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Young Researchers Seminar 2011
DTU, Denmark, June 8 - 10, 2011
Young Researchers Seminar 2013
Lyon, France , June 5-7 2013
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
Pedro A. Serigos
The University of Texas at Austin
2THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
• High demand for safer roads
• # of wet-weather accidents increases as skid resistance of pavement decreases
• Pavement surface friction becomes an important component of Pavement Management Systems
• Pavement surface friction is affected by its texture. More specifically, the micro- and the macro-texture.
component wavelength Scale
uneveness 500mm < λShort stretch of
road
megatexture 50mm < λ < 500mm Tire
macrotexture 0.5mm < λ < 50mm Tire/road contact
microtexture λ < 0.5mmAggregates
texture
3
Mechanisms
• Skid Resistance requires transfer of frictional force
• Complex interplay between adhesion and hysteresis forces:– Hysteresis: energy loss due to
deformation of tire
– Adhesion: short-term bond between atoms of tires and road
Source: Moore (1972). “The Friction and Lubrication of Elastomers”. Pergamon Press, Oxford.
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Role of Texture Components
Texture Component
Main Function Main Benefit
Macro-TextureRapid drainage Avoid Hydroplaning
Deformation of tire Hysteresis
Micro-TexturePenetrates the thin layer of
water → tire/pavement contact
Adhesion
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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• Low speed and high speed friction measurements
• Skid resistance is currently evaluated at a spot
Methods to evaluate friction
British Pendulum Tester Dynamic Friction TesterLocked-wheel skid trailer
Source: http://www.nippou.com Source: http://www.pavementinteractive.org/
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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• Spot measurements of macro-texture
• High-speeds measurements of macro-texture
Methods to measure texture
Sand-Patch Circular Track Meter Road Surface Analyzer
Source: http://www.pavementinteractive.org/
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Future capabilities
• As technology advances, the density of the scans will increase allowing for the characterization of micro-texture at highway speeds.
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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• Textures that affect friction include both micro- and macro-texture. Currently only macro-texture is being measured.
• Previous studies found a weak relationship between friction and macro-texture.
• Separate contribution of micro and macro-texture on skid resistance is currently not fully understood.
Problems and Motivation
SKID RESISTANCE = f(MACRO,MICRO)
Vision: Network level monitoring of skid resistance as a function of both micro-and macro-texture.
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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1) Quantifying the improvement on the prediction of skid resistance when accounting for both macro- and micro-texture of the surface.
2) Compares different ways to characterize the micro-texture to determine which one better predicts skid resistance.
Types of Pavement surface texture
MACRO-TEXTURE
FINE COARSE
MIC
RO
-TE
XTU
RE SMOOTH
SHARP
Objectives of the study
