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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

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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

9

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

10

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

11

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

12

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

13

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

14

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

15

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

17

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

21

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)

22

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

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Thanks for your attention!

Questions?

THE CONTRIBUTION OF MICRO- AND MACRO-TEXTURE TO THE SKID RESISTANCE OF PAVEMENTS