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METHODS Method 1. Initial evaluation When to use. The initial evaluation consists of a data review to identify the presence of protected populations in a study area and to determine the level of potential noise impact. The objective of this method is to determine whether a detailed noise analysis is needed and if there is potential for noise impacts to be experienced by protected populations. The results will be important in planning for the time and resources needed to conduct a thorough noise assessment and, if necessary, for enhanced public outreach and detailed environmental justice assessment to characterize distributive effects. The initial evaluation should be performed early on in project planning or during the scoping phase of environmental review. The information needed and required tools are straightforward and easy to use. Analysis. There are three main steps to this analysis, each described below. Step 1 - Define the impact area. Use the geometry of the project (such as the roadway or rail centerline) and any larger construction areas (such as interchanges or rail terminals) to define the area of potential noise effects. For roadways, determine if the segment is highly traveled, such as a freeway or arterial, or lightly traveled. As a guide, consider defining the area of potential effects as being within 150 meters of either side of the centerline for highly traveled segments and within 60 meters of the centerline for lightly traveled segments (Forkenbrock and Weisbrod 2001, p. 130). For initial assessment of transit noise, the area of potential effects can be determined using the FTA guidelines for transit noise assessment (FTA 1995, Chapter 4, Table 4-1). In general, a distance of 750 ft (230 m) will capture all likely noise effects from common linear transit system features. For larger transit system features, such as yards and storage and maintenance facilities, a distance of 2,000 ft (610 m) should be used from the center point of facilities. This distance is also reasonable for evaluating temporary noise effects of highway and transit construction. For relatively small projects, this step can be performed efficiently using desktop information, such as hardcopy maps. For larger projects, it will be more efficient to use buffer analysis in GIS to define the area of potential effects. Step 2 Identify protected populations, affected land uses, and activities. Overlay the area of potential noise effects with demographic information and, if available, information on the location of sensitive receptors. Depending on whether you are evaluating a roadway or rail project, assign land uses in the area of potential effects to the corresponding FHWA or FTA categories. Use as input a combination of small-scale census data (blocks and block groups), land use information, and sensitive receptor information collected through a field study and/or through interviewing neighborhood residents. Step 3 Perform noise impact screening analysis. If the results of Step 2 indicate that residences, work places, or other activity centers used by protected populations are likely to be affected, perform the noise impact screening analysis. This is the final step in determining if noise can be expected to be enough of a concern to justify a more detailed analysis. For highway 238

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projects, the TNM provides lookup tables that can be used to perform the screening analysis (FHWA 2004). In some states, models other than TNM are used to evaluate noise impacts. If the TNM is not available, procedures specific to the model in use should be used to conduct the screening analysis. For transit projects, the FTA noise screening procedure can be used (FTA 1995). Data needs, assumptions, and limitations. Protected population information needed for an initial assessment includes census maps showing minority and low-income populations and information on receptors that neighborhood residents feel should be protected. For highway projects, the following information is needed to use the TNM lookup tables: Volume and speed information for automobiles, medium trucks, heavy trucks, motorcycles, and buses; Terrain information (i.e., pavement, lawns, etc.); Distances from centerline to receptors; and Noise barrier information including distance from centerline and height (optional). For transit projects, the following information is needed to perform the FTA noise screening procedure: List of transit project features (e.g., commuter rail stations and mainlines, bus ways, maintenance facilities) and Distances from noise source to receptors. As screening procedures, the FHWA and FTA make numerous simplifying assumptions. The TNM lookup tables assume free-flow traffic at a single speed on a straight roadway. Multiple barriers cannot be evaluated. The receptor height is assumed to be constant, always 1.5 meters. The FTA noise screening procedure is based on considerable research into the maximum distance of effects that can be expected in most transit project configurations. The distances are based on the formulas used in the FTA's detailed assessment, with a factor added to ensure conservative results. For either screening technique, the detailed assessment is required if project noise levels are found to approach levels that require abatement. Results and their presentation. Figure 10-3 shows a summary table and map excerpt for a hypothetical initial assessment of a proposed light rail transit (LRT) expansion project. The map shows the rail centerline and major cross streets. The area of potential impact was defined based on such FTA criteria as census-block-group areas within 230 meters of the rail centerline. The block-group areas are categorized based on relative level of environmental justice concern, computed using the environmental justice index (EJI) (See Chapter 2). For each block-group area, the table lists the estimated number of receptors and estimated number of potentially affected minority individuals. Based on the results in this example, a detailed transit project noise analysis would be required. In addition, a detailed environmental justice evaluation should be conducted for the areas of medium and high concern. These are the areas where targeted environmental justice evaluation 239

