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Analysis and Abatement Guidance

Highway Traffic Noise Regulation

The following discussion will address those requirements and point out the most important issues related to the requirements. Each section of 23 CFR 772 follows with a discussion of that section. Some sections are self explanatory and need only a sentence or two of discussion. Other, more complicated sections will have greater discussion. The regulation specifies the requirements highway agencies must meet when using Federal-aid funds for highway projects.

772.1 Purpose

PURPOSE. To provide procedures for noise studies and noise abatement measures to help protect the public health, welfare and livability, to supply noise abatement criteria, and to establish requirements for information to be given to local officials for use in the planning and design of highways approved pursuant to Title 23, United States Code(U.S.C.).

Protection of the public health and welfare is an important responsibility that FHWA helps to accomplish during the planning and design of a highway project. The U.S. Congress has directed FHWA to develop noise standards with passage of the 1970 Federal-Aid Highway Act. Concerned citizens and States encouraged Congress to provide this protection.

772.3 Noise Standards

NOISE STANDARDS. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local officials in this directive constitute the noise standards mandated by 23 U.S.C. 109(i). All highway projects which are developed in conformance with this directive shall be deemed to be in conformance with the Federal Highway Administration (FHWA) noise standards.

This section makes 23 CFR 772 in its entirety the FHWA highway traffic noise standard. The standard is required by 23 U.S.C. 109(i). Some people mistake the highway traffic noise abatement criteria for the FHWA standard. Early on, FHWA did not want to be restricted to specific highway traffic noise levels that are unachievable in many highway projects. The standard developed by FHWA best serves the public in terms of protection and reasonable cost.

772.5 Definitions

Benefited Receptor. The recipient of an abatement measure that receives a noise reduction at or above the minimum threshold of 5 dB(A), but not to exceed the highway agency's reasonableness design goal.

Common Noise Environment. A group of receptors within the same Activity Category in Table 1 that are exposed to similar noise sources and levels; traffic volumes, traffic mix, and speed; and topographic features. Generally, common noise environments occur between two secondary noise sources, such as interchanges, intersections, cross-roads.

Date of Public Knowledge. The date of approval of the Categorical Exclusion (CE), the Finding of No Significant Impact (FONSI), or the Record of Decision (ROD), as defined in 23 CFR 771.

Design Year. The future year used to estimate the probable traffic volume for which a highway is designed.

Existing Noise Levels. The worst noise hour resulting from the combination of natural and mechanical sources and human activity usually present in a particular area.

Feasibility. The combination of acoustical and engineering factors considered in the evaluation of a noise abatement measure.

Impacted Receptor. The recipient that has a traffic noise impact.

L10. The sound level that is exceeded 10 percent of the time (the 90th percentile) for the period under consideration, with L10(h) being the hourly value of L10.

Leq. The equivalent steady-state sound level which in a stated period of time contains the same acoustic energy as the time-varying sound level during the same time period, with Leq(h) being the hourly value of Leq.

Multifamily Dwelling. A residential structure containing more than one residence. Each residence in a multifamily dwelling shall be counted as one receptor when determining impacted and benefited receptors.

Noise Barrier. A physical obstruction that is constructed between the highway noise source and the noise sensitive receptor(s) that lowers the noise level, including stand alone noise walls, noise berms (earth or other material), and combination berm/wall systems.

Noise Reduction Design Goal. The optimum desired dB(A) noise reduction determined from calculating the difference between future build noise levels with abatement, to future build noise levels without abatement. The noise reduction design goal shall be at least 7 dB(A), but not more than 10 dB(A).

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.

Property Owner. An individual or group of individuals that holds a title, deed, or other legal documentation of ownership of a property or a residence.

Reasonableness. The combination of social, economic, and environmental factors considered in the evaluation of a noise abatement measure.

Receptor. A discrete or representative location of a noise sensitive area(s), for any of the land uses listed in Table 1.

Residence. A dwelling unit. Either a single family residence or each dwelling unit in a multifamily dwelling.

Statement of Likelihood. A statement provided in the environmental clearance document based on the feasibility and reasonableness analysis completed at the time the environmental document is being approved.

Substantial Construction. The granting of a building permit, prior to right-of-way acquisition or construction approval for the highway.

Substantial noise increase. One of two types of highway traffic noise impacts. For a Type I project, an increase in noise levels of 5 to 15 dB(A) in the design year over the existing noise level.

Traffic Noise Impacts. Design year build condition noise levels that approach or exceed the NAC listed in Table 1 for the future build condition; or design year build condition noise levels that create a substantial noise increase over existing noise levels.

Type I Project.

  1. The construction of a highway on new location; or,
  2. The physical alteration of an existing highway where there is either:
    1. 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; or,
    2. 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; or,
  4. The addition of an auxiliary lane, except for when the auxiliary lane is a turn lane; or,
  5. The addition or relocation of interchange lanes or ramps added to a quadrant to complete an existing partial interchange; or,
  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 per § 772.5 then the entire project area as defined in the environmental document is a Type I project.

Type II Project. A Federal or Federal-aid highway project for noise abatement on an existing highway. For a Type II project to be eligible for Federal-aid funding, the highway agency must develop and implement a Type II program in accordance with section 772.7(e).

Type III Project. 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.

Most of these definitions are self explanatory. However, the definitions for Design Goal, Design Year, Type I Projects, Type II Projects and Type III Projects warrant further attention because they introduce new items or clarify longstanding terms. Clarification on some terms occurs where they appear in the regulation.

Design Goal

The Noise Reduction Design Goal is a reasonableness factor indicating a specific reduction in noise levels that highway agencies use to identify that a noise abatement measure effectively reduces noise. It is a comparison of the design year noise level with the abatement measure to the design year noise level without the abatement measure. Some States already used a noise reduction design goal to specify a substantial decrease as discussed in prior FHWA guidance. The Noise Reduction Design Goal establishes a criterion, selected by the highway agency that noise abatement must achieve. The design goal is not the same as acoustic feasibility, which is the minimum level of effectiveness of a noise abatement measure on impacted receptors. Acoustic feasibility indicates that the noise abatement measure can at a minimum achieve a discernible reduction in noise levels. For the Noise Reduction Design Goal, the highway agency will choose a single value within the range of 7-10 d(BA) for use on all projects and will determine a number of benefited receptors that must achieve the design goal for the abatement measure to achieve this reasonableness criterion. If an abatement measure does not meet the Noise Reduction Design Goal , the measure is not reasonable for inclusion in the project's plans, specifications and estimates and is not eligible for federal funding.

Type I Projects

Highway on New Location

Construction of a highway on new location is self-explanatory. There is no highway before the construction, and there will be one afterwards. The addition of interchanges and ramps (e.g., adding a ramp in a quadrant to complete an existing partial interchange, adding a new lane to an existing ramp that is carried all the way to the mainline, etc.) to existing highways would also be a highway on new location and must be classified as a Type I project.

Physical Alteration of an Existing Highway

Changes in vertical alignment cover a variety of scenarios that are not limited to physical changes to the roadway. Changes to side slopes or other terrain features may also result in a Type I project. A project that exposes a receptor to a new noise source due to a vertical change or includes vertical changes that expose the receptor(s) to previously a shielded traffic noise source(s) is a Type I project. For example, a project that involves cutting back a slope that exposes a receptor to an existing highway is a Type I project. Similarly, a project that changes an at grade intersection to an overpass is a Type I project, because it substantially alters the vertical alignment of the roadway, exposes receptors to a new noise source and the operational improvements likely result in increased speeds and more noise.

Changes in the horizontal alignment that reduce the distance between the source and receiver by half or more result in a Type I project.

Identification of the physical alteration of an existing highway which increases the number of through traffic lanes requires considering the through traveled way--that portion of the highway constructed for the movement of vehicles, exclusive of the shoulders and turn lanes. The addition of a full lane to the mainline of a highway is a Type I project.

The addition of an auxiliary lane is also a Type I project, unless the auxiliary lane is a turn lane. 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 (including bus or truck lanes) 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.

The addition of bus or truck climbing lanes to existing highways can create significant changes in alignment and/or add through-traffic lanes, and is therefore classified as a Type I project.

The addition of a new through lane requires analysis on both sides of the highway whether the new lane(s) are all in one direction of travel or in both directions. New through lanes result in added capacity, more traffic and usually, more traffic noise.

Similarly, the addition of high-occupancy vehicle (HOV) lanes or high occupancy toll (HOT) 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. Highway traffic noise analysis is required for both sides of the highway even HOV or HOT lanes added to one side of the highway. Frequently, HOV or HOT projects cause little or no change in the existing or future noise environment. However, highway traffic noise impacts may occur, since existing noise levels may already approach or exceed noise abatement criteria. In these instances, the highway agency must consider and implement abatement if feasible and reasonable.

New lanes also occur due to restriping projects. In this case, the pavement width may remain the same, but the project designates an additional traffic lane(s) by restriping the existing pavement.

No Change between Existing and Future Highway Traffic Noise Levels

A commonly held viewpoint is that a highway traffic noise analyses is not necessary for projects that do not change the noise environment - that is, no change in the noise levels from those that exist today or no change in the noise levels from those that will exist in the future if no project is implemented (e.g., 70 dB(A) existing and 70 dB(A) in the future, with or without the project). However, the FHWA highway traffic noise regulations were developed to specifically address the improvement of situations where existing highway traffic noise levels are already high (i.e., a highway traffic noise impact already exists). Thus, highway traffic noise analyses are required for all Type I projects, even when there is no change in the surrounding noise environment. A parallel occurs with highway projects that upgrade or improve substandard safety features even though the overall goal of the project is not specifically safety-related. A project with any Type I work is a Type I project, and a highway traffic noise analysis is required for the entire project, as defined in the project's environmental document.

