Sound Barriers

Where can I find your sound barrier policy?

The Maryland Department of Transportation State Highway Administration (MDOT SHA) Sound Barrier Policy can be found here.

What is accomplished through noise abatement?

The primary objective of the MDOT SHA Noise Abatement Program is to fulfill the responsibility outlined by the Federal Highway Administration (FHWA). The FHWA noise regulation, found at 23 CFR 772, requires a highway agency to investigate traffic noise impacts in areas adjacent to federally funded highways for the proposed construction of a highway on a new location or the reconstruction of an existing highway that either significantly changes the horizontal/vertical alignment or increases the number of through-traffic lanes.

Through feasible and reasonable noise abatement, MDOT SHA aims to:

  • provide discernable abatement
  • enable impacted residents standing three feet apart outside their homes to hold normal conversations without needing to yell
  • provide uniformly consistent noise levels (without hotspots)
  • block line-of-sight from the highway to the community

How do I inquire about reducing highway traffic noise?

To inquire about highway traffic noise, please complete the online form, or call toll free at 1-888-228-5003.

What are the factors used by MDOT State Highway Administration in determining my community's eligibility for a sound barrier?

MDOT SHA will determine if the community is impacted by highway traffic noise and if the construction of a sound barrier is reasonable and feasible. Only barriers that are determined to be both reasonable and feasible will be approved.

My community was notified that it was eligible for a sound barrier but no sound barrier has yet been constructed. Why?

Sometimes, the construction of a Type II sound barrier is both feasible and reasonable, and the community deemed eligible for construction of a sound barrier. However, funds may not be available. In such a case, the project is placed on an eligibility wait list and the barrier will be constructed when funds are available.

What properties are considered “impacted” and “benefited?”

The following impact levels are the most commonly used:

Type I

A sensitive land use is impacted if:

  • Design year noise levels are projected to equal or exceed 66 dB(A) - OR –
  • Projected noise levels are anticipated to increase over the existing year’s noise levels by the amount shown in Table below. For example, if a land use has an existing noise level of 41 dB(A), the design year noise level must increase by at least 15 dB(A) for a noise impact to occur.


Existing Noise Level

Projected Increase

45 dB(A) or less

15 dB(A)

46 dB(A)

14 dB(A)

47 dB(A)

13 dB(A)

48 dB(A)

12 dB(A)

49 dB(A)

11 dB(A)

50 dB(A) or greater

10 dB(A)

Type II

A noise-sensitive use is impacted if existing noise levels equal or exceed 66 dB(A).

A “benefited property” is one that benefits from a sound barrier by up to a five-decibel noise level reduction but is not necessarily impacted.

Why was the impact level set at 66 decibels?

Research shows that conversation between two people standing three feet apart and speaking in a normal voice is impaired above a noise level of 66 decibels.

Note: 66 decibels is less noisy than a vacuum cleaner (70 decibels) and a lawnmower (90 decibels).

When will MDOT SHA conduct a noise measurement by request?

A noise measurement will only be conducted at a person’s request if that person’s community meets preliminary criteria for a Type II project. An important criterion is "date eligibility." For a Type II project, a majority of the impacted residences should have existed prior to the original construction of the highway.

Also, examining the topography of the area and its horizontal distance from the highway must lead to a determination that noise abatement measures can be implemented and will be effective.

Do local officials have input?

Yes. The control of highway noise, to be effective and comprehensive, must be done in partnership between MDOT SHA and local land use planning officials. MDOT SHA will share results of all highway traffic noise analysis with local government officials, and encourage local communities and developers to practice noise compatible development.

How do I report that an existing wall is damaged?

Sound barriers built by the State are maintained by the State. To submit a complaint about a damaged wall, complete the online form or call toll free at 1-888-228-5003.

What can be done to regulate "Jake Brakes?”

Compression release engine brakes are usually installed in large trucks and trailers. Jake Brakes are a brand of these engine breaks manufactured by Jacobs Vehicle Systems. Cummings makes a C-brake and other companies make similar systems. Jake Brakes reduce stress on a truck’s hydraulic brake system, extending its life and reducing the danger of overheating and fatigue. On the other hand, this technology is associated with increased engine noise.

