POTENTIAL IMPROVEMENT IN DATA INTERPRETATION REGARDING SIMULTANEOUS MEASUREMENT OF FRICTION COEFFICIENT AND IRI - FC and IRI
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POTENTIAL IMPROVEMENT IN DATA INTERPRETATION REGARDING SIMULTANEOUS MEASUREMENT OF FRICTION COEFFICIENT AND IRI
Authors 2
• Leoš Nekula, Měření PVV, Czech Republic
• Josef Stryk, CDV: Transport Research Centre, Czech Republic
josef.stryk@cdv.cz tel.: 00420 541 641 330
• Pavla Nekulová, Brno University of Technology, Czech Republic
• pavla.nekulova@vutbr.cz tel.: 00420 739 302 146
• Ilja Březina, CDV: Transport Research Centre, Czech Republic
#SURF2018Contents 3
• INTRODUCTION
• ADVANTAGES OF SIMULTANEOUS MEASUREMENT OF FC AND IRI
• EXAMPLES OF DEVICES MEASURING PARAMETER FC AND IRI
SIMULTANEOUSLY:
– CZECH DEVICE TRT + EXPERIENCE WITH MEASUREMENT IN THE CZECH REPUBLIC
– AUSTRIAN DEVICE ROADSTAR
– AUSTRALIAN DEVICE iSSAVe
• EXAMPLE OF PERFORMED MEASUREMENT BY TRT DEVICE
• CONCLUSIONS
#SURF2018Introduction 4
• multi-functional measuring devices simultaneously:
– measure pavement surface unevenness (IRI) and rut depth
– measure macro-texture of pavement surface (MPD)
– and report occurrence of distresses
• devices measuring a single parameter:
– skid resistance properties - longitudinal friction coefficient (LFC) or sideway friction coefficient (SFC)
– bearing capacity - FWD, TSD (Traffic Speed Deflectometer), …
– continual thickness of layers - GPR (Ground Penetrating Radar)
– noise - CPX method (Close-ProXimity)
• other combinations of testing methods:
– ARRB - Intelligent Pavement Assessment Vehicle (iPAVe) - combination of (TSD) and Hawkeye equipment (unevenness,
rutting, texture) + automated cracking
– EU project RPB HealTec - fusion of GPR, infrared thermography and air-coupled ultrasound in structural pavement
condition surveys
– ARRB - Intelligent Safe Surface Assessment Vehicle (iSSAVe) - combination of skid resistance device and Hawkeye
equipment) + automated cracking
• The devices for measuring skid resistance standardly measure only the longitudinal or sideway friction
coefficient.
#SURF2018Advantages of simultaneous measurement
5
of FC and IRI
Advantages:
• measurement results in the same driving path, with the same localization, and at the same time
• the interactions of these two parameters can be searched for
• the impact of pavement unevenness on the results of skid resistance measurements has not been
practically studied
• the longitudinal unevenness of pavement may affect friction coefficient at higher measuring
speeds, specially in case the measurement of skid resistance is carried out by a device without
sufficient vertical load of a measuring wheel or possibility to control it
• this impact cannot be objectively investigated with low-weight measuring trailers
#SURF2018Devices measuring FC 6
EU technical specifications for determining skid resistance CEN/TS 15901:
CEN/TS 15901: Name: Device: Stat. wheel force [N]
-1 RoadSTAR with longitudinal fixed slip ratio (LFCS) 3500
-2 ROAR with longitudinal controlled slip (LFCRNL) 1200
-3 ADHERA with longitudinal controlled slip (LFCA) 2500
-4 TRT with longitudinal controlled slip (LFCT) 1000
-5 ROAR device with longitudinal controlled slip (LFCRDK): 1200
-6 SCRIM measuring the sideway force coefficient (SFCS) 1962
-7 Griptester with longitudinal fixed slip ratio (LFCG) 250
-8 SKM measuring the sideway force coefficient (SFCD) 1960
-9 DWWNL measuring the longitudinal friction coefficient (LFCD) 1962
-10 Skiddometer BV-8 with longitudinal block measurement (LFCSK) 3500
-11 SRM with longitudinal block measurement (LFCSR) 3500
-12 BV 11 and Saab f.t. with longitudinal controlled slip (SFT) 1000
-13 Odoliograph measuring the sideway force coefficient (SFCO) 2700
-14 ViaFriction with longitudinal controlled slip (LFCN) -
-15 IMAG with longitudinal controlled slip (LFCI) 1700 #SURF2018
- 2000Devices measuring FC 7
SRM
#SURF2018ARRB device iSSAVe 8
Intelligent Safe Surface Assessment Vehicle
300 km / 150 km
– SFC (20º angle)
in both wheel paths
– unevenness
– macro-texture
In compliance with the British standard m. speed = 50 or 80 km/h – cracks - LCMS
Standard BS 7941-1:2006. stat. wheel force = 2000 N – asset imagery
#SURF2018Austrian device RoadSTAR 9
• Road Surface Tester of Arsenal Research
• using a modified Stuttgart skiddometer - measuring LFC