Weigh Stations, Rest Stops and Toll Plazas

Expansion or new construction of weigh stations, rest stops and toll plazas require analysis as Type I projects. They require special attention and consideration for determining existing and future noise levels. These land uses include a mix of stationary and mobile sources. Noise analysts should develop a methodology in coordination with the highway agency noise coordinator to determine existing and future noise levels at these locations.

NEPA versus 23 CFR 772 Analysis Requirements

There is a major difference between NEPA and 23 CFR 772 requirements for determining highway traffic noise impacts. Under NEPA, a proposed alternative is compared with a baseline (the future, no-build scenario, also called the no-build alternative) to determine whether highway traffic noise impacts will occur. That is, the proposed project causes an impact when it changes the noise level compared to the no-build condition. Changes that are less than 3 dB(A) may be considered negligible or unimportant under NEPA because they are barely perceptible. The absolute noise level, however, may be important to consider if it reaches or exceeds the level of speech interference, i.e., the NAC for that land activity category. Some highway agencies require analysis of the no build and comparison to existing and or future noise levels to satisfy NEPA. 23 CFR 772 does not require analysis of the no build scenario.

23 CFR 772, however, defines highway traffic noise impacts differently: a highway traffic noise impact occurs when a build alternative's predicted noise level approaches or exceeds the NAC, or represents a substantial increase over existing noise levels. Even if predicted noise levels decrease in the future as a result of the project, e.g. from 72 dB(A) to 69 dB(A) at a Category B site, there is still a highway traffic noise impact under 23 CFR 772, and abatement must be considered.

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

Tiered Environmental Impact Statements (EIS's)

The highway agency should coordinate with the FHWA Division Office for projects developed under a Tiered EIS with regard to application of a Type I designation. In most cases, it is appropriate to make the Type I project designation under the Tier 2 environmental document.

Type II Projects

The following discussion outlines measures that can be taken in the Federal-aid highway program to abate highway traffic noise problems along existing highways. The discussion highlights the prioritization process for highway projects that provide this abatement and presents information on the methods used by selected States to accomplish the prioritization.

Background

The Federal Aid Highway Act of 1970 required the FHWA to develop highway traffic noise standards for use in the planning and design of new highway projects. These standards were promulgated, in the form of a regulation, by FHWA on February 8, 1973. Later, because of pressure received from a number of States, this provision was amended by the Federal Aid Highway Act of 1973 to permit the control of highway traffic noise on previously constructed highways. As a result, FHWA's highway traffic noise regulation, currently contained in 23 CFR 772, was revised to provide for Federal participation in noise abatement projects along existing highways. The regulation defines these types of projects as Type II projects (these projects are also often referred to as retrofit projects). The development and implementation of Type II projects are not mandatory requirements of Federal law or regulation. A program to implement such projects results from a strictly optional decision by a State to provide highway traffic noise abatement along existing highways.

Type II Project Requirements

The FHWA highway traffic noise regulations limits funding participation of Type II highway traffic noise abatement measures for projects approved before November 28, 1995, or projects proposed along lands where land development or substantial construction predated the highway. In addition, FHWA will not approve highway traffic noise abatement measures at locations where such measures were previously determined not to be feasible and reasonable for a Type I project.

When considering abatement measures for Type II projects, the "date of the existence of development" along the highway is often mixed. Some development will predate the existence of any highway and some development will have occurred after the original highway was constructed. If a highway agency elects to implement Type II projects, the highway agency and the FHWA Division Office should jointly establish appropriate procedures to determine ways to address locations with different dates of development.

Type II projects that utilize Federal funding in whole or part must satisfy 23 CFR 772 and NEPA requirements. Normally, a Type II project will qualify as a Categorical Exclusion, unless other environmental impacts are identified that require additional investigation. Despite the level of documentation, a Type II project requires the same level of analyses and documentation as is required for a Type I project.

Developing a Type II Program

The highway traffic noise regulation provides highway agencies with considerable flexibility for designing their own Type II highway traffic noise abatement program, including the very important task of individual project prioritization. The regulation requires that the overall highway traffic noise abatement benefits outweigh the overall adverse social, economic, and environmental (SEE) effects and the costs of the highway traffic noise abatement measures. This determination relies on good judgment by highway agencies, rather than prescriptive Federal procedures since the individual States are in the best position to make these determinations on a local basis.

These procedures consider factors related to the land development. Factors to consider include:

  1. The amount of development that predates the existence of any highway;
  2. The amount of development that occurred after the construction of a highway but prior to the existence of Federal requirements related to highway traffic noise; and
  3. The amount of development that predates a major change in the character of a highway, e.g., the highway has changed from a low-speed, local street to a high-speed freeway. The highway agency should utilize the "date of the existence of development" procedures when approving abatement measures for Type II projects. Federal could prorate participation in proportion to the amount of pre-existing development.

A highway agency voluntarily requesting Federal-aid participation for eligible Type II projects is required to perform a highway traffic noise analysis of sufficient scope to:

  1. Identify that a highway traffic noise impact exists,
  2. Demonstrate that the proposed highway traffic noise abatement measures will reduce the highway traffic noise impact, and
  3. Determine that the overall highway traffic noise abatement benefits outweigh the overall adverse social, economic, and environmental effects and the costs of the highway traffic noise abatement measures.

While the first two criteria are relatively easy to quantify, the third criterion, along with cost considerations, becomes more difficult to quantify. The FHWA has not developed or specified any one method of analysis for Type II projects. Instead, States are encouraged to use good judgment in the consideration of all relevant factors, both beneficial and adverse. The FHWA does not expect all factors to be quantified, but does expect a decision based on the SEE benefits and detriments of the highway traffic noise abatement measures. If a highway agency chooses to engage in a Type II Program, FHWA requires the highway agency to develop a priority ranking system to allow for consistent and uniform application throughout the State.

Projects for Type II highway traffic noise abatement may include the following abatement measures:

  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, and
  4. Noise insulation of public use or nonprofit institutional structures

Priority Rating Systems

The highway agencies have great flexibility in developing and structuring a Type II program. One program management tool that highway agencies have found to be essential is a priority rating system. Such a system enables them to uniformly and equitably handle highway traffic noise impacts and complaints along existing highways while providing a rational basis for an important part of a very tough decision making process. A priority ranking system is required by 772.7(e). Use of a priority rating system indicates the relative priority of individual projects with other potential Type II projects in a State. Factors to consider include:

  1. Applicable State law,
  2. Type of development to be protected,
  3. Magnitude of the highway traffic noise impact,
  4. Cost: total amount cost per receiver,
  5. Population density of the affected area,
  6. Day/night use of the property,
  7. Feasibility and practicability of highway traffic noise abatement at the site,
  8. Availability of funds,
  9. Existing noise levels,
  10. Achievable noise reduction,
  11. Intrusiveness of highway traffic noise,
  12. Public's attitude,
  13. Local government's efforts to control land use adjacent to the highway,
  14. Date of construction of adjoining development,
  15. Increase in highway traffic noise since the development was constructed,
  16. Local noise ordinances,
  17. Feasibility of abating the highway traffic noise with traffic control measures.

These factors are not in any order, but indicate that highway agencies should base implementation of a Type II program upon a wide range of varying considerations.

Please see Appendix E for Type II program examples.

Type III Projects

Type III projects describe any project that does not fulfill the criteria of a Type I or Type II project. Generally, the list of projects described in 23 CFR 771.117(c) and (d) comprise the list of Type III projects, with some exceptions; as discussed below, where the project clearly meets the definition of a Type I or Type II project.

771.117(c)(6) The installation of noise barriers or alterations to existing publicly owned buildings to provide for noise reduction.

771.117(c)(12) Improvements to existing rest areas and truck weigh stations.
Improvements to existing rest areas and truck weigh stations that involve increased capacity for overnight parking, relocation of parking facilities closer to noise sensitive land uses or other changes in the configuration of the facility that would meet the description of a Type I project.

771.117(c)(13) Ridesharing activities
Construction or expansion of an existing ride-share lot and access roads to a ride-share lot are a Type I project.

771.117 (d)(1) Modernization of a highway by resurfacing, restoration, rehabilitation, reconstruction, adding shoulders, or adding auxiliary lanes (e.g., parking, weaving, turning, climbing).
Construction of auxiliary lanes other than turn lanes are a Type I project per the definition of a Type I project provided in 772.5.

771.117 (d)(3) Bridge rehabilitation, reconstruction or replacement or the construction of grade separation to replace existing at-grade railroad crossings.

Construction of a grade separation to replace existing at-grade railroad crossings is a Type I project because it results in either a new highway on new alignment or a significant change in the vertical alignment of an existing highway. In some cases, the grade separation project results in an overall benefit to the noise environment due to reduced requirements to sound train horns at grade separated crossings. Highway agencies may consider this benefit in the noise analysis. Bridge replacements may result in a Type I project if the bridge is realigned or is substantially different from the existing bridge.

771.117 (d)(5) Construction of new truck weigh stations or rest areas.

Construction of new truck weigh stations or rest areas is a Type I project per the definition of a Type I project provided in 772.5.

Sometimes, unusual projects fall outside the standard definition of a Type I project. Generally, if a project results in a new noise source, the highway agency should consider a noise analysis for the project. The regulation does not preclude highway agencies from performing a noise analysis for a project that does not strictly meet the Type I or Type II criteria, but may result in a new noise source.

