Summary of Noise Barriers Constructed by December 31, 2022

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:

overall and unit cost
average height, length, area
location
year of construction
insertion loss
NAC category(s)
material(s)
features
foundation
project type

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.

Inventory Summary and Tables:

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 a.varela-margolles@dot.gov.

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:

49 State DOTs have built at least one barrier.
37 State DOTs have each built at least 10 miles of barriers.
- 16 of those State DOTs have built at least 100 miles of barriers.
Three State DOTs have built no barriers.

The data also shows that from 1963 through the end of 2022:

Just seven State DOTs account for over half (51.3%) of total barrier length in linear feet.
Six State DOTs account for about half (50.1%) of total barrier cost in 2022 dollars.

Available Noise Abatement Strategies:

The FHWA noise regulation (23 CFR 772):

Allows Federal funding of feasible and reasonable noise abatement associated with certain types of highway projects (Type I and Type II projects).
Allows the purchase of land in order to prevent noise sensitive development adjacent to the highway for Type I projects only.
Allows the insulation of Activity Category D facilities.
Limits Federal funding for the construction of noise barriers in the absence of a highway project (Type II projects), to those communities where land development or substantial construction predated the existence of any highway.
Gives each State DOT the flexibility to determine the feasibility and reasonableness of various noise abatement options for Type I projects and to set up a Type II program if they choose.

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:

Noise compatible planning by requiring that developers construct developments in ways that minimize noise impacts, and
Land use control strategies, which regulate land development to prohibit noise-sensitive land uses adjacent to a highway.

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.

Highway Traffic Noise Barrier Construction Trends:

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):

From 2020 to 2022 (the current reporting period):

States constructed 22,534,945 square feet of noise barriers (All types).
- This is 1,368,258 square feet more than the last reporting period from 2017 to 2019².
- 1,060,164 square feet of these were Type II barriers
The barriers totaled 222 linear miles in length.
- This represents 18 fewer miles than the last reporting period.
- 14 of these miles were associated with Type II barriers.
- 16 of these miles were State or Toll funded barriers.
Total construction costs for these barriers were approximately $925 million.
- Construction costs for this period represent 8.5% of total expenditures since program inception in 1963.
- Of the $925 million, Type II barriers accounted for $33.8 million, or 4% of expenditures.
At least³ 95.8% of these barriers were constructed to protect land uses that include Activity Category B â€“ outdoor residential land uses.
The average noise reduction was 7 dB(A).
Absorptive materials were used on at least⁴ 40% of the barriers built this period.

From 2017 to 2019 (the previous reporting period):

States constructed 21,166,687 square feet of barriers.
The barriers totaled 257 linear miles in length.
Total construction costs for these barriers were approximately $783 million.

From 1963 to 2022:

Forty-eight states and the Commonwealth of Puerto Rico constructed 300,101,207 square feet of barriers.
- This total includes the square footage for barriers which were later demolished, as well as the square footage for their replacements if they were constructed by December 31, 2022.
The barriers total 3,866 linear miles in length.
Total construction costs for these barriers were approximately $10.8 billion.
- The average unit cost for these barriers has been $41.93/square foot.
These barriers have an average height of 14 feet.
- Average barrier height varies by state from a low of 7 feet to a high of 18 feet.
Alabama, the District of Columbia and Rhode Island have not constructed any noise barriers to date.

Average Unit Costs (combining all materials and barrier types:

From 2020-2022 it was $48.76 per square foot.
- For Type II barriers during this period, it was $28.81 per square foot.
From 2017-2019 it was $53.49 per square foot.
- For Type II barriers during this period, it was $45.81 per square foot.
For the past decade, from 2010 to 2019, it was $46.84 per square foot.
- For Type II barriers during this period, it was $42.25 per square foot.

Type II Barrier Construction (since 1963):

The first Type II barrier reported dates to 1973. It was a berm/wood combination barrier in Michigan that cost $308,554 in 2022 dollars.
Type II barriers account for approximately 14% of all square footage.
States have constructed 42,093,691 square feet of Type II barriers.
The barriers total 560 linear miles in length.
Total construction costs for these barriers were $1.7 billion.
The average unit cost for Type II barriers was $40.62/square foot.
These barriers have an average height of 14 feet.
Twenty-eight states have reported building at least one Type II noise barrier.

Materials Used (since 1963) ⁵:

Barriers constructed with a single material make up 85% of all barriers â€“
- Concrete comprises 59% of these barriers.
- Block represents 16% of these barriers.
- Wood comprises 5% of these barriers.
- Metal, berm, and brick together account for another 4% of single material barriers.
- 'Other' materials comprise the final 1% of these barriers.
  - This category includes - Acrylic, Acrylite, Carsonite, Composite, Fiberglass, Glass, Plastic Opaque, Plastic Transparent, PVC, Rubber, or Undefined Other.
Barriers constructed with a combination of materials make up 12% of all barriers.
Absorptive materials were used on over 11% of all barriers.
At least 30% of barriers have a Reflective surface ⁶.

Items of Note:

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.

Summary:

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.