Learning ObjectivesLearning Objectives Explain the importance of conducting Explain the importance of conducting
roughness and surface friction evaluationsroughness and surface friction evaluations Describe the different types of roughness Describe the different types of roughness
survey methods, equipment types, and survey methods, equipment types, and roughness indicesroughness indices
Describe the different types of friction Describe the different types of friction measuring equipmentmeasuring equipment
List the different categories of surface List the different categories of surface texturetexture
Learning Objectives Learning Objectives (continued)(continued)
Explain the importance of measuring Explain the importance of measuring surface texture as part of a surface friction surface texture as part of a surface friction evaluationevaluation
Describe the different types of texture-Describe the different types of texture-measuring devicesmeasuring devices
Explain the advantages of using IRI and IFI Explain the advantages of using IRI and IFI over other indicesover other indices
Describe how roughness- and friction-Describe how roughness- and friction-related information influences the selection related information influences the selection of rehabilitation activitiesof rehabilitation activities
Why is it important to assess Why is it important to assess roughness and friction?roughness and friction?
Both affect “functional” performanceBoth affect “functional” performance
Roughness leads to increases in: Roughness leads to increases in: Vehicle operating costsVehicle operating costs User delayUser delay AccidentsAccidents User dissatisfactionUser dissatisfaction
Friction loss leads to increases in wet Friction loss leads to increases in wet weather accidentsweather accidents
Definition of RoughnessDefinition of Roughness Deviations in pavement surface that affect Deviations in pavement surface that affect
ride qualityride quality
Caused by:Caused by: Built-in surface irregularitiesBuilt-in surface irregularities Traffic and environmentTraffic and environment
Purpose of a Purpose of a Roughness SurveyRoughness Survey
Identify areas of severe roughnessIdentify areas of severe roughness
Determine relative roughness between Determine relative roughness between projectsprojects
Gauge benefits of various rehabilitation Gauge benefits of various rehabilitation activities by measuring roughness before activities by measuring roughness before and after constructionand after construction
Roughness Survey TypesRoughness Survey Types
1.1.Ride quality surveys (serviceability)Ride quality surveys (serviceability) Subjective methodSubjective method Simple assessment toolSimple assessment tool
2.2.Objective roughness surveysObjective roughness surveys Quantitative unbiased methodQuantitative unbiased method Various types of equipment are Various types of equipment are
availableavailable
Ride Quality SurveysRide Quality SurveysServiceabilityServiceability
Subjective measure of user’s perception Subjective measure of user’s perception of pavement rideabilityof pavement rideability
Measurement scaleMeasurement scale Zero (very poor) to Five (very good)Zero (very poor) to Five (very good) Working range: 1.5 to 4.5Working range: 1.5 to 4.5
Trigger levels for rehabilitation depend on Trigger levels for rehabilitation depend on speed and level of trafficspeed and level of traffic
Correlations with other roughness indicesCorrelations with other roughness indices
Roughness Measuring Roughness Measuring EquipmentEquipment
Response-Type Road Roughness Response-Type Road Roughness Measuring Systems (RTRRMS)Measuring Systems (RTRRMS) MaysmeterMaysmeter PCA RoadmeterPCA Roadmeter BPR RoughometerBPR Roughometer
Inertial Road Profiling Systems (IRPS)Inertial Road Profiling Systems (IRPS) ICC ProfilerICC Profiler K.J. Law ProfilometerK.J. Law Profilometer South Dakota ProfilerSouth Dakota Profiler
Response-Type Road Response-Type Road Roughness Measuring Systems Roughness Measuring Systems
(RTRRMS)(RTRRMS) Measure vehicle responseMeasure vehicle response AdvantagesAdvantages
Low initial and operating costsLow initial and operating costs Ease of operationEase of operation High measuring speedsHigh measuring speeds
DisadvantagesDisadvantages Output sensitive to vehicle Output sensitive to vehicle
characteristicscharacteristics Requires frequent calibrationRequires frequent calibration
Inertial Road Profiling Inertial Road Profiling Systems Equipment (IRPS)Systems Equipment (IRPS)
Measure actual pavement profileMeasure actual pavement profile AdvantagesAdvantages
Relatively accurate and repeatable Relatively accurate and repeatable profile measurementsprofile measurements
Used to calibrate RTRRM systemsUsed to calibrate RTRRM systems DisadvantagesDisadvantages
High capital and operating expensesHigh capital and operating expenses Complexity of systemsComplexity of systems
