Purpose
Highway traffic noise analysts often ask "how much analysis is sufficient?" for a project which will require the use of Federal-aid highway funds. The following discussion is meant to assist in answering that question.
Background
Two different laws control the evaluation of highway traffic noise impacts: NEPA and the Federal-aid Highway Act of l970, which added Section l09(i) to Title 23 of the U.S. Code of Federal Regulations. They require environmental evaluation of Federal or Federal-aid highway projects, and reasonable and feasible mitigation of identified impacts. The FHWA regulations for mitigation of highway traffic noise in the planning and design of federally-aided highways are contained in 23 CFR 772, "Procedures for Abatement of Highway Traffic Noise and Construction Noise."
The FHWA noise regulations require, during the planning and design of all Type I highway projects, the following: (1) identification of traffic noise impacts; (2) examination of potential mitigation measures; (3) the incorporation of reasonable and feasible noise mitigation measures into the highway project; and (4) coordination with local officials to provide helpful information on compatible land use planning and control. Type I highway projects are those that involve "... construction of a highway on new location or the physical alteration of an existing highway which significantly changes either the horizontal or vertical alignment or increases the number of through-traffic lanes."
The regulations contain noise abatement criteria, which represent the upper limit of acceptable highway traffic noise for different types of land uses and human activities. The regulations do not require that the noise abatement criteria be met in every instance. Rather, they require that every reasonable and feasible effort be made to provide noise mitigation when the noise abatement criteria are approached or exceeded, or when the predicted traffic noise levels substantially exceed the existing noise levels (these two conditions are defined as traffic noise impacts). Compliance with the noise regulations is a prerequisite for the granting of Federal-aid highway funds for construction or reconstruction of a highway.
General guidance related to the format, content, and processing of NEPA and Section 4(f) studies and documents describes the three classes of actions which prescribe the level of documentation required in the NEPA process.
These classes of actions are the following:
I. Categorical Exclusion (CE)
A Categorical Exclusion is for an action that does not individually or cumulatively have a significant environmental impact.
II. Environmental Assessment/Finding of No Significant Impact (EA/FONSI)
An Environmental Assessment is for an action in which the significance of the environmental impact is not clearly established. A Finding of No Significant Impact is a written document incorporating the EA and any other appropriate environmental documents and in which the Federal Agency agrees that there is no significant impact.
III. Environmental Impact Statement (EIS)
An EIS is for an action that will significantly affect the environment.
Noise Analysis
The level of detail and effort for the traffic noise analysis required on each alternative of a proposed project should be commensurate with the type of project and the impacts and/or issues with which it is associated.
The general content of a traffic noise analysis is discussed in Paragraph 772.9b of 23 CFR 772 (see page 11).
Categorical Exclusion
In considering traffic noise analysis for a CE, it is necessary to make a distinction between two cases. These are (a) CEs which are not Type I projects as defined in 23 CFR 772 (the vast majority of CEs will not be Type I projects) and (b) CEs which are Type I projects.
Projects that are not Type I: No analysis of any kind is required, except for the extremely rare instance in which the project itself is expected to create a noise impact. Such projects must be dealt with on a case by case basis in accordance with NEPA.
Projects that are Type I: Noise analysis is required by 23 CFR 772 although none may be necessary to demonstrate NEPA compliance. The analysis should include:
End of Analysis.
As an example of how steps (1), (2), (3), (4) and (5) might be performed, suppose a highway is to be relocated about 150 meters from its existing alignment. There are currently 400 autos/hour, 20 medium trucks/hour, and 32 heavy trucks/ hour in the noisiest hour and all vehicle speeds are about 88 km/h. The general terrain is flat and grassy (i.e., acoustically soft). Future traffic is expected to double. There are nine residences near the relocation alignment, five which are 60 meters from the relocation alignment, and four which are 30 meters from the relocation alignment. Existing noise level near these residences is 60 dBA Leq during PM peak hour.
The SHA uses the following definitions:
The above is a fictitious example and must not be construed as containing FHWA recommended definitions. A more thorough discussion of reasonableness and feasibility may be found in the discussion on "Reasonableness and Feasibility (see pp. 50-66)." The particular use of the factors noted above, while consistent with this discussion, is only one example of an application for decisionmaking.
Application of the nomographs to estimate future noise levels at a distance of 15m gives levels of 66, 65 and 71 dBA for autos, medium trucks, and heavy trucks respectively (using future traffic volumes which are double existing volumes) or a combined level of 73 dBA using decibel addition rules. Applying the adjustment for doubling distance from a noise source at a soft site (4.5 decibel decrease for every doubling of distance), the five sites 60 meters from the road would each receive about 64 dBA (PM peak) in the future. Since the existing noise levels are about 60 dBA, this is not a substantial increase. The 64 dBA also does not approach the Noise Abatement Criterion of 67 dBA for a residence. Therefore, given the SHA's definitions of "...substantially exceeds existing noise levels..." and "...approach or exceed...," there is no traffic noise impact at these five sites.
At the four residences closest to the highway, we apply the adjustment for doubling distance from a noise source at a soft site. This results in the conclusion that this site would receive about 68 dBA from the road in the future. Therefore, there is a noise impact at the site and abatement must be considered as follows:
Given all of the above, the SHA considers abatement to be reasonable at this site even though the cost of the barrier slightly exceeds the SHA's cost/receptor criterion.
End of Analysis
Environmental Assessment/Finding of No Significant Impact
In considering traffic noise analysis for an EA/FONSI, it is desirable to distinguish between three cases. These are (a) EA/FONSIs for projects that are not Type I, (b) EA/FONSIs for projects on low volume roads, and (c) EA/FONSIs for projects on high volume roads. The SHA should define low volume roads. Both low and high volume roads may occur in rural, suburban or urban areas.
Projects that are not Type I: The analysis requires only that an explanation be provided as to whether the project itself will create a noise impact. The few instances where the project will have an impact on noise levels will have to be examined on a case-by-case basis in accordance with NEPA.
Projects that are Type I and are on Low Volume Roads: The analysis requires the same steps as in the case of CEs for Type I projects, except that each alternative under consideration (including the "no build" alternative) requires a separate analysis. This, thus, includes:
End of Analysis.
Projects that are Type I and are on High Volume Roads: The analysis should include for each alternative under consideration (including the "no build" alternative):
End of Analysis.
Environmental Impact Statements
Projects that are not Type I:
Occasionally, an EIS is done for a project that is not Type I (e.g., a turning lane which brings traffic close to some critical environmental resource). However, these instances are unusual and must be dealt with on a case-by-case in accordance with NEPA.
Projects that are Type I:
For all Type I projects, noise analysis is required by both NEPA and 23 CFR 772. The analysis should include the following for each alternative under detailed study (including the "no build" alternative):
End of Analysis.
Design of the Project:
Effort is also needed during the design of the highway project. One of the best engineering practices is the use of multidisciplinary design teams. The incorporation of a highway traffic noise specialist, a landscape architect, a maintenance engineer, a highway safety engineer, a hydraulic engineer, and a structural engineer should help produce noise mitigation that is functional, practical and aesthetically pleasing.
