners impacted should be in favor of the barrier.







PROJECT EXAMPLES


The following examples are meant to illustrate specific applications of the previously discussed Type I eligibility criteria.



EXAMPLE 1



The proposed project will widen an existing 4-lane freeway to 8 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 would be required to significantly reduce the noise level in the area.


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, less than the 2,700 square feet maximum allowed.




EXAMPLE 2



The proposed project will construct a two-lane highway. Twelve single-family homes are located in a residential area in the vicinity of 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 in the area does not exceed the impact threshold of 66 dBA and will not exceed the existing noise level by up to 10 dBA.






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

 

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