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Presentation delivered at the CalAPA Spring Asphalt Pavement Conference April 9-10, 2014 in Ontario. Topic: New asphalt pavement smoothness specificaitons and measurement technology is discussed in depth.
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Inertial Profiler The New Approach to
Measuring SmoothnessPeter Vacura
CalAPA Spring Conference April 9-10, 2014
Smoothness Topics
ProfilographInertial ProfilerInternational Roughness Index (IRI/MRI)CertificationSpecifications
SubmittalsAcceptance CriteriaCorrective Measures
Analysis Tool - ProVAL
Benefits of Smooth Pavements
Comfortable rideSmoother roads:
last longer, stay smoother longer,safer, saves money
How Did We Measure Pavement Smoothness?
Until recently, pavement smoothness was measured using a California profilograph and straightedgeThe first profilograph was invented by Francis Hveem and constructed in 1940 by the Materials and Research Division of the California Division of Highways.
California Profilograph
How Smoothness is Quantified using a Profilograph?
Profile Index0.2 inch blanking band0.0 inch (Zero) blanking band
Must Grinds0.3 inches in 25 feet
Limitations of Profilograph
Because its front and rear wheels are in contact with the pavement surface, the profilograph cannot accurately measure the pavement profile.
Limitations of Profilograph
Actual Profile
Profilograph Trace
Phantom Bumps
Dip
Dip
Inertial Profiler
Inertial Profiler
Front Mount Rear Mount
Side Mount
Ride Comfort Depends on:Human Response to Vibration
Vehicle Response to the Road
Road Roughness
Inertial Profiler Components
AccelerometerReference elevation
Laser Height SensorHeight relative to reference
Distance Measuring Instrument Longitudinal distance
AccelerometersAccelerometers are used in a wide variety of equipment and personal electronics including seismology equipment, car alarm systems, and crash detection/air bag deployment sensors.In profilers, they measure the movement of the vehicle body
Laser Height SensorsThe laser height sensors measure the distance from the reference plane to the pavement surface. They operate around 16KHz. At 60 mph they can take about 15 readings per inch of vehicle travel.
Dot Laser
Line Laser
Calibration Site InformationThe site is located in the median of Interstate 80 at the Sacramento Regional Transit Light Rail station (Watt/I-80) parking lot.Two test sections (asphalt and concrete) University of California Pavement Research Center with the assistance of the Pavement Program and METS will administer calibration programCalibration tests will be conducted 2 to 4 times per year (March, May and July for 2014)
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Reference Profiler
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HMA TEST SECTIONPCC TEST SECTION
N
Calibration Site
Vehicle TestsBlock Test
AASHTO R57-10, Section 5.3.2.3.1This test will be conducted on a relatively flat and level areaIt’s purpose is to check the height measurements from the height sensor(s) of the test vehicle using blocks of known heights (i.e. 0.5 inch, 1.0 inch, 2.0 inch).
Bounce TestAASHTO R57-10, Section 5.3.2.3.2It’s purpose is to ensures that the data from the height sensor and accelerometer are legitimate and being properly combined to compute the longitudinal elevation profile
Distance Measurement Index TestAASHTO R56-10, Section 8.4Tests accuracy of profilers distance measurement instrument (DMI) 21
Vehicle TestsEquipment Precision (Repeatability)
AASHTO R56-10, Section 8.3.1.2Compare ten Inertial Profiler runs over same test section against each otherCalculate repeatability agreement scoreScore of 0.92 or greater is required
Equipment Accuracy (Reproducibility)AASHTO R56-10, Section 8.3.1.4Compare several inertial profiler runs over same test section against a reference profilerCalculate accuracy agreement scoreScore of 0.90 or greater is required
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Testing Results
Failed tests (Equipment or Operator)May re-test the following day (if site available)Only one re-test per operator/equipment allowed
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How is Smoothness Quantified using an Inertial Profiler?
International Roughness Index (IRI)Computer Algorithm
Areas of Localized Roughness (aka “must grinds”)Isolated areas of roughness
International Roughness Index
The International Roughness Index (IRI) is a scale for roughness based on the simulated response of a generic motor vehicle to the roughness in a single wheel path of the road surface. IRI is used to define a characteristic of the longitudinal profile of a traveled wheel track.