PS&E Review:
When a highway project is being reviewed by the FHWA Division Office, the environmental document should be used to check for noise mitigation required on the project. Either the CE determination, the FONSI, or the EIS Record of Decision (ROD) should be reviewed to determine the suggested location of noise barriers that have been determined to be reasonable and feasible. Project files should clearly document the reasons why any noise mitigation listed as likely to be implemented in the environmental document has been found not to be reasonable and feasible during the design process.
Introduction
The procedures and requirements contained in 23 CFR 772 constitute the noise standards mandated by 23 U.S.C. 109(i). All applicable Federal-aid highway projects must conform to these standards. 23 CFR 772 specifically applies to any project defined as a Type I project--a proposed Federal or Federal-aid highway project for the construction of a highway on new location or the physical alteration of an existing highway which significantly changes either the horizontal or vertical alignment or increases the number of through-traffic lanes. This discussion is meant to address the FHWA requirements for highway traffic noise analyses related to Federal-aid highway projects which increase the number of through-traffic lanes (hereafter referred to as lane addition projects).
Environmental Processing
If a project is not a Type I project as defined by 23 CFR 772, a noise analysis is not required except in the extremely rare incidence in which the project itself is expected to create a noise impact. Such projects must be dealt with on a case by case basis in accordance with NEPA. The addition of a through-traffic lane is specifically defined as a Type I project and must be analyzed as discussed below. A noise analysis must be done for Type I projects. This analysis may range from a simple screening process utilizing a nomograph to the use of computer software depending on the complexity of the project.
If noise impacts as defined by 23 CFR 772 are not identified, no further analysis is necessary regardless of whether the project is advanced as a CE, EA/FONSI, or an EIS. However, if noise impacts are identified, additional analysis must be done to determine the significance of the impacts. This determination of significance should be based on consideration of the context and intensity of the impacts as discussed in the Council on Environmental Quality (CEQ) Regulation (40 CFR, Part 1508.27). In analyzing highway traffic noise impacts, context should consider the extent of the noise impact. Is the impact on an isolated residence? If noise impacts occur for 50 people, is it in a village with a population of 100, in a town of 5,000, or in a city of 50,000? Intensity should consider the noise levels associated with the impact. Are the predicted absolute noise levels 60 dBA, 70 dBA, or 80 dBA? Is the predicted increase over existing noise levels only 1 or 2 dBA, or is it 10 dBA, 20 dBA, or 30 dBA?
Highway traffic noise is only one area to be considered in the environmental processing of a proposed highway project. The significance of identified traffic noise impacts should be used to help decide whether to process the project with a CE, a Finding of No Significant Impact (FONSI), or an EIS. If project impacts, including noise impacts, are deemed not to be significant, the project may be processed with a CE or a FONSI. However, if noise impacts are determined to be significant, the project must be processed with an EIS. 23 CFR 772 states that a traffic noise impact occurs when predicted traffic noise levels substantially exceed the existing noise levels. In documenting the increase in existing noise levels in the environmental processing of a project, care should be taken to avoid the use of the phrase "significant increase" due to the CEQ definition of "significance." The phrase "substantial increase" should always be used to address this type of potential traffic noise impact.
Noise Impacts
Analysis for lane addition projects must follow the procedures outlined in 23 CFR 772. These procedures require: (1) identification of existing activities, (2) determination of existing noise levels, (3) prediction of future traffic noise levels, and (4) determination of traffic noise impacts. Traffic noise impacts occur when the future traffic noise levels approach or exceed the NAC contained in 23 CFR 772 or when the future traffic noise levels substantially exceed the existing noise levels. For lane addition projects, the definition of traffic noise impact in 23 CFR 772 applies to the total noise level of the facility being expanded rather than to just the incremental noise level increase caused by the added lanes.
Many lane addition projects will result in a small, imperceptible increase of future noise levels over existing noise levels (1-3 dBA). This is almost always the case if the lanes are added in the median of an existing multi-lane divided highway or on the outside of an existing highway which is at grade or on fill. A slightly larger, but still small, increase in noise may occur if lanes are added on the outside of an existing highway in cut where additional cutting of sideslopes must be done thereby reducing some of the noise shielding provided by the cut. An exception to this may occur when two-lane highways are expanded to four or more lanes since this modification will substantially increase the traffic capacity of the facility and potentially move the noise source closer to a receiver. Projects of this last type, therefore, may substantially increase the future traffic noise levels over the existing noise levels.
Most traffic noise impacts occur on a lane addition project when future total noise levels near the expanded facility approach or exceed the NAC. In most urban locations where lanes need to be added, existing noise levels along the facility already approach or exceed the NAC. Thus, receptors near the facility are experiencing a traffic noise impact even before the new lanes are added and the traffic capacity is increased. Obviously, in this situation, a traffic noise impact will almost certainly occur in the analysis of the lane addition project even though the added lanes do not increase (or substantially increase) future traffic noise levels over the existing noise levels or the future traffic noise levels for the "no-build" alternative. Nevertheless, as defined in 23 CFR 772, a traffic noise impact occurs in this situation, and it must be identified.
From the above discussion, it can be seen that the incremental noise increase caused by the added lanes is usually not the governing factor for identifying a traffic noise impact on a lane addition project. Rather, it is the total noise level for the final facility that usually determines whether or not a traffic noise impact will be identified. This is not to say that the incremental noise increase from the added lanes is unimportant. It in fact is one of the factors that should be considered in determining whether or not a proposed abatement measure is reasonable (see the discussion following in the noise abatement section). For this reason, the traffic noise analysis should include a comparison between the future traffic noise levels for the expanded facility and the "no-build" alternative for the design year.
Noise Abatement
23 CFR 772 also requires that noise abatement measures be considered if a traffic noise impact is identified for a Type I project. Abatement consideration should weigh the abatement benefits, costs, and overall social, economic, and environmental effects. Abatement measures which are found to be reasonable and feasible must be incorporated in the project. If a traffic noise impact is identified for a lane addition project as discussed above, abatement must be considered as a part of the project being proposed. Such consideration cannot be delayed to a future date or be made part of a Type II program--an entirely voluntary State program for addressing traffic noise impacts along existing highways.
When considering noise abatement measures, every reasonable effort should be made to obtain a substantial noise reduction (defined by typical State practice to be a reduction of 5 dBA or more). All the abatement measures listed in 23 CFR 772 should be considered. However, for a lane addition project, measures such as traffic management, alteration of alignment, or purchase of land for use as a buffer zone usually either do not provide a substantial noise reduction or are found to be not reasonable and feasible due to cost, right-of-way requirements, or project purpose. Thus, noise barriers are the abatement measure most often associated with the concept of noise abatement on lane addition projects. The consideration of noise abatement must result in a determination of reasonableness and feasibility.
