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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. What is a Type III project?
  5. How are existing noise levels determined?
  6. How are future noise levels determined?
  7. How do we determine noise impacts?
  8. What is a substantial increase?
  9. If impacts are identified, must abatement be provided?
  10. What is meant by providing "feasible" highway traffic noise abatement?
  11. What is meant by providing "reasonable" highway traffic noise abatement?
  12. What types of abatement measure are eligible for Federal-aid funding?
  13. Can quieter pavement be used as abatement?
  14. Will vegetation reduce noise levels?
  15. Are TNM contours allowed for impact determination or abatement consideration?
  16. Are owners or renters surveyed for abatement?
  17. What are the FHWA Noise Abatement Criteria (NAC)?
  18. How were the FHWA NAC developed?
  19. What is a Category A activity?
  20. What is a Category B activity?
  21. What is a Category C activity?
  22. What is a Category D activity?
  23. How do we determine and abate noise levels for Category D (interior) activities?
  24. What is a Category E activity?
  25. What is a Category F activity?
  26. What is a Category G activity?
  27. What is meant by permitted?
  28. Are multi-family dwellings analyzed for impacts and considered for abatement?
  29. What is the method for analyzing abatement for multi-story land uses, such as multi-family apartments or condos?
  30. What is the methodology for analysis of Category C,D and E land uses?
  31. What noise barrier standards are required?
  32. What are the Federal standards for highway traffic noise?
  33. Are payments allowed for noise damages?
  34. 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?
  35. Why are some communities eligible for noise abatement and others are not?
  36. What's new in Construction Noise?
  37. How does noise affect Section 4(F) properties?
  38. What are the differences between NEPA and 23CFR772?
  39. What is Noise Compatible Planning (NCP)?
  40. How are noise levels determined when user defined vehicle types or other extenuating factors, such as tunnels or rest stops, are involved?
  41. How are trails and trail crossings defined in the context of 23 CFR 772?
  42. What is a trail crossing?

  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 State DOT noise contact list. (PDF 160KB)

  2. What is a Type I project?

    (1) The construction of a highway on a new location;
    (2) The physical alteration of an existing highway where there is either:
    (i) Substantial Horizontal Alteration. A project that halves the distance between the traffic noise source and the closest receptor between the existing condition to the future build condition;
    (ii) Substantial Vertical Alteration. A project that removes shielding therefore exposing the line-of-sight between the receptor and the traffic noise source. This is done by either altering the vertical alignment of the highway or by altering the topography between the highway traffic noise source and the receptor; or,
    (3) The addition of a through-traffic lane(s). This includes the addition of a through-traffic lane that functions as a HOV lane, High-Occupancy Toll (HOT) lane, bus lane, or truck climbing lane;
    (4) The addition of an auxiliary lane, except for when the auxiliary lane is a turn lane;
    (5) The addition or relocation of interchange lanes or ramps added to a quadrant to complete an existing partial interchange;
    (6) Restriping existing pavement for the purpose of adding a through-traffic lane or an auxiliary lane; or,
    (7) The addition of a new or substantial alteration of a weigh station, rest stop, ride-share lot or toll plaza.
    (8) If a project is determined to be a Type I project under this definition then the entire project area as defined in the environmental document is a Type I.

    Highway agencies should take a broad approach to defining turn lanes when considering projects with auxiliary lanes. Generally, consideration for auxiliary lanes on local roads should be limited to those that could be used as a through lane rather than lanes used for parking, speed change, turning or storage for turning weaving. For interstates, limit consideration to auxiliary lanes between two closely spaced interchanges to accommodate weaving traffic and auxiliary lanes carried through one or more interchanges.

  3. What is a Type II project?

    Usually called a retrofit project, a Type II project is 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 State's discretion. Projects of this type are proposed solely at the option of a State DOT, and specific requirements for the project are determined by the individual State DOT. 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.

  4. What is a Type III project?

    A Type III project is a Federal or Federal-aid highway project that does not meet the classifications of a Type I or Type II project. Type III projects do not require a noise analysis.

  5. How are existing noise levels determined?

    Existing noise levels can be determined by one of the following 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.
  6. How are future noise levels determined?

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

  7. 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. The FHWA noise regulation requires State DOTs to 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.

  8. What is a substantial increase?

    A substantial increase is a 5 to 15 dBA increase over existing noise levels. States are allowed to define what a substantial increase is in their policy within the above range. A substantial increase impact is not limited by the absolute noise level.

