Highway Noise Issues Public is Demanding Quieter Pavements! Governor’s Derby Breakfast, Louisville, KY.
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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
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