Template for Type III Project Documentation

Project Name:
The referenced project meets the criteria for a Type III project established in 23 CFR 772. Therefore, the project requires no analysis for highway traffic noise impacts. Type III projects do not involve added capacity, construction of new through lanes or auxiliary lanes, changes in the horizontal or vertical alignment of the roadway or exposure of noise sensitive land uses to a new or existing highway noise source. _____ DOT acknowledges that a noise analysis is required if changes to the proposed project result in reclassification to a Type I project.

772.7 Applicability.

(a) This regulation applies to all Federal or Federal-aid Highway Projects authorized under title 23, United States Code. Therefore, this regulation applies to any highway project or multimodal project that:

  1. Requires FHWA approval regardless of funding sources, or
  2. Is funded with Federal-aid highway funds.

(b) In order to obtain FHWA approval, the highway agency shall develop noise policies in conformance with this regulation and shall apply these policies uniformly and consistently statewide.

(c) This regulation applies to all Type I projects unless the regulation specifically indicates that a section only applies to Type II or Type III projects.

(d) The development and implementation of Type II projects are not mandatory requirements of section 109(i) of title 23, United States Code.

(e) If a highway agency chooses to participate in a Type II program, the highway agency shall develop a priority system, based on a variety of factors, to rank the projects in the program. This priority system shall be submitted to and approved by FHWA before the highway agency is allowed to use Federal-aid funds for a project in the program. The highway agency shall re-analyze the priority system on a regular interval, not to exceed 5 years.

(f) For a Type III project, a highway agency is not required to complete a noise analysis or consider abatement measures.

The regulation applies to all Type I and Type II projects that require FHWA approval and/or receive Federal-aid funding. The implementation of a Type II program is optional and not mandatory. Type III projects do not require a noise analysis.

Written State Highway Traffic Noise Policies

All highway agencies must adopt written statewide highway traffic noise policies approved by FHWA. Division Administrators are delegated the authority to approve the State policies after a coordinated review that includes the FHWA headquarters noise staff and Resource Center personnel with highway noise expertise. The policies must demonstrate compliance with 23 Code of Federal Regulations Part 772 and the highway traffic noise policy contained herein. Send copies of approved policies to HEPN-20. The approved policy is the primary document the highway agency uses to implement the requirements of the regulation. In some cases, the highway agency may use separate noise policy and guidance documents. In this case, both documents require FHWA approval following the above process.

772.9 Traffic Noise Prediction.

(a) Any analysis required by this subpart must use the FHWA Traffic Noise Model (TNM), which is described in "FHWA Traffic Noise Model" Report No. FHWA-PD-96-010, including Revision No. 1, dated April 14, 2004, or any other model determined by the FHWA to be consistent with the methodology of the FHWA TNM. These publications are incorporated by reference in accordance with section 552(a) of title 5, U.S.C. and part 51 of title 1, CFR, and are on file at the National Archives and Record Administration (NARA). For information on the availability of this material at NARA, call (202) 741-6030 or go to http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. These documents are available for copying and inspection at the Federal Highway Administration, 1200 New Jersey Avenue, SE, Washington, DC 20590, as provided in part 7 of title 49, CFR. These documents are also available on the FHWA's Traffic Noise Model Web site at the following URL: http://www.fhwa.dot.gov/environment/noise/index.htm.

(b) Average pavement type shall be used in the FHWA TNM for future noise level prediction unless a highway agency substantiates the use of a different pavement type for approval by the FHWA.

(c) Noise contour lines may be used for project alternative screening or for land use planning to comply with § 772.17, but shall not be used for determining highway traffic noise impacts.

(d) In predicting noise levels and assessing noise impacts, traffic characteristics that would yield the worst traffic noise impact for the design year shall be used.

FHWA Traffic Noise Model (FHWA TNM)

The FHWA TNM, version 2.5 (or the latest version), is required for use in all highway traffic noise analyses for Federal-aid highway projects that begin on or after May 2, 2005. The FHWA will update 23 CFR 772 as necessary to accommodate new or updated releases of the FHWA TNM. For additional information regarding the FHWA TNM, please go to http://www.fhwa.dot.gov/environment/noise/traffic_noise_model/.

Average Pavement

Highway agencies must use TNM average pavement when analyzing future conditions unless there is an agreement with FHWA to use a different pavement type. States may propose use of a different pavement type for approval by coordinating with FHWA. The highway agency must demonstrate that a current TNM pavement is an acoustic match for a pavement used by the State, or provide sufficient data to FHWA to incorporate a specific pavement within the TNM.

Noise Contours

Noise contour lines are useful for screening and to provide information to local officials (772.17); however, some caution is necessary when using noise contour lines. Noise analysts usually develop the noise contours using the Noise Contour function of the FHWA TNM, or by modeling discrete receiver points and extrapolating between them. Either method can result in an inaccurate portrayal of the noise environment. When using the Noise Contour function, users must ensure the grid spacing provides a sufficient resolution to provide good results and when using discrete receivers, the user must ensure the receivers are close enough to enable relatively accurate extrapolation between receiver points.

Traffic Characteristics

Highway traffic noise levels sensitive to traffic characteristics used to predict future traffic noise levels. The "worst hourly traffic noise impact" occurs at a time when truck volumes and vehicle speeds are the greatest, typically when traffic is free flowing and at or near level of service (LOS) C conditions. The numbers of medium and heavy trucks are very important. In large urban areas, this worst hourly traffic noise impact will usually not coincide with peak traffic periods, when LOS may drop to D or less.

Estimation of the worst hourly traffic noise provides flexibility to highway agencies to consider the effects of seasonal traffic or limit consideration to the typical worst noise hour experienced within the project area.

Posted vs. Operating Speeds

Highway agencies should use either the posted speed limit or the operating speed (highest overall speed at which a driver can travel on a given highway under favorable weather conditions and under prevailing traffic conditions, with any time exceeding the safest speed as determined by the design speed on a section-by-section basis) to predict highway traffic noise levels. Highway agencies should use the operating speed if it is determined to be consistently higher than the posted speed limit. In determining the operating speed along an existing highway, the first step is to identify the period during which the worst highway traffic noise impacts occur. Then determine the speed driving a vehicle in the traffic stream and recording the average speed. Speed may also be determined by using radar meters or other devices to measure speeds at a point along the highway (with no adjustments to the actual instrument measurements). Use caution when using radar meters to determine speed since the presence of a radar meter may result in speeds below the typical speed for the facility. Average measured speeds arithmetically to calculate a time mean speed (as defined in Highway Capacity Manual 2000). Use the "traffic stream" speed or the time-mean speed to represent the operating speed.

772.11 Analysis of Traffic Noise Impacts

(a) The highway agency shall determine and analyze expected traffic noise impacts.

  1. For projects on new alignments, determine traffic noise impacts by field measurements.
  2. For projects on existing alignments, predict existing and design year traffic noise impacts.

(b) In determining traffic noise impacts, a highway agency shall give primary consideration to exterior areas where frequent human use occurs.

(c) A traffic noise analysis shall be completed for:

  1. Each alternative under detailed study;
  2. Each Activity Category of the NAC listed in Table 1 that is present in the study area;
    1. Activity Category A. This activity category includes the exterior impact criteria for 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 for the area to continue to serve its intended purpose. Highway agencies shall submit justifications to the FHWA on a case-by-case basis for approval of an Activity Category A designation.
    2. Activity Category B. This activity category includes the exterior impact criteria for single-family and multifamily residences.
    3. Activity Category C. This activity category includes the exterior impact criteria for a variety of land use facilities. Each highway agency shall adopt a standard practice for analyzing these land use facilities that is consistent and uniformly applied statewide.
    4. Activity Category D. This activity category includes the interior impact criteria for certain land use facilities listed in Activity Category C that may have interior uses. A highway agency shall conduct an indoor analysis after a determination is made that exterior abatement measures will not be feasible and reasonable. An indoor analysis shall only be done after exhausting all outdoor analysis options. In situations where no exterior activities are to be affected by the traffic noise, or where the exterior activities are far from or physically shielded from the roadway in a manner that prevents an impact on exterior activities, the highway agency shall use Activity Category D as the basis of determining noise impacts. Each highway agency shall adopt a standard practice for analyzing these land use facilities that is consistent and uniformly applied statewide.
    5. Activity Category E. This activity category includes the exterior impact criteria for developed lands that are less sensitive to highway noise. Each highway agency shall adopt a standard practice for analyzing these land use facilities that is consistent and uniformly applied statewide.
    6. Activity Category F. This activity category includes developed lands that are not sensitive to highway traffic noise. There is no impact criteria for the land use facilities in this activity category and no analysis of noise impacts is required.
    7. Activity Category G. This activity includes undeveloped lands.
      • (A) A highway agency shall determine if undeveloped land is permitted for development. The milestone and its associated date for acknowledging when undeveloped land is considered permitted shall be the date of issuance of a building permit by the local jurisdiction or by the appropriate governing entity.
      • (B) If undeveloped land is determined to be perrmitted, then the highway agency shall assign the land to the appropriate Activity Category and analyze it in the same manner as developed lands in that Activity Category.
      • (C) If undeveloped land is not permitted for development by the date of public knowledge, the highway agency shall determine noise levels in accordance with 772.17(a) and document the results in the project's environmental clearance documents and noise analysis documents. Federal participation in noise abatement measures will not be considered for lands that are not permitted by the date of public knowledge.