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work should be performed. Possible evaluation activities could include public outreach; interviews to identify receptors that the minority communities would like to have protected; and detailed assessment to determine if noise mitigation measures adequately protect minority individuals. Relative Potentially level of EJ affected Receptors Block concern minority in area of group (EJI) individuals effects 5005 Medium 0 0 9001 High 163 58 6023 Medium 32 20 6021 Low 63 84 7021 Medium 63 35 5064 Low 19 61 Figure 10-3. Initial noise evaluation results for LRT corridor expansion Assessment. The highway and transit initial evaluations are effective techniques for quickly identifying whether a project or project alternatives would have noise impacts. The objective of these evaluations is to determine if more detailed and costly noise assessment is warranted. Desktop techniques or GIS buffer analysis can then easily be used to identify the potential for noise effects to protected populations. Use of these techniques should be limited to early project planning stages or to the beginning stages of an environmental review. Data needs are relatively low, and little expertise in either noise modeling or GIS is needed to perform the evaluation. As a result, this technique can readily be used to evaluate distributive noise effects at the system and corridor level. Method 2. Highway project noise analysis When to use. A detailed highway project noise analysis should be conducted in the following situations: Along a newly constructed segment of roadway, Where significant horizontal or vertical alignment shifts will occur, 240

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When significant traffic volume increases are expected as a result of the project, and When an initial evaluation indicates the potential for adverse noise effects to protected populations. If an alignment shift or traffic volume increases are substantial enough to cause a noise impact, a detailed analysis should be considered. Any capacity increase will generally cause alignment shifts or involve new roadway connections and traffic volume changes that require a detailed noise analysis. In addition to roadway characteristic changes, proximity to sensitive noise receptors should also be considered. If there are no sensitive receptors within several hundred feet of a roadway project, a detailed analysis may not be needed. Analysis. The four steps in the analysis are described below. Step 1 Run detailed highway noise model. Detailed highway noise analyses usually incorporate the FHWA noise model (described previously) to determine noise levels at discrete receptor locations. After impact areas are determined, a detailed noise mitigation analysis is conducted. This analysis will generally include the introduction of a barrier, such as a noise wall or an earthen berm, between the roadway and the receiver. The noise-level results of the mitigation analysis are used to determine whether noise mitigation is reasonable and feasible. A reasonable noise wall would meet cost-effectiveness criteria, which are typically determined by the state highway agency. A feasible noise wall is one that could be constructed without causing another unwanted impact, such as a safety problem from loss of line of sight or another environmental impact. Cost effectiveness can be determined by analyzing noise levels with and without noise barriers, counting the number of houses that will experience a noise-level reduction, and calculating the cost of the barrier that produces the noise-level reduction. State highway agencies will often have a dollar value that is considered cost-effective, typically $3,000-4,000 per decibel reduction per household. The publication, Highway Traffic Noise Analysis and Abatement Policy and Guidance (FHWA 1995), assists state highway agencies in setting local policies. Step 2 Overlay with demographic information and tabulate results. This step is similar to the process described under Method 1. The only differences are the level of detail provided by the noise impact model and the more thorough review of the demographic data used, including data collection from surveys and/or interviews. Step 3 Evaluate distribution. To evaluate distributive effects, you must estimate the number of affected persons in each population cohort. You must also assign an estimated level of effect to each individual, such as an estimated decibel level or a category of high-, medium-, or low- impact. A basic technique for estimating the number of individuals and their demographic characteristics is to assign population percentages to receptors based on the census blocks and block groups that they fall in. Thus, if the receptors are housing units, you multiply the number of housing units by the average persons per household and the minority and low-income population percentages reported for the block group in which they fall. Adding estimates of the number and 241