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Spot MeasurementsSM
OO
TH
MIC
RO
-TEX
TUR
E
SHA
RP
MACRO-TEXTURE
FINE COARSE
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Collected data
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
British Pendulum Tester (BPT)
• Low Speed Friction (approx. 10km/h)
• Wet Surface Condition
• Widely used and standardized (ASTM E303-98)
• The testing error fell within 1.00 BPN at a 95 % confidence level
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Collected data
Circular Track Meter (CTM)
• Laser scans a circumference of 892mm
• Sampling rate: 1 point every 0.87mm
• Widely used and standardized (ASTM E2157)
AMES Laser Texture Scanner (LTS)
• Laser scans of 7212 points per line
• Sampling rate: 1 point every 0.015mm
• Max area of scan 100mm x 75mm
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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LTS Scanned Line
0 5 10 15 20 25 30 35 40 45 50
-3
-2
-1
0
1
2
3
micro
macro
profile
Longitudinal coordinate (mm)
Surf
ace
hei
gh
t (m
m)
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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15.5 16 16.5 17 17.5 18 18.5 19 19.5
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
micro
macro
profile
LTS Scanned Line
Longitudinal coordinate (mm)
Surf
ace
hei
gh
t (m
m)
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Calculated Parameters
• Spatial Domain• Amplitude
Mean Profile Depth:
Root Mean Square:
Max Profile Height:
• Spacing
2-Points Slope Variance:
6-Points Slope Variance:
15.5 16 16.5 17 17.5 18 18.5 19 19.5
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
micro
macro
profile
Source: ASTM E1845 – 09
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
𝑹𝑴𝑺 =𝟏
𝑵 𝒊=𝟏
𝑵
𝒉𝒊𝟐
𝑴𝑷𝑯 = 𝒎𝒂𝒙 𝒉𝒊 −𝒎𝒊𝒏 𝒉𝒊
𝑺𝑽𝟐𝒑𝒕𝒔 =𝟏
𝑵 𝒊=𝟏
𝑵 𝒉𝒊+𝟏 + 𝒉𝒊∆𝒙
𝟐
𝑺𝑽𝟔𝒑𝒕𝒔 =𝟏
𝑵 𝒊=𝟏
𝑵 𝒉𝒊+𝟑 − 𝟗 ∗ 𝒉𝒊+𝟐 + 𝟒𝟓 ∗ 𝒉𝒊+𝟏 − 𝟒𝟓 ∗ 𝒉𝒊−𝟏 + 𝟗 ∗ 𝒉𝒊−𝟐 − 𝒉𝒊−𝟑𝟔𝟎 ∗ ∆𝒙
𝟐
16
Contact Area and Baseline
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Power Spectral Density (PSD)
101
102
103
10-1
100
101
102
103
104
105
106
log(Frequency) [cycles/period]
log(P
SD
)
section 1
section 2
section 3
section 4
micro 1st decade
0.5mm
macro 1st decade
50mm
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Calculated Parameters
• Frequency Domain
– Slope of the linearized PSD
– Y intercept of the linearized PSD
101
102
103
10-1
100
101
102
103
104
105
106
log(Frequency) [cycles/period]
log(P
SD
)
section 1
section 2
section 3
section 4
micro 1st decade
0.5mm
macro 1st decade
50mm
log 𝑃𝑆𝐷 = 𝛽0 + 𝛽1 ∗ log(𝑓𝑟𝑒𝑞)
log(Freq)
log
(PSD
)
The correlation coefficient of the PSD for the 28 scanned
surfaces was > 0.98
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Friction vs MPD
20
30
40
50
60
70
80
90
100
110
120
0 0.2 0.4 0.6 0.8 1FR
ICTI
ON
BP
T
MICRO-TEXTURE MPD (LTS)
MPD - LTS
Linear (MPD - LTS)
20
30
40
50
60
70
80
90
100
110
120
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
FRIC
TIO
N B
PT
MACRO-TEXTURE MPD (CTM)
MPD - CTM
Linear (MPD - CTM)
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Comparison of Models
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
• Reference Model (only macro-texture):
• Incorporating the Micro-Texture Spectral Parameters:
Variable t-stat p-valueAdjusted
R2
𝛽𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷 4.84 0.000.670
𝛽𝑇𝑟𝑒𝑎𝑡 2.61 0.02
