Transcript Asphalt Pavement Patching

Highway Noise Issues
Public is Demanding Quieter Pavements!
Governor’s Derby Breakfast,
Louisville, KY
Presentation Outline
• Quantifying Noise
• Measuring Pavement Noise
• Mitigation Methods
• Comparison of Pvmt. Surfaces
• Arizona’s Quiet Pavements
How Do We Quantify Noise?
How Do We Quantify Noise?
0
20
40
60
Discomfort
Pain Threshold
Hearing Threshold
1000
100
10
1
Sound
0.1
Pressure,
0.01
N/sq. m.
0.001
0.0001
0.00001
0.000001
Conversation
The Decibel Scale
80
Decibel Level
100
120
140
Increasing the Decibel Level by
10 Doubles the Sound Intensity
Sound Intensity
The Decibel Scale
16
14
12
10
8
6
4
2
0
60
70
80
Decibels
90
100
75 Decibels
The individual is exposed to a
combined total 78 Decibels
75 Decibels
The Decibel Scale
A reduction of 3 dB(A) is like doubling
the distance from the noise.
67 dB(A)
50 ft
The Decibel Scale
A reduction of 3 dB(A) is like doubling
the distance from the noise.
67 dB(A) - 3 dB(A) = 64 dB(A)
100 ft
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 Bypass Method
(ISO 11819-1)
Close-proximity (CPX) Method
NCAT Close Proximity
Noise Trailer
Comparison of CPX versus
Side-Line Measurements
Indianapolis - September 2003
CPX (Sound Pressure or Sound Intensity)
Chart Title
97.5
97
SMA
96.5
96
95.5
95
Dense Graded Asphalt
94.5
94
93.5
Porous Friction Course
93
Porous Friction Course
92.5
92
67
68
69
70
71
72
Pass-by Measurements
Offset: 23 dB(A)
73
74
75
76
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
Controlled Through Obstructions
Average 1 dBA for each 2 ft of Wall Above
Line of Sight
Wall 10’
above LOS
Noise Walls
Effective only for those in line-of-sight.
Does not reduce
noise at source.
Sound or
Noise Walls
Noise Barrier Effectiveness
Must Justify Expense
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
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 densegraded 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
Engineering
Firm
• Readings taken
before and after
B/S Overlay
• A 4-6 decibel
reduction
between old PCC
and new asphalt
OGFCs Reduce Noise, Eliminate
Hydroplaning, Increase Wet
Friction, and Minimize Spray
I-74 in Ohio
Driving on Dense HMA onto OGFC then
back onto Dense HMA
Texas Highway
Driving 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)
Summary: Effect of Pavement
Surface
• 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-96068, May 1996)
Arizona DOT Uses ARFC to
Provide Quiet Pavements
• ADOT is Spending $34M to Overlay
PCCP in the Phoenix Metropolitan
• The ARFC is Minus 9.5mm & 9-9.5%
Binder
• 12.5 mm Thick When Used on Flexible
Pavement
• 25 mm Thick When Used on PCCP
• ADOT Uses Pavement Type (ARFC) as a
Noise Mitigation Strategy (4 dBA)
Recorded Noise Levels from CPX
Recorded Noise Levels from CPX
Summary
– Highway noise very important to public
– Small changes in dB(A) level very
noticeable
• reduction of 3dB(A) like doubling distance
or halving traffic
– Sound barriers expensive and not very
effective
– Controlling Noise at the Source is Best
Option
• Dense HMA 2-4dB(A) quieter than PCC
• OGFCs 1-9dB(A) quieter than Dense HMA