an assessment of automated pavement distress ... · an assessment of automated pavement distress...

Stage 4 Distribution, March 31, 2009

November 2008

Technical Memorandum: UCPRC-TM-2008-13

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Authors:Bruce Steven, John T. Harvey,

and Bor-Wen Tsai

Work Conducted as part of Partnered Pavement Research Center Strategic Plan Element 3.3: Support for Implementation of Caltrans PMS

PREPARED FOR: California Department of Transportation (Caltrans) Division of Research and Innovation Division of Pavements

PREPARED BY:

University of California Pavement Research Center

Davis and Berkeley


UCPRC-TM-2008-13 ii

DOCUMENT RETRIEVAL PAGE Technical Memorandum No.:UCPRC-TM-2008-13

Title: An Assessment of Automated Pavement Distress Identification Technologies in California

Author: Bruce Steven, John T. Harvey, and Bor-Wen Tsai

Prepared for: California Department of Transportation, Division of Research and Innovation, Division of Pavements

FHWA No.

Work Submitted December 3, 2008

Date:March 31, 2009

Strategic Plan Element No: 3.3

Status: Draft

Version No:Stage 4 review draft

Abstract: This technical memorandum describes work undertaken to evaluate the state of the practice for automated image capture and subsequent rating of pavement distresses. The Caltrans Pavement Condition Survey (PCS) crew, UCPRC personnel, and six automated condition survey vendors evaluated ten 500-foot long sections in an area near Davis, California that encompassed a wide range of pavement types and distresses. The distress evaluations were performed using a newly developed distress matrix containing elements that are based on the underlying mechanisms of pavement distress, elements of which have been incorporated into the 2008 Caltrans PCS. Use of this new matrix will facilitate development of network-level pavement performance models, and will also provide “feedback” to Mechanistic-Empirical pavement design models. It was found that the vendors are able to collect images of sufficient resolution and clarity at highway speeds to enable distress evaluations to be performed. It was also found that the different distress-type definitions need to be refined by Caltrans/UCPRC to be simpler and more precise for the new automated data collection PCS manual current under development.

Keywords: Pavement condition survey, linescan camera, pavement distress, pavement management system, automated image processing, crack detection

Proposals for implementation: Develop new distress-type definitions that are based on identification of crack geometries and locations. Include IRI in vendor RFQ process.

Related documents:

Signatures:

B. Steven 1st Author

J. Harvey Technical Review

D. Spinner Editor

J. Harvey Principal Investigator

J. Holland Caltrans Contract Manager


UCPRC-TM-2008-13 iii

DISCLAIMER

The contents of this report reflect the views of the authors who are responsible for the facts and accuracy

of the data presented herein. The contents do not necessarily reflect the official views or policies of the

State of California or the Federal Highway Administration. This report does not constitute a standard,

specification, or regulation.

ACKNOWLEDGMENTS

This work was funded and managed by the California Department of Transportation, Division of

Research and Innovation, under the direction of Nick Burmas, Joe Holland, Michael Samadian, and

Alfredo Rodriguez. The technical lead for Pavement Standards Team was Peter Vacura of the Division of

Pavement Management. The authors would also like to thank members of the Caltrans Pavement

Condition Survey crew for their help in refining distress definitions and in performing the manual survey

of the test sections, and the members of the Caltrans PMS Expert Task Group for their many suggestions

and comments. The authors would also like to thank Erwin Kohler for help in setting up the test sections.

PROJECT OBJECTIVES

The purpose of the work included in this technical memorandum is to evaluate the state of the practice

with respect to automated methods for recording and measuring pavement distress, and to make

recommendations for changes to the Caltrans Pavement Condition Survey manual for use with automated

data collection.


