willingness to accept, revealed preference, stated preference, and others, a summary of CBA is included in this report as Appendix F. In the appendix, OMB guidance on CBA is mentioned, but emphasis has been placed on EPA procedures because of the agency’s experience with this subject. Where possible, suggestions have been made as to how EPA procedures would apply to CBA for noise issues.
The FAA has also been developing CBA tools for use around airports. A summary of these activities is given in the next section to provide an introduction to what FHWA might develop for CBA of noise reduction along the nation’s highways.
The methods being developed by FAA to perform a CBA of measures for mitigating aircraft noise illustrate useful applications of the general concepts described earlier in this chapter.1 It is well documented that aircraft noise has a range of undesirable impacts, primarily felt by people living around airports. These include physical effects, such as annoyance (e.g., interference in speech communication and activities), sleep disturbance, impacts on school learning and academic achievement, physical and mental health effects, building rattling and other noise, and compromised work performance (WHO, 2004). These effects result in monetary impacts, such as lower property values, health costs, and personal and business economic costs. To perform CBA, aircraft noise must be related to these impacts.
The sound at a given point from one aircraft in flight is typically measured (or estimated) and then expressed in decibels in a metric called the effective perceived noise level. This metric is used by the FAA as a measure of airplane noise emission. This metric takes into account the nonuniform response of the human ear, tonal corrections, and other factors. Then the noise from a representative sample of flights (typically for one day) can be combined into a measure, such as the standard DNL metric, in which the sound energy from multiple events is averaged, and a 10-dB correction is made for flights that occur between 10 p.m. and 7 a.m. DNL and other average measures have been shown to correlate with community response to aircraft noise, as shown, for example, in Table 7-1.
It is important to recognize that responses to aircraft noise vary widely among people and communities, as illustrated in Figure 7-2. Note that for aircraft noise levels typical of communities within 5 miles of airports (55 to 65 dB DNL), the proportion of the population “highly annoyed” varies from 0 to 75 percent. This variability in personal and community response suggests that monetization methods based on statistical distributions, or that accept ranges of inputs, may be most relevant. Thus, the DNL metric is most useful for summary assessments but may not adequately describe the effects of noise on a specific impacted population; it is also sometimes difficult to explain the DNL concept to the public. Information on this subject can be found in a report by the National Research Council Transportation Research Board (Eagan, 2007).
Because it is difficult to assess independent impacts of noise on annoyance, sleep, health, school learning, and so on, it is typical to use one of two methods as surrogates for the total impact of noise. The first of these is the change in property value associated with aircraft noise. Many studies have statistically analyzed this relationship, typically presenting it in terms of a noise depreciation index (NDI) with units of percentage of property value loss per decibel. The results of many of these studies are shown graphically in Figure 7-3 (left). Figure 7-3 (right) shows the results of willingness-to-pay (WTP) studies based on carefully designed surveys of people who live near airports; the typical metric is euros per decibel per household per year. The “X” marks an equivalent value between the two measures (assuming an appropriate average house price and depreciation level).
Both measures of economic impact reflect the wide variability that is characteristic of personal and community responses to noise. Nevertheless, both methods (observing real estate transactions and surveying people) produce similar results in terms of overall value and a similar range of values from low to high. Thus, they provide a basis for estimating the economic impacts of aircraft noise—as a surrogate for estimating the large number of individual impacts, many of which overlap in meaning and are difficult to value (e.g., the relationship between sleep disturbance, stress, and school or work performance).
The FAA Office of Environment and Energy, in collaboration with Transport Canada and the National Aeronautics and Space Administration, is developing a comprehensive suite of software tools for a thorough assessment of the environmental effects and impacts of aviation noise. The main purpose is to develop a new capability to characterize and quantify interdependencies among aviation-related noise and emissions, impacts on health and welfare, and industry and consumer costs, under different policy, technology, operational, and market scenarios. The three main functional components of the tools suite are the Environmental Design Space (EDS), which is used to estimate aircraft CAEP/8 performance trade-offs for different technology assumptions and policy scenarios; the Aviation Environmental Design Tool (AEDT), which takes as input detailed fleet descriptions and flight schedules and produces estimates of noise and emissions inventories at global, regional, and local levels; and the Aviation Environmental Portfolio Management Tool (APMT), which is the framework within which policy analyses are conducted and which provides additional functional capabilities. APMT functional capabilities include an economic model of the aviation industry, with inputs of different policy and market scenarios and existing and potential new aircraft types (the latter from EDS or other sources). It then simulates the behavior of airlines, manufacturers, and consumers, producing a detailed fleet and schedule of flights for each scenario year for input to AEDT. APMT also takes the outputs from AEDT (or other similar tools) and performs comprehensive environmental impact analyses for global climate change, air quality, and community noise. These environmental impacts are quantified using a broad range of metrics (including, but not limited to, monetized estimates of human health and welfare impacts, thereby enabling both cost effectiveness and cost-benefit analyses). Additional information can be found in ICAO (2007) and on the FAA website.