International Roughness International Roughness Index (IRI)Index (IRI)
Current roughness measurement standardCurrent roughness measurement standard
Correlates to RTRRM systemsCorrelates to RTRRM systems
Scale: 0 to 20 m/km (0 to 1267 in/mi)Scale: 0 to 20 m/km (0 to 1267 in/mi)
2 m/km (125 in/mi) is typical break point 2 m/km (125 in/mi) is typical break point between between roughrough and and smoothsmooth pavements pavements
Standard for FHWA HPMS DatabaseStandard for FHWA HPMS Database
Roughness Data VariabilityRoughness Data Variability
Seasonal and daily environmental effectsSeasonal and daily environmental effects
Lateral positioningLateral positioning
Differences in operator practice (between-Differences in operator practice (between-operator variability)operator variability)
Differences between equipment devices Differences between equipment devices (between-device variability)(between-device variability) Manufacturing differencesManufacturing differences Calibration problemsCalibration problems
Definition ofDefinition ofSurface FrictionSurface Friction
Force developed at pavement-tire Force developed at pavement-tire interface that resists slidinginterface that resists sliding
Influenced by:Influenced by: Surface textureSurface texture Surface drainage (cross-slope)Surface drainage (cross-slope)
Purpose of a Surface Purpose of a Surface Friction SurveyFriction Survey
Assess safety concernsAssess safety concerns HydroplaningHydroplaning Wet weather accidentsWet weather accidents
Target testing in areas of poor surface Target testing in areas of poor surface condition:condition: Smooth macrotexture (polishing or Smooth macrotexture (polishing or
inadequate finishing)inadequate finishing) Inadequate pavement cross slopeInadequate pavement cross slope
How do you adequately assess How do you adequately assess surface frictional characteristics? surface frictional characteristics?
Historical methodHistorical method——Measure friction Measure friction directly (“skid number”)directly (“skid number”)
Recent research indicates that “surface Recent research indicates that “surface texture” MUST also be consideredtexture” MUST also be considered
What is surface texture?What is surface texture? Characteristics that contribute to surface Characteristics that contribute to surface
frictionfriction Microtexture – Roughness of individual Microtexture – Roughness of individual
pieces of aggregatepieces of aggregate MacrotextureMacrotexture
General coarseness of pavement surfaceGeneral coarseness of pavement surface Formed water channels (grooving)Formed water channels (grooving) Large impact on surface frictionLarge impact on surface friction
Friction Survey Measurement Friction Survey Measurement Equipment TypesEquipment Types
Locked-wheel testersLocked-wheel testers
Side force testers (Mu Meter, SCRIM)Side force testers (Mu Meter, SCRIM)
Fixed slip testers (Gripster)Fixed slip testers (Gripster)
Variable slip testers (Norsemeter ROAR)Variable slip testers (Norsemeter ROAR)
Note: These devices do NOT measure texture!Note: These devices do NOT measure texture!
Friction Measuring DevicesFriction Measuring DevicesExamples of Other DevicesExamples of Other Devices
Mu MeterMu Meter(side force tester)(side force tester)
SCRIMSCRIM(side force tester)(side force tester)
Norsemeter ROARNorsemeter ROAR(variable slip tester)(variable slip tester)
Surface Texture Measuring Surface Texture Measuring DevicesDevices
Volumetric (“Sand Patch”) methodVolumetric (“Sand Patch”) method
Outflow meterOutflow meter
Circular track meter (CTMeter)Circular track meter (CTMeter)
High-speed laser-based devices High-speed laser-based devices (ROSAN, most laser-based profilers)(ROSAN, most laser-based profilers)
Surface Texture MeasurementSurface Texture MeasurementHigh-speed Laser-Based DevicesHigh-speed Laser-Based Devices
ROSANvROSANv
High-Speed Inertial High-Speed Inertial ProfilersProfilers
International Friction Index International Friction Index (IFI)(IFI)
Incorporates simultaneous measurements Incorporates simultaneous measurements of friction and macrotextureof friction and macrotexture Speed constant (SSpeed constant (Spp)) Friction number (F60)Friction number (F60)
Becoming friction measurement standardBecoming friction measurement standard Modern high-speed measuring equipment Modern high-speed measuring equipment
measure IFI directlymeasure IFI directly
ReviewReview Why is it important to conduct roughness Why is it important to conduct roughness
and surface friction evaluations?and surface friction evaluations? What are the two types of roughness What are the two types of roughness
measuring equipment? measuring equipment? What are two types of friction measuring What are two types of friction measuring
equipment?equipment? What are the three categories of surface What are the three categories of surface
texture?texture?
