Pavement Ride Quality

Nicholas Vitillo, Ph. D.

Center for Advanced Infrastructure and Transportation

CAIT

TopicsDescription of Ride Quality

International Roughness Index (IRI) Summary

Equipment used to measure wheel track profiles

Issues with measuring and analyzing pavement profiles

Pay Adjustment Examples

NJDOT Certification Facility

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Components of Pavement Roughness Surface Tolerance – deviations for a flat surface

Roughness – the summary of irregularly spaced variations in surface tolerance that induce vibrations in the vehicle defined over a length of the road

Repeated Waves – regularly spaced unevenness that causes vibrations in the vehicle

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Roughness and Smoothness

• Roughness: Deviations of a surface from a true planer surface with characteristic dimensions that affect ride quality

• Smoothness: Lack of roughness, free of bumps and dips that cause discomfort to traveling public

Roughness or Smoothness

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Wheel Track ProfileLongitudinal Slices of the Pavement Surface

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Wheel Track Profile

Pavement Ride Quality Index

International Roughness Index

IRI in in/mile

ProVAL 3.0

IRI is a summary of the vertical movement of a vehicle caused by the pavement profile over a given distance.

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NJ IRI Guidelines

IRIInterstates Freeways NHS Hwys

Non-NHS Hwys

Other County Hwys

New 0 - ? Excellent Excellent ExcellentResurfacing ? - 60Excellent Excellent Excellent

60 - 95 Good95 - 150150 - 170170 - 200 Deficient200 - 285 Deficient Fair

>285 Deficient

FairGood

FairGood

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Profile Equipment-Measure Wheel Track Profile

Standard Profiler - Rod and Level and Walking Profilers

Slow Speed – Light Weight Profilers

High Speed – Portable and Full Size Profilers

““Gold Standard”Gold Standard”

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Measuring the “True” Profile

Walking

Profiler

Standard pavement profiling devices

Rod and LevelWalking Profilers

Calibration/Correlation

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Lightweight Profilers

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Portable Profilers Dynatest Portable

Roadware Portable

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High Speed Profiler - ICC Profiler

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Measurement IssuesAll Profilers are NOT created equal

DMI

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Height Sensor Footprint

T-6600DNC 690

Typical Laser

DipStick

2 in

ARRB WB

9.5 Inches

12 Inches

Sampling Intervals

Footprint Shapes

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Height Sensor Footprint

2 in

6 Inches

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Measurement IssuesAll Profilers are NOT created equal

Different Sampling Intervals

Different Accelerometers

Different Distance Measuring Instruments

Different Start Sensors

Different Data Processing – “Black Box”

How can we get equivalent Ride Quality values?

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FiltersPavement profiles are made up of an infinite number of profiles of different wave lengths

Filters help to remove the information that does not affect Ride Quality

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Filters Types:Smoothing (low pass)

Removes the short wave lengths – Rumble strips

Anti-smoothing (high pass)

Removes the long wave length – Rolling hills

Filter Sets can be specified and developed that get rid of wave lengths at both ends to leave the wave lengths that influence the roughness that we feel when riding on the pavement

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Filter Issues•Some profilers process the collected profiles through their “black box” filters on board the vehicle. The filtering algorithms are proprietary.

•Other profilers allow output of unfiltered profile data for processing by third party software (RoadRuf or ProVal).

•There are numerous types of filters available to process the profiles.

•The calculation of the smoothness statistic (IRI) is dependent on the filter set(s) used.

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Filters - Smoothing (low pass)

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NJDOT Certification Facility• Check Calibrations of Profiler Sub-Systems

• Correlate NJDOT and Contractor Profilers against NJDOT Standard Profiler on three levels of roughness

• Check the Operators ability to check equipment calibrations and operate the Profiler

• Certify the Operator and Profiler for Ride Quality Measurement and Analyses on NJDOT paving projects

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NJDOT Certification FacilityAASHTO MP 11 Standard Equipment

Specification for Inertial Profilers

AASHTO PP 49 Standard Practice for Certification of Inertial Profilers

AASHTO PP 50 Standard Practice for Operating Inertial Profilers and Evaluating Pavement Profiles

AASHTO PP 51 Standard Practice for a Pavement Ride Quality Specification when Measured Using Inertial Profiling Systems

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NJDOT Certification Facility• Pre-operational checks on profiler• Operating speed• Lead-in distance• Lateral Positioning• Longitudinal Positioning/Triggering• Checks during data collection• Post-operational checks• Verification Sites

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Pre-operational Checks• Tire pressure

• Visual check of sensors

• Static sensor check

• Bounce test

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Lead-in Distance• Profiler needs a lead-in distance to bring it up to

speed and to initialize filters used for profile computation

• Inadequate lead-in will cause errors in profile at start of section

Lead In Distance Start of Section

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Advantages of Automated Triggering• Data collection can be initiated at exact start

of the section

• Roughness features can be identified at correct location in the field based on profile data (using DMI and GPS)

• Repeatability of profile data and roughness indices can be evaluated

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Inertial Profiler Certification Specification

• Procedure to evaluate repeatability of profile data and comparison of inertial profiler profile with reference profile

• Procedure to evaluate repeatability of ride statistics computed from profile data and comparison of ride statistics obtained from reference profile

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Correlation of Data

Measurement(from profiler)

Mea

sure

men

t(f

rom

Sta

ndar

d D

evic

e)

IRI Adjustment

IRISTD = A * IRIP+B

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Ensuring SmoothnessWith a Little Work And Patience We Can Get Through

the Wrinkles

Questions?