The final determination of reasonableness of noise abatement should be made only after a careful and thorough consideration of a wide range of criteria. The importance that a State places on any one criterion can vary depending on the specific circumstances for a particular project. For example, on a lane addition project where (1) there is little if any difference between the future traffic noise levels for the expanded facility and the future traffic noise levels for the "no-build" alternative, and (2) a majority of the development along the highway occurred after initial construction of the highway, the State may decide that these criteria are very important in determining the reasonableness of noise abatement. While the remaining criteria for determining reasonableness (e.g, noise reduction, cost, community support, etc.) under this scenario may individually be less important, they should still be evaluated since, on balance, they may offset the negative aspects of the first two criteria. On another project, for example, where a majority of the adjacent development occurred prior to initial construction of the highway, other criteria, such as noise reduction, cost, etc., may take on added importance.
Summary
A proposed Federal-aid highway project which increases the number of through-traffic lanes is defined by 23 CFR 772 as a Type I project. A noise analysis must be done for this type of project to identify any potential noise impacts as defined by 23 CFR 772. The level of analysis required can vary based upon the anticipated noise impacts associated with the project. If noise impacts are identified, the significance of these impacts must be determined. The project must be processed with a CE, a FONSI, or an EIS, as appropriate, based on the significance of noise impacts as well as other environmental impacts. Furthermore, if noise impacts are identified, noise abatement measures must be considered and if they are found to be reasonable and feasible, they must be incorporated into the project. The determination of reasonableness and feasibility should be based on a careful and thorough consideration of many factors and not on any one criterion.
These types of projects must be classified as Type I projects as defined by 23 CFR 772. The addition of interchanges/ramps/auxiliary lanes/ truck climbing lanes, etc. to existing highways can certainly create significant changes in alignment and/or add through-traffic lanes, and SHAs have a responsibility to ensure that all reasonable and feasible mitigation measures are incorporated into the projects to minimize noise impacts and enhance the surrounding environment to the extent practicable.
Similarly, the addition of high-occupancy vehicle (HOV) lanes to highways are also Type I projects, whether added in the median or on the outside of the existing highway, since they add through-traffic lanes. Traffic noise analysis is required for both sides of the highway, even when HOV lanes are only being added on one side of the highway. Frequently, HOV projects cause little or no change in the existing or future noise environment. However, traffic noise impacts occur since existing noise levels already approach or exceed FHWA noise abatement criteria. In these instances, abatement must be considered and implemented if found to be reasonable and feasible.
Noise analyses are only required for Federal-aid highway projects that are Type I projects or that create a noise impact as a result of the project. No noise analysis is required for widenings of less than one through-traffic lane width, unless there is a significant change in either the horizontal or vertical alignment or the project itself is expected to create a noise impact. Noise analyses are required in all instances where a through-traffic lane is added to a highway. Two different laws control the evaluation of highway traffic noise impacts: NEPA and the Federal-aid Highway Act of l970.
The FHWA noise regulations require noise analyses for all Type I projects, defined as projects that involve construction of a highway on new location or the physical alteration of an existing highway which significantly changes either the horizontal or vertical alignment or increases the number of through-traffic lanes. Such analyses must be done to meet FHWA and Title 23 requirements.
If a project does not meet the definition of a Type I project, no noise analysis is required, except for the extremely rare incidence in which the project itself is expected to create a noise impact. A traffic noise impact occurs when the predicted traffic noise levels approach or exceed FHWA's NAC or when the predicted traffic noise levels substantially exceed the existing noise levels. If the project itself is expected to create a noise impact (i.e., the predicted no-build noise levels do not approach or exceed the NAC and the predicted build noise levels either approach or exceed the NAC or substantially exceed the no-build noise levels), a noise analysis must be done to meet the requirements of NEPA.
NOTE:A commonly held viewpoint is that noise analyses should not be necessary for projects that will not change the noise environment - that is, not change the noise levels from those that exist today or not change the noise levels from those that will exist in the future if no project is implemented (e.g., 70 dBA existing and 70 dBA in the future, with or without the project). However, the FHWA noise regulations were developed to specifically address the improvement of situations where existing noise levels are already high (i.e., a traffic noise impact already exists). Thus, noise analyses are required for all Type I projects, even when there is no change in the surrounding noise environment. A parallel can be drawn with highway projects where substandard safety features are upgraded or improved even though the overall goal of the project is not specifically safety-related.
Introduction
It is FHWA's policy to ensure that all reasonable and feasible mitigation measures are incorporated into projects to minimize noise impacts and enhance the surrounding noise environment to the extent practicable. This commitment to minimize noise impacts and enhance the noise environment must be fulfilled through prudent application of FHWA's noise regulations - 23 CFR 772.
23 CFR 772 requires that ..."before adoption of a final environmental impact statement or finding of no significant impact, the highway agency shall identify noise abatement measures which are reasonable and feasible and which are likely to be incorporated in the project".... This is frequently the most difficult part of the traffic noise analysis for a proposed highway project. SHA decisionmakers often ask, "What does the phrase reasonable and feasible mean? How should we determine reasonableness and feasibility?" The following discussion is intended to assist in answering these questions.
Background:
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.). Reasonableness is a more subjective criterion than feasibility. It implies that common sense and good judgement were applied in arriving at a decision.
Reasonableness should be based on a number of factors -- not just one criterion.
A determination of reasonableness for abatement measures should include consideration of items such as the following:
NOTE: Safety, maintenance, and drainage concerns for noise abatement measures should be addressed during preliminary and final project design. These issues should be part of the feasibility determination and can usually be resolved through use of good design practices.
The above listing is not intended to be all encompassing. Rather, it is intended to indicate some of the factors that should be considered in determining the reasonableness of proposed noise abatement measures. Each SHA should develop and utilize its own criteria for determining reasonableness. Reasonableness should be determined through a rational, open process which utilizes a method flexible enough to meet individual situations yet firm enough to be uniformly and consistently applied. The methods used to determine reasonableness should be appropriately influenced by public perception of the problem of highway traffic noise. States where the public is more reactive to the problem of traffic noise should have a more identifiable and comprehensive approach to determining reasonableness. The main point to remember is that the final determination of reasonableness of noise abatement should be made only after a careful and thorough consideration of a wide range of criteria. Lastly, consideration of the criteria should not be rigid -- that is, the specific circumstances for a particular project should be regarded in applying the criteria.
The previous discussion has been general in its approach. The following discussion is meant to be specific and indicate how the criteria or factors should be considered.
The most commonly used noise abatement measure is the construction of a noise barrier. Therefore, the remainder of this discussion will address the consideration of highway traffic noise barriers and discuss how specific factors should be applied in noise barrier decisionmaking. This discussion should be used as a guide by States in establishing criteria and procedures for noise abatement decisionmaking.
Abatement Decisionmaking:
A highway traffic noise abatement decisionmaker should answer the following questions:
Why are criteria and procedures needed?
Good program management supports the need for highway traffic noise abatement decisionmaking criteria and procedures. The decision on whether or not to build a noise barrier must not be arbitrary or capricious, and its reasoning should be available and supportable, particularly if the answer is "no" and the affected residents want a barrier to be constructed. The decision must be based upon consistent, uniform application of established criteria and procedures. Written policies should be established.