𝐵𝑃𝑁= 𝛼 + 𝛽𝑀𝑃𝐷𝑚𝑎𝑐𝑟𝑜 ∗ 𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷+ 𝛽𝑡𝑟𝑒𝑎𝑡 ∗ 𝑇𝑟𝑒𝑎𝑡+ 𝛽𝑙𝑃𝑆𝐷𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 ∗ 𝑙𝑃𝑆𝐷𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡+ 𝛽𝑙𝑃𝑆𝐷𝑠𝑙𝑜𝑝𝑒 ∗ 𝑙𝑃𝑆𝐷𝑠𝑙𝑜𝑝𝑒
𝐵𝑃𝑁= 𝛼 + 𝛽𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷 ∗ 𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷+ 𝛽𝑡𝑟𝑒𝑎𝑡 ∗ 𝑇𝑟𝑒𝑎𝑡
VariableMicro-texture spectral Parameters
t-stat p-value Adjusted R2
𝛽𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷 2.63 0.01
0.775𝛽𝑇𝑟𝑒𝑎𝑡 4.19 0.00
𝛽𝑙𝑃𝑆𝐷𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 3.16 0.00
𝛽𝑙𝑃𝑆𝐷𝑠𝑙𝑜𝑝𝑒 -0.08 0.94
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Comparison of Models
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
• Incorporating the Micro-Texture Spatial Parameters:
𝐵𝑃𝑁 = 𝛼 + 𝛽𝑀𝑃𝐷𝑚𝑎𝑐𝑟𝑜 ∗ 𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷 + 𝛽𝑡𝑟𝑒𝑎𝑡 ∗ 𝑇𝑟𝑒𝑎𝑡 + 𝛽𝑡𝑟𝑒𝑎𝑡 ∗ 𝑀𝑖𝑐𝑟𝑜𝑝𝑎𝑟𝑎𝑚𝑖𝑏𝑎𝑠𝑒𝑙𝑖𝑛𝑒𝑗
Adjusted R2 (t-stat of 𝜷𝒎𝒊𝒄𝒓𝒐)
Micro-texture ParameterBaseline
1 mm 5 mm 10 mm 20 mm
Am
pli
tud
e
MPDMedian 0.739 (2.626) 0.703 (1.805) 0.669 (0.946) 0.660 (0.647)
Mean 0.668 (1.016) 0.659 (0.562) 0.657 (0.383) 0.652 (0.229)
RMSMedian 0.730 (2.483) 0.707 (1.931) 0.688 (1.548) 0.676 (1.163)
Mean 0.670 (1.128) 0.662 (0.821) 0.661 (0.686) 0.657 (0.560)
MPHMedian 0.735 (2.481) 0.687 (1.492) 0.667 (0.809) 0.661 (0.547)
Mean 0.663 (0.822) 0.657 (0.392) 0.653 (0.242) 0.648 (0.079)
Slo
pe SV2pts
Median 0.744 (2.625) 0.701 (1.804) 0.671 (1.100) 0.665 (0.821)
Mean 0.664 (0.727) 0.660 (0.457) 0.657 (0.355) 0.653 (0.250)
SV6pts
Median 0.746 (2.641) 0.703 (1.827) 0.671 (1.087) 0.665 (0.814)
Mean 0.664 (0.725) 0.659 (0.447) 0.657 (0.346) 0.653 (0.242)
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Comparison of Models
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
• Spatial Parameters Calculated on Active Area:
𝐵𝑃𝑁 = 𝛼 + 𝛽𝑀𝑃𝐷𝑚𝑎𝑐𝑟𝑜 ∗ 𝑀𝑎𝑐𝑟𝑜𝑀𝑃𝐷 + 𝛽𝑡𝑟𝑒𝑎𝑡 ∗ 𝑇𝑟𝑒𝑎𝑡 + 𝛽𝑡𝑟𝑒𝑎𝑡 ∗ 𝑀𝑖𝑐𝑟𝑜𝑝𝑎𝑟𝑎𝑚𝑖𝐴𝑐𝑡𝑖𝑣𝑒𝐴𝑟𝑒𝑎
Micro-texture
Parameters
calculated on
Adjusted R2 (t-stat of 𝜷𝒎𝒊𝒄𝒓𝒐)
Amplitude Slope
MPD RMS MPH SV2pts SV6pts
Entire Profile 0.739 (2.626) 0.730 (2.483) 0.735 (2.481) 0.744 (2.625) 0.746 (2.641)
Active Area 0.763 (3.073) 0.762 (3.006) 0.761 (2.95) 0.772 (3.094) 0.776 (3.137)
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Conclusions
• The skid resistance at low speeds of the wet pavement surfaces was significantly affected by both the micro- and the macro-texture of the pavement surface.
• Incorporating the characterization of the surface micro-texture to the macro-texture significantly improved the prediction of the pavement skid resistance.
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS
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Conclusions
• Comparing micro-texture parameters:
– Frequency domain (best predictor of pavement BPN):• The intercept of linearized PSD significantly affected the BPN but the slope did not.
• The greater the value of the PSD, the greater the low-speed skid resistance.
– Spatial domain:• The 6-point Slope Variance ( among slope parameters) and the MPD (among
amplitude parameters) were the best predictors of the low-speed skid resistance.
• Regardless of the parameter, the significance was maximized when calculated using a 1mm baselength and the median of the individual baselines.
– Accounting for the contact area between the pavement and the vehicle tire significantly improved the prediction of the BPN.
THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS