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)