Pavement Ride Quality Nicholas Vitillo, Ph. D. Center for Advanced Infrastructure and Transportation

CAIT Topics Description 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

CAIT 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

CAIT 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

CAIT Wheel Track Profile Longitudinal Slices of the Pavement Surface

CAIT 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.

CAIT NJ IRI Guidelines

CAIT 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”

CAIT Measuring the “True” Profile Walking Profiler Standard pavement profiling devices Rod and Level Walking Profilers Calibration/Correlation

CAIT Lightweight Profilers

CAIT Portable Profilers Dynatest Portable Roadware Portable

CAIT High Speed Profiler - ICC Profiler

CAIT Measurement Issues All Profilers are NOT created equal DMI

CAIT Height Sensor Footprint 9.5 Inches 12 Inches Sampling Intervals Footprint Shapes

CAIT Height Sensor Footprint 6 Inches

CAIT Measurement Issues All 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?

CAIT Filters Pavement 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

CAIT 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

CAIT 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.

CAIT Filters - Smoothing (low pass)

CAIT 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

CAIT NJDOT Certification Facility AASHTO MP 11Standard Equipment Specification for Inertial Profilers AASHTO PP 49Standard Practice for Certification of Inertial Profilers AASHTO PP 50Standard Practice for Operating Inertial Profilers and Evaluating Pavement Profiles AASHTO PP 51Standard Practice for a Pavement Ride Quality Specification when Measured Using Inertial Profiling Systems

CAIT 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

CAIT Pre-operational Checks Tire pressure Visual check of sensors Static sensor check Bounce test

CAIT 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

CAIT 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

CAIT 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

CAIT Correlation of Data Measurement (from profiler) Measurement (from Standard Device) IRI Adjustment IRI STD = A * IRI P +B

CAIT Ensuring Smoothness With a Little Work And Patience We Can Get Through the Wrinkles Questions?