International Roughness Index
Moving Average Filter (Low Pass)
Where B = 250 mm (9.8 in) for IRI(represents tire contact with ground)
Quarter Car (Golden Car) Filter
Standard Special ProvisionDefinition – IRI/MRI
0.1 mile 0.1 mile
ETW
RWP = Right Wheel PathLWP = Left Wheel Path
ETW
Direction of Travel
RWP
LWP
IRI = 58 in/mi
IRI = 64 in/mi
IRI = 60 in/mi
IRI = 62 in/mi
Direction of Travel
MRI = 60 in/mi MRI = 62 in/mi
Standard Special ProvisionHMA Acceptance Values
MRI for each 0.1 mile section of a lane
Standard Special ProvisionAreas of Localized Roughness
“Must Grinds” are now defined as “Areas of Localized Roughness”Areas of localized roughness uses a continuous IRI for each wheel path with a 25 ft intervalAreas of localized roughness that exceed 120(160) in/mile must be corrected regardless of the IRI values of a 0.1 mile section
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Standard Special ProvisionAreas of Localized Roughness
0
50
100
150
200
250
300
350
0 25 50 75 100 125 150 175 200 225
Distance (feet)
IRI (
in/m
i)
25-foot sliding window
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Standard Special ProvisionAreas of Localized Roughness
“Must Grinds” will now be called “Areas of Localized Roughness”Areas of localized roughness use a continuous IRI for each wheel path with a 25 ft intervalAreas of localized roughness that exceed 120 in/mile must be corrected regardless of the IRI values of a 0.1 mile section
Standard Special ProvisionCertification
Inertial Profiler must be certified within the last 12 monthsProfiler Operator must be certified within the last 12 monthsContractors must obtain certification from the California Certification Site (no longer Texas Transportation Institute)
Standard Special ProvisionSubmittals
Within 5 business days before start of profiling or changing profile or operator
Inertial Profiler certificationOperator certificationManufacturer’s recommended calibration and verification tests
Within 2 business days after profiling engineer approved test section
Cross correlation test results36
Standard Special ProvisionSubmittals
Provide data within 2 business days after each day of profilingProfile data must include:
Raw profile data for each lane (ppf extension)ProVAL ride quality analysis report in IRI for both wheel pathsProVAL ride quality analysis report in MRI for each laneProVAL smoothness assurance analysis report in IRI for both wheel pathsGPS dataManufacturer’s recommended calibration and verification resultsAASHTO calibration and verification test results
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Standard Special ProvisionSubmittals
Provide data within 2 business days after each day of profilingProfile data must include:
Raw profile data for each lane (ppf extension)ProVAL ride quality analysis report in IRI for both wheel pathsProVAL ride quality analysis report in MRI for each laneProVAL smoothness assurance analysis report in IRI for both wheel pathsGPS dataManufacturer’s recommended calibration and verification resultsAASHTO calibration and verification test results
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Standard Special ProvisionSmoothness Measurement
Contractor to notify Engineer of start location by station and start time at least 2 business days before profilingBegin and end station will be marked on pavement shoulder before profilingFollowing “leave out” areas will be recorded
Begin and end of all bridge approach slabsBegin and end of all bridgesBegin and end of all culverts visible on the roadway surface
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Standard Special ProvisionSmoothness Correction
For HMA, if the final surface does not comply with the smoothness acceptance values the contractor can do the following:
Grind the pavement to within specified tolerancesRemove and replace itPlace an overlay of HMA
For PCC, if the final surface does not comply with the smoothness acceptance values the contractor can do the following:
Grind the pavement to within specified tolerancesRemove and replace it 40
Standard Special ProvisionQuality Assurance
Caltrans will independently collect profile dataFor each 0.1 mile section, the contractor’s IRI values must be within 10 percent of Caltrans’ IRI values
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Inertial Profiler Benefits
Collects data at a high rate of speed (approx. 30 mph to 60 mph)Collects data for both wheel paths simultaneouslyNo traffic controlSafer$$$$ Savings
Standard Special ProvisionProVAL Reports
Ride Quality Analysis Report
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Ride Quality AnalysisProVAL Reports
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Standard Special ProvisionProVAL Reports
Smoothness Assurance Analysis Report
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Smoothness Assurance AnalysisProVAL Reports
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Standard Special ProvisionProVAL Reports
Profiler Certification Analysis Report(Cross correlation test)
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Profiler Certification Analysis Cross Correlation Test
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Websites of Interest
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Smoothpavements.com (FHWA)Roadprofile.com (ProVAL)
CT Pavement Websitehttp://www.dot.ca.gov/hq/maint/Pavement/Offices/Pavement_Engineering/Smoother_Pavements.html
Equipment SuppliersAmes Engineering (amesengineering.com)
Dynatest (dynatest.com)Surface Systems and Instruments (Smoothroad.com)