UCPRC-TM-2008-13 iv


UCPRC-TM-2008-13 v

TABLE OF CONTENTS Acknowledgments ...................................................................................................................................... iii Project Objectives ...................................................................................................................................... iii List of Tables .............................................................................................................................................vii List of Figures............................................................................................................................................. ix 1 Introduction.................................................................................................................................... 1

1.1 Pavement Condition Survey Techniques Used by Caltrans Prior to 2008 .................................. 1 1.2 Pavement Condition Survey Techniques Implemented in 2008 PCS.......................................... 3 1.3 Future Pavement Condition Survey Techniques Used by Caltrans............................................. 3 1.4 Need to Assess State-of-the-Technology for Automated Distress Collection............................. 4 1.5 Objective of this Technical Memorandum .................................................................................. 4

2 Pavement Distress Definitions ...................................................................................................... 7 3 Pavement Condition Rodeo........................................................................................................... 9

3.1 Rodeo Details .............................................................................................................................. 9 3.2 Manual Survey and Desktop Survey ......................................................................................... 11 3.3 North Carolina DOT Data Collection Rodeo and Workshop .................................................... 12

4 Survey Results .............................................................................................................................. 17 4.1 Section 1: Old Davis Road On-Ramp to NB SR113 ................................................................. 17

4.1.1 Alligator A and B Cracks ...................................................................................................... 18 4.1.2 Cracks Between and Outside the Wheelpaths....................................................................... 19 4.1.3 Roughness and Rutting ......................................................................................................... 21

4.2 Section 2: NB SR113................................................................................................................. 22 4.2.1 Alligator A and B Cracks ...................................................................................................... 22 4.2.2 Cracks Between and Outside the Wheelpaths....................................................................... 24 4.2.3 Roughness and Rutting ......................................................................................................... 25

4.3 Section 3: NB SR113................................................................................................................. 25 4.3.1 Rigid Transverse Cracks ....................................................................................................... 26 4.3.2 Rigid Joints and Cracks Filled with Sealant.......................................................................... 27 4.3.3 Rigid Faulting, Roughness, and Rutting ............................................................................... 27

4.4 Section 4: NB SR113................................................................................................................. 27 4.4.1 Rigid Corner Cracks.............................................................................................................. 28 4.4.2 Rigid Joints and Cracks Filled with Sealant.......................................................................... 29 4.4.3 Rigid Faulting, Roughness, and Rutting ............................................................................... 29

4.5 Section 5: WB SR16.................................................................................................................. 29


UCPRC-TM-2008-13 vi

4.6 Section 6: WB SR16.................................................................................................................. 29 4.6.1 Alligator A and B Cracks ...................................................................................................... 30 4.6.2 Cracks Between and Outside the Wheelpaths....................................................................... 31 4.6.3 Roughness and Rutting ......................................................................................................... 33

4.7 Section 7: SB I505..................................................................................................................... 33 4.7.1 Roughness and Rutting ......................................................................................................... 34

4.8 Section 8: EB I80....................................................................................................................... 34 4.8.1 Rigid Longitudinal Cracks .................................................................................................... 35 4.8.2 Rigid Transverse Cracks ....................................................................................................... 35 4.8.3 Rigid Joints and Cracks Filled with Sealant.......................................................................... 35 4.8.4 Rigid Faulting, Roughness and Rutting ................................................................................ 35

4.9 Section 9: EB I80....................................................................................................................... 36 4.9.1 Rigid Longitudinal Cracks .................................................................................................... 37 4.9.2 Rigid Transverse Cracks ....................................................................................................... 37 4.9.3 Rigid Joints and Cracks Filled with Sealant and Joint/Crack Spalling ................................. 37 4.9.4 Rigid Faulting, Roughness, and Rutting ............................................................................... 37

4.10 Section 10: EB I80..................................................................................................................... 38 4.10.1 Alligator A and B Cracks.................................................................................................. 38 4.10.2 Cracks Between and Outside the Wheelpaths................................................................... 39 4.10.3 Digouts and Patches.......................................................................................................... 41 4.10.4 Roughness and Rutting ..................................................................................................... 41

4.11 Section 11: EB I80..................................................................................................................... 41 4.11.1 Alligator A and B Cracks.................................................................................................. 42 4.11.2 Cracks Between and Outside the Wheelpaths................................................................... 44 4.11.3 Roughness and Rutting ..................................................................................................... 45

4.12 Roughness Results..................................................................................................................... 45 5 5 Findings and Conclusions......................................................................................................... 53

5.1 Image Capture ........................................................................................................................... 53 5.2 Image Analysis .......................................................................................................................... 54 5.3 Recommended Changes to the Distress Definitions.................................................................. 55 5.4 Recommended Changes Regarding Quality Assurance for IRI Measurements ........................ 56 5.5 Recommendations for the Vendor Evaluation Part of the RFQ Process ................................... 57 5.6 Overall Recommendations ........................................................................................................ 57

Appendix: Summary of IRI (m/km) Values for All Vendors and All Sections ................................... 58


UCPRC-TM-2008-13 vii

LIST OF TABLES Table 2.1: Distress Descriptions in PCS Manual for 2008 Used for Rodeo ................................................ 8 Table 3.1: Site Locations ........................................................................................................................... 10 Table 3.2: Alphabetical List of Participating Vendors............................................................................... 11 Table 3.3: Detailed Descriptions of Vendor Equipment............................................................................ 13 Table 4.1: Section 1, Alligator A Cracking ............................................................................................... 19 Table 4.2: Section 1, Alligator B Cracking................................................................................................ 19 Table 4.3: Section 1, Combined Total for Alligator A and B Cracking .................................................... 19 Table 4.4: Section 1, Alligator C Cracking................................................................................................ 20 Table 4.5: Section 1, Short Transverse Cracks Outside the Wheelpath..................................................... 21 Table 4.6: Section 1, Transverse Cracks.................................................................................................... 21 Table 4.7: Section 1, Longitudinal Cracks................................................................................................. 21 Table 4.8: Section 2, Alligator A Cracking ............................................................................................... 23 Table 4.9: Section 2, Alligator B Cracking................................................................................................ 23 Table 4.10: Section 2, Combined Total for Alligator A and B Cracking .................................................. 23 Table 4.11: Section 2, Alligator C Cracking.............................................................................................. 24 Table 4.12: Section 2, Short Transverse Cracks Outside the Wheelpath................................................... 24 Table 4.13: Section 2, Transverse Cracks.................................................................................................. 24 Table 4.14: Section 2, Longitudinal Cracks............................................................................................... 25 Table 4.15: Section 3, Rigid Transverse Cracks ........................................................................................ 27 Table 4.16: Section 4, Rigid Corner Cracks .............................................................................................. 28 Table 4.17: Section 6, Alligator A Cracking ............................................................................................. 31 Table 4.18: Section 6, Alligator B Cracking.............................................................................................. 31 Table 4.19: Section 6, Combined Total for Alligator A and B Cracking .................................................. 31 Table 4.20: Section 6, Alligator C Cracking.............................................................................................. 32 Table 4.21: Section 6, Short Transverse Cracks Outside the Wheelpath................................................... 32 Table 4.22: Section 6, Transverse Cracks.................................................................................................. 32 Table 4.23: Section 6, Longitudinal Cracks............................................................................................... 32 Table 4.24: Section 8, Rigid Transverse Cracks ........................................................................................ 35 Table 4.25: Section 9, Rigid Transverse Cracks ........................................................................................ 37 Table 4.26: Section 10, Alligator A Cracking ........................................................................................... 39 Table 4.27: Section 10, Alligator B Cracking............................................................................................ 39 Table 4.28: Section 10, Combined Total for Alligator A and B Cracking ................................................ 39 Table 4.29: Section 10, Alligator C Cracking............................................................................................ 40


