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Effective Methods for Environmental Justice Assessment (2004)

Chapter: Chapter 10 - Noise

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231 CHAPTER 10. NOISE OVERVIEW Any undesirable sound can be considered noise. Vehicle engine, vehicle exhaust, tire-pavement interaction, locomotive engine and exhaust, locomotive horn, train wheel-track interaction, and jet engine noises all result from everyday transportation activities. These noises also are among those most often cited as causing the highest levels of annoyance. Various transportation modes can generate sound levels great enough to cause hearing loss and tinnitus (i.e., ringing in the ears). It is unlikely, however, that very many people will be exposed long enough to experience actual hearing loss or damage, except in the workplace environment. Health effects are therefore not the most common transportation noise issue. A much more common concern is the annoyance that persistent noise causes for individuals living, working, or participating in other daily activities near transportation facilities. The FHWA and the FTA have developed methods to determine project noise levels and whether these levels are significant enough to be defined as an impact. The results of these standard methods can readily be used to perform environmental justice assessment. Impacts can occur either as a result of noise level increases or of threshold exceedance. The impact criteria adopted by FHWA and FTA have been developed over time and are based on surveys and research on annoyance and aggravation. Both the FHWA and FTA use impact level as an indication that noise mitigation should be considered. The FTA has stratified impact levels into three classifications: no impact, impact and severe impact. In general, environmental justice assessments of distributive noise effects should use these standard impact classifications and threshold levels only as a starting point. Evaluating the level of effects against standard thresholds is not acceptable as a final determination of “adverse effect” as the term is used in this guidebook. Perceptions of what constitutes an adverse noise effect can vary considerably from individual to individual and from community to community. For transportation projects, the noise impact criteria are therefore not designed to be absolute. Rather, the criteria may be used as a guide to determine whether levels of an effect must be mitigated according to regulation. Various methods are used to evaluate project noise level increases and net project noise levels. The FHWA and FTA have slightly different methods, and each can be used to evaluate distributive effects to protected populations. Results of both FHWA and FTA noise assessments commonly indicate the number of sensitive receptors (locations at which noise is measured) that would experience an impact (e.g., 57 residences). Thus, analyses usually are performed at discreet locations within the study area. In some instances, noise level contours are used to determine the number of receptors. Both contour-based and receptor-based results can be used to evaluate distributive effects to protected populations. It can generally be expected that receptors near a project will incur the greatest noise level increase and sustain the greatest net noise level. Noise impacts of road and rail construction and operation are localized, and normally are experienced at the first row of houses or properties

232 adjacent to transportation projects. Properties further from the project often are protected from noise by the first row of properties. Due to the localized nature of noise impacts, it is often acceptable to evaluate the potential for effects to protected populations by assuming a maximum distance at which impacts could occur. This assumed distance can be used to perform a quick buffer analysis in a geographic information system (GIS). If sensitive receptors are located within the area of potential effects, more sophisticated noise receptor or contouring techniques can then be used to characterize the level of effects and the sensitive receptors that would experience them. Regardless of the approach selected, noise analysis results can be overlaid with demographic information in GIS to evaluate effects to protected populations. STATE OF THE PRACTICE Noise modeling analyses frequently are conducted using models developed by the FHWA and the FTA, and transportation projects are evaluated according to the criteria established by each agency. This section describes how noise is evaluated and presents the FHWA and FTA criteria. Table 10-1 lists common transportation factors that affect neighborhood noise levels. See FHWA (1992), FHWA (1995), and FTA (1995) for further information. Reviewing transportation projects with these factors in mind will help to identify projects in which noise should be assessed. Table 10-1. Transportation factors affecting neighborhood noise levels Factor Description Traffic volume Traffic noise increases with traffic volume. Two thousand vehicles per hour sound twice as loud as 200 vehicles per hour. Traffic speed Traffic noise increases with traffic speed. Traffic at 65 miles per hour sounds twice as loud as traffic at 30 miles per hour. Vehicle types Trucks are especially noisy. A single truck sounds as loud as 28 automobiles at 55 miles per hour. Traffic flow Free-flow traffic and stop-and-go traffic create different noise problems. Distance from roadway Sound levels decrease in proportion with the square of distance from the source. Traffic noise is not usually a serious problem more than 150 meters from a heavily traveled road or more than 30 to 60 meters from lightly traveled roads. Barriers Barriers such as buildings and walls are highly effective ways to deflect noise from residential areas or other sensitive receptors. Land use The level of acceptable noise intensity varies by land use. Even moderate noise levels may be unacceptable near churches, hospitals, schools, and other sensitive receptors. Construction Noise from transportation construction projects, although temporary, can cause serious disruptions and should be evaluated as part of noise studies. Source: Derived from Forkenbrock and Weisbrod 2001, p. 130.

233 Sound level and the noise pattern (continuous, random, or repeated) all are important in characterizing nuisance levels. Absolute noise levels, or the net change in noise levels due to a transportation system change, are thus only part of what must be considered in an effort to understand how a community may respond to altered noise patterns. FHWA. The highway traffic noise prediction requirements, noise analyses, noise abatement criteria, and requirements for informing local officials comprise the noise standards mandated by 23 U.S.C. 109(i). See FHWA (1995) for further information. All highway projects developed in conformance with this noise regulation are considered to be in conformance with the FHWA noise standards. Table 10-2 shows the current FHWA Noise Abatement Criteria (NAC). The NAC are defined in hourly A-weighted decibels expressed as Leq(h) or L10(h). A decibel (dB) is the most common unit of noise measurement. Because the human ear has differing levels of sensitivity to high- pitched and low-pitched sounds, highway traffic noise measurements are adjusted to approximate human hearing. These adjusted measurements are known as A-weighted decibels (dBA). Table 10-2. Noise abatement criteria hourly A-weighted sound level in decibels Activity category Leq(h) L10(h) Description of activity category A 57 (Exterior) 60 (Exterior) Lands on which serenity and quiet are of extraordinary significance and serve an important public need and where the preservation of those qualities is essential if the area is to continue to fulfill its intended purpose B 67 (Exterior) 70 (Exterior) Picnic areas, recreation areas, playgrounds, active sports areas, parks, residences, motels, hotels, schools, churches, libraries, and hospitals C 72 (Exterior) 75 (Exterior) Developed lands, properties, or activities not included in Categories A or B above D None None Undeveloped lands. E 52 (Interior) 55 (Interior) Residences, motels, hotels, public meeting rooms, schools, churches, libraries, hospitals, and auditoriums Source: FHWA 1995, p. 7. Although the A-weighted sound level may adequately indicate the level of environmental noise at any instant in time, community noise levels vary continuously. Most environmental noise includes a conglomeration of noise from distant sources that creates a relatively steady background noise in which no particular source is identifiable. A single descriptor called the equivalent sound level (Leq) is used. Leq is the mean A-weighted sound level during a measured time interval. It is the “equivalent” constant sound level that would have to be produced by a given source to equal the measured fluctuating level. The Day-Night Average Sound Level (Ldn) is defined as the A-weighted equivalent sound level for a 24-hour day with a 10 dBA penalty applied to nighttime levels (10 p.m. to 7 a.m.) to compensate for the increased sensitivity to noise during the quieter nighttime hours.