Vehicles with improperly maintained, defective, or modified exhaust systems make the loud noise associated with engine breaking and, thus, violate the noise limits established by the State. Law enforcement agencies enforce State laws relating to exhaust systems and excessive or unusual noise. Maryland Law prohibits vehicles from:

A vehicle equipped with a Jake Brake, or a similar engine retardant system, may be lawfully operated on highways in Maryland, as use of this equipment is not prohibited by Maryland Vehicle Law.

Does MDOT SHA provide noise insulation for private residences?

No, MDOT SHA does not fund such projects. Note that fixing double pane windows, sealing wall cracks, and hanging of heavy draperies can help reduce noise from highway traffic. (Source: Washington State Dept. of Transportation Website, Noise FAQ)

Can I build my own noise wall?

Yes. Some residents choose to build their own walls to protect their property from highway traffic noise. These walls are normally made from wood and located at the property line. To reduce noise levels, the wall should have no gaps, should block the line of sight of the noise source, and should be long enough to enclose the area to be protected. These walls are not funded by MDOT SHA.

What is noise masking?

Some residents use white noise, such as noise from a fan or waterfall, to drown out traffic noise. While some people report success with this technique, it is not a practical noise abatement tool on a community scale and is not sponsored by MDOT SHA. (Source: Washington State Dept. of Transportation Website, Noise FAQ)

Can vegetation such as trees and shrubs effectively reduce highway traffic noise?

Yes. Research shows that a 5 dBA reduction in noise can result from building a stand of vegetation 100 feet wide, and up to a maximum reduction of 10 dBA from a stand of at least 200 feet wide. The following features must also exist:

  • A mixture of low growth (shrubs and bushes) and tall mature trees of sufficient density that the highway cannot be seen.
  • Tree height of at least 15 feet above the line of sight (straight line view between the houses and the highway).
  • A mixture of deciduous and evergreen plants to maximize effectiveness in both winter and summer.

Note: These types of vegetated areas are typically natural and not man-made. Such features are impractical to plant or replace, especially along a highway. However, these areas are preserved whenever possible. In more practical terms, one or more rows of trees may be planted to provide some psychological relief and to act as a visual shield from highway traffic.

What if my community was refused a barrier? Am I eligible now? When will I be eligible?

Your community can appeal a decision. Appeals of decisions not to build sound barriers are considered by the Secretary of the Department of Transportation and the State Highway Administrator. An appeal is considered when there is a question about the interpretation/application of the sound barrier policy criteria or there is a question about the preparation and accuracy of the technical noise analysis. Noise policy criteria are not the basis for appeal.

Note: If MDOT SHA initiates highway improvements near your community, MDOT SHA may conduct a noise analysis affecting eligibility.

How does MDOT SHA’s highway noise policy address FHWA guidance on “Use of Freeway Shoulders for Travel?”

In February 2016, the Federal Highway Administration (FHWA) provided guidance entitled Use of Freeway Sho​ulders for Travel. The implementation of part-time shoulder use along Freeway is a Type 1 project. Inside shoulder use is less likely to have noise impacts compared to right side part-time shoulder use, which places the traffic closer to sensitive receptors. Lower speed with the similar traffic characteristics is less likely to have noise impacts compared to the higher speed with similar traffic characteristics.

Abatements that may be considered for part-time shoulder use include, but are not limited to:

  • Construction of noise barriers (landscaping is NOT considered a noise abatement measure).
  • Traffic management measures, such as traffic control devices and signing for prohibition of certain vehicle types, time-use restrictions for certain vehicle types, modified speed limits, and exclusive lane designations.
  • Acquisition of property (typically undeveloped or unimproved) for establishing a buffer zone to prevent future development that would be adversely affected by traffic noise.
  • Noise insulation of land use facilities, defined in 23 CFR 772 as Activity Category D to address INTERIOR noise impact. These facilities include auditoriums, day care centers, schools, libraries, hospitals and medical facilities, places of worship, public meeting rooms, public or nonprofit institutional structures, radio, television, and recording studios. This abatement measure is ONLY applicable if: 
    • Exterior abatement is determined not to be feasible and reasonable, or 
    • If no noise sensitive exterior uses exist on the subject property.