UCPRC-TM-2008-13 viii

Table 4.30: Section 10, Short Transverse Cracks Outside the Wheelpath................................................. 40 Table 4.31: Section 10, Transverse Cracks................................................................................................ 40 Table 4.32: Section 10, Longitudinal Cracks............................................................................................. 40 Table 4.33: Section 10, Digouts................................................................................................................. 41 Table 4.34: Section 11, Alligator A Cracking ........................................................................................... 43 Table 4.35: Section 11, Alligator B Cracking............................................................................................ 43 Table 4.36: Section 11, Combined Total for Alligator A and B Cracking ................................................ 43 Table 4.37: Section 11, Alligator C Cracking............................................................................................ 44 Table 4.38: Section 11, Short Transverse Cracks Outside the Wheelpath................................................. 44 Table 4.39: Section 11, Transverse Cracks................................................................................................ 44 Table 4.40: Section 11, Longitudinal Cracks............................................................................................. 45 Table 4.41: Summary of the Means and Standard Deviations of Ln(IRI). ................................................. 49


UCPRC-TM-2008-13 ix

LIST OF FIGURES Figure 3.1: Map of rodeo circuit. ............................................................................................................... 11 Figure 3.2: Downward pavement images of a flexible pavement.............................................................. 15 Figure 3.3: Downward pavement images of a rigid pavement. ................................................................. 16 Figure 4.1: Photo of Section 1, Old Davis Road On-Ramp to NB SR 113................................................. 18 Figure 4.2: Photo of Section 2, NB SR113. ............................................................................................... 22 Figure 4.3: Photo of Section 3, NB SR113. ............................................................................................... 26 Figure 4.4: Photo of Section 4, NB SR113. ............................................................................................... 28 Figure 4.5: Photo of Section 6, WB SR16. ................................................................................................ 30 Figure 4.6: Photo of Section 7, SB I505. ................................................................................................... 33 Figure 4.7: Photo of Section 8, EB I80. ..................................................................................................... 34 Figure 4.8: Photo of Section 9, EB I80. ..................................................................................................... 36 Figure 4.9: Photo of Section 10, EB I80. ................................................................................................... 38 Figure 4.10: Photo of Section 11, EB I80. ................................................................................................. 42 Figure 4.11: Summary of IRI (m/km) values for all vendors, all sections, and all subsections.................. 46 Figure 4.12: Summary of IRI (m/km) values for all vendors and all subsections (with

mean-trend lines). .......................................................................................................................... 47 Figure 4.13: Mean IRI (m/km) versus mean standard deviation across vendors for each subsection. ...... 49 Figure 4.14: Mean IRI (m/km) versus mean standard deviation across vendors for each

asphalt-surfaced subsection. .......................................................................................................... 50 Figure 4.15: Mean IRI (m/km) versus mean standard deviation across vendors for each

PCC-surfaced subsection. .............................................................................................................. 50 Figure 4.16: IRI distributions of all the vendors across all the sections: (a) Histogram and

(b) QQ-plot. ................................................................................................................................... 51


UCPRC-TM-2008-13 x

METRIC TO U.S. STANDARD CONVERSIONS

Symbol Convert From Convert To Symbol Conversion

LENGTH

mm millimeters inches in mm x 0.039

m meters feet ft m x 3.28

km kilometers mile mile km x 1.609

AREA

mm2 square millimeters square inches in2 mm2 x 0.0016

m2 square meters square feet ft2 m2 x 10.764

VOLUME

m3 cubic meters cubic feet ft3 m3 x 35.314

kg/m3 kilograms/cubic meter pounds/cubic feet lb/ft3 kg/m3 x 0.062

L liters gallons gal L x 0.264

L/m2 liters/square meter gallons/square yard gal/yd2 L/m2 x 0.221

MASS

kg kilograms pounds lb kg x 2.202

TEMPERATURE (exact degrees)

C Celsius Fahrenheit F °C x 1.8 + 32

FORCE and PRESSURE or STRESS

N newtons poundforce lbf N x 0.225

kPa kilopascals poundforce/square inch lbf/in2 kPa x 0.145

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380.

