4415-11

A Working Guideline for Highway Noise Barrier Construction

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In response to traffic generated noise, Congress included a provision in the Federal-Aid Highway Act of 1970 which required the Federal Highway Administration (FHWA) to develop standards for the abatement of highway noise in federal-aid projects. These standards are published as Part 772 of Title 23 of the Code of Federal Regulations.

In June of 1995, "Highway Traffic Noise Policy and Guidance" was issued by the Federal Highway Administration (FHWA). In compliance with this guidance, the following represents the Department's written statewide noise policy. As such, the policy contains the Department's standards and procedures on the analysis and abatement of highway traffic generated noise for Type I projects. A Type I project is defined as a federal-aid 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. For the purposes of this policy, the addition of one (1) mile or more of ramps, collector distributor lanes or auxiliary lanes or any additional lane which allows the public to travel from one interchange to another on limited access roadways is considered an increase in the number of through lanes. A significant change in alignment is defined as the halving of the distance between existing roadways and any noise sensitive receiver.

Noise considerations are part of the planning, design and construction of all Federal-aid projects; however some locations will still experience unabated noise impacts. Noise barriers can only be constructed where reasonable and feasible. Therefore, a procedure is necessary to determine when and where additional expenditure of public funds for noise barriers is considered reasonable and feasible.

Nationally, noise level prediction is based upon the FHWA Highway Traffic Noise Prediction Model (STAMINA) or Traffic Noise Model (TNM). However, the national vehicle emission levels contained in the STAMINA model have been replaced by emission levels measured in Georgia. In assessing traffic noise levels from a proposed project or determining the dimensions of a noise barrier, the national average source heights will be used.

Two methods are used for identifying a noise impact. First is a comparison of predicted noise levels with FHWA's noise abatement criteria (NAC). Any predicted noise level that approaches or exceeds the applicable noise abatement criterion is considered an impact. For the purpose of this policy, the Department has defined noise levels within 1dB of the NAC as approaching criteria. The second method is a comparison of predicted traffic noise levels with existing noise levels. A site is considered to be impacted if there is a substantial increase from existing levels. For the purpose of this policy, a substantial increase occures when the future predicted noise levels exceed 60 dBA L10 or 57 dBA Leq and there is an increase of at least 10 dBA or more over existing levels. Only exterior areas of frequent human use would be considered for abatement measures unless there are no exterior activities likely. Frequent human exterior use areas are defined as exterior areas with a permanent fixture for the purpose of outdoor recreation (e.g. patios, decks, porches, permanently affixed picnic tables, grills, etc.). Any interior predictions should be coordinated with the State Environmental/Location Engineer on an individual case basis.

In order for a residential area to be considered for noise barriers, it must be "planned, designed, and programmed" before the date of "public knowledge" of the highway project. In determining the time relationship between residential development and public knowledge, the date a residential area is "planned, designed, and programmed" means the date foundation construction begins and the date of "public knowledge" of the highway project means the date of approval of the CE, FONSI or ROD document.

Georgia does not consider it reasonable to construct barriers for sites with predicted noise levels below 60 dBA. The Department does not consider barrier construction reasonable at locations where site characteristics would require a wall height of greater than 30 feet or where breaks in the barrier for points of access (e.g. driveways and cross streets) would cause the barrier to be ineffective. The Department also does not consider a barrier reasonable at locations where site characteristics prohibit a wall from obtaining a 5 dBA or greater reduction in noise levels or where the barrier would pose overriding safety and maintenance problems (i.e. across existing bridges, large drainage or culverts etc.). Each of these cases will be determined on a case by case basis. FHWA noise abatement policy identifies a 5 dBA decrease in noise as a readily noticeable decrease, therefore, whenever a noise barrier is proposed, it will be designed to achieve a minimum noise reduction of 5 dBA at all impacted sites. An impacted site is described as a single family home, apartment, individual townhouse/condominium unit, mobile home, school, church, or any other noise sensitive location. A barrier must be at least 6 feet in height when replacing a right-of-way fence. Although noise barriers can be up to 30 feet in height they are designed to shield only the first story of multi-story structures. A benefitted site is described as any dwelling that receives a 5 dBA or greater reduction as the result of the construction of noise abatement.

