Populations Exposed to Significant Airport Noise Have Declined Because of Improvements in Aircraft Technology

The number of people exposed to airport noise has been steadily  declining for several decades, according to FAA. In light of the shrinking airport noise contours discussed above,  FAA’s enforcement of grant eligibility criteria—related to noise exposure  maps and the assessment of interior residential noise—creates a risk that  some noise grants may not have met eligibility criteria, especially in the  edges of the noise contour where noise may be below DNL 65 dB. Grants Are Widely Used for Noise Insulation Projects and Land Acquisition

Since fiscal year 1982, FAA has provided about $5.8 billion in AIP noise  grants to 481 commercial and general aviation airports, reflecting broad  participation in the program by airports through the program’s history. In the first decades of the program, noise grants largely went to projects  in areas most significantly impacted by airport noise—generally areas  closest to airports—while grants in more recent years have gone to  projects in areas that are less significantly impacted, but still deemed to  be exposed to DNL 65 dB or higher noise levels (see fig. 5). Outdated Noise Exposure Maps and Inconsistent Application of Interior Noise Standards Increase Risks for Noise Grant Funds

We found that many of the FAA-accepted maps used to determine project  eligibility for noise grants are outdated and could overstate the actual size  of the DNL 65+ dB areas around airports, putting some federal grant  investments at risk of funding projects that do not meet the eligibility  criteria. In  addition, nine of the 126 airports with maps from 1999 or before  received a total of $87.6 million in grants in fiscal years 2010 and  2011 for residential insulation projects in the DNL 65-69 dB area of  the official map. FAA’s Strategic Goal for Noise Reduction Is Not Linked to Noise Grant Program

FAA has established an overall agency goal for addressing airport  noise—which covers all noise-related agency efforts, not just the AIP  noise grant program—to reduce the population living in significantly noise   This goal  impacted areas to below 300,000 people nationwide by 2018.is articulated in the Department of Transportation’s fiscal year 2013  performance plan, FAA’s long-range strategic plan—Destination 2025— and other FAA performance documentation. As a result of establishing a strategic goal and a corresponding measure  of progress that do not account for AIP noise grants results, there is  insufficient performance information about the nature and extent of  remaining airport noise exposure and the contribution of noise grants in  mitigating the impact of that exposure. Without this information, Congress and  FAA program managers cannot make fully informed decisions about what  the noise grant program can reasonably be expected to address in the  future and the extent to which noise exposure remains a constraint on  growth. Airports Continue to Plan Noise Mitigation Projects, but of a Changing Nature

The 2011 National Plan of Integrated Airport Systems (NPIAS) report,  which includes airport projects from fiscal years 2011 through 2015,  shows continued plans for noise mitigation projects, but a drop in the  number of projects and the number of airports planning them. The 2011 NPIAS report to Congress includes planned  AIP-eligible projects. Some communities around airports that are exposed to significant airport  noise are not likely to receive residential noise insulation. Airports are free  to choose not to perform residential noise insulation projects because  developing an NCP—a necessary step for the airport to take to receive  AIP funds for such projects—is voluntary. To the  extent that airports without NCPs continue not to participate in the Part  150 program, the people living in areas significantly impacted by airport  noise may never receive the benefits of noise mitigation.is about a third of the remaining population that FAA’s MAGENTA model  estimated is exposed to significant airport noise. Second, approximately one-third of the estimated remaining  population exposed to significant airport noise resides near airports that  have yet to and may never establish an NCP. After 30 years, it appears  unlikely that this population will ever be reached by the current program. DOT and FAA officials provided  technical comments that we incorporated as appropriate. We acknowledged these actions in our report, but these  targets, results, and reporting are not linked to FAA’s strategic noise goal  and measurement approach nor are they included in FAA’s reporting on  progress toward that strategic goal. FAA reviewed our recommendations and agreed to consider them for  action. Appendix I: Objectives, Scope, and Methodology