(d) The analysis of traffic noise impacts shall include:

  1. Identification of existing activities, developed lands, and undeveloped lands, which may be affected by noise from the highway;
  2. For projects on new or existing alignments, validate predicted noise level through comparison between measured and predicted levels;
  3. Measurement of noise levels. Use an ANSI Type I or Type II integrating sound level meter;
  4. Identification of project limits to determine all traffic noise impacts for the design year for the build alternative. For Type II projects, traffic noise impacts shall be determined from current year conditions;

(e) Highway agencies shall establish an approach level to be used when determining a traffic noise impact. The approach level shall be at least 1 dB(A) less than the Noise Abatement Criteria for Activity Categories A to E listed in Table 1;

(f) Highway agencies shall define substantial noise increase between 5 dB(A) to 15 dB(A) over existing noise levels. The substantial noise increase criterion is independent of the absolute noise level.

(g) A highway agency proposing to use Federal-aid highway funds for a Type II project shall perform a noise analysis in accordance with §772.11 of this part in order to provide information needed to make the determination required by §772.13(a) of this part.

Determining Existing Noise Levels

Noise measurements taken in the project study area determine existing noise levels for projects on new alignment. There are times when a combination of measurement and modeling are appropriate, such as in areas that are already heavily developed. Existing noise levels for projects on existing alignment are usually determined through modeling per 772.11(a)(2). Analysts may combine modeling with noise measurements to help determine existing noise levels and establish the loudest noise hour. Please note that use of the term predict within the regulation references modeling.

Traffic Noise Impacts

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

  1. Future noise levels are approach or exceed the NAC; or
  2. Future noise levels result in a substantial increase over the existing noise environment (substantial increase).

To assess the highway traffic noise impact of a proposed project, highway agencies must evaluate both criteria. While the FHWA highway traffic noise regulations do not define "approach or exceed," all highway agencies must establish a definition of "approach" that is at least 1 dB(A) less than the NAC in a whole decibel form for use in identifying impacts in a highway traffic noise analyses.

Impact Determination

These sound levels are to determine impacts. These are the absolute levels requiring consideration for abatement for all Activity Categories except Category F. Design highway traffic noise abatement to meet or exceed the highway agency's reasonable design goal - not to attain the noise abatement criteria.

Highway traffic noise impacts can occur below the NAC. The NAC are not the Federal standards or desirable noise levels; they are not design goals for noise barrier construction. 23 CFR 772 as a whole constitutes the standards mandated by the Federal-Aid Highway Act of 1970. Highway agencies should design traffic noise abatement to achieve the reasonableness design goal as defined in their noise policy. The NAC are absolute values which, when approached or exceeded, require the consideration of highway traffic noise abatement measures. State highway agencies may not establish minimum thresholds for consideration of noise abatement. The highway agency must consider noise abatement for projects predicted to result in highway traffic noise impacts.

A highway traffic noise impact can occur even if predicted future highway traffic noise levels are lower than existing levels, as long as the predicted future levels approach or exceed the NAC.

Substantial Increase

The 23 CFR 772 purposefully provides the highway agencies with flexibility to establish their own definition of "substantial increase." A 5dB(A) increase is a discernible increase in noise levels and a 10 dB(A) increase in noise levels is a doubling of the perceived loudness while a 15 dB(A) increase in noise levels represents more than a doubling of the loudness. Factors such as available resources, the public's attitudes toward highway traffic noise, and the absolute noise levels may influence a State's definition. highway agencies may define a "substantial increase" to be a 5 dB(A) to 15 dB(A) increase in noise levels. A "substantial increase" may occur at any absolute noise level, i.e., there is a not a threshold below which a "substantial increase" does not occur. The FHWA will accept a uniformly and consistently applied well reasoned definition. The highway agency must define substantial increase in the State highway traffic noise policy.

Substantial increase impacts occur due to the increase in noise level and are independent of an absolute noise level. For example, a State's substantial increase criterion is 15 dBA. If the existing noise level at a receptor is 30 dBA and the design year build noise level is 45 dBA, then the receptor is impacted. There is no minimum threshold for substantial increase impacts.

In documenting any substantial increase in highway traffic noise levels in the environmental documentation for a project, take care to avoid the use of the phrase "significant increase." FHWA Technical Advisory 6640.8A discourages the use of the word "significant" in FHWA documents because it is seldom meaningful in and of itself. (http://environment.fhwa.dot.gov/projdev/impTA6640.asp) If it is used, it should be used in a manner consistent with the Council on Environmental Quality definition at 40 CFR 1508.27. Always use the phrase "substantial increase" to address this type of potential highway traffic noise impact.

Noise Abatement Criteria (NAC)

The use of subjective descriptors to describe highway traffic noise impacts is not required. Highway traffic noise impacts occur based upon the definition contained in 23 CFR 772. This definition does not contain subjective descriptors. If there are impacts, the highway agency must consider highway traffic noise abatement measures and implement them if found to be feasible and reasonable. Traffic noise impacts do not occur without a project. Discussion of impacts in a noise analysis is relevant only when discussing the build alternatives under study. Existing and no build noise levels may exceed the NAC, but they are not impacts because no project occurs in either case. Describing existing and no build noise levels as impacts may result in public concern about noise abatement, since State highway agencies are required to consider noise abatement where noise impacts occur.

In developing the NAC contained in the highway traffic 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. The FHWA established values for the NAC by attempting to balance the control of future increases in highway traffic noise levels and the economic, physical, and aesthetic considerations related to highway traffic noise abatement measures. The FHWA considered several in establishing the criteria, including

  1. Hearing impairment:

    This approach considers 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 not practicable to reduce highway noise levels to these thresholds.

  3. Interference with speech communication:

    There is a lot of available research usefully applied to the problem of highway traffic noise. The NAC are noise levels associated with interference of speech communication and are a compromise between noise levels that are desirable and those that are achievable. FHWA believes that our regulations provide a balanced approach to the problem of highway traffic-generated noise.

Table 5: 23 CFR, Part 772, Table 1 Noise Abatement Criteria (NAC)
[Hourly A-Weighted Sound Level decibels (dBA)\1\]
Activity
Category
Activity Criteriea\2\ Evaluation
Location
Activity Description
Leq(h) L10(h)
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.
B\3\ 67 70 Exterior Residential
C\3\ 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\3\ 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

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

Activity Category A

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. The FHWA must approve a land use as Activity Category A before a noise analysis on an Activity Category A is initiated.

Activity Category A land uses are analyzed at this stricter standard even if the land use is identified within an activity category with a higher NAC.

Activity Category B

Activity Category B includes the exterior criteria for residential land use. This includes single family (including mobile home parks) and multi-family residences.

When analyzing areas with multi-family dwelling units, the analyst must identify all dwelling units predicted to experience highway traffic noise impacts. This may include units above the ground level. Consider abatement for all identified highway traffic noise impacts and implement abatement that is feasible and reasonable. Multi-family dwelling units often have associated common areas for recreational or other use. The highway agency should develop a method to evaluate the number of receptors used to represent these locations considering the use, potential use and capacity limits of the activity area. These common areas are typically available for use by residents of the entire multi-family facility rather than limited to those units near the highway. The number of receptors for common areas includes all users or potential users of the impacted common area(s).

Activity Category C

Category C includes the exterior areas of a variety of nonresidential land uses not specifically covered in Category A or B. This category may include public or private facilities. Determination of cost effectiveness is sometimes problematic for nonresidential land uses because it is difficult to determine the number of impacted receptors. Evaluation of other reasonableness factors is just like evaluating residential areas. Obtain the opinions of the owners and users through the public involvement process.

Campgrounds may cause some confusion when determining the appropriate land use category since some campgrounds, such as recreational vehicle parks, have long-term use and function as mobile home parks. The FHWA encourages highway agencies to carefully consider the context of the use of campground and similar facilities when identifying the appropriate land use category.

Section 4(f) properties must be analyzed as Activity Category C even if the land use without Section 4(f) designation would be exempt from analysis. Section 4(f) properties are analyzed at this stricter standard even if the Section 4(f) is identified within an activity category with a higher NAC.

Examples on Determining Cost-Reasonableness of Non-residential Land Uses.

Equivalent Number of Residences

This approach involves identifying the representative lot size of residential development and dividing the land area of portion of the park that is within the study area by the area of the representative lot size. For example, the typical lot size in a community is 60'x120' or 7,200 square feet (SF). Noise modeling predicts noise impacts from the project to a distance of 350'. A park in the community is adjacent to the project and has 1000' of frontage. The total impacted area of the park is 350,000 (SF). Divide this by the typical lot size of 7,200 SF for an equivalent number of receivers equal to 48.6. The park is representative of 49 receivers.

The Florida Method

The Florida DOT established a policy in A Method to Determine Reasonableness and Feasibility of Noise Abatement at Special Use Locations FL-ER-65-97 to evaluate cost reasonableness of nonresidential development. This method evaluates the intensity of use of the facility and assigns a value to each user to determine cost reasonableness.

Activity Category D

Activity Category D includes the interior of a variety of nonresidential public and private facilities that may be sensitive to increase noise levels. Some land uses in Activity Category D overlap with some land uses in Activity Category C. Only consider the interior levels at these land uses after fully completing an analysis of any outdoor activity areas or determining that exterior abatement measures are not feasible or reasonable.

Activity Category E

Activity Category E is the exterior criteria for, motels, hotels, offices and other developed lands not included in A-D or F. When determining the number or receivers for Activity Category E land uses, the highway agency should make this determination in the same manner that the number or receivers were determined for multi-family residences. Example: If the number of receptors for an apartment complex was determined by taking the total number of units in the building or if the determination involved the capacity limit for the pool or outdoor use area, then this philosophy should be applied to Activity Category E land uses as well.

Hotels and motels may cause some confusion when determining the appropriate land use category since all or part of some hotels and motels function as apartment buildings. The FHWA encourages highway agencies to carefully consider the context and use of hotels and motels when identifying the appropriate land use category.

Activity Category F

Activity Category F includes a number of land uses that are not sensitive to noise. No noise analysis is required for these locations.

