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Recommended Best Practices for the Use of the FHWA Traffic Noise Model (TNM)

Appendix H. Sample Checklist for Noise Abatement Design Reports

The sample checklist in this appendix is intended to be used for the preparation of a Noise Abatement Design Report, which provides the acoustical design details of the noise abatement measure under evaluation and documents the outcome of the feasibility/reasonableness determination. Such reports are used to assist in public involvement and to help survey public opinion on the noise abatement measures under consideration for their neighborhoods. The reports also are used by engineers to design the barriers and develop the plans and specifications for construction.

Customarily, one Noise Abatement Design Report is produced for each noise barrier under evaluation, unless two or more barriers are being evaluated together as part of a noise barrier system for one Common Noise Environment (CNE) with one cost-effectiveness metric. Some noise abatement design studies may consider only a single noise barrier for a single CNE, while other studies projects may consider multiple noise barriers for multiple CNEs. In the latter case, an overall noise barrier summary report also may be produced that includes all of the Noise Abatement Design Reports for each individual noise barrier, or noise barrier system, as well as a discussion of the public involvement process and other relevant information.

If an overall noise barrier summary report is produced for a highway project, it should include graphics to show the locations of all noise barriers that were evaluated for the study, including those found to be not feasible and/or not reasonable. Different symbols should be used in the graphics to depict the results of the feasibility/reasonableness determinations, i.e., “Not Feasible”, “Feasible and Not Reasonable”, and “Feasible and Reasonable”.

Checklist for Noise Abatement Design Reports

1. Title of Project and Barrier Number
2. Summary Table of Barrier Design Results
   • Measured existing noise levels in study area
   • Computed loudest-hour noise levels (no barrier)
   • Number of dwelling units/receptors in study area exposed to noise impact
   • Computed loudest-hour noise levels (with barrier)
   • Number and percentage of impacted receptors receiving at least 5 dBA insertion loss, and whether the barrier is feasible
   • Number and percentage of impacted receptors where noise reduction design goal is achieved
   • Total number of benefited receptors
   • Average barrier insertion loss for benefited receptors
   • Total barrier length
   • Barrier height range
   • Total barrier surface area
   • Total barrier cost and assumed unit cost
   • Need for sound absorptive materials
   • Computed SHA cost-effectiveness metric and whether the barrier is reasonable
3. Narrative Summary of Noise Barrier Characteristics and Benefits
   • Study background and participants
   • Noise measurements
   • Noise modeling, including roadway sources, terrain, and shielding characteristics, any unique characteristics of the study area that presents modeling challenges
   • Noise model validation details
   • Traffic data source and loudest hour determination
   • Characteristics of evaluated barrier (location, length, height, square feet, cost, need for sound absorptive material, etc.)
   • Details of the barrier's feasibility and reasonableness determination, including:
     • Any analysis of barrier concepts associated with a mix of Activity Categories B, C, and/or D to be benefited by the same barrier, and the details of that analysis
     • Number of impacted dwelling units/recreational receptors
     • Number and percentage of impacted receptors receiving at least 5 dBA insertion loss and whether the barrier is feasible
     • Number and percentage of impacted receptors where noise reduction design goal is achieved and whether that reasonableness criterion is achieved
     • Total number of benefited receptors
     • Insertion loss range and average
     • Cost-effectiveness metric calculation compared to SHA criteria
4. Table of Loudest-hour Noise Levels
   • Receptor number, location/address, Activity Category
   • Number of dwelling units and/or recreational units represented by each receptor
   • No-barrier L_eq
   • With-barrier L_eq
   • Barrier insertion loss
5. Table of Barrier Design Data and Sound Attenuation Line
   • Barrier location referenced to roadway baseline station number
   • Barrier X and Y coordinates
   • Elevation of ground at barrier base
   • Elevation of top of barrier
   • Height of barrier above ground
6. Table of Receptor Locations
   • Receptor number and location/address
   • Receptor X, Y and Z coordinates
7. Table of Noise Measurement and Model Validation Results
   • Site number and location/address
   • Measured Total L_eq and Traffic-only L_eq, if different/available
   • TNM-predicted noise levels using traffic counted during measurement program as input
   • Site-by-site differences between measured and predicted sound levels, and average for all sites
8. Table of Traffic Data Used in Noise Analysis
   • Roadways modeled
   • Loudest-hour Auto, Medium Truck and Heavy Truck volumes and speeds
9. Graphics of Study Area, Barrier, Noise Receptors and Results
   • Two similar graphics may be produced, different only in the labeling of receptors
   • Both graphics should include:
     • Base map of aerial photography if possible
     • Noise measurement sites
     • All receptor locations
     • The location of the proposed noise barrier, with station labeling to match the barrier design table
     • Elevation contours, if available
   • In one graphic, the receptor labels should indicate receptor site numbers to match the tables
   • In the second graphic, the receptor labels should indicate three sound-level values: no-barrier L_eq, with-barrier L_eq, and insertion loss. In this graphic, it is useful to color-code the receptor symbols for the following four categories: impacted and benefited, impacted and not benefited, not impacted but benefited, not impacted and not benefited.
10. Public Involvement
    • Discussion of public meetings and survey/voting details and results, as appropriate.

I have reviewed the report entitled ________________________________________________ and I have determined that it complies with the guidance and checklists in this document as well as with SHA policies and FHWA Regulations and Guidance.

Supervisor signature Date