(Revised March 2003)


UCPRC-TM-2008-13 1

1 INTRODUCTION

The main purpose of the project titled “Partnered Pavement Research Center (PPRC) Strategic Plan

Element 3.3 (SPE 3.3), Support Implementation of a Caltrans Pavement Management System” is for the

University of California Pavement Research Center (UCPRC) to provide support to the California

Department of Transportation (Caltrans) in developing and/or adapting and implementing the required

elements of a Pavement Management System (PMS). In May 2007, the Caltrans State Pavement Program

Manager (SPPM) prepared a document titled “Pavement Management System Action Plan 2007” (SPPM

Action Plan). This document was subsequently approved by the Director of Caltrans as the action plan for

the implementation of a PMS. The SPPM Action Plan identified four phases:

1. PMS Database

2. Pavement Structure Inventory and Annual Update (i.e., as-built updates)

3. Pavement Condition Survey—Baseline and Annual Update

4. PMS Upgrade to Include Pavement Performance Prediction

The UCPRC is responsible for designated activities as set out in the scoping documents for the project

with the main purpose of providing support to Caltrans for implementation of a PMS and quality

assurance for the initial collection of PMS data. Caltrans has final responsibility and accountability for

successful implementation of its PMS.

This technical memorandum details work undertaken to partially fulfill Phase 3, the Pavement Condition

Survey.

1.1 Pavement Condition Survey Techniques Used by Caltrans Prior to 2008

Prior to 2008, a portion of the Caltrans network was manually (meaning performed by humans as opposed

to machines) surveyed each year in order to rate the surface condition of the network; the survey

identified pavement distresses and other conditions that might warrant maintenance activity. A “manual”

survey means that people visually observe the surface of the pavement, either by walking on the shoulder

or by traveling in a vehicle, and record the type, severity, and extent of the different distresses. The survey

was done to assist Caltrans in justifying, prioritizing, and allocating rehabilitation and maintenance

funding and to provide data for federal and state reporting requirements.


UCPRC-TM-2008-13 2

The Caltrans Pavement Condition Survey (PCS) is an inventory of the existing pavement surface

conditions intended to assess the condition of the entire state highway network. The Caltrans PCS is a

continuous, 12-month process, cycling on the calendar year. All the state’s routes are surveyed during

each cycle. Pavement condition is established by observing the severity and extent of surface distress.

After data from the PCS is combined with a ride-quality measurement—which is based on calculation of

International Roughness Index (IRI) values for each rated lane from longitudinal profile measurements—

a picture of the condition of the state highway network is created. Pavement performance models require

collection of distress and ride quality for the same sections of pavement year after year, creating a time

series of performance that can then be used to predict future performance.

Distresses that cause a change in the vertical profile of the pavement either in the transverse direction, i.e.,

rutting in asphalt-surfaced pavements, or in the longitudinal direction, i.e., faulting in concrete-surfaced

pavements, were previously estimated visually from the shoulder. These distresses were rated as either

being present or not being present, and there was a great deal of inconsistency in their estimation from

year to year because of the subjective nature of the yes/no rating and the difficulty of seeing rutting and

faulting from the shoulder.

The annual surveys were previously completed by a team of between six and eight Caltrans personnel.

For rigid pavements, the pavement condition raters continuously surveyed the outside two lanes of the

rigid pavements while, summarizing the condition for every one-mile section. Inner lanes on routes with

more than two lanes in one direction were not surveyed. Flexible pavements were evaluated by rating a

100-ft (30-m) section of pavement within a length of pavement of similar condition. “Similar” conditions

were assessed while traveling at traffic speed, referred to as a “windshield survey.” While this method of

selecting rating sections can be used to establish a representative view of the condition of the entire

network for each year, it could not be used to create accurate time-series trends of pavement condition

because of year-to-year variations in the start and end locations of pavement sections with similar

conditions; these variations resulted from choices made by different personnel operating in the field or

were due to changes in pavement condition. The locations of the 100-ft rating sections were not recorded;

instead the beginning and end locations of the “similar” pavement were recorded using the in-vehicle

distance measuring instruments (DMI). The ride quality of the pavement, as reported by International

Roughness Index (IRI), was measured separately for every lane-mile of the network.

