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Noise Policy FAQs- Frequently Asked Questions

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  1. What is the Federal-State relationship?
  2. What is a Type I project?
  3. What is a Type II project?
  4. How are existing noise levels determined?
  5. How are future noise levels determined?
  6. How do we determine noise impacts?
  7. What is a substantial increase?
  8. If impacts are identified, must abatement be provided?
  9. What is meant by providing "feasible" highway traffic noise abatement?
  10. What is meant by providing "reasonable" highway traffic noise abatement?
  11. What types of abatement measure are eligible for Federal-aid funding?
  12. Can quieter pavement be used as abatement?
  13. Will vegetation reduce noise levels?
  14. Are TNM contours allowed for impact determination or abatement consideration?
  15. Do owners or renters vote for abatement?
  16. What are the FHWA Noise Abatement Criteria (NAC)?
  17. How were the FHWA NAC developed?
  18. What is a Category A activity?
  19. What is a Category B activity?
  20. What is a Category C activity?
  21. What is a Category D activity?
  22. What is meant by Planned, Designed and Programmed? The summary should include a summary of Date of Public Knowledge (follow this with Category D receivers???)
  23. What is a Category E activity?
  24. How to we determine and abate noise levels for Category E (interior) activities?
  25. Are multi-family dwellings analyzed for impacts and considered for abatement?
  26. What is the method for analyzing abatement for multi-story land uses, such as multi-family apartments or condos?
  27. What is a special use location and how do we analyze them?
  28. What is a severe impact?
  29. What noise barrier standards are required?
  30. What are the Federal standards for highway traffic noise?
  31. Are payments allowed for noise damages?
  32. When only one side of the highway has a noise barrier, does the noise level increase for the opposite side of the highway where there is no noise barrier?
  33. Why are some communities eligible for noise abatement and others are not?
  34. What's new in Construction Noise?
  35. When should an analyst use the FHWA TNM 2.5 noise model compared to FHWA TNM 2.5 Look-up for screening purposes?
  36. How does noise affect Section 4(F) properties?
  37. What are the differences between NEPA and 23CFR772?
  38. What is Noise Compatible Planning (NCP)?
  39. How are noise levels determined when user defined vehicle types or other extenuating factors, such as tunnels or rest stops, are involved?
  1. What is the Federal-State relationship?

    The Federal Highway Administration (FHWA) is the designated government agency for administering the federal-aid highway program. This program makes funds available to the States each year by legislative formula to assist in their highway construction and improvement programs. The States select the projects they will undertake by priority. They then must develop these projects according to Federal requirements, considering project alternatives and potential impacts. The States are also responsible for the planning, design, and construction of highways within their jurisdictions. FHWA reviews each State's work to make sure it satisfactorily meets Federal requirements. Additionally, we provide technical advice and give approvals at key stages of project development.

    Since each State has specific knowledge of the highway projects in their State, FHWA will provide contact information to the State Department of Transportation (SDOT) noise contact. The SDOT noise contact will be able to address the public concerns regarding a specific project, noise complaint, or request for a noise barrier. Click here to go to the SDOT noise contact list. (PDF 160KB)

  2. What is a Type I project?

    A noise analysis must be performed, and if impacts identified, noise abatement must be considered for

    1. A new highway on new location,
    2. A modification to an existing highway, or
      1. The identification of a physical alteration of an existing highway which increases the number of through-traffic lanes requires the consideration of the through traveled way-that portion of the highway constructed for the movement of vehicles, exclusive of the shoulders and auxiliary lanes. The lane addition must include a full lane width, i.e., 12 feet, and must increase the capacity of the highway. The addition of a full lane to the mainline of a highway must be classified as a Type I project.
      2. The addition of an auxiliary lane should also be classified as a Type I project, if the auxiliary lane is long enough to function as a through-traffic lane and/or increase capacity. An auxiliary lane that is added between interchanges to improve operational efficiency should be classified as a Type I project, if the lane is at least 1.5 miles long or if the lane is made continuous through an interchange. The addition of truck-climbing lanes to existing highways can create significant changes in alignment and/or add through-traffic lanes, if the truck-climbing lane is long enough to function as a through-traffic lane and/or increase capacity.
      3. Similarly, the addition of a high-occupancy vehicle (HOV) lanes to highways are also Type I projects, whether added in the median or on the outside of the existing highway, since they add through-traffic lanes. Traffic noise analysis is required for both sides of the highway, even when HOV lanes are only being added on one side of the highway. Frequently, HOV projects cause little or no change in the existing or future noise environment. However, traffic noise impacts may occur, since existing noise levels may already approach or exceed the FHWA noise abatement criteria. In these instances, abatement must be considered and, if found to be feasible and reasonable, must be implemented.
    3. A significant alteration of the horizontal or vertical alignment. A significant alteration of horizontal or vertical alignment. FHWA does not define "significant change in alignment;" we allow State DOTs to do this. Montana is one of 5 states that have definitions or language addressing this in their state noise policy; I've excerpted wording from the policies below. As you can see, the wording on horizontal alignment is typically "halving the distance from the roadway to the receiver" and that on vertical alignment varies from a 5-foot change to a 6 to 9-meter change. The general approach seems to be that for a change in alignment to be "significant," there should be at least a 3-dBA (barely perceptible) increase in traffic noise levels. If a State has a definition of what is a significant change in horizontal or vertical alignment, we recommend the definition be written in their policy.

  3. What is a Type II project?

    Usually called a retrofit project, a proposed Federal or Federal-aid highway project for noise abatement on an existing highway. Type II projects are not mandatory and are at a States' discretion. Projects of this type are proposed solely at the option of a SDOT, and specific requirements for the project are determined by the individual SDOT. Federal participation in the funding of such projects is limited to those that propose abatement measures along lands that were developed prior to construction of the original highway. For guidance on a Type II program, please contact the FHWA noise team. Please access our Highway Traffic Noise Analysis and Abatement policy (PDF 325KB) and go to Page 55 of the actual document (or Page 59 of 71 in the Adobe Counter).

  4. How are existing noise levels determined?

    Existing noise levels can be determined by one of three methods:

    1. Actual sound level measurements taken at representative receivers: these measurements should be performed at the worst hour.
    2. Prediction by using the Traffic Noise Model provided there are no other noise sources present
    3. Combination of sound level measurements and prediction with the Traffic Noise Model after validation or calibration; validation and calibration do not need to be performed at the worst traffic hour.
  5. How are future noise levels determined?

    Future noise levels are determined by using the FHWA Traffic Noise Model® (FHWA TNM®).

  6. How do we determine noise impacts?

    A traffic noise impact occurs when the existing or future noise levels approach or exceed the noise abatement criteria (NAC) or when predicted future traffic noise levels substantially exceed the existing noise level, even though the predicted levels may not exceed the NAC. This definition reflects the FHWA position that traffic noise impacts can occur under either of two separate conditions:

    1. When noise levels are unacceptably high (absolute level); or
    2. When a proposed highway project will substantially increase the existing noise environment (substantial increase).

    In order to adequately assess the noise impact of a proposed project, both criteria must be analyzed. While the FHWA noise regulations do not define "approach or exceed," all State DOTs must establish a definition of "approach" that is at least 1 dB(A) less than the NAC for use in identifying traffic noise impacts in traffic noise analyses. The determination of "approach" should be expressed in a whole decibel. Please access our Highway Traffic Noise Analysis and Abatement policy (PDF 325KB) and go to Page 7 of the actual document (or Page 11 of 71 in the Adobe Counter).

  7. What is a substantial increase?

    A substantial increase is typically 10 to 15 dBA increase over existing noise levels. States are allowed to define what a substantial increase is in their policy.

  8. If impacts are identified, must abatement be provided?

    If impacts are identified, then the alternative abatement measurements must be considered, and implemented, if feasible and reasonable.