Activity Category G

Activity Category G includes undeveloped lands. Although consideration of mitigation is not required under 23 CFR 772, the highway agency must determine and document highway traffic noise levels and provide this information to local officials. The minimum information to provide is the distance to the impact threshold of each land use category. By providing local government with the best estimate of future noise levels, the highway agency may place responsibility for noise abatement on local government and/or property owner.

A highway agency proposing to use Federal-aid highway funds for a Type II project shall perform a noise analysis in accordance with §772.11 in order to provide information needed to make the determination required by §772.13(a).

Section 772.11(d) lists the minimum requirements needed to evaluate impacts and abatement for each alternative under detailed study for the proposed highway project. The analysis should present the highway traffic noise impacts and evaluation of alternative abatement measures in a comparative format. This approach clearly identifies the potential highway traffic noise impacts and likely abatement measures associated with the various alternatives.

Section 772.11(d)(1) requires the identification of existing activities and developed lands. This identification includes not only the type (e.g., residential, commercial), but also the number or extent of activities. Some analysts overlook this quantification. Quantification of existing activities is vital to address the extent of the highway traffic noise impact on the people living near the highway project. This quantification is also important to determine the number of receptors that benefit from a proposed highway traffic noise abatement measure.

Receiver Locations for Highway Traffic Noise Analyses

A receiver location is an area where analysts measure and/or model highway traffic noise levels. The choice of receiver locations in highway traffic noise analyses rests with the noise analyst; receiver locations are normally restricted to "exterior areas of frequent human use." Interior locations are only used where there are no outside activities (e.g., in places of worship, hospitals, libraries, theaters, etc.) or where the exterior areas have characteristics that prevent highway traffic noise impacts on exterior activities (e.g., located far from the highway or already shielded from highway traffic noise). highway agencies typically use one of three locations for exterior receivers:

  1. At or near the highway right-of-way line;
  2. At or near a building in residential or commercial areas; or
  3. At an area between the right-of-way line and a building where frequent human activity occurs, such as a patio, pool, or play area in the yard of a home.

Any of these locations are acceptable, as long as a highway agency chooses one location and applies it uniformly and consistently in all its analyses. The State's noise policy may require methods to determine receiver locations.

Exterior Areas of Frequent Human Use

"Exterior areas of frequent human use" are normally located on the ground level, but may include balconies of multi-story residences. When analyzing areas with multi-family dwelling units (e.g., apartments, condominiums, etc.), the analyst should choose an exterior area, such as a patio, playground, or picnic area between the highway and the actual building, if one exists. If there are no ground level exterior areas, the analyst may choose a balcony/deck location for analysis.

A highway agency needs to evaluate the context and intensity of the land use when determining frequent human use.

For Category D, if there are no "exterior areas of frequent human use," the analyst should complete the analysis using interior noise abatement criteria.

Predicting Interior Noise Levels

For preliminary analysis, noise analysts may collect field measurements or use the TNM to estimate the noise reduction factors rather than obtaining the factors from detailed acoustical analysis. In the absence of calculations or field measurements, compute interior noise level predictions by subtracting noise reduction factors from the predicted exterior levels for the building in question, using the information in Table 6. Noise analysts should take interior noise measurements for the final noise analysis and abatement design for locations where highway agencies consider noise insulation as an abatement measure.

Table 6: Building Noise Reduction Factors
Building Type Window Condition Noise Reduction Due to
Exterior of the Structure
All Open 10dB
Light Frame Ordinary Sash (closed) 20dB
Storm Windows 25dB
Masonry Single Glazed 25dB
Double Glazed 35dB
*The windows shall be considered open unless there is firm knowledge that the windows are in fact kept closed almost every day of the year.

FHWA publication FHWA-DP-45-1R, Sound Procedures for Measuring Highway Noise: Final Report provides procedures to measure building noise reductions.

Study Area

Section 772.11(d)(4) requires the highway agency to identify all receptors impacted by a project. This approach to determining the study area provides flexibility and avoids establishing an arbitrary distance for study that may not be appropriate in all cases. Use of the model is probably the easiest way to determine the extent of impacts from a specific highway.

Existing Highway Traffic Noise Measurements

Existing highway traffic noise measurements are made to represent an hourly equivalent sound level, Leq(h). Statistical accuracy requires minimum measurements of approximately eight minutes. Most highway agencies have automated measurement equipment and typically measure 15-minute time periods to represent the Leq(h). This is acceptable if unusual events do not occur during the noisiest hour. Measurements along low-volume highways may require longer measurement periods (e.g., 30-60 minutes) to attain desirable statistical accuracy. If information is not available to identify the noisiest hour of the day or if there is public controversy at a specific location, 24-hour measurements may be necessary.

Use noise meters with sufficient accuracy to yield valid data for the particular project (ANSI S1.4-1983, TYPE II or better). Adopt and follow procedures to ensure measurements have consistent and supportable validity. Note traffic conditions, climatic conditions, and land uses at the time of measurement.

Model Validation

23 CFR 772.11(d)(2) requires validation to verify the accuracy of noise model runs used to predict existing noise levels for the project (This has nothing to do with validation of the FHWA TNM model, which accomplished in the TNM Validation Study).The model is validated if existing highway traffic noise levels and predicted highway traffic noise levels for the existing condition are within +/-3 dB(A).

Validation of the model requires a series of noise measurements along a project, preferably taking noise measurements within each noise sensitive area (NSA) or neighborhood along with simultaneous traffic counts and determination of vehicle speeds. In certain situations, consider multiple measurements at each location at different times and different days to account for variations in traffic. Measurements should be performed in accordance with the methodology presented in Measurement of Highway Related Noise FHWA-PD-96-046. Model the sites using traffic volumes and speeds collected during the measurement. If the measured and predicted highway traffic noise levels are within +/3 dB(A) for measurements taken at an NSA, then the model is considered valid and can be used to predict existing highway traffic noise levels for that NSA. If the model is not within +/-3 dB(A) for all the measurements, then the model is not considered valid until additional measurements are made or until the analyst identifies the reason for the discrepancy and makes a correction within the model. In some circumstances, it is not possible to identify a specific reason for not validating a specific measurement location. In these circumstances, document the discrepancy in the noise analysis report. Do not make adjustments to the receiver to account for the difference in measured and modeled levels.

Model Calibration

Calibration of a noise model, where the user adjusts the noise level at a specific receiver to account for differences between measured and modeled noise levels, is not routinely advisable. Problems with validating most models usually are due to input errors rather than problems with the model and users are encouraged to exhaust input options prior to making receiver adjustments. Typically, calibration involves the situations where the model is consistently over-predicting or under-predicting by an amount greater than 3 dBA. Adjusting the model by the difference between the measured and predicted values is a possible solution. The analyst must determine and document the reasons or causes for the difference between measured and predicted highway traffic noise levels and the actual level of the adjustment. Generally, differences in measured and predicted noise levels greater than +/- 3 dBA occur due to a site condition not accounted for in the model such as ground type, meteorological effects or contributions from non-transportation related noise sources.

Prediction of Future Highway Traffic Noise Levels for Study Alternatives

The next step involved in the highway traffic noise study is analysis of the noise levels expected to occur with the proposed highway. Estimate noise levels for each of the potential project alternatives. Some States require analysis of the "do-nothing" or no-build case to satisfy NEPA requirements. Document the method used to predict highway traffic noise levels and traffic data for the various alternatives.

Identification of Highway Traffic Noise Impacts for Study Alternatives

A highway traffic noise impact occurs when:

  1. The projected highway traffic noise levels approach or exceed the noise abatement criteria in 23 CFR 772, or
  2. The projected highway traffic noise levels substantially exceed existing highway traffic noise levels in an area.

The next step in the highway traffic noise analysis involves a comparison of the predicted noise levels for each project alternative with the highway traffic noise abatement criteria and existing noise levels. This comparison identifies any highway traffic noise impacts associated with each alternative in terms of a substantial increase in noise levels or approach or exceeding of the NAC.

Table 5 lists the highway traffic NAC from 23 CFR 772. Each State defines a substantial noise increase in its highway traffic noise policy based on the parameters provided in 23 CFR 772.11(f). Highway agencies must consider abatement when the noise analysis identifies future highway traffic noise impacts. Highway traffic noise analyses should recognize and consider absolute noise levels as well as substantial increases in noise levels when identifying highway traffic noise impacts and when considering highway traffic noise abatement measures.

Please see Appendix B for additional information on noise analysis documentation.

772.13 Analysis of Noise Abatement

(a) When traffic noise impacts are identified, noise abatement shall be considered and evaluated for feasibility and reasonableness. The highway agency shall determine and analyze alternative noise abatement measures to abate identified impacts by giving weight to the benefits and costs of abatement and the overall social, economic, and environmental effects by using feasible and reasonable noise abatement measures for decision-making.

(b) In abating traffic noise impacts, a highway agency shall give primary consideration to exterior areas where frequent human use occurs.

(c) If a noise impact is identified, a highway agency shall consider abatement measures. The abatement measures listed in §772.15(c) of this chapter are eligible for Federal funding.

  1. At a minimum, the highway agency shall consider noise abatement in the form of a noise barrier.
  2. If a highway agency chooses to use absorptive treatments as a functional enhancement, the highway agency shall adopt a standard practice for using absorptive treatment that is consistent and uniformly applied statewide.

(d) Examination and evaluation of feasible and reasonable noise abatement measures for reducing the traffic noise impacts. Each highway agency, with FHWA approval, shall develop feasibility and reasonableness factors.

