Traffic Noise Analysis Workshop October 17, 2007.

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: www.paturnpike.com

2

http://www.paturnpike.com/

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:

1) WarrantedWarranted;2) FeasibleFeasible;3)

ReasonablenessReasonableness.

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 Noise Sensitive Areas

NSA A NSA B

NSA C NSA 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).


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: 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

11

NSA A NSA B

NSA C NSA D

Sample Project Area Showing Noise Sensitive Areas

12

NSA A NSA B

NSA C NSA D

Sample Project Area Showing Noise Sensitive Areas 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).


13

Sample Noise Monitoring Meter at Monitoring Site

14

ExampleMonitoring 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.


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.


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.


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.


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


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


Comparison of existing and future predicted noise levels to determine if mitigation investigation is warrantedwarranted:

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


Mitigation Investigation If warrantedwarranted, sites are reviewed to determine

the feasibilityfeasibility and reasonablenessreasonableness 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 NoiseAnalysis Methodology

(continued)

23

FeasibilityFeasibility 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?


(continued)

24

ReasonablenessReasonableness 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.


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 Questions & Answers

16

Traffic Noise Analysis Workshop October 17, 2007.

Documents

Transcript of Traffic Noise Analysis Workshop October 17, 2007.