  9. What is meant by providing "feasible" highway traffic noise abatement?

    Feasibility deals primarily with objective engineering considerations (e.g., can a barrier be built given the topography of the location; can a substantial noise reduction be achieved given certain access, drainage, safety, or maintenance requirements; are other noise sources present in the area, etc.). Safety, maintenance, and drainage concerns for noise abatement measures should be addressed during preliminary and final project design. These issues should be part of the feasibility determination and can usually be resolved through use of good design practices. Also, noise barriers are infeasible when they are unable to obtain a substantial noise reduction. The minimal substantial reduction allowed is 5 dB. States define what a substantial reduction is. Some require an average of 5 dB noise reduction for all impacted receivers while others require at least one receiver to achieve a substantial reduction of 7 or 10 dB. Please access our Highway Traffic Noise Analysis and Abatement policy (PDF 325KB) and go to Page 41 of the actual document (or Page 45 of 71 in the Adobe Counter).

  10. What is meant by providing "reasonable" highway traffic noise abatement?

    Reasonableness is a more subjective criterion than feasibility. It implies that common sense and good judgment were applied in arriving at a decision. Reasonableness should be based on a number of factors not just one criterion. The criteria used for determining feasibility and reasonableness should indicate a broad consideration of conditions that apply in a given location. The criteria should allow identification of the overall benefits, as well as the overall adverse social, economic, and environmental effects, of the noise abatement. Quantification of each of the criteria allows their use in making a more objective decision. This should allow the decision to be more supportable and more easily explained. The criteria should be responsive to the need to provide noise abatement. Conversely, the effects on overall cost to the highway program should be considered when quantifying the criteria. Consequently, the criteria need to be prudently developed. This paper later presents an example of quantification of abatement criteria. Flexibility is an important element of good noise abatement decision making criteria and procedures. The criteria and procedures should be objective enough to be quantifiable, but they should also be flexible enough to allow the decision maker to make meaningful judgments on a case-by-case basis for special circumstances. The criteria and procedures should permit consideration of "gray areas" and should not always be rigidly applied. There may be instances where abatement should be found to be feasible and reasonable even though it is found to fall outside some of the established criteria and procedures, e.g., it costs more than the reasonable cost index (including it protects a fewer number of people), absolute traffic noise levels are lower but increases in existing noise levels are great, changes in noise levels are small but the absolute levels are high, or increases in noise levels since initial development occurred are great. Please access our Highway Traffic Noise Analysis and Abatement policy (PDF 325KB) and go to Page 42 of the actual document (or Page 46 of 71 in the Adobe Counter).

  11. What types of abatement measure are eligible for Federal-aid funding?

    There are several alternative abatement measures allowed for use of Federal-aid funds. All alternative abatement measures should be considered for each project and addressed in the NEPA document. These alternative abatement measures are:

    1. Traffic management measures (e.g., 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),
    2. alteration of horizontal and vertical alignments,
    3. acquisition of property rights (either in fee or lesser interest) for construction of noise barriers,
    4. Construction of noise barriers (including landscaping for aesthetic purposes) whether within or outside the highway right of way,
    5. acquisition of real property or interests therein (predominately unimproved property) to serve as a buffer zone to preempt development which would be adversely impacted by traffic noise. This measure may be included in Type I projects only, and
    6. noise insulation of public use or nonprofit institutional structures.
  12. Can quieter pavement be used as abatement?

    Quieter pavement is not currently allowed by FHWA, unless the State is a part of a Quiet Pavement Pilot Program (QPPP). Click here for information regarding a QPPP. This does not preclude a State DOT from using quieter pavement on non-Federal-aid projects.

  13. Will vegetation reduce noise levels?

    Vegetation is not considered as noise abatement, especially when involving Federal-funded projects. Vegetation must be a minimum of 100 feet thick, a minimum of 20 feet high, and so dense that it cannot be seen through in order to provide a 5-dBA noise reduction. Anything less than that thickness will not help much for the noise. Of course, the psychological effect (out of sight out of mind) can be beneficial. Federal funds can be used for vegetation near barriers for aesthetic and visual purposes.

  14. Are TNM contours allowed for impact determination or abatement consideration?

    FHWA does not recommend using contours to determine impacts or for abatement consideration. Contours should only be used for planning purposes, specifically when following 772.15(a), which states: The best estimation of future noise levels (for various distances from the highway improvement) for both developed and undeveloped lands or properties in the immediate vicinity of the project.