  9. 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.

  10. 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 must be acoustically feasible. The minimal substantial reduction allowed is 5 dB. States define the number of impacted receptors that must achieve a 5 dB(A) reduction.

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

    Reasonableness is based on three required criteria, but may be influenced by consideration of optional criteria. The criteria used for determining reasonableness indicate a broad consideration of conditions that apply in a given location. The required reasonableness criteria focus on three areas.

    1. Highway agencies must determine the desires of the benefiting residents and property owners. The FHWA approved noise policy for each State outlines the procedure used to make this determination, but this process generally involves surveying.
    2. Highway Agencies must also consider the cost of abatement per benefiting receptor. The cost is based on historical construction costs for abatement. Some States allow for a quantity of noise barrier per benefited receptor rather than using a cost per benefited receptor.
    3. Reasonable abatement must also achieve a noise reduction design goal at benefited receptors. The highway agency chooses the design goal in a range of 7-10 dB(A) and a number of benefited receptors that must achieve this goal to meet this reasonableness criterion. Any receptor that meets or exceeds the design goal is counted toward satisfying the criterion.
  12. What types of abatement measure are eligible for Federal-aid funding?

    There are several alternative abatement measures allowed for use of Federal-aid funds. The noise analysis must at a minimum consider abatement in the form of a noise barrier and consider other measures where they are applicable. 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. Construction of noise barriers, including acquisition of property rights, either within or outside the highway right of way. Landscaping is not a viable noise abatement measure.
    4. 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.
    5. Noise insulation of Category D land uses. Post-installation maintenance and operational costs for noise insulation are not eligible for Federal-aid funding.
  13. 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.

  14. Will vegetation reduce noise levels?

    Vegetation is not considered as noise abatement, especially when involving federally funded projects. Vegetation must be a minimum of 100 feet thick, a minimum of 20 feet high, and sufficiently dense so that it cannot be seen through in order to provide a 5-dBA noise reduction. Anything less than that thickness will not result in any significant noise reduction. 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.

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

    Contours may not be used to determine impacts or for abatement consideration. Contours should only be used for planning purposes, specifically when following 772.9(c), 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.

  16. Are owners or renters surveyed for abatement?

    772.13(d)(2)(i) requires consideration of the viewpoints of the residents and owners of benefited receptors.

  17. 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. Traffic noise impacts occur based upon the definitions contained in 23 CFR 772.5. If impacts are identified, noise abatement measures must be considered and, if found to be feasible and reasonable must be implemented.1

    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)2 Analysis Location Description of Activity Category
    A 57 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.
    B3 67 70 Exterior Residential.
    C3 67 70 Exterior

    Active sport areas, amphitheaters, auditoriums, campgrounds, cemeteries, day
    care centers, hospitals, libraries, medical facilities, parks, picnic areas,
    places of worship, playgrounds, public meeting rooms, public or nonprofit institutional
    structures, radio studios, recording studios, recreation areas, Section

    4(f) sites, schools, television studios, trails, and trail crossings.
    D 52 55 Interior

    Auditoriums, day care centers, hospitals, libraries, medical facilities, places of
    worship, public meeting rooms, public or nonprofit institutional structures, radio studios, recording studios, schools, and television studios.

    E 72 75 Exterior

    Hotels, motels, offices, restaurants/bars, and other developed lands, properties or activities not included in A–D or F.

    F      

    Agriculture, airports, bus yards, emergency services, industrial, logging, maintenance facilities, manufacturing, mining, rail yards, retail facilities, shipyards,utilities (water resources, water treatment, electrical), and warehousing.

    G      

    Undeveloped lands that are not permitted.

    1Either Leq(h) or L10(h) (but not both) may be used on a project.
    2Either Leq(h) and L10(h) Activity Criteria values are for impact determination only, and are not design standards for noise abatement measures.
    3Includes undeveloped lands permitted for this activity category.
  18. 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, interference with speech communication was most 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.

  19. 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.

  20. What is a Category B activity?

    Activity Category B includes single and multi-family residences. Some States also include long term stay hotels in Category B.

  21. What is a Category C activity?

    Activity Category C includes active sport areas, amphitheaters, auditoriums, campgrounds, cemeteries, day care centers, hospitals, libraries, medical facilities, parks, picnic areas, places of worship, playgrounds, public meeting rooms, public or nonprofit institutional structures, radio studios, recording studios, recreation areas, Section 4(f) sites, schools, television studios, trails, and trail crossings. Each State DOT must adopt standard practices for analyzing these land uses that is consistent and uniformly applied statewide.