What criteria should be used?
The criteria used for determining reasonableness and feasibility should indicate a broad consideration of conditions that apply in a given location. The criteria should allow identification of the overall benefits, as well as the overall adverse social, economic, and environmental effects, of the noise abatement. Remembering the previous listing of possible criteria, the following criteria might be chosen:
How should these criteria be used in making a decision?
Quantification of each of the criteria allow their use in making a more objective decision. This should allow the decision to be more supportable and more easily explained. The criteria should be responsive to the need to provide noise abatement. Conversely, the effects on overall cost to the highway program should be considered when quantifying the criteria. Consequently, the criteria need to be prudently developed. This paper later presents an example of quantification of abatement criteria.
Should criteria and procedures allow "room for judgement?"
Flexibility is an important element of good noise abatement decisionmaking criteria and procedures. The criteria and procedures should be objective enough to be quantifiable, but they should also be flexible enough to allow the decisionmaker to make meaningful judgements on a case-by-case basis for special circumstances.
The criteria and procedures should permit consideration of "gray areas" and should not always be rigidly applied. There may be instances where abatement should be found to be reasonable and feasible even though it is found to fall outside some of the established criteria and procedures, e.g., it costs more than the reasonable cost index (including it protects a fewer number of people), absolute traffic noise levels are lower but increases in existing noise levels are great, changes in noise levels are small but the absolute levels are high, or increases in noise levels since initial development occurred are great.
This discussion will present an example of how a State might quantify the criteria and procedures used in abatement decisionmaking. The definitions and numerical values shown are samples of choices a State might make and should not be construed as FHWA recommendations. Each State should determine its own definitions and values. FHWA comments are provided throughout the example.
EXAMPLE: (The following text, without FHWA comments, is an example of how a State might write criteria and procedures)
Feasibility (example of State policy):
Feasibility deals with engineering considerations - that is, can a substantial noise reduction be achieved given the conditions of a specific location. Is the ability to achieve noise reduction limited by: (1) topography; (2) access requirements for driveways, ramps, etc.; (3) the presence of local cross streets; or (4) other noise sources in the area, such as aircraft overflights? All these considerations affect the ability of noise barriers to achieve an actual noise reduction.
It is State policy that construction of a noise barrier is NOT FEASIBLE if a 5 dBA noise reduction cannot be achieved.
FHWA COMMENT 1: A noise barrier which just breaks the line-of-sight from the source to the receiver will achieve a 5 dBA noise reduction. A 5 dBA reduction in noise is readily perceptible. Noise barriers which do not achieve at least a 5 dBA reduction in noise are not prudent expenditures of public funds and, therefore, should not be built. When a noise barrier is considered, every reasonable effort should be made to obtain a substantial noise reduction - normally in the range of 5-10 dBA.
Reasonableness (example of State policy):
Reasonableness is a more subjective criterion than feasibility. It implies that common sense and good judgement have been applied in arriving at a decision. Reasonableness should be based on a number of factors, with regard for all of the individual, specific circumstances of a particular project.
It is State policy that the final determination of reasonableness will be made only after a careful and thorough consideration of a wide range of criteria. However, noise barriers will definitely not be built if most affected residents do not want them.
FHWA COMMENT 2: In accordance with FHWA noise regulations, the views of the impacted residents should be a major consideration in determining the reasonableness of abatement. Barriers should definitely not be built if most of the impacted residents do not want them.
The following criteria will normally be used to determine the reasonableness of a noise barrier (NOTE: "Yes" means construction of a barrier is reasonable; "no" means construction of a barrier is not reasonable; "high" and "low" indicate differences in importance):
<$20,000/residence = HIGH YES; $20-25,000/residence = LOW YES; $25-30,000/residence = LOW NO; >$30,000/residence = HIGH NO
FHWA COMMENT 3: Several points that should be remembered regarding barrier cost are the following:
>80% = HIGH YES; 50-80% = LOW YES; 40-50% = LOW NO; <40% = HIGH NO
FHWA COMMENT 4: The views of the impacted residents should be a major consideration in reaching a decision on abatement measures to be provided. As noted previously, barriers will definitely not be built if most affected residents do not want them. There are, however, no easy methods to determine residents' views or to arrive at a conclusion regarding residents' desires. Commercial establishments' desire for visibility should be considered, and mixed commercial and residential development should be accommodated. Some SHAs 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 residents' wishes.
>80% = HIGH YES; 50-80% = LOW YES; 30-50% = LOW NO; <30% = HIGH NO
FHWA COMMENT 5: The date of development should be an important part of the determination of reasonableness. It is appropriate to give more consideration to development that predated initial highway construction, whose residents have experienced the greatest traffic noise impacts over the longest period of time. More SHAs should use this criterion in determining reasonableness.
>80% = HIGH YES; 50-80% = LOW YES; 30-50% = LOW NO; <30% = HIGH NO
FHWA COMMENT 6: It is acceptable and desirable to give more consideration to residents who have experienced traffic noise impacts for a longer period of time.
>70 dBA = HIGH YES; 65-70 dBA = LOW YES; 60-65 dBA = LOW NO; <60 dBA = HIGH NO
FHWA COMMENT 7: It is acceptable to give more consideration to areas with higher absolute traffic noise levels. Absolute noise levels typically found along highways, 60-75 dBA, are usually deemed undesirable and cause complaints from adjacent residents. Normally, the higher the levels, the greater the number of complaints.
>10 dBA = HIGH YES; 5-10 dBA = LOW YES; 3-5 dBA = LOW NO; <3 dBA = HIGH NO
FHWA COMMENT 8: It is acceptable to give more consideration to areas with larger increases over existing noise levels. This gives greater consideration to projects for highways on new location and major reconstruction than it does to projects of smaller magnitude along existing highways.
>5 dBA = HIGH YES; 3-5 dBA = LOW YES; <3 dBA = HIGH NO
FHWA COMMENT 9: It is acceptable to give more consideration to areas where larger changes in traffic noise levels are expected to occur if the project is constructed than if it is not. Again, this gives greater consideration to highway projects with major changes in roadway location or design.
FHWA COMMENT 10: SHAs sometimes give less consideration for abatement to areas of mixed zoning or development and to areas where existing zoning is expected to change to a less noise-sensitive use. SHAs also sometimes give more consideration to areas that can demonstrate that efforts have been made at the local level to prevent incompatible growth and development along highways. These additional considerations are both acceptable and desirable.
