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This report examines the noise abatement feasibility and reasonableness factors in the Federal Highway Administration (FHWA) noise regulation in 23 Code of Federal Regulations (CFR) Part 772 (the "regulation') as implemented in individual state highway agency (SHA) noise policies.
Feasibility and reasonableness are determined based on the effect the abatement measure has on adjacent noise "receptors." A receptor is an activity area on a parcel of property being studied for noise impacts from a nearby highway project. Receptors can be residential or non-residential land uses.
The way that non-residential receptors are treated in a project noise study - how their intensity of use and placement on the property are determined - can have a significant effect on the feasibility and reasonableness of a noise abatement measure. Task 2 of this research, reported separately, examined receptors on non-residential land uses and addressed alternative methods to quantify the number of receptors at these locations. The focus of Task 3 is on residential receptors only.
The feasibility and reasonableness factors that have been studied include:
The analysis examines how changes in the permissible ranges for all of the factors affect noise abatement decisions while the other factors remain static. The analysis also examines how changes to multiple factors in combination affect decisions. The goal was to identify combinations of factors that are likely to result in inclusion of noise abatement or exclusion of noise abatement
The first subtask was to examine each factor individually and in combination with each other to identify optimized combinations of values. The first objective of this subtask was to identify the range in potential decisions based on the combinations permitted under the regulation. A second objective of this subtask was to aid in future guidance and planning.
The second subtask was to apply the results of the first subtask. This work included performing a sensitivity analysis on the feasibility and reasonableness factors to identify outcomes of possible combinations of factors. It also included applying the combinations to actual highway projects to identify the effects of changes in these factors individually and in combination with the likelihood of abatement.
The viewpoints criteria are not included in the above analysis because the viewpoints of benefited owners and residents are not solicited until after a noise barrier analysis has shown that a barrier is feasible and reasonable through application of the feasibility criterion and the NRDG and CE reasonableness criteria.
The viewpoints criteria and the current voting processes for obtaining those viewpoints were separately examined in the second phase of this research. Included are an inventory, compilation, and analysis of the viewpoints criteria through a review of all of the SHA policies. Additionally, representatives from six SHAs with whom the researchers had worked or were familiar with their programs were contacted to learn firsthand of their experiences. Of interest were the perceived positive and negative features, experiences in implementing and applying the process, and any revisions or plans to improve their policies within the current framework of 23 CFR 772. Finally a study of the effects on decisions of changes in the voting patterns and viewpoints factors is presented for a real-world case.
The study results include all digital files developed for this analysis, including noise prediction model runs and spreadsheets, which have been delivered to FHWA.
Another part of this research was the development of two tools to evaluate the effects of policy changes on the feasibility and reasonableness of noise abatement. That work is included in a separate report. These two tools allow users to evaluate various combinations of factors to determine the effects of policy changes on the feasibility and reasonableness of abatement. One of the tools also includes the capability for testing variations in the factors comprising the viewpoints criterion.