234 Leq(h) is most commonly used to evaluate project noise impacts. These NAC levels are only to be used to determine impact, and by definition are the absolute levels at which abatement must be considered. Depending on the circumstances of the project being analyzed, it may be necessary to mitigate noise levels that fall either below the NAC or below state-designated criteria. When noise abatement is required, it should be designed to achieve a substantial noise reduction. It is generally not acceptable to merely reduce noise levels to just below the NAC. Figure 10-1 provides an A-weighted decibel scale showing commonly experienced noises for comparison with the FHWA NAC in L10(h). Zero dBA is defined as the faintest sound that can be heard by the human ear. To most people, 60 dBA is perceived as twice as loud as 50 dBA, and 70 dBA is perceived as four times as loud as 50 dBA. Figure 10-1. Commonly experienced noise levels Source: FHWA 1992, p. 3, reproduced from Forkenbrock and Weisbrod 2001. State highway authorities have the power to determine how to implement the NAC. States can thus develop criteria for abatement levels that approach or exceed the NAC. For example, a state could establish abatement criteria for noise levels that are within 1 to 2 decibels of the NAC, or it could set abatement requirements for noise levels that exceed the NAC. States also have the authority to establish impact criteria for decibel level increases. Under such criteria, the absolute 90 dBA is 16 times louder than 50 dBA 80 dBA is 8 times louder than 50 dBA 70 dBA is 4 times louder than 50 dBA 60 dBA is 2 times louder than 50 dBA 50 dBA 0 dBA Modified motorcycle (no muffler) Medium truck Air-conditioning unit Clothes dryer Refrigerator

235 noise level is not at issue. Rather, the criteria recognize that significant increases in noise levels may have adverse effects in and of themselves. The FHWA model was redeveloped in 2002 and is called the Traffic Noise Model (TNM). This model provides noise levels at discrete receptor locations and also can be used to create noise level contours (Forkenbrock and Weisbrod 2001). FTA. The FTA Transit Noise and Vibration Impact Assessment criteria are shown in Figure 10-2 and Table 10-3. Similar to the FHWA criteria, FTA criteria provide a threshold at which noise abatement must be considered. The FTA criteria are a set of complex curves that incorporate a comparison of existing noise levels with predicted project-generated noise levels. Existing noise exposure (dBA) P ro je c t n o is e e x p o s u re , C a te g o ry 1 a n d 2 la n d u s e s (d B A ) P ro je c t n o is e e x p o s u re , C a te g o ry 3 la n d u s e s (d B A ) NO IMPACT 40 40 45 50 55 60 65 70 75 80 45 45 50 50 55 55 60 60 65 65 70 70 75 75 80 80 85 IMPACT SEVERE IMPACT Note: Noise exposure is in terms of Leq(h) for Category 1 and 3 land uses, Ldn for Category 2 land uses. Figure 10-2. FTA transit noise and vibration impact Source: FTA 1995. The FTA analysis procedure uses a spreadsheet to determine project-generated noise levels, which are then compared to existing noise levels. The results of these analyses are not net noise levels at discrete receptors but impact levels (no impact, impact, or severe impact) at discrete receptors. This information is sometimes used to create impact level contours. These contours can be used along with GIS to determine whether disparate impacts occur based on net noise levels (FTA 1995).

236 Table 10-3. Land use categories and metrics for transit noise impact criteria Land use category Noise metric (dBA) Description of land use category 1 Leq(h)* (outdoor) Tracts of land where quiet is an essential element of their intended purpose. This category includes lands set aside for serenity and quiet and for such land uses as outdoor amphitheaters and concert pavilions, as well as for National Historic Landmarks with significant outdoor use. 2 Ldn(h) (outdoor) Residences and buildings where people normally sleep. This category includes homes, hospitals, and hotels where a nighttime sensitivity to noise is assumed to be of utmost importance. 3 Leq(h)* (outdoor) Institutional land uses with primarily daytime and evening use. This category includes schools, libraries, and churches where it is important to avoid interference with such activities as speech, meditation, and concentration on reading material. Buildings with interior spaces where quiet is important, such as medical offices, conference rooms, recording studios, and concert halls fall into this category, as do places for meditation or study associated with cemeteries, monuments, museums. Certain historical sites, parks, and recreational facilities are also included. * Leq for the noisiest hour of transit-related activity during hours of noise sensitivity. Mitigation. Noise mitigation is often considered as a part of a transportation project study if a noise impact is expected. Results of noise analyses may include the mitigated noise levels, and could still result in project noise impacts even though all reasonable and feasible measures were included. Noise mitigation measures include barriers such as noise walls or earthen berms; other measures include reducing speeds, limiting truck usage, or moving roadway alignments further from a receptor. Consideration also should be given to possible side effects of noise mitigation, such as aesthetics, safety, and visibility. These effects can be evaluated using techniques provided in other chapters of this guidebook. Examples of impacts include blocked views of features considered valuable by property owners, such as sunlight, wetlands, parks, and other aesthetic views. Communication with residents is an important element in determining whether any planned mitigation is desirable. SELECTING AN APPROPRIATE METHOD OF ANALYSIS Table 10-4 provides a summary of the methods presented in this chapter. Because noise is one of the most common community concerns with transportation projects, noise evaluation methods for highway, transit, and rail projects are well developed and commonly used. Both the FHWA and the FTA have developed standards and guidance for evaluating noise impacts. Integrating standard noise-effect information with demographic information therefore is the best way to perform an environmental justice assessment of noise effects. The demographic information must adequately characterize the activity spaces within which protected populations

