Traffic Noise Analysis Workshop October 17, 2007

 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. What is the Purpose of this Workshop? 1

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: 2

 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”: 1)Proposes noise abatement for existing highways without the improvements listed above. Source: Making Sound Decisions About Highway Noise Abatement – PennDOT & FHWA What are the Types of Noise Projects? 3

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

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

 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? Noise Sensitive Areas (NSA) 6

7 Sample Project Area

8 Sample Project Area Showing N oise S ensitive A reas NSA ANSA B NSA CNSA D

 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). Typical Traffic Noise Analysis Methodology 24-hr vs. Short-Term Monitoring 9

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:1 st row receptor vs. 2 nd row receptor.  Identify individual monitoring sites that could present anomalies within the NSA.  Other sites potentially included to assist in noise model calibration. Typical Traffic Noise Analysis Methodology 10

11 NSA ANSA B NSA CNSA D Sample Project Area Showing N oise S ensitive A reas

12 NSA ANSA B NSA CNSA D Sample Project Area Showing N oise S ensitive A reas and Monitoring Sites

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). Typical Traffic Noise Analysis Methodology 13

Sample Noise Monitoring Meter at Monitoring Site 14

Example Monitoring Site Sketch Form 15

 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. Typical Traffic Noise Analysis Methodology 16

 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. Typical Traffic Noise Analysis Methodology 17

 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. Typical Traffic Noise Analysis Methodology 18

 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. Typical Traffic Noise Analysis Methodology 19

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 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 Typical Traffic Noise Analysis Methodology

warranted  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 Typical Traffic Noise Analysis Methodology

Mitigation Investigation warranted feasibilityreasonableness  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. Typical Traffic Noise Analysis Methodology (continued) 23

Feasibility Feasibility requirements:  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? Typical Traffic Noise Analysis Methodology (continued) 24

Reasonableness 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. Typical Traffic Noise Analysis Methodology Cont. 25

26 Representative Sample Area: Benefited vs. Non-Benefited Sites Impacted and Benefited 1. Noise levels exceed Noise Abatement Criteria 2. Receive a minimum of 3 dBA noise reduction due to mitigation Benefited 1. Noise levels do NOT exceed Noise Abatement Criteria 2. Receive a minimum 5 dBA noise reduction due to mitigation

28 Final Design Measures 16 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;

Final Design Measures (continued) 16 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; 8.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.

30 Questions & Answers 16