  22. What is a Category D activity?

    Activity Category D includes auditoriums, day care centers, hospitals, libraries, medical facilities, places of worship, public meeting rooms, public or nonprofit institutional structures, radio studios, recording studios, schools, and television studios. Highway agencies may consider abatement of interior locations at Category D land uses where exterior abatement is not feasible or reasonable.

  23. How do we determine and abate noise levels for Category D (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 (PDF 325KB) 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.

  24. What is a Category E activity?

    Activity Category E includes a variety of commercial activities to include hotels, motels, offices, restaurants/bars, and other developed lands, properties or activities not included in A–D or F.

  25. What is a Category F activity?

    Activity Category F includes a variety of land uses that are not considered sensitive to noise such as agriculture, airports, bus yards, emergency services, industrial, logging, maintenance facilities, manufacturing, mining, rail yards, retail facilities, shipyards, utilities (water resources, water treatment, electrical), and warehousing.

  26. What is a Category G activity?

    Activity Category G includes undeveloped lands that are not permitted. Undeveloped lands that are permitted by the date of public knowledge should be treated as the developed use for the purposes of the noise analysis and consideration for abatement of project related noise impacts.

  27. What is meant by permitted?

    A definite commitment to develop land with an approved specific design of land use activities as evidenced by the issuance of a building permit. The rule effective July 13, 2011 eliminated use of planned, designed and programmed and requires issuance of a building permit as the trigger to indicate a definite commitment to develop the property in question has occurred. Some areas do not issue building permits. In these cases, the highway agency may use other triggers such as the presence of foundations to indicate a commitment to develop.

  28. 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 regulation requires consideration of each residence in a multi-family dwelling unit. 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 balconies and patios are used by 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.

  29. 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 provide abatement for the ground floor, but additional analysis should be performed to abate impacts to 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.

  30. What is the methodology for analysis of Activity Category C, D and E land uses?

    Activity Category C, D and E land uses are generally any location that is not a residence, but may be sensitive to noise impacts. This would include any of the land uses listed in Categories C, D and E above.
    Each highway agency has methodology in the noise policy that provides approaches to determining the number of receptors represented by a land use.

  31. 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.

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

    The Federal noise regulation at 23 CFR 772 constitutes the official Federal noise standard. The Noise Abatement Criteria are often misidentified as the noise standard, but the NAC is only a part of the Noise Standard.  The entire Part 772 is the Noise Standard.

  33. 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 being used properly. 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 a third-party contractor, thus prohibiting the property owner from receiving funds directly to construct the abatement measure.

  34. 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 is 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.

  35. 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 determinations deal with engineering considerations (e.g. can the barrier be built and does it achieve at least a substantial reduction). Reasonableness determinations consider many other economic, social, and environmental factors. Barrier cost, residents' desire for abatement, increase in noise level, absolute noise level, etc., are some 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 or acoustic feasibility considerations. If it is determined to not be reasonable, then the cost is usually higher than the cost reasonableness allowance, the residents did not desire abatement, or it was not possible to achieve a design that met the noise reduction design goal. Other reasonableness factors could have contributed to a determination that a barrier is not reasonable. If barriers are determined to not be feasible or reasonable, they are not built.

  36. 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).

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

    For additional information on Section 4(f) refer to 23 CFR 774.

  38. 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 is the cause. 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.

  39. 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.

  40. 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.

  41. How are trails and trail crossings defined in the context of 23 CFR 772?

    On July 13, 2011, the FHWA implemented updates to Title 23 Code of Federal Regulations Part 772 (23 CFR 772) incorporating a requirement to consider noise impacts to trails and trail crossings as Activity Category C land uses within Table 1 of 23 CFR 772. Subsequent to implementing the updated regulation, states have requested additional detail on how FHWA defines trails.

    Trails and trail crossing as Activity Category C receptors under the current 23 CFR 772 are defined in 23 USC 206(a)(2)(A-F) of the recreational trails program. Motorized water activities and recreational trails as described in 23 USC 206(a)(2)(G) are noise generators (Activity Category F) and consideration for noise impacts is not required.

  42. What is a trail crossing?

    Trail crossings describe locations where trails cross surface transportation facilities that are part of a Type I project.

Updated: 04/24/2013
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