Now that criteria for reasonableness and feasibility have been established, the following checklist can be used:
NOISE BARRIERS FOR PROJECT:
| Feasibility | ||||
|---|---|---|---|---|
| Yes | No | |||
| Can a 5 dBA noise reduction be achieved? | ____ | ____ | ||
| Reasonableness | ||||
| REASONABLENESS FACTORS | YES | NO | ||
| High | Low | Low | High | |
| 1. Cost/residence | ____ | ____ | ____ | ____ |
| 2. Residents' desires | ____ | ____ | ____ | ____ |
| 3. Development vs. highway timing | ____ | ____ | ____ | ____ |
| 4. Development existence | ____ | ____ | ____ | ____ |
| 5. Build level 65 dBA | ____ | ____ | ____ | ____ |
| 6. Build level 5 dBA greater than existing | ____ | ____ | ____ | ____ |
| 7. Build level 3 dBA greater than no-build | ____ | ____ | ____ | ____ |
| 8. ADDITIONAL CONSIDERATIONS: | ||||
| DECISION | ||||
| Are barriers feasible? | Yes____ | No____ | ||
| Are barriers reasonable? | Yes____ | No____ | ||
REASONS FOR DECISION:
What data are needed to complete the checklist?
To complete the checklist, do the following:
COMMENT 11: As previously stated, residences must include all dwelling units, e.g., owner-occupied, rental units, mobile homes, etc. When counting residences to determine reasonableness, all "benefitted" residences must be included, regardless of whether or not they were identified as impacted (each unit in a multifamily building must be counted as one residence in determining both impacts and benefits).
COMMENT 12: Noise barriers should be designed to achieve a substantial noise reduction. SHAs normally define substantial noise reduction in the range from 5-10 dBA. A decision must also be made to provide this reduction either at a location in the middle of the barrier or at a location near the end of the barrier. NOTE: Remember the rules-ofthumb for trial barrier height and length. Height: 5 dBA for the height to break the line-of-sight between the source and receiver plus 1.5 dBA for each 1 meter in height thereafter. Length: 8 times the distance from the barrier to the receiver.
COMMENT 13: Most SHAs use a value in the range from $160-215/sqmt to estimate barrier cost, for posts and barrier material in place.
The examples in this paper (1) consider residences that receive at least a 3 dBA noise level reduction to be "benefitted," (2) design for an 8 dBA barrier insertion loss (must have at least 5 dBA), and (3) use $160/sqmt to estimate barrier cost.
Project Examples:
The following examples are meant to illustrate specific applications of the previously discussed reasonableness and feasibility criteria. It should be noted that inclusion of a larger number of criteria in procedures allows for greater flexibility in abatement decisionmaking.
EXAMPLE 1:
The proposed project will widen an existing 4-lane freeway to 8 lanes. Ten single -family homes are impacted in a stable, residential neighborhood. Seven of the homes were constructed prior to 1955; the other three were built between 1970 and 1983. Typical noise levels for residences in rural areas, such as this was prior to 1955, are 45-50dBA. A 2-lane highway was originally constructed in the area in 1965 and was later widened to 4 lanes in 1975. The existing noise level in the area is 66 dBA. A future build noise level of 68 dBA and a future no-build noise level of 68 dBA are predicted for the design year (2011). A 4¼ meter high noise barrier will reduce noise for the ten homes by 8 dBA and will cost $290,000. All the residents want a noise barrier to be constructed. Highway traffic noise is not currently considered in local land use planning.
See the checklist for Example 1 below.
Example 1 illustrates a typical widening of an existing freeway. Existing noise levels change very little, and there is no difference between future build and no-build noise levels. The barrier cost per residence exceeds the established cost index. SHAs frequently use these factors alone to support a "no" decision for noise barriers. However, often the affected areas are stable, well established neighborhoods where traffic noise has increased noise levels substantially over time, as in this example. These factors, along with the slight exceedance of the cost index, could result in a "yes" decision. This example illustrates a flexible application of reasonableness criteria for a "gray area," as shown by the checklist.
EXAMPLE 2:
The proposed project will widen an existing 2-lane highway to 4 lanes. Ten single-family homes are impacted in area with mixed residential and commercial zoning, which has not changed in the last two decades. Two of the homes were constructed in the 1920's, two between 1950 and 1960, and six since 1987. A gravel roadway was originally paved in 1948, and several reconstructions of the paved highway have occurred since then. The existing noise level in the area is 69 dBA. A future build noise level of 73 dBA and a future no-build noise level of 71 dBA are predicted for the design year (2011). An 3½ meter high noise barrier will reduce noise for the ten homes by 6 dBA and will cost $240,000. All the residents want a noise barrier to be constructed.
See the checklist for Example 2 below.
Example 2 illustrates another "gray area" using the checklist. The affected residents want a barrier, the cost is reasonable, and the future build noise level is 73 dBA. Many SHAs would make a decision of "yes" for a noise barrier, and this is acceptable. However, since most development in the area is recent, the difference between future build and no-build noise levels is slight, and the area has mixed zoning, the answer could also be "no." Again, this example illustrates flexibility in the decisionmaking process.
EXAMPLE 3:
The proposed project will construct a 4-lane highway on new location. Eleven single-family homes are impacted in a residential neighborhood. All of the homes were built in the 1960's except one that has been constructed in the last year. The existing noise level in the area is 45 dBA. A future build noise level of 72 dBA and a future no-build noise level of 45 dBA are predicted for the design year (2011). A 3 meter high noise barrier will reduce noise for ten of the homes by 7 dBA (the eleventh home will receive 2 dBA reduction) and will cost $385,000. Residents in seven of the homes want a barrier; residents in the other four do not.
See the checklist for Example 3 below.
Example 3 illustrates abatement decisionmaking for a highway on new location. The project has a large increase in existing noise levels, as well as a large difference between future build and no-build noise levels. Noise levels will be almost eight times as loud as they are now - there will be a big change in the noise environment. Most SHAs would say the answer for abatement is "no," solely because the barrier cost exceeds the reasonable cost index by 50%. However, while being important, cost should not always be the overriding factor in abatement decisionmaking. The extenuating circumstances for this project clearly point to strong consideration of a "yes" answer.
EXAMPLE 1 see discussion above:
| Yes | No | |
| Can a 5 dBA noise reduction be achieved? | __X__ | ____ |
| REASONABLENESS FACTORS | YES | NO | ||
| High | Low | Low | High | |
| 1. Cost/residence | ____ | ____ | __X__ | ____ |
| 2. Residents' desires | __X__ | ____ | ____ | ____ |
| 3. Development vs. highway timing |
____ | __X__ | ____ | ____ |
| 4. Development existence | __X__ | ____ | ____ | ____ |
| 5. Build level 65 dBA | ____ | __X__ | ____ | ____ |
| 6. Build level 5 dBA greater than existing |
____ | ____ | ____ | __X__ |
| 7. Build level 3 dBA greater than no-build |
____ | ____ | ____ | __X__ |
| 8. ADDITIONAL CONSIDERATIONS: | Traffic noise not currently considered in local land use planning activities. 7 of 10 homes built before highway. Noise in area has increased by 20 dBA over time. Area will have gone from no highway to an 8- lane freeway. | |||
| Are barriers feasible? | Yes__X__ | No____ |
| Are barriers reasonable? | Yes__X__ | No____ |
REASONS FOR DECISION: More importance given to the residents' desire for a barrier, the existence of 70 % of the homes prior to the highway, a 20 dBA increase in noise levels over time, and going from no highway to an 8-lane freeway.