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demographic characteristics of persons using nonresidential receptors completes the tabulation. A more precise approach would be to tabulate the number of individuals linked to receptors and their demographic characteristics based on results of surveys and interviews of neighborhood residents, even to the level of property-by-property information if possible. Step 4 Compare against alternative scenarios. A common need is to compare existing conditions with future-year build/no-build scenarios, both with and without mitigation options. This will demonstrate if the project is likely to generate noticeable increases in noise levels to protected populations and will also indicate the locations in which those increases may be expected. If premitigation distributive effects are identified, it is especially important to evaluate whether or not the mitigation options adequately reduce noise levels in areas of concern. When performing this analysis, it is not advisable to apply the NAC, FTA, or state-derived criteria. Rather, once a potential for unequal distributive effects has been identified, the net increase or decrease in noise levels should be evaluated without respect to threshold criteria. When evaluating the co-distribution of effects and protected populations, it is often helpful to visualize the information. Throughout the guidebook we present many examples of maps serving this function. Figure 10-3 is one example. Figure 10-4 shows a graphical visualization of results. Both premitigation and postmitigation future-year noise level estimates for 30 housing unit receptors with an estimated exposed population of 100 persons are displayed. The performing agency set the noise abatement threshold at 50 dBA Leq(h), which is two dBA below the FHWA NAC of 52 dBA (interior) for residences. Thus, by the performing agency's definition, 50 dBA is the level at which noise abatement must be performed. Further, the agency established a threshold of concern at 45 dBA, indicating that concern over noise could be expressed by community members at levels from 45 to 50 dBA and that mitigation measures might be required within this range. The top chart shows the premitigation dBA exposure for members of protected population groups compared to other exposed individuals. This chart shows that a higher proportion of individuals in protected population groups were likely to experience noise exposure levels above 47 dBA when compared to the rest of the population in the impact area. The chart also shows that there are individuals who would experience noise levels above the 50 dBA mitigation threshold (if no individuals were exposed above 50 dBA, the "percent of population" beyond that number would be zero). The bottom chart gives the postmitigation dBA exposure comparison. This chart shows that (a) no individuals are exposed to noise levels above the noise abatement threshold of 50 dBA, and (b) the proportion of individuals in protected population groups exposed to 45 to 50 dBA is equal to that of the population as a whole. It is important when using this technique to compare the rest of the population to both (a) the percent of the protected population and (b) the total number of individuals in the protected population group that would experience adverse noise effects. This can be done by preparing one set of graphs with percent of population as the vertical axis (as in Figure 10-4), and another set of graphs with the number of persons as the vertical axis. 242

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Premitigation noise exposure comparison 45 40 Other population 35 Protected population Percent of population 30 25 Threshold Mitigation of concern required 20 Unequal exposure at levels above 45 dBA 15 10 5 0 0-25 26-35 36-40 41-45 46-50 51-60 Noise exposure (Leq(h)) Postmitigation noise exposure comparison 45 Other population 40 Protected population 35 Percent of population 30 25 Threshold Mitigation of concern required 20 15 10 5 0 0-25 26-35 36-40 41-45 46-50 51-60 Noise exposure (Leq(h)) Figure 10-4. Evaluation of pre- and postmitigation noise assessment results by percent of population Both evaluations are necessary to determine distributive effects because in certain study areas a majority of the affected population may belong to protected groups. Figure 10-5 displays results of the same dataset evaluated in Figure 10-4, but here the vertical axis measures number of persons. In the case of this particular dataset, evaluation by number of persons does not show any disproportionate effects to protected populations. For other study areas, however, the reverse could be true. 243

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Data needs, assumptions, and limitations. Data needs for a detailed highway noise analysis include the following: Traffic volumes: Traffic speeds and Vehicle classification information (autos, trucks, etc.); Roadway geometry, both horizontal and vertical; Topography; Land use information; and Some common assumptions (be certain they hold for the project in question): That the roadway is dry, Vehicle speeds are generally consistent, and Vehicle platooning is average. This approach of estimating the affected population and its demographic characteristics using receptors and census data will give you a general sense of the distribution of noise impacts among population groups. There are, however, extreme limitations to this technique due to the relatively coarse level of detail in the census compared to the localized nature of noise impacts. Although survey, interview, and property-by-property data collection techniques will provide more accurate and defensible results, the cost and time needed to collect the necessary information is a drawback. This limitation means that collecting data through survey and interview techniques is more cost effective for relatively small projects with few receptors in the area of effects. As the impact area and number of potential receptors increases, it may become necessary to rely on information such as census data to perform a study-area-wide evaluation, with follow-up data-gathering activities focused in areas where greater densities of protected populations are found. Results and their presentation. Detailed highway noise analyses usually include a description of any local noise rules or guidelines, diagrams showing noise receptor locations and potential noise mitigation locations, and tables showing noise levels at each sensitive receptor location. The noise levels provided often include existing noise monitoring, existing conditions modeling, future-year no-build modeling, future-year build modeling, and future-year build modeling with noise mitigation. Any noise level approaching or exceeding the federal noise abatement criteria or a state standard generally will generate a requirement for further mitigation and additional modeling. The results of the noise mitigation analysis will show the noise level reduction that could be achieved by the proposed mitigation and the cost per unit of decibel reduction per household. For purposes of evaluation, data presented in the form of graphs and maps may need to be relatively complex. In actuality, the number of categories displayed in Figures 10-4 and 10-5 has been simplified for presentation purposes. When presenting results to the public, it is also important that maps, charts, and other graphics be kept simple so that they convey very specific 244