  1. Feasibility:
    1. Achievement of at least a 5 dB(A) highway traffic noise reduction at impacted receptors. The highway agency shall define, and receive FHWA approval for, the number of receptors that must achieve this reduction for the noise abatement measure to be acoustically feasible and explain the basis for this determination; and
    2. Determination that it is possible to design and construct the noise abatement measure. Factors to consider are safety, barrier height, topography, drainage, utilities, and maintenance of the abatement measure, maintenance access to adjacent properties, and access to adjacent properties (i.e. arterial widening projects).
  2. Reasonableness:
    1. Consideration of the viewpoints of the property owners and residents of the benefited receptors. The highway agency shall solicit the viewpoints of all of the benefited receptors and obtain enough responses to document a decision on either desiring or not desiring the noise abatement measure. The highway agency shall define, and receive FHWA approval for, the number of receptors that are needed to constitute a decision and explain the basis for this determination.
    2. Cost effectiveness of the highway traffic noise abatement measures. Each highway agency shall determine, and receive FHWA approval for, the allowable cost of abatement by determining a baseline cost reasonableness value. This determination may include the actual construction cost of noise abatement, cost per square foot of abatement, the maximum square footage of abatement/benefited receptor and either the cost/benefited receptor or cost/benefited receptor/dB(A) reduction. The highway agency shall re-analyze the allowable cost for abatement on a regular interval, not to exceed 5 years. A highway agency has the option of justifying, for FHWA approval, different cost allowances for a particular geographic area(s) within the State, however, the highway agancy must use the same cost reasonableness/construction cost ratio statewide.
    3. Noise reduction design goals for highway traffic noise abatement measures. When noise abatement measure(s) are being considered, a highway agency shall achieve a noise reduction design goal. The highway agency shall define, and receive FHWA approval for, the design goal of at least 7 dB(A) but not more than 10 dB(A), and shall define the number of benefited receptors that must achieve this design goal and explain the basis for this determination.
    4. The reasonableness factors listed in §772.13(d)(5)(i), (ii) and (iii), must collectively be achieved in order for a noise abatement measure to be deemed reasonable. Failure to achieve §772.13(d)(5)(i), (ii) or (iii), will result in the noise abatement measure being deemed not reasonable.
    5. In addition to the required reasonableness factors listed in §§772.13(d)(5)(i), (ii) and (iii), a highway agency has the option to also include the following reasonableness factors: date of development, length of time receivers have been exposed to highway traffic noise impacts, exposure to higher absolute highway traffic noise levels, changes between existing and future build conditions, percentage of mixed zoning development, and use of noise compatible planning concepts by the local government. No single optional reasonableness factor can be used to determine reasonableness.

(e) Assessment of Benefited Receptors. Each highway agency shall define the threshold for the noise reduction which determines a benefited receptor as at or above the 5 dB(A), but not to exceed the highway agency's reasonableness design goal.

(f) Abatement Measure Reporting: Each highway agency shall maintain an inventory of all constructed noise abatement measures. The inventory shall include the following parameters: type of abatement; cost (overall cost, unit cost per/sq. ft.); average height; length; area; location (State, county, city, route); year of construction; average insertion loss/noise reduction as reported by the model in the noise analysis; NAC category(s) protected; material(s) used (precast concrete, berm, block, cast in place concrete, brick, metal, wood, fiberglass, combination, plastic (transparent, opaque, other); features (absorptive, reflective, surface texture); foundation (ground mounted, on structure); project type (Type I, Type II, and optional project types such as State funded, county funded, tollway/turnpike funded, other, unknown). The FHWA will collect this information, in accordance with OMB's Information Collection requirements.

(g) Before adoption of a CE, FONSI, or ROD, the highway agency shall identify:

  1. Noise abatement measures which are feasible and reasonable, and which are likely to be incorporated in the project; and
  2. Noise impacts for which no noise abatement measures are feasible and reasonable.
  3. Documentation of highway traffic noise abatement: The environmental document shall identify locations where noise impacts are predicted to occur, where noise abatement is feasible and reasonable, and locations with impacts that have no feasible or reasonable noise abatement alternative. For environmental clearance, this analysis shall be completed to the extent that design information on the alterative(s) under study in the environmental document is available at the time the environmental clearance document is completed. A statement of likelihood shall be included in the environmental document since feasibility and reasonableness determinations may change due to changes in project design after approval of the environmental document. The statement of likelihood shall include the preliminary location and physical description of noise abatement measures determined feasible and reasonable in the preliminary analysis. The statement of likelihood shall also indicate that final recommendations on the construction of an abatement measure(s) is determined during the completion of the project's final design and the public involvement processes.

(h) The FHWA will not approve project plans and specifications unless feasible and reasonable noise abatement measures are incorporated into the plans and specifications to reduce the noise impact on existing activities, developed lands, or undeveloped lands for which development is permitted.

(i) For design-build projects, the preliminary technical noise study shall document all considered and proposed noise abatement measures for inclusion in the NEPA document. Final design of design-build noise abatement measures shall be based on the preliminary noise abatement design developed in the technical noise analysis. Noise abatement measures shall be considered, developed, and constructed in accordance with this standard and in conformance with the provisions of 40 CFR 1506.5(c) and 23 CFR 636.109.

(j) Third party funding is not allowed on a Federal or Federal-aid Type I or Type II project if the noise abatement measure would require the additional funding from the third party to be considered feasible and/or reasonable. Third party funding is acceptable on a Federal or Federal-aid highway Type I or Type II project to make functional enhancements, such as absorptive treatment and access doors or aesthetic enhancements, to a noise abatement measure already determined feasible and reasonable.

(k) On a Type I or Type II projects, a highway agency has the option to cost average noise abatement among benefited receptors within common noise environments if no single common noise environment exceeds two times the highway agency's cost reasonableness criteria and collectively all common noise environments being averaged do not exceed the highway agency's cost reasonableness criteria.

Section 772.13(c)(1) requires consideration of noise barriers as an abatement measure when highway traffic noise impacts occur. Highway agencies may optionally consider use of the alternative abatement measures listed in 772.15(c)(2)-(5). As noted in Section 772.5, highway traffic noise impacts occur when noise levels approach or exceed the noise abatement criteria or when predicted levels substantially exceed existing levels. Consequently, this section requires consideration of highway traffic noise abatement for both of these types of noise impacts. However, measures such as traffic management, alteration of alignment, or purchase of land for use as a buffer zone usually do not provide a substantial noise reduction, or are determined to be not feasible and reasonable due to cost, right-of-way requirements, or project purpose. Noise barriers are the abatement measure most often associated with the concept of highway traffic noise abatement.

Abatement consideration should weigh the abatement benefits, costs, and overall SEE effects. The highway agency must incorporate abatement measures determined feasible and reasonable in project plans, specifications and estimates. If the highway agency identifies highway traffic noise impact for a project, they must consider abatement as part of the proposed project. The highway agency may not delay this consideration to a future date or make abatement part of a Type II program.

A feasible abatement measure provides at least a 5 dB(A) reduction in highway traffic noise levels. When highway traffic noise abatement is proposed, an attempt to achieve the greatest reduction possible is necessary by meeting the highway agency defined design goal.

Table 7: Relationship Between Decibel, Energy, and Loudness
A-Level Reduction % of Energy Removed Divide Loudness by
3 dB(A) 50 1.2
6 dB(A) 75 1.5
10 dB(A) 90 2
20 dB(A) 99 4

A reduction of 10 dB(A) (say 75 dB(A) to 65 dB(A)) is perceived by the public as a halving of the loudness. This is an easily recognizable change. 5 dB(A) and 7 dB(A) changes can also be recognized, but to a lesser degree. Keep two points in mind: (1) any reduction will improve the noise environment in such areas as annoyance, speech interference, task interference, etc., and (2) no matter the level of reduction, until noise reaches a very low level (about Leq = 55 dB(A)), the clearly audible highway traffic noise will continue to dominate the noise environment.

Noise Abatement Documentation

Good program management supports the need for highway traffic noise abatement decision-making criteria and procedures. The decision on whether or not to implement a highway traffic noise abatement measure must not be arbitrary or capricious. The reasoning should be available and supportable, particularly if the answer is "no" and is contrary to the desires of the affected residents. Highway agencies must base the decision on consistent and uniform application of established criteria and procedures and document the criteria and procedures in the State's highway traffic noise policy.

Present the following information for each abatement measure:

  1. Description of the measure
  2. Anticipated costs, problems, and disadvantages
  3. Predicted design year noise reduction compared to existing levels and other factors deemed necessary to report.

Section 13 ties the highway traffic noise regulation to the NEPA requirements. The choice of the word "likely" was deliberate. If a decision maker is to make an informed decision and make the public aware of the impacts, the State must make its intentions known. If the State later decides abatement is unwarranted, the decision should have strong support. Sates should qualify the meaning of "likely," to avoid confusion when noise abatement is determined unwarranted. When a project involves consideration of more than one barrier, the State should include a statement of "likelihood" for each barrier in the environmental document.

Example Statement of Likelihood

Based on the studies thus far accomplished, the State intends to install highway traffic noise abatement measures in the form of a barrier at ____. These preliminary indications of likely abatement measures are based upon preliminary design for a barrier cost of $_____ that will reduce the noise level by ___dB(A) for ____ residences. If it subsequently develops during final design that these conditions have substantially changed, the abatement measures might not be provided. A final decision of the installation of the abatement measure(s) will be made upon completion of the project's final design and the public involvement processes.

The viewpoints of the impacted residents and property owners should be a major consideration in determining the reasonableness of highway traffic noise abatement measures for proposed highway construction projects. These viewpoints should be determined and addressed during the environmental phase of project development. The will and desires of the public should be an important factor in dealing with the overall problems of highway traffic noise. highway agencies should incorporate highway traffic noise consideration in their on going activities for public involvement in the highway program, i.e., and reexamine the residents' views on the desirability and acceptability of abatement periodically during project development.

