Updated July 2023
The Federal Highway Administration's (FHWA) highway noise regulation (23 CFR 772.13(f)) requires each state department of transportation (State DOT) to maintain an inventory of all constructed noise abatement measures. The inventory must include the following:
The inventory contains the data supplied by 52 State DOTs which includes all 50 States plus Washington DC and Puerto Rico. The latest update includes new data from State DOTs from 2020 to 2022, as well as edits to increase the accuracy of the previous years' data. The inventory now contains a nationwide database of noise barriers constructed from 1963 to 2022.
FHWA provides a downloadable Excel sheet to allow users to view and filter the data within the nationwide noise barrier inventory. Selected graphs are also available. For any questions, please contact firstname.lastname@example.org.
This narrative discusses noise barrier trends from 1963 to 2022; with a focus on the years 2020-2022, which is the most recent collection period.
The 1963-2022 data reflects the flexibility State DOTs have in noise abatement decision-making:
The data also shows that from 1963 through the end of 2022:
The FHWA noise regulation (23 CFR 772):
States balance the abatement's benefits against its costs before making decisions on their use.
Options available outside of FHWAs regulation include local zoning and planning strategies. State and Local governments can implement these methods of noise abatement, which are the most effective:
This inventory reports on abatement strategies implemented by State DOTs since 1963, which had the earliest reported noise barrier. Noise barriers (walls and berms) have been the preferred form of abatement used by State DOTs of the options available under 23 CFR 772 1. Noise barrier materials include concrete, block, wood, metal, earth berms, brick, fiberglass and plastics, composites, noise absorptive materials, and combinations of all these materials.
The full dataset submitted by the State DOTs is available for searching, viewing, and downloading on the following pages. FHWA summarized the information received from the State DOTs into graphs and tables. The data reveals the following information and trends (all costs below are reported in 2022 dollars):
One notable item for this reporting period was the addition of available GIS data for some of the reported barriers. In addition, some State DOTs dedicated considerable staff time and effort to completely updating their inventory submissions, inclusive of previous years. As such, the data for previous years as reported this year, may or may not be comparable to what was reported for previous years at the time of past collections. Some states continue to report difficulty determining noise barrier costs with the increase in use of alternative project delivery approaches such as design-build where barrier costs are not itemized separately.
A new trend that is expected to continue is the demolition and reconstruction of older noise barriers. As the highway system continues to age and require new Type I projects, older barriers may have to be removed or relocated to accommodate new roadway geometries. Barriers totaling 1,597,075 square feet have been reported as 'demolished and replaced'.
It also is important to note that cost data in the listing are approximate due to varying state practices for estimating costs. The data represent best estimates of State DOTs for barrier construction. There may be non-uniformity and/or anomalies in the data due to differences in individual State DOT definitions of barrier information and the project features the particular State DOT includes in the reported noise barrier costs.. Some years and periods contain more and better-quality data than others, this can also affect the averages as presented. Typically, data completeness and quality has improved through time.
Finally, rounding errors may cause some totals to be slightly more or less than 100% in the trend values noted above. For the actual values, please see the following pages, which contain the State DOTs datasets.
Since 1963, forty-eight states and the Commonwealth of Puerto Rico have constructed highway traffic noise barriers while three (Alabama, District of Columbia and Rhode Island) have not. The most notable trend in highway traffic noise barrier construction is that since State DOTs built the first noise barriers they have averaged spending $208 million of highway program funds annually for this form of noise abatement. The average annual spending for this reporting period (2020-2022) was $308 million per year. Since the first highway traffic noise barrier was constructed in 1963, seventy-one (73%) of all spending has been for Type I projects, and nineteen percent (15%) for Type II projects 7.
1 This report only includes noise barriers as a noise mitigation measure. Costs and types of insulation for NAC D have not been reported by any State DOT. In addition, no State DOT has utilized the acquisition of a buffer zone as a noise abatement measure. Costs and reductions for other avoidance measures, such as re-alignment, have not been documented.
2 Data collection for the 2017-2019 collection was impacted by the global COVID-19 pandemic, and the originally reported value for the 2017-2019 collection was 19,839,740 ft2. However, some State DOTs reported older barriers during the 2022 collection. This resulted in an updated total value of 21,166,687 square feet for the 2017 to 2019 period.
3 From 2020 to 2022, 660,673 square feet of barriers had no NAC reported. This is 2.93% of the total square footage for this reporting period.
4 From 2020 to 2022, 1,213,188 square feet (5.4%) of barriers did not have a surface treatment reported.
5 3% of barriers did not report a material.
6 1% (3,121,876 square feet) of barriers were reported as having 'Both' absorptive and reflective surfaces, and these are not included in the totals above for either category. 56.8% (170,332,500 square feet) of barriers reported no surface treatment.
7 Barriers reported by State DOTs may not have a Type assigned (2% of expenditures); or may be listed as using State (5%), Toll (0.2%), Combination (4%), or County, Other, or Local (each < 1% of expenditures) funds. These make up the remaining 12% of barrier expenditures since 1963.