Summary of Noise Barriers Constructed by December 31, 2007

By

U.S. Department of Transportation
Federal Highway Administration
Office of Natural and Human Environment
Noise Team
Washington, D.C.

August 2009

The Federal-aid highway program has always been based on a strong State-Federal partnership. At the core of that partnership is a philosophy of trust and flexibility, and a belief that the States are in the best position to make investment decisions that are based on the needs and priorities of their citizens. The FHWA noise regulation gives each state department of transportation (SDOT) flexibility to determine the feasibility and reasonableness of noise abatement and balancing of the benefits of noise abatement against the overall adverse social, economic, and environmental effects and costs of the noise abatement measures. The SDOT must base its determination on the interest of the overall public good, keeping in mind all the elements of the highway program (need, funding, environmental impacts, public involvement, etc.).

Highway traffic noise should be reduced through a program of shared responsibility. State and local governments should practice compatible land use planning and control near highways. Local governments should use their power to regulate land development in such a way that noise-sensitive land uses are prohibited from being located adjacent to a highway, or that development is planned, designed, and constructed in such a way that noise impacts are minimized. It should be noted that FHWA noise regulations limit Federal participation in the construction of noise barriers along existing highways to those projects that are proposed along lands where land development or substantial construction predated the existence of any highway.

The flexibility in noise abatement decision-making is reflected by data indicating that some states have built many noise barriers and some have built none. Through the end of 2007, 46 SDOTs and the Commonwealth of Puerto Rico have constructed over 2,506 linear miles of barriers at a cost of over $3.35billion ($4.47 billion in 2007 dollars). Four states and the District of Columbia have not constructed noise barriers. Ten SDOTs account for approximately sixty-four percent (63%) of total barrier length and seventy-two percent (71%) of total barrier cost.

This paper contains lists data supplied by SDOTs. Cost data in the listing are approximate due to varying state practices for estimating costs and because the cost could not be estimated that for 50 miles of barriers. The data represent best estimates of SDOTs for barrier construction. There may be non-uniformity and/or anomalies in the data due to differences in individual SDOT definitions of barrier information and the project features the SDOT includes in the cost of noise barriers. Additionally, California did not provide data from 1999 through 2004 and limited data for 2005 through 2007. This lack of information affects the quality of data for these years, since California's noise barriers represent a significant portion of total US noise barriers.

Highway Traffic Noise Barrier Construction Trends

Tables 1-9 provide data on barrier construction, height, materials, and unit costs (all cost information is in 2007 dollars). The following points may be made concerning noise barriers:

Approximately twenty-nine percent (29%) of total expenditures have occurred in the last five years; thirty-six (36%) in the last 10 years and sixty-six (66%) in the last 15 years].

Through the end of 2007, the overall average unit cost, combining all materials, is $24 per square foot. The average unit cost, combining all materials, for the last 10 years is approximately $27 per square foot.

Approximately 184 miles of barriers have been built with highway program monies other than Federal-aid.

Overall by length, approximately seventy-seven percent (78%) of Federal-aid barriers have been Type I (a barrier built on a highway project for the construction of a highway on new location or the physical alteration of an existing highway which significantly changes either the horizontal or vertical alignment or increases the number of through-traffic lanes).

Forty-six states and the Commonwealth of Puerto Rico have constructed more than 1,803 linear miles of Type I barriers, at a total cost of approximately $3.5 billion.

Twenty-seven states have constructed at least one Type II noise barrier (a barrier built along an existing highway, i.e., a retrofit noise barrier), at a total cost of more than $1.08 billion.

Four states and the District of Columbia have not constructed any noise barriers to date: Alabama, Montana, Rhode Island, and South Dakota.

Eighty-nine percent (89%) of barriers that have been constructed range in height from 6-20 feet. One percent (1%) of barriers are less than 6 feet tall and ten percent (10%) are more than 20 feet tall. The overall average barrier height is 14 feet.

Barriers have been made from materials that include concrete, block, wood, metal, earth berms, brick, and combinations of all these materials. Concrete and block, for single material barriers, represent the majority of total material usage [fifty-four percent (54%) and nineteen percent (19%), respectively] and wood six point nine percent (6.9%). Metal, berm, and brick together account for approximately five point six percent (5.6%) of the total. Twelve percent (12%) of all barriers have been constructed with a combination of noise barrier materials. Almost three percent (2%) have been constructed with absorptive materials. One percent (1%) has been constructed with other materials, such as recycled materials, plastics, composite polymers, etc.

Average unit costs for all years for all barrier materials range between $6-31 per square foot, with earth berms averaging only $6 per square foot and brick at $31 per square foot. Concrete has been the most popular material; however, its cost, $27 per square foot, is toward the high end of the range. Overall average costs for wood, metal, and combination barriers are approximately the same ($19, $17, and $19 per square foot, respectively). Absorptive barriers average $27 per square foot in cost.

Unit costs for barriers do not always appear to increase as the barrier height increases (Note: This may be due to non-uniformity and/or anomalies in the data reported by SDOTs).

Barrier height averages from 7-18 feet. Vermont has the shortest average barrier height and Maryland has the tallest average barrier height.

Barrier average unit costs range from $6 per square foot in Delaware to $42 per square foot in Massachusetts.

Summary

Forty-six States and the Commonwealth of Puerto Rico have constructed highway traffic noise barriers; four States and the District of Columbia have not. The most notable trend in highway traffic noise barrier construction is that since SDOTs the built the first noise barriers in the early 1960's they average spending more than $100 million of highway program funds annually for this form of noise abatement. Starting in 1995, SDOTs have averaged spending more than $196 million per year. Since the first highway traffic noise barrier was constructed, sixty-nine percent (78%) of all spending has been for Type I projects, and twenty-six percent (22%) for Type II projects.

Most barriers have been made from concrete or masonry block and range from 9-23 feet in height, and average $24 per square foot in cost.