237 may be subject to increased noise levels. Because noise impacts are highly localized, detailed information that identifies demographic characteristics of persons associated with specific properties (i.e., living, working, or otherwise spending significant amounts of time at a site) is preferred over census data. Census data can be used to evaluate distributive effects in cases where the affected area is relatively large or where only screening-level results are needed. Table 10-4. Summary of methods for analyzing noise effects Method Assessment level Appropriate uses Use when Data needs Expertise required 1. Initial evaluation Screening Project, corridor and system initial review to identify potential for noise effects In early planning stages and for initial environmental review or for evaluating projects with limited noise effects or with few nearby noise receptors Low Spreadsheet, knowledge of census data, GIS helpful 2. Highway project noise analysis Detailed Assess noise exposure levels from transportation projects Highway construction and operation noise effects must be evaluated in detail and there is potential for effects to protected populations High FHWA Transportation noise model, knowledge of demographic data, GIS helpful 3. Transit project noise analysis Screening/ detailed Assess noise exposure levels from transit projects Transit construction and operation noise effects must be evaluated in detail and there is potential for effects to protected populations Medium/ high FTA noise/vibration evaluation methods, know- ledge of demo- graphic data, spreadsheet, GIS helpful Three general methods are described in the next section of this chapter. The first method, initial evaluation, can be used in most situations (highway, transit, rail, and multiple modes) to determine if there is potential for noise effects and if protected population groups could experience those effects. It does not, however, provide information on the level of noise effects or if protected populations would be disproportionately affected. The method is best suited for identifying projects that require more thorough evaluation and for targeting specific sites within an affected area that may require environmental justice outreach and detailed assessment. The second and third methods are based on FHWA and FTA noise assessment standards and can be used to perform detailed environmental justice assessment relative to noise effects of highway projects and transit projects, respectively.

238 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

239 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

240 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. Block group Relative level of EJ concern (EJI) Potentially affected minority individuals Receptors in area of 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,

241 • 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

242 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.

243 Premitigation noise exposure comparison Noise exposure (Leq(h)) P e rc e n t o f p o p u la ti o n 0 0-25 26-35 36-40 46-50 Threshold of concern Unequal exposure at levels above 45 dBA Mitigation required 41-45 51-60 5 10 15 20 25 30 35 40 45 Other population Protected population Postmitigation noise exposure comparison Noise exposure (Leq(h)) P e rc e n t o f p o p u la ti o n 0 0-25 26-35 36-40 46-50 Threshold of concern Mitigation required 41-45 51-60 5 10 15 20 25 30 35 40 45 Other population Protected population 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.

