Traffic Noise Analysis Workshop - Understanding Highway Noise Procedures

1. Traffic Noise Analysis Workshop October 17, 2007

2. What is the Purpose of this Workshop? • This Workshop was created to provide an overview and greater insight into how Traffic Noise Analysis is conducted for highway projects. • No specific discussions regarding the anticipated results of the NE Extension Widening Project Final Noise Results will occur during this workshop. • The workshop will conclude with a Question/Answer session. 1

3. Policy Overview • Legal basis for performing Traffic Noise Analyses: • Federal – FHWA Title 23 CFR Part 772; • State – PennDOT Publication #24, Project Level Highway Traffic Noise Handbook, May 2007; • PTC follows the established Federal and State policies; • These resources are available on-line and can found by accessing the PTC’s website: www.paturnpike.com 2

4. What are the Types of Noise Projects? • Type I Projects: • Highway Projects that would: 1) Construct a highway on a new location; 2) Increase number of through-traffic lanes or; 3) Physically alter an existing highway in a way that significantly changes the horizontal or vertical alignments. • Type II Projects: • Also referred to as “Retrofit Projects”: • Proposes noise abatement for existing highways without the improvements listed above. Source: Making Sound Decisions About Highway Noise Abatement – PennDOT & FHWA 3

5. Noise Abatement Consideration • Highway noise abatement analysis employs a three-step process for determining when and where mitigation would be proposed for a project: 1) Warranted; 2) Feasible; 3) Reasonableness. 4

6. Typical Traffic Noise Analysis Methodology • Identification of noise-sensitive land use in the corridor. 5

7. Noise Sensitive Areas (NSA) • What is a NSA? • A NSA is an organizational tool comprised of subjective boundaries based on common noise source elements and geographic proximity. • Typically extends 500 ft from the edge of the highway shoulder; • Example: choose roadway segments (overpass) as a logical termini since they provide a break in an acoustically designated zone. • How is a NSA Delineated? 6

8. Sample Project Area 7

9. Sample Project Area Showing Noise Sensitive Areas NSA A NSA B NSA C NSA D 8

10. Typical Traffic Noise Analysis Methodology24-hr vs. Short-Term Monitoring • 24-hour Noise Monitoring to determine peak traffic noise hours. • Short-term noise monitoring: • Purpose – to assist in the development of a traffic noise model. • Performed during peak traffic noise hours or equivalent periods (derived from 24-hour data). 9

11. Typical Traffic Noise Analysis Methodology How are Monitoring Sites selected? • Based on land use. • Sites typically represent land use that is acoustically dominated by traffic noise from the subject roadway: Ex: 1st row receptor vs. 2nd row receptor. • Identify individual monitoring sites that could present anomalies within the NSA. • Other sites potentially included to assist in noise model calibration. 10

12. Sample Project Area Showing Noise Sensitive Areas NSA A NSA B NSA C NSA D 11

13. Sample Project Area Showing Noise Sensitive Areas and Monitoring Sites NSA A NSA B NSA C NSA D 12

14. Typical Traffic Noise Analysis Methodology Data collected during short-term monitoring period: • Traffic counts and classifications from nearby roadways; • Site sketches to accurately show location of noise monitoring site; • Weather conditions; • Seasonal consideration; • Ambient noise sources other than traffic noise; • Irregular noise events during the monitoring period (low-flying planes, dogs barking, etc). 13

15. Sample Noise Monitoring Meter at Monitoring Site 14

16. Example Monitoring Site Sketch Form 15

17. Typical Traffic Noise Analysis Methodology • Noise Modeling • What is the Purpose? • Development of an accurate noise model allows prediction of present-day and future case noise levels. • Model is also used to develop mitigation alternatives if mitigation is warranted. 16

18. Typical Traffic Noise Analysis Methodology • Model Calibration • FHWA Traffic Noise Model (TNM) is a state-of-the-art analytical computer program used for predicting noise impacts in the vicinity of highways operating throughout the country. • FHWA TNM was developed and validated through the U.S. Department of Transportation’s John A. Volpe National Transportation Systems Center, Acoustics Facility. • This program replaces the prior FHWA-approved noise model STAMINA/OPTIMA. 17