The location of noise barriers should be as far from the edge of pavement as practical. Safety, maintenance, aesthetics, cost, and noise attenuation should also be considered when determining barrier locations. Where construction does not significantly increase the cost of the wall, noise walls should also serve as limited access barriers in lieu of a ROW fence. In fill sections, it will be necessary to increase the width of the fill sufficient to have a desirable clear zone between the noise wall and the edge of the pavement or a sufficient distance from the back of the guardrail to the wall facing, whichever is applicable.

The cost per benefitted dwelling to construct the noise barrier must be considered in determining if a noise barrier is cost effective for a given site. To aid in the determination of reasonable cost, the Department uses the following formula:

Reasonable Cost =	(Number of Impacted Dwellings receiving a minimum 5 dBA reduction
	x $50,000)
	+ (Number of additional dwellings not impacted which receive a minimum 5 dBA reduction from the construction of the abatement
	x $25,000)
		>= Estimated Cost of Barrier

In determining cost effectiveness of noise barriers, the Department will consider cemeteries and other similar land uses associated with scattered, infrequent events not usually associated with peak traffic periods to fall into FHWA category B. For cost estimation such land uses will be considered as one impacted site.

For parks and other open lands used for the purpose of outdoor recreation the number of impacts will be derived from using one impact per 100 linear feet of impacted road frontage.

Noise abatement for schools, hospitals, hotels and motels, public meeting rooms, churches, libraries and auditoriums will be considered under FHWA category B or E, depending on the characteristics of the facility, and will be considered on a case by case basis. Cost effectiveness will be calculated using one impact per impacted room consisting of an exterior wall with opening windows exposed to the roadway or each room impacted under the interior noise level criteria outlined in category E. The Department considers a room to be any area separated by permanent walls, e.g. Classroom, Cafeteria, Library, Gymnasium, patient room, waiting room, Hotel/Motel room, etc.

The concerns of impacted residents will be included in determining the reasonableness of a noise barrier. These concerns will be requested at the location and design public hearing. After a barrier has been determined to be reasonable and feasible the Department will meet again with the benefitted residents to present final noise abatement details and to solicit residents final concerns and opinions on the reasonableness of abatement. A barrier will not be built if it is not wanted by a majority of the benefitted residents.

A noise barrier is not considered cost effective if the barrier cost is more than the reasonable cost calculated above. The estimated cost of the barrier in the formula shown above should be calculated by multiplying the cost per square foot by the total square footage of noise wall needed. The cost per square foot is presently (2003) $15.00 per square foot. This cost will be reviewed and updated at least every three years.

In some cases, short gaps may exist between areas of impacts. The closure of these gaps should be considered on a project by project basis and must be approved by the Chief Engineer. In instances where noise barriers would exceed the Reasonable Cost, property owners may be offered the option to share the cost of abatement. This option applies only to existing and planned/programmed developments along current federal aid projects that meet all other Department and FHWA criteria. In these circumstances the residents must pay all costs that exceed the Department's reasonable cost criteria. The Department suggests that property owners seek funding from their local governments. All barriers are to be constructed on Department right-of-way and will be the sole property of the Department. The property owners shall pay the Department an amount equal to the estimated cost, currently $15.00 per square foot of the barrier that exceeds the Reasonable Cost limit. Payment shall be made to the Department prior to the bid letting and the Department will provide the property owners with notification 90 days prior to opening bids. The property owners' final share will be based on the actual construction costs.

The signed final environmental document containing a description of the noise analysis will be provided to the local jurisdiction.

See also Board Policy 2E-2 Traffic Noise Control

Authored by the Office of Environment/Location, 404-699-4401

Document History:

• adopted by Board: 07/21/94
• revised by Board: 03/20/97
• added to TOPPS: 04/15/97
• removed from Board Policy 8/16/01
• updated and placed in Preconstruction, Environment/Location 11/14/03
• reviewed: 04/01/05
• reviewed: 11/27/06

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