244 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

245 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 Noise exposure (Leq(h)) N u m b e r o f p e rs o n s 0 0 1-25 26-35 41-45 Threshold of concern Mitigation required 36-40 46-50 2 4 6 8 10 12 14 16 18 Other population Protected population Postmitigation noise exposure comparison Noise exposure (Leq(h)) N u m b e r o f p e rs o n s 0 0-25 26-35 36-40 46-50 Threshold of concern Mitigation required 41-45 51-60 5 10 15 20 25 Other population Protected population 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:

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

247 • 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:

248 • Project alignment, both horizontal and vertical; • Topography; • System operation plan; • Vehicle technology (e.g., light rail transit [LRT], diesel multiple unit [DMU]); • Land use characteristics and location; and • Demographic information (same as for Method 2). Results and their presentation. Results of transit noise projects are sometimes presented as tables listing neighborhoods with impacted sites, including number of residences. This information may be obtained by specifically analyzing each neighborhood individually or by drawing project impact contours on maps. The primary result is to document the number of impacted properties. Results of the distributive effects assessment can be presented using the techniques described in Method 2. Assessment. Graphical presentations of noise impacts usually include maps with boundaries showing where impacts occur. It is relatively simple to combine results with protected population information to assess environmental justice for transit projects, although data collection may be time consuming in areas where environmental justice concern is high. If the project evaluation identifies an impact or severe impact, noise mitigation will need to be considered. Noise mitigation for transit projects includes more options than are available for a highway project. One key difference is that the source (i.e., train) can have mitigation measures applied directly to it. These may include wheel skirts, wheel damping to prevent squealing, and a special configuration of the vehicle to hide mechanical devices, such as air conditioners, under the vehicle. Mitigation measures may also include greasing tracks at curves to prevent squealing or building barriers in the form of walls or earthen berms to block the line of sight. The impacts of any mitigation measures would need to be considered, including the detrimental effect of applying grease to tracks and the potential security and loss of visibility due to barriers. RESOURCES 1) Federal Highway Administration (FHWA). 1995. Highway Traffic Noise and Abatement Policy and Guidance. Washington, DC: United States Department of Transportation. The Federal Highway Administration’s site on highway traffic noise provides links to numerous resources, including the highway traffic noise guide for 1995. The information can be found at http://www.fhwa.dot.gov/environment/noise. In addition, the FHWA procedures for traffic noise analysis and abatement are described in 23 CFR 772, available at http://www.fhwa.dot.gov/legsregs/directives/fapg/cfr0772.html. 2) Federal Transit Administration (FTA). 1995. Transit Noise and Vibration Impact Assessment. Washington, DC: U.S. Department of Transportation. Much of the information used to describe the Transit Project Noise Analysis method is from the FTA’s Transit Noise and Vibration Impact Assessment guide. The entire document is

249 available at http://www.hmmh.com. To access the report, follow the links to rail and transit noise, FTA guidance manual. Information is also available from the FTA at http://www.fta.dot.gov/office/planning/ep/subjarea/noisevibration.html, which includes a direct link to the spreadsheets to be used for the detailed analyses. REFERENCES Center for MicroComputing in Transportation (McTrans). 2000. “Traffic Noise Model.” Available at http://mctrans.ce.ufl.edu/featured/trafficnoise. Federal Highway Administration (FHWA). 2004. Highway Traffic Noise Model, Version 2.5. Washington, DC: FHWA. Description found at http://www.trafficnoisemodel. org/Version_25.html. Federal Highway Administration (FHWA). 1992. Highway Traffic Noise. Washington, DC: Government Printing Office. Forkenbrock, David J., and Glen E. Weisbrod. 2001. Guidebook for Assessing the Social and Economic Effects of Transportation Projects. NCHRP Report 456, Section 9, “Traffic Noise,” pp. 129-142. Transportation Research Board, National Research Council. Washington, DC: National Academy Press. Also available at http://trb.org/trb/publications/ nchrp/nchrp_rpt_456-a.pdf.

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 532: Effective Methods for Environmental Justice Assessment is designed to enhance understanding and to facilitate consideration and incorporation of environmental justice into all elements of the transportation planning process, from long-range transportation systems planning through priority programming, project development, and policy decisions. The report offers practitioners an analytical framework to facilitate comprehensive assessments of a proposed transportation project’s impacts on affected populations and communities.

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