  15. Do owners or renters vote for abatement?

    The owner of a dwelling should be surveyed for the affected public's view for or against proposed noise abatement.

  16. What are the FHWA Noise Abatement Criteria (NAC)?

    The FHWA NAC are objective absolute noise levels for varying land use categories where an impact is triggered. The use of subjective descriptors to describe traffic noise impacts is not required. Traffic noise impacts occur based upon the definition contained in 23 CFR 772. This definition does not contain subjective descriptors. If impacts are identified, noise abatement measures must be considered and, if found to be feasible and reasonable must be implemented.

    Table 5 : 23 CFR, Part 772, Table 1 Noise Abatement Criteria (NAC) Hourly A Weighted Sound Level in Decibels (dBA)*
    Activity Category Leq(h) L10(h) Description of Activity Category
    A 57 (Exterior) 60 (Exterior) Lands on which serenity and quiet are of extraordinary significance and serve an important public need and where the preservation of those qualities is essential if the area is to continue to serve its intended purpose.
    B 67 (Exterior) 70 (Exterior) Picnic areas, recreation areas, playgrounds, active sports areas, parks, residences, motels, hotels, schools, churches, libraries, and hospitals.
    C 72 (Exterior) 75 (Exterior) Developed lands, properties, or activities not included in Categories A or B above.
    D     Undeveloped lands.
    E 52 (Interior) 55 (Interior) Residences, motels, hotels, public meeting rooms, schools, churches, libraries, hospitals, and auditoriums.
    *Either Leq(h) or L10(h) (but not both) may be used on a project.
  17. How were the FHWA NAC developed?

    In developing the NAC contained in the noise regulations, the FHWA attempted to strike a balance between that which is most desirable and that which is feasible. Factors such as technical feasibility, the unique characteristics of highway generated noise, cost, overall public interest, and other agency objectives were important elements in the process of setting a standard. Establishing values for the NAC was approached by attempting to balance the control of future increases in highway noise levels and the economic, physical, and aesthetic considerations related to noise abatement measures. Numerous approaches were considered in establishing the criteria, including:

    1. Hearing impairment: This approach deal in terms of very loud noises seldom encountered for a highway project beyond the roadway proper.
    2. Annoyance, sleep, and task interference or disturbance: This approach was desirable in principle but was insufficiently researched to be useful in practice.
    3. Interference with speech communication:

    However, this approach was usefully applied to the problem of highway traffic noise. Thus, it should be remembered that the NAC are based upon noise levels associated with interference of speech communication and that the NAC are a compromise between noise levels that are desirable and those that are achievable. FHWA believes that our regulations provide a well balanced approach to the problem of highway traffic-generated noise.

  18. What is a Category A activity?

    Activity Category A includes lands on which serenity and quiet are of extraordinary significance and serve an important public need and where the preservation of those qualities is essential if the area is to continue to serve its intended purpose. Some examples of lands that have been analyzed as Activity Category A receivers include the Tomb of the Unknown Soldier, a monastery, an outdoor prayer area of a facility for nuns, and an amphitheater.

  19. What is a Category B activity?

    Activity Category B includes picnic areas, recreation areas, playgrounds, active sports areas, parks, residences, motels, hotels, schools, churches, libraries, and hospitals. All land uses except residences listed as Activity Category B are often treated as special use facilities due to the difficulty in determining the number of receiver units. Each State DOT should adopt a standard practice for analyzing these special use facilities that is consistent and uniformly applied statewide.

  20. What is a Category C activity?

    Activity Category C includes developed lands, properties, or activities not included in Categories A or B. This category would include commercial and industrial land uses. In most cases, the owner of a Category C does not desire mitigation, typically in the form of a barrier, which could block access or advertisement of their location. Impacts must still be identified and if impacted, mitigation considered. Early communication with Category C land uses can be helpful to the consideration of mitigation. Often times, areas of mixed use, specifically where Category B and C receiver units, can be difficult.