Review (continued)Review (continued) Why it is important to measure surface Why it is important to measure surface
texture as part of a surface friction texture as part of a surface friction evaluation?evaluation?
What are two of the different types of What are two of the different types of texture-measuring devices?texture-measuring devices?
What are the advantages of using IRI and What are the advantages of using IRI and IFI (over other indices)?IFI (over other indices)?
How do roughness and friction affect the How do roughness and friction affect the selection of rehabilitation alternatives?selection of rehabilitation alternatives?
Henry, J. J. 2000. Henry, J. J. 2000. Evaluation of Pavement Friction Evaluation of Pavement Friction CharacteristicsCharacteristics. Synthesis of Highway Practice No. 291. . Synthesis of Highway Practice No. 291. National Cooperative Highway Research Program, National Cooperative Highway Research Program, Transportation Research Board, Washington, DC.Transportation Research Board, Washington, DC.
Karamihas, S. M., T. D. Gillespie, R. W. Perera, and S. D. Karamihas, S. M., T. D. Gillespie, R. W. Perera, and S. D. Kohn. 1999. “Guidelines for Longitudinal Pavement Kohn. 1999. “Guidelines for Longitudinal Pavement Profile Measurement.” Profile Measurement.” NCHRP Report 434NCHRP Report 434. . Transportation Research Board, Washington, DC.Transportation Research Board, Washington, DC.
Ksaibati, K., R. McNamara, W. Miley, and J. Armaghani. Ksaibati, K., R. McNamara, W. Miley, and J. Armaghani. 1999. “Pavement Roughness Data Collection and 1999. “Pavement Roughness Data Collection and Utilization.” Utilization.” Transportation Research Record 1655Transportation Research Record 1655. . Transportation Research Board, Washington, DC.Transportation Research Board, Washington, DC.
Key ReferencesKey References
Sayers, M. W. and S. M. Karamihas. 1998. Sayers, M. W. and S. M. Karamihas. 1998. The Little The Little Book of Profiling—Basic Information about Measuring and Book of Profiling—Basic Information about Measuring and Interpreting Road ProfilesInterpreting Road Profiles. University of Michigan . University of Michigan Transportation Research Institute, Ann Arbor, MI. Web Transportation Research Institute, Ann Arbor, MI. Web address: www.umtri.umich.edu/erd/roughness.address: www.umtri.umich.edu/erd/roughness.
Smith, K. L., K. D. Smith, L. D. Evans, T. E. Hoerner, and Smith, K. L., K. D. Smith, L. D. Evans, T. E. Hoerner, and M. I. Darter. 1997. “Smoothness Specifications for M. I. Darter. 1997. “Smoothness Specifications for Pavements.” Web Document #1, Final Report NCHRP Pavements.” Web Document #1, Final Report NCHRP Project 1-31. Transportation Research Board, Project 1-31. Transportation Research Board, Washington, DC. Washington, DC.
Key References Key References (continued)(continued)
ASTM E 274, ASTM E 274, Skid Resistance of Pavements Using a Full-Skid Resistance of Pavements Using a Full-Scale TireScale Tire
ASTM E 965, ASTM E 965, Measuring Pavement Macrotexture Depth Measuring Pavement Macrotexture Depth Using a Volumetric TechniqueUsing a Volumetric Technique
ASTM E 1845, ASTM E 1845, Calculating Pavement Macrotexture Profile Calculating Pavement Macrotexture Profile DepthDepth
ASTM E 1859, ASTM E 1859, Friction Coefficient Measurements Friction Coefficient Measurements Between Tire and Pavement Using a Variable Slip Between Tire and Pavement Using a Variable Slip TechniqueTechnique
ASTM E 1926, ASTM E 1926, Calculating International Roughness Index Calculating International Roughness Index of a Pavement Surfaceof a Pavement Surface
ASTM E 1960, ASTM E 1960, Calculating International Friction Index of a Calculating International Friction Index of a Pavement SurfacePavement Surface
Applicable ASTM Applicable ASTM StandardsStandards