EXAMPLE 2: (see discussion above)
| Yes | No | |
| Can a 5 dBA noise reduction be achieved? | __X__ | ____ |
| REASONABLENESS FACTORS | YES | NO | ||
| High | Low | Low | High | |
| 1. Cost/residence | ____ | __X__ | ____ | ____ |
| 2. Residents' desires | __X__ | ____ | ____ | ____ |
| 3. Development vs. highway timing | ____ | ____ | ____ | __X__ |
| 4. Development existence | ____ | ____ | __X__ | ____ |
| 5. Build level 65 dBA | __X__ | ____ | ____ | ____ |
| 6. Build level 5 dBA greater than existing | ____ | ____ | __X__ | ____ |
| 7. Build level 3 dBA greater than no-build | ____ | ____ | ____ | __X__ |
| 8. ADDITIONAL CONSIDERATIONS: | Area has mixed commercial and residential zoning. | |||
| Are barriers feasible? | Yes__X__ | No____ |
| Are barriers reasonable? | Yes____ | No__X__ |
REASONS FOR DECISION: More importance given to the recent development in the area (6 homes since 1987), only a 2 dBA increase in build over no-build noise levels, and mixed zoning in the area.
EXAMPLE 3: (see discussion above)
| Yes | No | |
| Can a 5 dBA noise reduction be achieved? | __X__ | ____ |
| REASONABLENESS FACTORS | YES | NO | ||
| High | Low | Low | High | |
| 1. Cost/residence | ____ | ____ | ____ | __X__ |
| 2. Residents' desires | ____ | __X__ | ____ | ____ |
| 3. Development vs. highway timing | __X__ | ____ | ____ | ____ |
| 4. Development existence | __X__ | ____ | ____ | ____ |
| 5. Build level 65 dBA | __X__ | ____ | ____ | ____ |
| 6. Build level 5 dBA greater than existing | __X__ | ____ | ____ | ____ |
| 7. Build level 3 dBA greater than no-build | __X__ | ____ | ____ | ____ |
| 8. ADDITIONAL CONSIDERATIONS: | This will be a 4-lane highway on new location in an established neighborhood. Noise levels will increase by 27 dBA over existing levels. The future build noise levels will be 27 dBA greater than the future no-build levels. Most residents want a barrier. | |||
| Are barriers feasible? | Yes__X__ | No____ |
| Are barriers reasonable? | Yes__X__ | No____ |
REASONS FOR DECISION: More importance given to a 4-lane highway on new location, a 27 dBA increase over existing noise levels, a 27 dBA increase in build over no-build noise levels, and most residents' desire for a barrier.
Summary:
One of the most difficult parts of traffic noise analysis is determining the reasonableness and feasibility of abatement. FHWA has previously issued guidance containing a general discussion on the determination of reasonableness and feasibility. The guidance recommended consideration of a wide range of criteria and listed possible criteria. However, the guidance did not address the details of how to consider the criteria. This discussion has addressed the details of determining the reasonableness and feasibility of noise abatement. Specific examples have been shown. The date that development occurred along highways should be an important criterion in determining the reasonableness of noise abatement.
Good program management supports the need for highway traffic noise abatement decisionmaking policies. Abatement decisionmaking must not be arbitrary and capricious. The reasoning for decisions should be available and supportable. Objective, quantifiable decisionmaking criteria can aid in promoting better public understanding and acceptance of decisions.
Inclusion of a wide range of reasonableness criteria provides greater flexibility in abatement decisionmaking. Such flexibility is essential to allow for consideration of special circumstances in individual cases. Policies should not be rigidly applied.
Purpose
Highway traffic noise is a major contributor to overall transportation noise. It emanates from newly constructed highways and from highways that are already in place. People often ask what can be done to deal with highway traffic noise problems along existing highways. The following discussion outlines measures that can be taken in the Federal-aid highway program to abate existing traffic noise problems. 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 included a provision which required the FHWA to develop 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 traffic noise on previously constructed highways. As a result, FHWA's 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 noise abatement along existing highways.
FHWA Noise Regulations
The FHWA noise regulations indicate that Type II projects will not normally be approved for those activities and land uses which come into existence after May 14, 1976, because the FHWA publicly stated at that time that local governments must help control highway traffic noise impacts through noise compatible land use planning and zoning. The intent of this provision is to establish a date to determine Federal-aid eligibility for Type II projects based upon time of land development. The exact date for eligibility is not specifically defined in the regulation. Each SHA and accompanying FHWA Division Office is encouraged to establish a mutually acceptable specific date to determine Federal-aid eligibility for Type II projects and then consistently apply this date to all Type II abatement locations. One possible date for consideration that has evolved is the date of issuance of a building permit. Other dates used by States to determine eligibility include the date of recording of the plat plan and the date of actual construction. While there may be a wide variation in time for the dates that are used, any of the dates are acceptable to determine the existence of development, if they are agreeable to both the SHA and the FHWA Division Office and are consistently applied.
Noise abatement measures may be approved for activities and land uses that come into existence after May 14, 1976, provided that local authorities have taken measures to exercise land use control over the remaining undeveloped lands adjacent to highways in the local jurisdiction to prevent further development of incompatible activities. These measures may include any of the noise abatement measures contained in the FHWA publication, "The Audible Landscape."
An SHA voluntarily requesting Federal-aid participation for eligible Type II projects is required to perform a noise analysis of sufficient scope to: (1) identify that a traffic noise impact exists, (2) demonstrate that the proposed noise abatement measures will reduce the traffic noise impact, and (3) determine that the overall noise abatement benefits outweigh the overall adverse social, economic, and environmental effects and the costs of the 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 judgement 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 social, economic, and environmental benefits and disbenefits of the noise abatement measures.
Projects for Type II noise abatement may include the following 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. The construction of noise barriers is the mitigation measure most often associated with the concept of traffic noise abatement.