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messages to the viewer. Figure 10-6 provides an example of how the graphs presented in Figures 10-4 and 10-5 could be simplified even further to present results to the public. Premitigation noise exposure comparison 18 16 Other population Number of persons 14 Protected population 12 10 Threshold Mitigation of concern required 8 6 4 2 0 0 1-25 26-35 36-40 41-45 46-50 Noise exposure (Leq(h)) Postmitigation noise exposure comparison 25 Other population Protected population 20 Number of persons 15 Threshold Mitigation of concern required 10 5 0 0-25 26-35 36-40 41-45 46-50 51-60 Noise exposure (Leq(h)) Figure 10-5. Evaluation of pre- and postmitigation noise assessment results by number of persons Assessment. The goal of a detailed noise analysis is to completely characterize noise levels before and after a project. If noise mitigation is included as part of the project, details about the location and cost-effectiveness of the mitigation should be clearly defined: 245

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Ensure that adequate public outreach is performed in locations where members of protected population groups may be affected. Premitigation noise exposure comparison 80 70 Other population Percent of population 60 Protected population 50 40 Unequal exposure to protected population 30 20 10 0 No concern Possible nuisance Noise abatement effects required Level of noise effect Postmitigation noise exposure comparison 100 Other population Percent of population Protected population 50 No exposure at levels that may cause nuisance or at levels that would require noise abatement 0 0 0 No concern Possible nuisance Noise abatement effects required Level of noise effect Figure 10-6. Pre- and postmitigation findings of environmental justice assessment Identify the level of effects to protected populations. Evaluate whether effects are equitable. 246

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Ensure that postmitigation exposure levels are no higher to members of protected population groups than to other individuals. Because noise usually only impacts receptors immediately adjacent to a roadway project, specific property information is preferred over use of census or other zonal demographic data to identify locations where protected populations may be exposed. Method 3. Transit project noise analysis When to use. Considering that transit projects must be located amidst or close to concentrations of people, noise and vibration impacts can be a concern throughout the planning and project development phases. This method offers transportation planners flexibility in addressing noise and vibration at different stages in the development of a project and at different levels of detail, depending on the types of decisions that need to be made. Analysis. Three levels of analysis may be used, depending on the type and scale of the project, the stage of project development, and the environmental setting. The technical content of each level is summarized below: Screening procedure. Identifies noise-sensitive land uses in the vicinity of a project and whether there is likely to be an impact. It also serves to determine the study area for further analysis when sensitive locations are present. The screening process may be all that is required for many of the smaller transit projects that qualify for categorical exclusion (CE). This procedure is performed as part of the initial evaluation (Method 1) described above. When noise-sensitive receptors are present, two levels of quantitative analysis are available to predict impact and assess the need for mitigation measures. General assessment. Identifies the location and estimated severity of noise and vibration impacts in the areas identified in the screening procedure. For major capital investments, the general assessment provides the appropriate level of detail to compare alternative modes and alignments. It can be used in conjunction with established highway noise prediction procedures to compare and contrast highway, transit, and multimodal alternatives. For other types of transit projects, this level is used to more closely examine projects that show possible impacts as a result of screening. For many smaller projects, this level may be sufficient to define impacts and prepare mitigation as necessary. Detailed analysis. Quantifies impacts through an in-depth analysis usually only performed for a single alternative. The detailed analysis delineates site-specific impacts and mitigation measures for the preferred alternative in major investment projects during preliminary engineering. For smaller projects, detailed analysis may be warranted as part of the initial environmental assessment if there are potentially severe impacts due to close proximity of sensitive land uses. Results of the FTA analysis can be used to evaluate distributive effects using the same steps as described for the detailed FHWA analysis (Method 2) described above. Data needs, assumptions, and limitations. This type of analysis requires the following data: 247