19. Typical Traffic Noise Analysis Methodology • TNM Inputs • 3-D representation of roadways – digitized from engineering design files; • Observed traffic counts and classifications for subject roadways; • Significant topography, represented as 3-D terrain lines; • Other features that affect sound wave propagation such as irregular ground zones, median barriers, shoulder barriers, etc. 18

20. Typical Traffic Noise Analysis Methodology • If the model accurately predicts sound levels within 3 dBA of the monitored levels, the model is considered calibrated. • 3 dBA is mandated as this represents the typical change in dBA detectable to the human ear. • If the model cannot duplicate the monitored sound levels, this can be rectified by checking for dominant ambient noise sources other than traffic or resolved by re-monitoring sites. 19

21. Typical Traffic Noise Analysis Methodology Prediction of Existing and Future Worst-case traffic noise levels: • Purpose – to determine if noise abatement consideration is warranted. • Calibrated model used as basis for other models. • Significant changes incorporated to predict existing and future noise levels. 20

22. Typical Traffic Noise Analysis Methodology Existing/Future No-Build case: • Yearly worst-case peak-hour traffic volumes and compositions are used in place of field observed numbers. • Traffic Data projected 20 Years in Future is used to establish future conditions. Future Build case: • Future worst-case peak-hour traffic volumes and composition; • Geometric alterations of the roadway footprint/elevation/configuration; • Significant changes to terrain or other features that affect traffic noise propagation. 21

23. Typical Traffic Noise Analysis Methodology • Comparison of existing and future predicted noise levels to determine if mitigation investigation is warranted: • Noise levels approach or exceed 67 dBA (defined as 66 dBA or greater); • Significant increase of future noise levels above existing (>10 dBA increase). 22

24. Typical Traffic NoiseAnalysis Methodology(continued) Mitigation Investigation • If warranted, sites are reviewed to determine the feasibility and reasonableness of mitigation. • Accomplished by assessing the TNM Barrier configurations of the future-case Noise Model. • Model amended to reflect potential 3-D barrier configurations. • Barrier configurations can be manipulated in the model by changing location, length, and height to achieve optimal noise level reduction for impacted sites. 23

25. Typical Traffic NoiseAnalysis Methodology(continued) Feasibilityrequirements: • Can mitigation provide a minimum of 5 dBA reduction in noise levels at the majority of impacted sites? • Can mitigation be designed and physically constructed at the appropriate location? • Will the mitigation create a safety problem? • Will mitigation restrict access for vehicular or pedestrian travel? • Will the placement of the mitigation make it inaccessible for maintenance? • Will the barrier impact utilities or drainage? 24

26. Typical Traffic NoiseAnalysis MethodologyCont. Reasonableness requirements: • Cost/benefit analysis to determine if effective mitigation falls within cost limitations; • FHWA allows for up to $50,000 per benefited residence and Pennsylvania has adopted this maximum number; • Who are the benefited residences? * Impacted Sites – minimum of 3 dBA insertion loss. * Non-impacted sites – minimum of 5 dBA insertion loss. • If the total cost of mitigation is less than or equal to $50,000 per benefited residence, than mitigation is considered reasonable. 25

27. Representative Sample Area:Benefited vs. Non-Benefited Sites Impacted and Benefited1. Noise levels exceed Noise Abatement Criteria 2. Receive a minimum of 3 dBA noise reduction due to mitigationBenefited1. Noise levels do NOT exceed Noise Abatement Criteria 2. Receive a minimum 5 dBA noise reduction due to mitigation 26

28. Final Design Measures 1. Focus is on identifying detailed mitigation for NSAs meeting the warranted/feasible/reasonable requirements; 2. Verify land usage consistency from prior design phase; 3. Duplicate and expand noise monitoring effort performed in preliminary design phase; 4. Develop highly detailed noise models to meet final design specifications; 5. Determine extent of sites warranting noise abatement; 16

29. Final Design Measures(continued) 6.Perform mitigation investigation to determine feasibility and reasonableness for sites warranting abatement consideration; 7. Provide an opportunity for public involvement for those communities anticipated to qualify for a barrier. This includes the opportunity to vote on whether or not a barrier is desired and, if so, to provide input on the residential-side color and texture of the barrier; • Proposed abatement will be reviewed with design engineers to develop the Type, Size and Length (TS&L) Package. This package will contain detailed schematics showing location of caissons, individual panel heights, and aesthetic treatments to be used for the noise barriers. 16

30. Questions & Answers 16