The key words in this paragraph are feasible and reasonable. Feasibility deals primarily with 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 predominating noise sources present in the area, etc.). Reasonableness is a more subjective criterion than feasibility. It implies that the highway agency applied common sense and good judgment in arriving at a decision. Reasonableness should be based on a number of factors not just one criterion. For a detailed explanation of feasibility and reasonableness of abatement, see the discussions in Section IV: Highway Traffic Noise Analysis and Documentation.

Determining Feasible and Reasonable Highway Traffic Noise Abatement

Feasibility deals primarily with 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.). Address safety, maintenance, and drainage concerns for highway traffic noise abatement measures 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.

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

Reasonableness is a more subjective criterion than feasibility. It implies that decision makers applied good judgment in arriving at a decision. Reasonableness should be based on a number of factors not just one criterion.

Determining Benefited Receptors

When determining receiver units for the reasonableness criteria, include all benefited residences, regardless of whether they are impacted. Highway agencies must define the threshold of noise reduction, which determines a "benefited" residence as a reduction of not less than 5 dB(A) per 23 CFR 772.13(e).

Feasibility

Feasibility generally deals with considering whether it is possible to build an abatement measure given site constraints and whether the abatement measure provides a minimum reduction in noise levels. Feasibility is limited by:

  1. Topography,
  2. Access requirements for driveways, ramps, etc.,
  3. The presence of local cross streets, or
  4. Are other noise sources in the area (e.g. aircraft over flights)?
  5. Addressing the project purpose
  6. Drainage
  7. Utilities
  8. Maintenance
  9. Noise reduction (acoustic feasibility)

Acoustic Feasibility

A noise abatement measure is NOT FEASIBLE unless the measure achieves a noise reduction of at least 5 dB(A) for the number of impacted receptors the highway agency identified in their noise policy. Blocking the line of site between the source and receptor usually provides a 5 dB(A) noise reduction.

Reasonableness

Viewpoint of Affected Residents and Property Owners

FHWA highway traffic noise regulation requires consideration of the viewpoints of the impacted residents and property owners in determining the reasonableness of abatement. Highway agencies should not provide abatement if most of the residents and owners do not want it. There are, however, no easy methods to determine viewpoints or arrive at a conclusion regarding their desires. Decision makers should also consider commercial establishment's desire to maintain visibility, but the primary consideration is to provide abatement for impacted noise sensitive land uses. Available technologies, in the form of transparent noise barriers, provide highway agencies with the opportunity to satisfy the concerns of commercial activities and those who desire noise abatement.

Some highway agencies reach a decision after holding public meetings or conducting personal surveys. Others require that local officials or a community group submit a letter stating the affected receptors' wishes. In the case of rental properties, consider the views of both the owner and the residents in the decision making process.

Allowable Cost of Highway Traffic Noise Abatement

Cost of an abatement measure is an important consideration but only one of three reasonableness factors that must be considered. Each highway agency is required to incorporate a cost index in their highway traffic noise policy. Most highway agencies typically determine reasonable cost by using either a cost/receiver or cost/receiver/dB(A) reduction index. Recently, some States started using a maximum square footage per benefitted residence.

Some highway agencies may choose to implement a tiered approach to cost reasonableness based on regional cost differences within the State. This approach conforms to the regulation. However, the ratio of the unit cost of abatement and the reasonable cost per residence must remain the same statewide.

Example of Regional Cost Differences

In one part of a State, the unit cost for noise barrier construction is $15 per square foot and the allowable cost per benefitting residence is $20,000. In another part of the State with higher construction and materials cost, the unit cost for noise barrier construction is $30 per square foot. The allowable cost per benefiting residence in the more expensive location is $40,000 since the unit cost in the more expensive are is double the unit cost in other areas of the State.

Highway agencies must ensure that the reasonable cost of abatement is justified based on actual construction costs and clearly communicate all reasonableness criteria to the public.

Appendix F provides information on using construction costs to help determine the reasonable cost of abatement.

Noise Reduction Design Goal

The objective of noise abatement is not to reduce predicted noise levels to the noise abatement criteria. The goal of noise abatement is to provide a substantial reduction in noise level as defined by the design goal. A predicted noise level of 69 dB(A) for a Category B activity (see Table 5) should not be reduced to the noise abatement criterion of 67 dB(A). 23 CFR 772.13(d)(2)(iii) introduces the requirement for highway agencies to identify a design goal of at 7-10 dBA to encourage design and construction of effective noise abatement measures. The highway agency will establish the design goal within their noise policy. The noise abatement measure must meet or exceed the highway agency design goal to achieve this reasonableness criterion. Choosing a decibel reduction between 7 and 10 defines the design goal, howeve:, actual noise reductions can exceed the design goal.

Determining Receptors

Receivers are discrete points within a noise model that represent noise sensitive land uses. An individual receiver may represent multiple receptors. The highway agency highway traffic noise policy must clearly delineate the method used to count receptors in the noise analysis. The number of receptors should include all dwelling units, e.g., owner-occupied, rental units, mobile homes, etc. Count each unit in a multifamily building as one receptor. The highway agency highway traffic noise policy must also delineate how receptor units are determined for special land uses, such as parks, recreation areas, cemeteries, etc.

Optional Reasonableness Factors

In addition to the required reasonableness factors listed in §§772.13(d)(2)(i), (ii) and (iii), a highway agency has the option to also include the following reasonableness factors: date of development, length of time receivers have been exposed to highway traffic noise impacts, exposure to higher absolute highway traffic noise levels, changes between existing and future build conditions, percentage of mixed zoning development, and use of noise compatible planning concepts by the local government. Since the viewpoints of affected residents and property owners, allowable cost of highway traffic noise abatement and noise reduction design goal are the required factors and no single optional reasonableness factor can be used to determine reasonableness, by default, any optional reasonableness factor can only be used to go above and beyond a highway agecie's feasible and reasonable noise abatement. This typically would result in allowing a higher allowable cost based on the number of additional resonableness factors that are satisfied. However, the use of more than one optional reasonableness factor can be used to determine if a noise abatement measure is reasonable or not.

Date of Development

When considering date of development for Type I projects, some highway agencies categorize land uses into those that predate the existence of the highway and those developed after the highway and consider land uses that predate the highway more favorably than land uses postdating the highway.

Date of development can be important for highway agencies with an established record of providing noise compatible planning information to local officials and for highway agencies that have established an outreach program to provide noise compatible planning strategies in accordance with 772.17(b). After an outreach program is in place, highway agencies may include date of development as part of the reasonableness determination. Highway agencies may not use date of development as a single criterion to determine reasonableness per 772.13(d)(2)(v).

Highway agencies are encouraged to use caution when considering date of development as a reasonableness criterion. The requirement to inform local officials about noise compatible planning is a longstanding component of 23 CFR 772; however, implementation of that requirement by highway agencies was historically inconsistent. The noise policy needs to outline how the highway agency satisfies 772.17.

This discussion on the date of development applies to Type I projects only since date of development has specific meaning to Type II projects per 772.15(b).

Length of Time Receivers Have Been Exposed to Highway Traffic Noise Impacts.

It is acceptable to give weight to receivers that have been exposed to traffic noise impacts for longer periods of time than other receivers.

Exposure to Higher Absolute Highway Traffic Noise Levels

It is acceptable to give weight to areas with higher absolute highway traffic noise levels. Typically absolute noise levels found along highways range from 60-80 dB(A). When using this criterion remember impact levels for the various NAC activity categories.

Changes Between Existing and Future Build Conditions

It is acceptable to give weight in decision making to changes between the existing and future build condition. This approach gives greater consideration to projects for highways on new location and major reconstruction than it does to projects of smaller magnitude along existing highways. Additionally, a small increase at a higher absolute level (e.g., 70 dB(A) to 75 dB(A)) can be more important and justify greater consideration than a similar increase at a lower absolute level (e.g., 50 dB(A) to 55 dB(A)). Likewise, a large increase at a lower absolute level (e.g., 40 dB(A) to 55 dB(A)) can be less important and justify less consideration than a similar increase at a higher absolute level (e.g., 55 dB(A) to 70 dB(A)).

Mixed Zoning Development

It is acceptable to give less consideration for abatement to areas of mixed zoning or development and to areas where existing local plans call for zoning changes to a less noise sensitive use.

Noise Compatible Planning

It is acceptable to give added weight to areas that demonstrate implementation of efforts to prevent incompatible growth and development along highways.

Abatement Measure Reporting

The requirements of 772.13(f) replace the triennial noise abatement inventory. Information collected is largely the same, but the language in the regulation allows for reporting of abatement measures other than noise barriers. The New York and Ohio Departments of Transportation developed noise barrier inventory management systems to accommodate the reporting requirements and to assist with identifying noise barrier maintenance needs. FHWA recommends that highway agencies develop protocols for the collection and reporting of this information to ensure they provide accurate and useable data.

Third Party Participation

To comply with environmental justice requirements, when a noise barrier's cost is higher than the highway agency's cost allowance, it is not acceptable to allow a third party to contribute funds to make up the difference. A third party may contribute funds to make functional or aesthetic enhancements to a noise barrier already determined to be feasible and reasonable.

A highway agency may consider local participation for Type II projects if the noise abatement measure is feasible and reasonable without consideration for the local participation amount. For example, a state highway agency may require a local match of 20% of the cost of the Type II project. This amount may go toward paying for the project, but not to offset costs of abatement that exceed the cost reasonableness criterion in the state noise policy. The feasibility and reasonableness determination is performed independently of the local contribution.

