Highway Noise Issues

Public is Demanding Quieter Pavements!

Governor’s Derby Breakfast,

Louisville, KY

• Quantifying NoiseQuantifying Noise

• Measuring Pavement NoiseMeasuring Pavement Noise

• Mitigation MethodsMitigation Methods

• Comparison of Pvmt. SurfacesComparison of Pvmt. Surfaces

• Arizona’s Quiet PavementsArizona’s Quiet Pavements

Presentation OutlinePresentation Outline

How Do We Quantify Noise?

The Decibel Scale

0.0000010.000010.00010.0010.010.1

110

1001000

Sound Pressure, N/sq. m.

0 20 40 60 80 100 120 140

Decibel Level

Hea

rin

g T

hre

sho

ld

Discomfort

Co

nve

rsat

ion

Pai

n T

hre

sho

ld

How Do We Quantify Noise?

0

246

8101214

16

Soun

d In

tens

ity

60 70 80 90 100

Decibels

The Decibel Scale

Co

nve

rsat

i on

Tra

in Ch

ain

Saw

Increasing the Decibel Level by 10 Doubles the Sound Intensity

75 Decibels

75 Decibels

The individual is exposed to a combined total 78 Decibels

The Decibel ScaleA reduction of 3 dB(A) is like doubling

the distance from the noise.

67 dB(A)

50 ft

The Decibel ScaleA reduction of 3 dB(A) is like doubling

the distance from the noise.

67 dB(A)

100 ft

- 3 dB(A) = 64 dB(A)

A 3dB(A) reduction corresponds to:

• doubling the distance

• reducing traffic volume by 50%

• reducing traffic speed by 25%

FHWA - Noise Abatement Criteria

67 dB(A)

“this is not an absolute value or design standard, only a level where noise mitigation must be considered”

•For new construction or reconstruction•(ISO 11819-1)

Side-Line Measurements

• Statistical By-pass Method (ISO 11819-1)

Close-proximity (CPX) Method

NCAT Close Proximity Noise

Trailer

Comparison of CPX versus Side-Line Measurements

Indianapolis - September 2003

Offset: 23 dB(A)

What Can Be Done to Mitigate Pavement Noise?

–Distance

–Obstructions• Noise Walls

• Earth Berms

• Trees/ Shrubs

–Control at the Source with Pavement Surface

Controlled Through Distance

Wall 10’ above LOS

Controlled Through Obstructions

Average 1 dBA for each 2 ft of Wall Above Line of Sight

Noise Walls

Effective only for those in line-of-sight.

Does not reduce noise at source.

Sound or Noise Walls

Walls– top 10 States in 1998 spent over $1.3M per mile

– do nothing to eliminate the noise at the source

Earth Berms– require a lot of land if very high

Vegetation– takes a long time to develop

– 200’ thick would only achieve a 10 dB reduction

Noise Barrier Effectiveness Must Justify Expense

Controlling At the Source

“Pavement / tire noise has been studied for well over 30 years and several large databases have been compiled in the last decade. NCHRP Synthesis 268 is a summary of the research findings of this extensively studied topic.”

Conclusions: “In general, when dense-graded asphalt and PCC pavements are compared, the dense-graded is quieter by 2 to 3 dB(A)”

A 3dB(A) reduction corresponds to:- doubling the distance- reducing traffic volume by 50%- reducing traffic speed by 25%

Conclusions: “Open-graded asphalt shows the greatest potential for noise reduction for passby noise. Reduction when compared to dense-graded asphalt ranged from 1 to 9 dB(A).”

A 9dB(A) reduction corresponds to:- a reduction in traffic noise by almost 50%!

I-64 Noise Study in Louisville

• By Local By Local Engineering Engineering FirmFirm

• Readings taken Readings taken before and after before and after B/S OverlayB/S Overlay

• A 4-6 decibel A 4-6 decibel reduction reduction between old PCC between old PCC and new asphaltand new asphalt

OGFCs Reduce Noise, Eliminate OGFCs Reduce Noise, Eliminate Hydroplaning, Increase Wet Hydroplaning, Increase Wet Friction, and Minimize SprayFriction, and Minimize Spray

I-74 in OhioI-74 in Ohio

Driving on Dense HMA onto OGFC then Driving on Dense HMA onto OGFC then back onto Dense HMA back onto Dense HMA

Texas HighwayTexas Highway

Driving on Dense Graded Mix then onto OGFCDriving on Dense Graded Mix then onto OGFC

Is It Cost Effective?

• A decrease of 2 dB means a reduction of five feet in wall height or for a mile of pavement a reduction of $528,000 (Average of $20/sf)

• OGFC is the quietest surface type. (Wayson, NCHRP Synthesis 268)

• SMA has also proven to be a quiet surface. (Wisconsin DOT, 1993)

• Dense graded HMA surfaces are quieter than PCC pavements. (Hibbs and Larson, Report FHWA-SA-96-068, May 1996)

Summary: Effect of Pavement Surface

Arizona DOT Uses ARFC to Provide Quiet Pavements

• ADOT is Spending $34M to Overlay PCCP ADOT is Spending $34M to Overlay PCCP in the Phoenix Metropolitan in the Phoenix Metropolitan

• The ARFC is Minus 9.5mm & 9-9.5% BinderThe ARFC is Minus 9.5mm & 9-9.5% Binder• 12.5 mm Thick When Used on Flexible 12.5 mm Thick When Used on Flexible

PavementPavement• 25 mm Thick When Used on PCCP25 mm Thick When Used on PCCP• ADOT Uses Pavement Type (ARFC) as a ADOT Uses Pavement Type (ARFC) as a

Noise Mitigation Strategy (4 dBA)Noise Mitigation Strategy (4 dBA)

Recorded Noise Levels from CPXRecorded Noise Levels from CPX

Recorded Noise Levels from CPXRecorded Noise Levels from CPX

– Highway noise very important to publicHighway noise very important to public

– Small changes in dB(A) level very noticeableSmall changes in dB(A) level very noticeable• reduction of 3dB(A) like doubling distance or halving reduction of 3dB(A) like doubling distance or halving

traffictraffic

– Sound barriers expensive and not very effectiveSound barriers expensive and not very effective

– Controlling Noise at the Source is Best OptionControlling Noise at the Source is Best Option• Dense HMA 2-4dB(A) quieter than PCCDense HMA 2-4dB(A) quieter than PCC

• OGFCs 1-9dB(A) quieter than Dense HMAOGFCs 1-9dB(A) quieter than Dense HMA

Summary