This report addresses the following objectives: (1) how airports’ noise  exposure has changed since federal noise grants were first funded, (2)  how Airport Improvement Program (AIP) grants have been used by  airports to mitigate noise and what have these grants achieved, and (3)  the likely future demand for AIP noise set-aside grants.
Why GAO Did This Study

The Federal Aviation Administration (FAA) predicts that air traffic in the United States will increase 20 percent by 2024. If not mitigated, the noise associated with these flights could significantly diminish the quality of life for communities surrounding airports and constrain an airports ability to expand. Over the last 30 years, Congress has provided billions of dollars in grants under the Airport Improvement Program to airports to reduce and mitigate significant noise exposure. FAAs overall strategic noise goal is to reduce the population exposed to significant noise to fewer than 300,000 people nationwide.
At your request, GAO (1) described how airport noise exposure has changed, (2) evaluated noise grant results, and (3) assessed potential future demand for these grants. GAO analyzed FAA data on noise grants, planned projects, and population exposure and reviewed relevant literature. GAO also conducted interviews with relevant airport and FAA officials and industry representatives, as well as visited seven airports that have used noise grants, judgmentally selected based on size, location, and other factors.

What GAO Found

The number of people in the United States exposed to significant airport noise has steadily declined from roughly 7 million people in 1975 to about 309,000 today. This change reflects large decreases in the size of areas that are exposed to significant airport noise and is primarily due to improvements in aircraft technology.
Since 1982, FAA has provided $5.8 billion in Airport Improvement Program noise grants to 481 airports for residential and public building noise insulation and land acquisition, among other project types. The majority of grants went to airports that voluntarily undertook Noise Compatibility Programs (NCP). While these funds benefitted thousands of people, GAO identified two areas of concern regarding FAAs enforcement of project eligibility criteria that creates a risk that some undetermined amount of grant funds may have gone to projects that do not meet FAAs project eligibility criteria. First, FAA does not always require airports to maintain updated and accurate noise exposure maps to define eligible project areas. For example, half of the noise exposure mapswhich show the areas around an airport that are exposed to significant airport noise and are a key element in determining project eligibilityare from the 1990s or earlier. For an airport to receive a noise grant, program criteria generally require that such maps are updated every 5 years, but nine airports received $87.6 million in grants in fiscal years 2010 to 2011 based on maps that predate 2000. Second, FAA has inconsistently implemented requirements that limit residential noise insulation projects to homes with interior noise levels above an established threshold. In the absence of FAA enforcement, airports have little incentive to update maps and limit residential treatment because doing so might eliminate planned projects expected by the public. Concurrent to GAOs review, FAA issued new guidance that should substantially address this risk if effectively implemented. Further, the results of noise grants are not linked to FAAs strategic noise reduction goal and measurement approach. For example, the goal does not include the results of noise insulation of homes and schools. As a result, there is insufficient performance information about the effects of noise grants and the extent to which noise exposure remains a constraint on airport growth.
There has been an increase in the estimated cost of planned noise mitigation projects in FAAs 2011 National Plan of Integrated Airport Systems report to Congress, but a number of indicators point to a future decline in demand for grants for noise projects. Specifically, the 2011 report, compared to prior reports, includes a smaller portion of projects in the most significantly noise-impacted areas. Further, since the 2001 report, the number of airports planning eligible noise projects is down 16 percent, with about half the number of planned projects. Additionally, fewer airports are developing new noise compatibility programs and many of the 234 airports with such programs may be completed. For example, 102 of 137 airports with an NCP more than 10 years old received no noise grants since 2007, an indication that those airports may have completed all eligible projects in those plans. Finally, about a third of the people living in significantly noise-impacted areas reside near airports that have not completed, and may never complete, an NCP, a necessary step before an airport can use noise grants for residential noise insulation. This population, therefore, may never be reached by FAAs grant program.

What GAO Recommends

GAO recommends that the Department of Transportation align its strategic goal for noise reduction with the results of the noise grant program and establish corresponding performance measures. The department provided technical comments and agreed to consider the recommendations.