772.15 Federal Participation

(a) Type I and Type II projects. Federal funds may be used for noise abatement measures when:

  1. Traffic noise impacts have been identified; and
  2. Abatement measures have been determined to be feasible and reasonable pursuant to §772.13(d) of this chapter.

(b) For Type II projects.

  1. No funds made available out of the Highway Trust Fund may be used to construct Type II noise barriers, as defined by this regulation, if such noise barriers were not part of a project approved by the FHWA before the November 28, 1995.
  2. Federal funds are available for Type II noise barriers along lands that were developed or were under substantial construction before approval of the acquisition of the rights-of-ways for, or construction of, the existing highway.
  3. FHWA will not approve noise abatement measures for locations where such measures were previously determined not to be feasible and reasonable for a Type I project.

(c) Noise Abatement Measures. The following noise abatement measures may be considered for incorporation into a Type I or Type II project to reduce traffic noise impacts. The costs of such measures may be included in Federal-aid participating project costs with the Federal share being the same as that for the system on which the project is located.

  1. 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.
  2. Traffic management measures including, but not limited to, 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.
  3. Alteration of horizontal and vertical alignments.
  4. Acquisition of real property or interests therein (predominantly 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 Activity Category D land use facilities listed in Table 1. Post-installation maintenance and operational costs for noise insulation are not eligible for Federal-aid funding.

Section 772.15(a) identifies the rules that guide the funding of highway traffic noise abatement on highway projects. These rules apply to Type I and Type II projects.

Highway agencies may not use Federal-aid highway funds as payment or compensation for a highway traffic noise impact through the purchase of a noise easement from a property owner. The FHWA highway traffic noise regulations limit use of Federal funds to reducing traffic noise impacts and providing highway traffic noise abatement benefits. Monetary compensation accomplishes neither of these requirements.

Section 772.15(b) limits funding participation of highway traffic noise abatement measures for projects approved before November 28, 1995 (the date of passage 1995 National Highway System Designation Act), or proposed where development or substantial construction predated the existence of the highway. If the existing highway is a six-lane freeway, this means development must have been in place prior to the construction of the first paved two-lane roadway. In addition, FHWA will not approve highway traffic noise abatement measures at locations where such measures were previously determined not feasible and reasonable for a Type I project.

When considering funding eligibility for Type II projects, often, the "date of the existence of development" along the highway is mixed. Some development predates the existence of the highway and some development will have occurred after construction of the original highway. In States that elect to implement Type II projects, the highway agency and its respective FHWA Division Office should jointly establish appropriate procedures to determine address locations with different dates of development. States may consider the current status of the highway in the decision-making process. For example, if most of the residential development occurred when the highway was a two-lane road, but now the highway is an interstate, it is appropriate to consider the neighborhood for Type II if the development occurred prior to requirements for highway agencies to consider highway noise for their projects.

Funding

The participating share for the highway traffic noise mitigation measure is the same as that for the system on which the project is located. Although most highway traffic noise abatement occurs along Interstate highways, highway agency's may use Federal funds for abatement measures along other types of highways, if highway traffic noise impacts exist and the project meets the criteria in 772.15(a).

Property owners cannot receive Federal funds as monetary compensation in lieu of noise abatement. It is the highway agency's responsibility to ensure that Federal funds are properly used.

Appendix C provides additional information about eligible abatement measures.

772.17 Information for local officials

(a) To minimize future traffic noise impacts on currently undeveloped lands of Type I projects, a highway agency shall inform local officials within whose jurisdiction the highway project is located of:

  1. Noise compatible planning concepts;
  2. The best estimation of the future design year noise levels at various distances from the edge of the nearest travel lane of the highway improvement where the future noise levels meet the highway agency's definition of "approach" for undeveloped lands or properties within the project limits. At a minimum, identify the distance to the exterior noise abatement criteria in Table 1;
  3. Non-eligibility for Federal-aid participation for a Type II project as described in §772.15(b).

(b) If a highway agency chooses to participate in a Type II noise program or to use the date of development as one of the factors in determining the reasonableness of a Type I noise abatement measure, the highway agency shall have a statewide outreach program to inform local officials and the public of the items in §772.17(a)(1)- (3).

Noise Compatible Planning

Highway traffic noise is a program of shared responsibility. The FHWA encourages State and local governments to practice noise compatible land planning and control near highways. Local governments may use their power to regulate land development to prohibit noise-sensitive land uses adjacent to a highway, or require developers to plan, design, and construct projects that minimize highway traffic noise impacts on adjacent developments.

The prevention of future impacts is one of the most important parts of highway traffic noise control. New development and highways can be compatible. But, local government officials need to know what highway traffic noise levels to expect from a highway and what techniques they can use to prevent future impacts. Highway agencies can inform local officials by including a table of future noise levels at specific locations or a figure of distances to typical noise levels along the roadway. Encourage local officials to make this such information available for disclosure in real estate transactions. Make local officials aware of the eligibility requirements for Federal-aid participation in Type II projects.

Date of Public Knowledge

Highway agencies must identify the date when they officially notify the public 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 FHWA and highway agencies are no longer responsible for providing highway traffic noise abatement for new development, which 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).

The FHWA and highway agencies are not responsible for providing highway traffic noise abatement for development determined permitted after the "date of public knowledge". However, for Type I project, the FHWA and highway agencies are responsible for analyzing and documenting the existing and future levels on these lands. The highway agency should make local governments aware of these results.

Statewide Outreach Program

Statewide outreach programs are at the discretion of the highway agency, but states must implement a program to use date of development as a reasonableness criterion or if the state chooses to implement a Type II program. The objective of the program is to provide information on noise compatible planning to local officials and avoid future noise impacts or to encourage local governments to enact requirements for developer provided noise abatement. States may apply the program by jurisdiction, but must develop a uniform and consistent approach for use statewide.

Example 1 - Jurisdiction Based Program: A State highway agency plans to widen the beltway around a major city. The beltway goes through several local jurisdictions providing the highway agency the opportunity to provide noise compatible planning information to the county commission, the metropolitan planning organization, various township trustees and officials from several cities and towns along the beltway. By implementing the statewide outreach program and providing noise compatible planning information to these officials, the highway agency may consider date of development for future projects in those jurisdictions. The key to a Jurisdiction Based Program is uniform and consistent application of the program on a project by project basis. A uniform and consistent approach makes this a statewide outreach program even though implementation of the program occurs gradually.

Example 2 - Statewide Program: A State may decide to implement the outreach program statewide in one effort. They may accomplish this by providing noise compatible planning information directly to local officials in all jurisdictions statewide, including notification of the intention to use date of development as part of the decision-making criteria when considering noise abatement.

772.19 Construction Noise

For all Type I and II projects, a highway agency shall:

(a) Identify land uses or activities that may be affected by noise from construction of the project. The identification is to be performed during the project development studies.

(b) Determine the measures that are needed in the plans and specifications to minimize or eliminate adverse construction noise impacts to the community. This determination shall include a weighing of the benefits achieved and the overall adverse social, economic, and environmental effects and costs of the abatement measures.

(c) Incorporate the needed abatement measures in the plans and specifications.

The impact of construction noise does not appear to be serious in most instances. Consider the following items to ensure adequate consideration of potential construction noise impacts during highway project development:

Construction Noise Analysis

Calculation of construction noise levels is usually not necessary for highway traffic noise analyses. The decision to develop a detail construction noise analysis usually results from combination of factors including the scale and scope of the project along with public concern about construction noise. In some cases, the decision to complete a construction noise analysis may occur after construction begins resulting from public complaints. It is best to anticipate public concerns so the project plans, specification and estimates include consideration for construction noise abatement where necessary.

Roadway Construction Noise Model

If the highway agency anticipates a construction noise impact at a particular sensitive receiver, they have the option to use the FHWA Roadway Construction Noise Model (FHWA RCNM). This model uses the database for 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 that allows the user to modify parameters to their needs. Users can activate and analyze multiple pieces of equipment simultaneously and define multiple receptor locations including land-use type and baseline noise levels. The FHWA RCNM calculates sound level results for multiple metrics.

The FHWA RCNM has two main uses:

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

Users may quickly create a variety of construction work scenarios and determine the impact of changing construction equipment and adding/removing the effects of shielding due to noise mitigation devices such as barriers. The user provides receptor information (description, land use and baseline sound levels) and equipment information (by choosing from the default list or adding new equipment). Find additional information regarding the FHWA RCNM at http://www.trafficnoisemodel.org/main.html.

Construction Noise Impacts

For the majority of highway projects, highway agencies may address potential impacts of highway construction noise in a general manner in the noise analysis; noting the temporary nature of the impacts. The analysis should indicate the anticipated types of construction and noise levels associated with these activities from information available in existing literature and present this information in the noise analysis.

Construction Noise Abatement Measures

Highway traffic noise analyses should identify measures to mitigate potential highway construction noise impacts using a common-sense approach. Highway agencies may incorporate low-cost, easy-to-implement measures into project plans and specifications (e.g., work-hour limits, equipment muffler requirements, location of haul roads, eliminate of "tail gate banging", ambient sensitive back-up alarms, community rapport, and complaint mechanisms).

Severe Construction Noise Impacts

Major urban projects with unusually severe highway construction noise impacts require extensive analyses. The analyst should identify sensitive receivers, existing noise levels, predicted construction noise levels and evaluate impacts to indicate their severity. Abatement measures may be quite costly and should be thoroughly discussed and justified in the analyses. The use of portable noise barriers and special quieting devices on construction equipment are possible alternatives for construction noise mitigation.

Updated: 02/03/2012
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