Type II Barrier States
Since the Type II noise program is optional, only 17 States have elected to participate in this program. The main reason for this is that Type II abatement projects must compete with all other construction needs of the States, and highway construction needs normally far exceed available funds. As of 1992, a listing of highway traffic noise barriers built by SHAs indicated that the 17 States constructed over 346 kilometers of Type II noise barriers at a cost of over $240 million in 1992 dollars. The following table summarizes the listing:
| State | Linear Length In Kilometers | Actual Cost (Millions) | Cost In 1992 Dollars (Millions) |
|---|---|---|---|
| California | 182.6 | $90.4 | $105.1 |
| Minnesota | 42.2 | 17.7 | 18.5 |
| Michigan | 28.6 | 16.2 | 18.5 |
| Maryland | 24.7 | 37.0 | 37.7 |
| Colorado | 21.7 | 4.9 | 5.4 |
| New York | 15.1 | 13.6 | 13.6 |
| Wisconsin | 10.4 | 11.6 | 11.8 |
| New Jersey | 6.9 | 11.4 | 11.5 |
| Connecticut | 5.1 | 2.1 | 2.8 |
| Oregon | 2.6 | 1.3 | 1.3 |
| Washington | 2.0 | 1.6 | 1.6 |
| Louisiana | 1.5 | 0.2 | 0.3 |
| Iowa | 1.1 | 0.4 | 0.5 |
| Georgia | 0.9 | 0.5 | 0.5 |
| Massachusetts | 0.4 | 0.7 | 0.8 |
| Florida | 0.3 | 0.1 | 0.1 |
| Ohio | 0.3 | 0.2 | 0.2 |
| _____ | _____ | _____ | |
| Total | 346.4 | $209.9 | $240.0 |
Priority Rating Systems
General Discussion
The SHAs have great flexibility in developing and structuring a Type II program. One program management tool that SHAs have found to be essential is a priority rating system. Such a system enables them to uniformly and equitably handle traffic noise impacts and complaints along existing highways while providing a rational basis for an important part of a very tough decisionmaking process. The FHWA strongly encourages the development and use of a priority rating system to indicate the relative priority of individual projects with other potential Type II projects in a State. Factors that may be considered include:
These factors are not meant to be all inclusive, but rather are meant to indicate that implementation of a Type II program should be based upon a wide range of varying considerations. A number of States with existing Type II programs have already developed specific methodologies for determining relative priorities among projects. California, which has built over 50% of existing Type II barriers, uses the following formula:
California: Priority Index =
(Achievable Reduction (db) × (Noise Level - 67) × Number of Living Units) ÷ (Cost ($1,000))
Michigan uses a similar formula:
Michigan: Priority Factor =
(Achievable Reduction × Number of Living Units Protected) ÷ (Barrier Cost)
A more complete discussion of the above formulas is included in the next section of this discussion. Connecticut and New Jersey have procedures that are representative of more complex priority rating systems. Whether relatively simple or more complex, the FHWA strongly encourages the development and use of procedures such as these for effective management of a Type II program.
Selected State Examples
Three States have been selected for a more detailed discussion of their priority rating systems. These States, which include California, Michigan, and Massachusetts have been selected because of their range of experience levels with the Type II noise program. California, as mentioned above, leads the country in the construction of Type II projects. Michigan also has many years of experience with a Type II noise program, although its program is considerably smaller than California's program. Massachusetts on the other hand is a good example of a State that has just established a Type II noise program.
California
NOTE:This California information was furnished in 1988.
The California Department of Transportation (CALTRANS) initiated its Type II noise program, which it refers to as the Community Noise Abatement Program, in 1974. This program provides for the construction of noise barriers adjacent to residential areas where: (1) the noise from an adjacent existing freeway exceeds the FHWA noise abatement criteria for residential land use (67 dBA Leq), and (2) the residential area existed prior to the construction of the adjacent freeway or prior to an alteration of the freeway which caused a substantial increase in noise levels (3 dBA).
In 1978, the State legislature passed a provision that required CALTRANS to develop and implement a priority ranking system for the installation of noise barriers along existing freeways in the California Freeway and Expressway System. In addition, this legislation required CALTRANS, when all freeways had been ranked in priority order and consistent with available funding, to recommend a program of construction of noise attenuation barriers beginning with the highest priority. Although this legislation required CALTRANS to establish a priority ranking of projects, it did not require a commitment of funds to the program, leaving that decision to the California Transportation Commission.
As a result, CALTRANS inventoried all the residential areas meeting the above noise level exposure and time of development criteria, and then segregated them into logical project limits. The individual projects were then assigned a priority index in accordance with the following formula:
PI = (AR × (NL − 67) × LU) ÷ (COST ($1,000))
Where:
PI = Priority Index
AR = Achievable Reduction*
NL = Measured Noise Levels, Leq
LU = Number of Living Units
* In order to be considered cost effective, the achievable reduction must equal or exceed 5 dBA.
Although CALTRANS' Type II Noise Program was initiated in 1974, it wasn't until the 1976-77 fiscal year that any substantial amount of funds were devoted to this program because of funding constraints. Current cost of this program is averaging about $1.7 million per kilometer, including the cost of landscaping and irrigation system modifications, incidental paving and the incorporation of safety shaped barriers where needed.
CALTRANS' current inventory of unconstructed projects shows a need of approximately $190 million (in 1987 dollars) for Type II projects. The current State Program includes $12.2 million for the Type II program for the 5 year period from the 1987-88 thru 1991-92 Fiscal Years, or just over $2.4 million annually. This is a substantial reduction compared to prior years when as much as $20 million annually was budgeted to the Type II program in California.
A unique feature of the CALTRANS Type II program is that State legislation allows cities or counties to construct noise barriers (to State standards) which are included in the State's Program, ahead of the time that such barriers reach a high enough priority for State funding. When the funding priority is reached, CALTRANS is then required to reimburse the city or county, without interest, for the cost of such barrier constructed. To date, three Cities have constructed noise barriers along State Highways under this provision of the Code.
CALTRANS generally initiates Type II projects by holding public informational type meetings with the residents affected. These meetings are held to explain the proposed project, such as wall locations, proposed wall heights, attenuation expected, and other potential benefits and disadvantages. A primary purpose of these meetings is to receive public comments on the perception of the project impact on the community and the people's feelings on proceeding with the project. Generally, CALTRANS' program has been accepted by the public and CALTRANS has been encouraged to construct the projects as soon as possible.
Michigan
The Michigan Department of Transportation (MDOT) constructed its first Type II noise barrier in 1973 as a result of public complaints and a realization that there were existing highway traffic noise problems. The decision to build the barrier was facilitated by the facts that sufficient right-of-way for a barrier already existed and that Federal-aid was available to participate in the cost. The MDOT had confidence that necessary resources to administer a Type II abatement program could be found if the program became long term.
Subsequent to construction of the first noise barrier, the MDOT was able to identify approximately 1100 potential Type II abatement sites along 560 kilometers of limited access highways using a staff of three persons for four months. The staff completed the inventory by visually identifying areas with potential traffic noise problems and then calculating noise levels using existing traffic and site data.
The MDOT has used several different formulas to prioritize Type II projects in the past. Experience has led to current use of the following formula:
Priority Factor = (Achievable Reduction × Number of Living Units Protected) ÷ (Barrier Cost)
Where:
Achievable Reduction - is the reduction at the first row of residences, halfway between the residence and the right-of-way line, based on a measurement of existing noise levels and calculations of the expected attenuation from a barrier of reasonable height.
Number of Living Units Protected - is the number of living units whose noise level will be reduced to or below 67 dBA Leq(h) after the barrier is built, usually including units constructed after the freeway as well as units constructed before the freeway. The MDOT reserves the right to exclude or lessen the consideration of units constructed after the freeway if they comprise the majority of protected units.
Barrier Cost - is a value of $820 per linear meter multiplied by the MDOT percentage share of a specific project. State law requires municipal governments of over 35,000 population to contribute between 1 and 1½% of the cost of noise barriers (as well as for bridges, pavement, etc.). The MDOT also requires the local government to pay the entire cost of highway project items deemed to be "optional" by the MDOT (this has not yet been applied to a Type II project).