• for standard conditions slip ratio is 18 % or 62.5 % = low and high slip device
• measuring speeds reach up to 120 km/h and the standard test speed is 60 km/h
• static wheel force for standard test conditions is 3 500 N
• it measures longitudinal unevenness
with the use of HRM profiler: 2 m beam
with 4 laser sensors
• other parameters:
– macro-texture (MPD)
– transversal unevenness (rut depth)
– surface distresses by line scan camera plus 6 video
cameras and 2 laser scanners
#SURF2018Czech device TRT 10
• Czech national reference device for measuring skid resistance - ČSN 73 6177:2015
• measuring LFC and IRI (profilometer with a dual-mass response system)
• using different slip ratio from 0 % to 100 %
• routine measurements are carried out with a slip ratio of 25 % = low slip device
• static wheel force is adjustable within the range of 500 to 1 400 N F = 1000 N
• measuring speeds: 40 to 120 km/h v = 60 and 80 km/h
• 2 new improved devices in 2018
new
#SURF2018Situation in the Czech Republic 11
• skid resistance of pavement surfaces is measured on network level – road databank
• Czech standard: ČSN 73 6177
– classification levels: 1 – 5
– requirements were added to this standard in 2009 – 4 types: for new roads, at the end of warranty period, to start
prepare a measure, to carry out the measure or lower traffic speed
– in 2015 the measurement speed for motorways was increased from 60 to 80 km/h
– detailed analyses – 5 different measurement speeds
• macro-texture (MPD, MTD), micro-texture (PTV): 5 class. levels, but skid resistance measurement
is preferred
#SURF2018Situation in the Czech Republic 12
• requirements for 4 parameters LFC, PTV, MPD or MTD according to classification levels:
Classification level
LFC,
all roads
speed > 50 km/h
speed ≤ 50 km/h
Acceptance testing of new roads
Requirements before the end of warranty period
Start to plan a measure
Carry out the measure
#SURF2018Situation in the Czech Republic 13
• LFC: measuring new pavements – before and after putting the road to the operation
before
• requirement of road
class. level 1 administrators
• problematic to clean
sufficiently
• preliminary result
after
• valid result of the
measurement to be compared
class. level 1 with requirements
#SURF2018Example of measurement by TRT device 14
Simultaneous measurement of FC and IRI
• measuring speed = 80 km/h on uneven surface
– first measurement was performed with controlled (stabilised) vertical wheel load = 1000 N
– second measurement was performed simulating response of the personal car
#SURF2018Example of measurement by TRT device 15
• controlled (stabilised) vertical wheel load = 1000 N
#SURF2018Example of measurement by TRT device 16
• simulating response of the personal car
#SURF2018Conclusions 17
• When the wheel is pressed against the pavement surface by a spring and, when overrunning
longitudinal unevenness, the change in wheel load is compensated by a shock absorber.
• The effectiveness of the system is based on technical condition of shock absorbers, vehicle speed,
and on the size of longitudinal unevenness.
• Higher speeds and unevenness leads to a decrease in vertical wheel load, reduction of the contact
area between tyre/road, and to higher risk of skidding, particularly on a wet road surface.
• The research of the impact on friction coefficient measured values after longitudinal unevenness
overrun is still in its beginning.
• This relation is important to monitor in case of measurements of friction coefficient carried out by
devices with a low or not controlled vertical load of a measuring wheel.
• Combining friction coefficient and IRI for the assessment of road pavement surface properties allows
for more accurate evaluation, which can be used for better judgment of skid resistance in terms of
traffic safety.
#SURF2018Prague candidate city to host WRC2023 18
#SURF2018Prague candidate city to host WRC 2023 19
#SURF2018SURF 2018 Brisbane 2.- 4. 5. 2018 20
Thank you for your attention.
• Leoš Nekula, Měření PVV, Czech Republic
• Josef Stryk, CDV: Transport Research Centre, Czech Republic
josef.stryk@cdv.cz tel.: 00420 541 641 330
• Pavla Nekulová, Brno University of Technology, Czech Republic
pavla.nekulova@vutbr.cz tel.:00420 739 302 146
• Ilja Březina, CDV: Transport Research Centre, Czech Republic
Questions?
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