  21. What is a Category D activity?

    Activity Category D includes undeveloped lands. Although consideration of mitigation is not required under 23 CFR 772, predicted noise levels still need to be determined and documented. If impacts occur, mitigation is left up to the property owner and/or local government. In these cases, the date of public knowledge and determination of planned, designed, and programmed development are important.

  22. What is meant by Planned, Designed and Programmed? The summary should include a summary of Date of Public Knowledge (follow this with Category D receivers???)

    Section 772.9(b)(1) also requires noise analysis for undeveloped lands for which development is "planned, designed, and programmed." The terms "... planned, designed, and programmed ..." mean that:

    1. A definite commitment has been made to develop the property in question, and
    2. There is also official knowledge (such as through a public agency) that such development has been "planned, designed, and programmed." A definite commitment means that a developer has shown a definite interest to develop the land within a reasonable period of time and has reached a point where he can no longer practically change his plans.

    The exact date for determining when undeveloped land is considered "... planned, designed, and programmed ..." for development is not specified in 23 CFR 772. Each State DOT and accompanying FHWA Division Office should establish a mutually acceptable specific milestone that is appropriate for the development process in their respective State. Any of the following dates are in conformance with FHWA policy and should be applied uniformly and consistently state-wide:

    1. Date of issuance of a building permit
    2. Date of final approval of the development plan, and
    3. Date of recording of the plat plan. Any of these dates are in conformance with FHWA policy.

    State DOTs must identify when the public is officially notified of the adoption of the location of a proposed highway project. This date establishes the "date of public knowledge" and determines the date when the Federal/State governments are no longer responsible for providing noise abatement for new development that occurs adjacent to the proposed highway project. The "date of public knowledge" cannot precede the date of approval of the Categorical Exclusion (CE), the Finding of No Significant Impact (FONSI), or the Record of Decision (ROD).

    This is very important for re-evaluations of NEPA documents. Development may have been planned, designed, and programmed since the new date of public knowledge based on the re-evaluation. The noise analyst must assess any changes to accurately consider impacts and mitigation.

  23. What is a Category E activity?

    Activity Category E is the indoor criteria for residences, motels, hotels, public meeting rooms, schools, churches, libraries, hospitals, and auditoriums. Indoor analysis should only be considered after fully completing an analysis of the outdoor activity areas

  24. How to we determine and abate noise levels for Category E (interior) activities?

    If no exterior areas of frequent human use are present, then the NAC Category E activity should be considered. The method for measuring an interior noise level is to measure the exterior noise level and use Table 7 from our Highway Traffic Noise Analysis and Abatement policy to subtract from the exterior value and determine the interior noise level. Go to Page 10 of the actual document (or Page 14 of 71 in the Adobe Counter).

    FHWA considered sound insulation as an abatement option for public use or non-profit institutional structures, especially where there is no exterior area of frequent human use. FHWA is not allowed to consider sound insulation for residences, except in cases where a severe impact is identified.

  25. Are multi-family dwellings analyzed for impacts and considered for abatement?

    All sensitive receptors, including multi-family dwellings are analyzed for noise impacts and if impacts are identified, then they are considered for abatement. The measurement location should be at the area of frequent human outdoor use. This can be difficult to determine and is best determined with a site visit. There may be locations where the balconies are used by the residents and thus should be the area of frequent human use. Other times there will be a communal outdoor area of frequent human use, such as a grill area, picnic tables, or playground. This could also be used as the measurement location.

  26. What is the method for analyzing abatement for multi-story land uses, such as multi-family apartments or condos?

    Generally it is not feasible and/or reasonable to build a noise barrier tall enough to mitigate noise for floors above the ground floor. However, FHWA recommends that the barrier design be optimized. Thus an analysis should be done to mitigate for the ground floor, but a further analysis should be performed in an attempt to mitigate for higher floors. There may be situations, specific to local terrain or other shielding objects, where a noise barrier is warranted reasonable and feasible for higher floors.

  27. What is a special use location and how do we analyze them?

    A special use location is typically any location that is not a residence or a commercial property where quantifying the impacts and analyzing abatement is difficult. This would include: picnic areas, recreation areas, playgrounds, active sports areas, parks, motels, hotels, schools, churches, libraries, and hospitals.

    The analysis for special use locations is typically done on a case-by-case basis. Several States have described how they handle special use locations. For example, some States will define a special use as equal to ten residences, while others will define a special use as equal to one residence. Other States will define the special use by dividing the special use lot frontage to the roadway as compared to the typical resid ential lot frontage to come up with a conversion factor. There are several others procedures for handling special use locations. If a State has a procedure, we recommend they place that procedure in their noise policy, to minimize environmental justice concerns. For some guidance, please view the Florida DOT's A Method to Determine Reasonableness and Feasibility at Special Use Locations

  28. What is a severe impact?

    A severe impact occurs when the absolute noise levels is 75 dBA or higher or there is an increase of 30 dBA or more over existing noise levels. Some States define what a severe impact is in their policy and have a procedure for dealing with severe impacts. Other States deal with severe impacts on a case-by-case basis.

  29. What noise barrier standards are required?

    There are no Federal requirements or FHWA regulations related to the selection of material types to be used in the construction of highway traffic noise barriers. Individual state departments of transportation (DOTs) select the material types to be used when building these barriers, as well as the testing procedures to be used in their evaluation. The state DOTs normally make this selection based on a number of factors such aesthetics, durability and maintenance, costs, public comments, seismic or wind considerations, etc. Discussion of the process for evaluating noise barrier products designed and manufactured privately before installation, including testing such as susceptibility to shatter, flame spread, material strength, etc., can be found in Chapter 10 of the Noise Barrier Design Handbook.

  30. What are the Federal standards for highway traffic noise?

    23 CFR 772 is the Federal Noise Regulation, thus the Noise Standard. The Noise Abatement Criteria are often confused as the noise standard.

  31. Are payments allowed for noise damages?

    Federal funds are not to be use to provide monetary compensation to property owners, but rather to abate highway traffic noise impacts. It is the State DOT's responsibility to ensure that Federal funds are properly being use. One way is to ensure proper use of Federal funds is to always contract out the construction of a highway traffic noise abatement measure to third-party contractor and thus, not allowing the property owner to receive fund directly to construct the abatement measure themselves.

  32. When only one side of the highway has a noise barrier, does the noise level increase for the opposite side of the highway where there is no noise barrier?

    Highway traffic noise levels are not substantially increased by construction of a noise barrier on the opposite side of a highway from a receiver. If both the direct noise levels and the reflected noise levels are not abated by natural or artificial terrain features, the noise increase is theoretically limited to 3 dB(A), due to a doubling of energy from the noise source. In practice, however, not all of the acoustical energy is reflected back to the receiver. Some of the energy is diffracted over the barrier, some is reflected to points other than the receiver, some is scattered by ground coverings (e.g., grass and shrubs), and some blocked by the vehicles on the highway. Additionally, some of the reflected energy to the receiver is lost due to the longer path that it must travel. Attempts to conclusively measure this reflective increase have never shown an increase of greater than 1-2 dB(A), an increase that is not perceptible to the average human ear.

  33. Why are some communities eligible for noise abatement and others are not?

    Noise abatement, typically a barrier, is required where noise impacts have been identified for a Type I project. Consideration of abatement is subject to the feasible and reasonable process. Feasibility deals with engineering considerations, e.g can the barrier be built and does it achieve at least a substantial reduction. Reasonableness considers many other economic, social, and environmental factors. Typically, this process deals with many subjective factors, which the procedure tries to make objective. Barrier cost, resident's desire for abatement, increase in noise level, absolute noise level, etc. are typical factors. States are allowed flexibility in the decision-making process and in defining their reasonableness factors. If a barrier is determined to not be feasible, it usually cannot be built for either engineering considerations or it does not achieve a substantial noise reduction (i.e. at least 5dBA). If it is determined to not be reasonable, then usually the cost is higher than the cost reasonableness allowance or the resident's did not desire abatement. Other reasonableness factors could have resulted in a barrier that is not reasonable. If barriers are determined to not be feasible or reasonable, they are not built.

  34. What's new in Construction Noise?

    The FHWA has recently updated their Construction Noise: Special Report of 1977. The Construction Noise Handbook is a best practices document based on State experience. It is a one-stop shopping document for construction noise with an extensive photo database. There is a CD-ROM currently available and a Web version will be available at the FHWA noise website in the near future. The FHWA Roadway Construction Noise Model (FHWA RCNM) is based on the construction noise prediction spreadsheet developed for the Central Artery/Tunnel Project in Boston, Massachusetts (CA/T Project). The CA/T Project is the largest urban construction project ever conducted in the United States and has the most comprehensive noise control specification ever developed in the United States. RCNM incorporates the CA/T Project's noise limit criteria and extensive construction equipment noise database, where these parameters can be modified according to each user's needs. Users can also activate and analyze multiple pieces of equipment simultaneously and define multiple receptor locations including land-use type and baseline noise levels, where the FHWA RCNM will calculate sound level results for multiple metrics.

    There are two main uses of the FHWA RCNM:

    1. To easily predict noise emission from construction equipment;
    2. To determine a construction work plan's compliance with noise criteria limits.

    A variety of construction work scenarios can be created quickly, allowing the user to determine the impact of changing construction equipment and adding/removing the effects of shielding due to noise mitigation devices such as barriers. The user is required to input receptor information (description, land use and baseline sound levels) and equipment information (either by choosing from the default list or adding a new equipment).

  35. When should an analyst use the FHWA TNM 2.5 noise model compared to FHWA TNM 2.5 Look-up for screening purposes?

    The method for determining noise impacts is not related to the type of NEPA document. For example, the FHWA TNM 2.5 Look-up screening procedure can be utilized if noise impacts are not anticipated to be significant, even if an Environmental Impact Statement (EIS) is required for the project. Or there may be a Categorical Exclusion (CE) required for the project, but the noise analyst performs full-blown FHWA TNM 2.5 models for the project because noise impacts are a major concern for the project.

    The use of the TNM 2.5 Look-up screening procedure requires consideration of the assumptions used for the screening model. The assumptions are for a level highway with surrounding flat terrain. The roadway used for the TNM 2.5 Look-up screening procedure assumes a 2-lane roadway. There have been studies showing the assumption for the number of lanes can affect predicted noise level because of Level of Service issues and also from pavement absorption or reflection. This is important to consider.

    Some States will utilize the TNM 2.5 Look-up screening procedure for instances where noise levels are not anticipated to approach or exceed the NAC. If the TNM 2.5 Look-up screening procedure demonstrates noise levels will be 60 dB(A) or higher, the analyst will perform a full-blown TNM 2.5 model run.

    Please access our Highway Traffic Noise Analysis and Abatement policy (PDF 325KB) and go to Page 32 of the actual document (or Page 36 of 71 in the Adobe Counter).

  36. How does noise affect Section 4(F) properties?

    The Section 4(f) regulations [Sec. 771.135 Section 4(f) (49 U.S.C. 303)] outlines that a constructive use does not occur due to highway traffic noise when:

    1. "The projected traffic noise levels of the proposed highway project do not exceed the FHWA noise abatement criteria as contained in Table 1, 23 CFR part 772 ..."
    2. "The projected traffic noise levels exceed the relevant threshold in paragraph (p)(5)(ii) of this section because of high existing noise, but the increase in the projected noise levels if the proposed project is constructed, when compared with the projected noise levels if the project is not built, is barely perceptible (3 dBA or less) ..."

    So, a constructive use may occur when the NAC is exceeded and there is an increase of at least 3 dB(A) over existing noise levels. For example, a ball field that exceeds the NAC level and has a 3 decibel increase would qualify for additional consideration. The consideration involves gathering additional information to determine substantial impairment. Look to see at what time the ball games are played (rush hour, weekends, times when traffic is not at its worse case). Measure the traffic noise levels as well as the noise levels of a typical ball game. Add the two levels together to get the future combined levels and compare that combined level to the existing ball game level. Keep in mind that you need to determine if the increase noise level is loud enough to substantially impair the game to the point that it can't be played correctly or at all. Keep in mind that the NAC is based on interference with speech communication.

  37. What are the differences between NEPA and 23CFR772?

    There is a major difference between NEPA and 23 CFR 772 requirements for determining traffic noise impacts. Under NEPA, a proposed alternative is compared with a baseline (the no-build alternative) to determine whether traffic noise impacts will occur, i.e. the proposed project itself must create the traffic noise impact. However, 23 CFR 772 utilizes the opportunity provided by a proposed project to consider mitigating current as well as future noise problems. Therefore, under 23 CFR 772, if the predicted noise level approaches or exceeds the Noise Abatement Criteria, there is a traffic noise impact regardless of whether or not the proposed project causes it. Even if existing noise levels decrease in the future, e.g. from 72 dB(A) to 69 dB(A), at a Category B site, there is still a traffic noise impact.

    A noise analysis based on NEPA requirements may also be necessary in the extremely rare instance where the project itself is expected to create a noise impact (e.g., side-slopes are flattened as part of a project to improve an intersection and the resultant traffic noise levels approach or exceed the NAC and are at least 3 dB(A) greater than existing noise levels). This type of project must be dealt with on a case-by-case basis in accordance with NEPA.

  38. What is Noise Compatible Planning (NCP)?

    Highway traffic noise should be reduced through a program of shared responsibility. Thus, the FHWA encourages State and local governments to practice compatible land use planning and control in the vicinity of highways. Local governments should use their power to regulate land development in such a way that noise-sensitive land uses are either prohibited from being located adjacent to a highway, or that the developments are planned, designed, and constructed in such a way that noise impacts are minimized.

    The prevention of future impacts is one of the most important parts of noise control. New development and highways can be compatible. But, local government officials need to know what noise levels to expect from a highway and what techniques they can use to prevent future impacts. This may be accomplished by including a table of future noise levels at specific locations or a figure of distances to typical noise levels along the roadway. States should provide this information to local governments; such information should be made available for disclosure in real estate transactions. Local officials should be made aware of the eligibility requirements for Federal-aid participation in Type II projects. Consideration of NCP will eliminate situations where the State DOT is unable, by law, to provide noise mitigation. Please visit our NCP webpage for additional information.

  39. How are noise levels determined when user defined vehicle types or other extenuating factors, such as tunnels or rest stops, are involved?

    The intended purpose of the Federal Highway Administration's Traffic Noise Model (FHWA TNM) is to analyze highway traffic noise. Since the FHWA TNM was not designed to be used to analyze racetrack noise, its accuracy in this capacity is unknown; however, it may be possible to use the FHWA TNM to help predict noise at racetracks. To use the FHWA TNM to analyze racetrack noise the following four (4) tasks would need to be completed. It should be noted that additional tasks may be required based on the specific scenario being analyzed.

    1. Measure a statistically sound number of similar types of racecars at a different racetrack using REMEL measurement methodology. This REMEL data is essential since racecars are not included in the FHWA TNM REMEL database.
    2. Determine the parameters necessary to develop a FHWA TNM user-defined vehicle for racecars. This requires knowing which of the 5 spectral shapes matches best with the racecars, as well as to determine the values for the other parameters necessary for input for a user-defined vehicle.
    3. The speeds at racetracks may exceed those measured for the FHWA TNM REMEL database, and if so will therefore be extrapolated.
    4. Examine the best way to model the racetrack, keeping in mind:
      1. That the traffic input will most likely be in hourly volumes,
      2. It may be necessary to model accelerations, and
      3. The ground in the center of the track should be modeled appropriately since the sound on the far side of a track will propagate over it.

    There may also be instances where other vehicle emission levels need to be measured and portions of this guidance should be followed. Common sense and good engineering judgment should be applied.

    In other instances, such as when all-terrain vehicles, snowmobiles, locations where vehicles are idling, such as overnight rest stops, or at the end of tunnels or where bridge-deck reflection affects noise levels, then the preferred procedure for noise level prediction is to measure at a comparable location and use that data to predict future noise levels.

To provide Feedback, Suggestions or Comments for this page contact Mark Ferroni at Mark.Ferroni@dot.gov.

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