The MDOT has guidelines containing procedures for public involvement in the Type II program. While the procedures outline formal contacts, meetings, presentations, and a public hearing, it has been found that performing all of the procedures is often not necessary. The MDOT has constructed many Type I noise barriers (barriers that are part of a new highway construction project), and in areas near those where noise barriers have previously been built, public involvement is mostly informal yet successful. Before proceeding to final design for a Type II project, the MDOT requires that local officials submit an adopted resolution stating their desire for a noise barrier. Local officials are also required to adopt a land use plan that controls development to lessen future noise problems. These two requirements add local involvement in dealing with traffic noise problems.
While no special funds have been designated to provide Type II noise abatement in Michigan, the MDOT has consistently chosen to spend existing highway funds for this purpose. Special efforts have been made through planning and programming to develop a program of projects reasonably in line with projected revenues. This has been a very difficult task since there are so many identified traffic noise problem areas along Michigan's freeways (there are approximately 500 sites that have been identified with noise levels above 72 dBA Leq(h)). Only one Type II project has been implemented as a result of the political process rather than through prioritization. Approximately 1 1/3 person years of noise staff time is required annually for Type II program activities. This includes complaint investigation and response, noise measurements, acoustic design of noise barriers, project development, contract monitoring, etc.
Massachusetts
Massachusetts built one Type II noise barrier in 1985 as a result of strong public complaints and the political process. Subsequently, a decision was made to develop an ongoing Type II program to respond to continuing public and political concern for highway traffic noise problems.
The Massachusetts Department of Public Works (MDPW) first developed a policy statement which outlined the MDPW's decision to apply the Type II program to all Interstate routes in Massachusetts under MDPW jurisdiction. These routes totaled 659 kilometers in length. Prior to conducting an inventory of traffic noise problem areas, the MDPW examined the effectiveness of 18 Type I noise barriers previously built along Interstate routes under MDPW control. This examination of existing noise barriers was used later to aid in establishing a Type II prioritization process. The MDPW then proceeded to follow the procedures outlined in its Type II policy statement. Noise levels were computed along the Interstate right-of-way lines using links from the "1987 Estimate of the Cost of Completing the National System of Interstate and Defense Highways in the Commonwealth of Massachusetts." Links 75 dBA Leq(h) or louder (approximately half the total kilometers) were retained for further consideration. Initially, the Massachusetts Type II program included only the loudest third of the 75 dBA or louder links - these were 79 dBA leq(h) or louder at the right-of-way line for approximately 128 kilometers of Interstate highways.
Next, all noise-sensitive land uses within 150 meters of the 75 dBA or louder links were identified. This was a very labor-intensive activity since land records for each town and city were reviewed to determine the date that a particular land use originated.
Actual noise barrier locations were identified next through field surveillance along the 128 kilometers of 79 dBA or louder Interstate highways. Areas with no noise-sensitive activities and areas with fewer than six residences were excluded in accordance with MDPW policy. The acoustical feasibility of noise barriers at problem locations along both sides of the highways was reviewed. Locations where it was acoustically impossible to achieve a 10 decibel noise reduction due to terrain conditions and locations where the Interstate highway noise did not predominate over local roadway noise by 5 decibels or more were eliminated from further consideration. The feasibility review resulted in a listing of 53 noise barriers that were deemed to be "acoustically feasible." The barriers were sized to obtain at least a 10 decibel noise reduction for at least one noise-sensitive activity. Only first-floor dwelling units were taken into account, and barrier heights were constrained to between 3.6 and 9.1 meters. The listing showed 53 barriers that ranged in height from 3.6 to 7.9 meters, that ranged in length from 366 to 2408 meters and that protected between 1 and 266 activities each.
The listing of 53 barriers was lastly prioritized using the following method:
Primary Rating:
This is a measure of the existing traffic noise impact summed over all noise-sensitive receivers for each noise barrier. The rating consists of a summation of "Priority Points" for each barrier, computed as follows:
Supplemental Rating:
This is a measure of the average cost-effectiveness of protecting the activities in the area of each noise barrier. It is computed as the barrier's estimated 1987 cost divided by the noise reduction and the number of protected units. It is abbreviated as the "Cost/Reduction/ Unit Rating" and has units of $/dB/unit.
The barrier listing was prioritized from highest to lowest according to the Primary Rating procedure. Where Primary Rating ties existed, the listing was prioritized according to the Supplemental Rating, where lower was better.
The MDPW does not have a set amount of funds that is to be budgeted annually for Type II noise abatement. Design is to proceed on the top two or three priority Type II noise barriers, and the programming and implementation of projects will follow. Additional work must be accomplished to make the Type II program ongoing, but the MDPW has developed a comprehensive, rational, well-documented beginning for aiding in the management of such a program.
Summary
The FHWA noise regulation allows a State to spend Federal-aid highway funds for projects to provide noise abatement along existing highways. These projects are called Type II projects and are implemented strictly at the option of a State - they are not mandatory requirements. The noise regulation provides States with considerable flexibility for designing their own Type II traffic noise abatement program, including the very important task of individual project prioritization. The regulation requires that the overall noise abatement benefits outweigh the overall adverse social, economic, and environmental effects and the costs of the noise abatement measures. This determination relies on good judgement by the States, rather than prescriptive Federal procedures since the individual States are in the best position to make these determinations on a local basis.
As of 1992, 17 States had elected to implement Type II noise abatement programs. This discussion has stressed the need for a sound, rational approach to determining individual Type II project priorities for effective management of Type II programs. Information has been presented for three State Type II programs. California has constructed the most Type II projects, Michigan has a long-standing Type II program, and Massachusetts is currently implementing such a program.
SHAs must identify when the public is officially notified of the adoption of the location of a proposed highway project. This date establishes the "date of public knowledge" and determines the date when the Federal/State governments are no longer responsible for providing noise abatement for new development which occurs adjacent to the proposed highway project. The FHWA has previously left entirely to a State the determination of the "date of public knowledge." However, from now on, the "date of public knowledge" cannot precede the date of approval of CEs, FONSIs, or RODs.
There are no Federal requirements directed specifically to traffic-induced vibration. All studies the SHAs have done to assess the impact of operational traffic-induced vibrations have shown that both measured and predicted vibration levels are less than any known criteria for structural damage to buildings. In fact, normal living activities (e.g., closing doors, walking across floors, operating appliances) within a building have been shown to create greater levels of vibration than highway traffic. Vibration concerns should be addressed on a case-by-case basis as deemed appropriate.
All SHAs must adopt written statewide noise policies that have been approved by FHWA. Regional Administrators are delegated the authority to approve the State policies; this authority may be redelegated to Division Administrators. The policies must demonstrate substantial compliance with the noise regulations, 23 Code of Federal Regulations Part 772, as well as with the reissued noise policies and guidance. Copies of draft policies should be sent to HEP-40 for review and comment; one copy of each approved policy should also be sent to HEP- 40.