In summary, because of the lack of recorded locations of the 100-ft rating sections and the fluid

boundaries of the “similar” pavement sections it is difficult to create reliable time-series plots of


UCPRC-TM-2008-13 3

pavement condition. Therefore it would not be practical to use the historical pavement condition data to

create performance predictions for the highway network.

1.2 Pavement Condition Survey Techniques Implemented in 2008 PCS

In 2008 and 2009, Caltrans pavement raters are using a modified set of distress definitions and metrics to

create the PCS. These distress metrics hybridize earlier and future metrics (Section 1.3) but they are

mostly based on a manual version of the latter. The new pavement distress definitions being used in the

current survey better represent the mechanisms that cause pavement distress than the previous definitions

did.

Another major change implemented in the current survey practice is the use of fixed locations for the

flexible sections to enable the same sections with consistent boundaries to be surveyed again in 2009.

This change will begin to provide the time series of year-to-year distress development needed to develop

pavement performance models. For the flexible and composite pavements, the section length was fixed,

with a length of one mile. For each one-mile section, the 100-ft survey section was located at the start of

the section. In addition, rigid distresses are now being recorded on a slab-by-slab basis, as opposed to the

previous use of an overall average percentage of slabs with cracking. The full-length of each one-mile

rigid segment was evaluated using a slow-speed driving survey of the outer two lanes, with the condition

survey van traveling on the shoulder. The location of the survey sections was fixed at the start of each

post mile—for example PM15.0, PM16.0, and so on—unless there were safety issues for the survey

crews.

In addition, GPS coordinates are now being taken manually from the shoulder so that the beginning and

end of pavement sections can be better identified in subsequent years.

1.3 Future Pavement Condition Survey Techniques Used by Caltrans

Beginning in July 2009, Caltrans intends to contract for services that use automated image capture and

ride quality vehicles to measure pavement condition at highway speeds. These data will then be analyzed

using a combination of automated and semi-automated techniques (as selected by the contractor) to create

the annual PCS. It is intended that the selected consultant will survey every lane-mile of the Caltrans

network on an annual basis, after the first year in which a partial survey will be completed. The automated

image and ride quality vehicles will be required to have integrated Differential Global Positioning System

(DGPS) equipment that automatically record the time and location of each measurement.


UCPRC-TM-2008-13 4

In the future, rutting and faulting, which are currently estimated visually as either present or absent (noted

in Section 1.1), will be measured using laser profiling equipment.

1.4 Need to Assess State-of-the-Technology for Automated Distress Collection

Over the past five years there have been major advances in the technologies used for capturing images of

the pavement surface and for identifying pavement distresses from these images. The Department intends

to write a Statement of Work for contracting of automated distress data collection services that requires

the use of best practice to complete the acquisition and analysis of the pavement condition data. In order

to do this, it was determined that a demonstration of current technology in one place at about the same

time was needed, using the new pavement condition survey matrix. It was also determined that the

demonstration needed to be held in California because (a) the results are specific to the Caltrans distress

matrix, (b) Caltrans has a wide range of pavement types and distresses, and (c) this choice of location

would provide Caltrans and UCPRC personnel the opportunity to discuss the technology with equipment

vendors. Invitations were sent to equipment vendors that had either developed and/or integrated current

technologies in distinct ways rather than to service providers that had purchased commercial turnkey

systems and only provided a data collection and analysis service. It must be emphasized that the point of

the demonstration was to look at different technologies, not to look at different consultants.

1.5 Objective of this Technical Memorandum

This technical memorandum reports the results of an equipment rodeo held during April and May of 2008.

The term rodeo, which was first used by the Texas Department of Transportation about 25 years ago

during evaluation of deflection measuring technologies, refers to an event at which a number of pieces of

equipment and/or equipment users perform the same tests on a set of pavement sections, and afterward

the test measurements are compared and documented.

The objectives of this automated condition survey equipment rodeo were two-fold: first, it sought to

evaluate the current state of the practice for equipment/technologies that capture pavement surface images

and secondly, it aimed to evaluate the various technologies/systems that pavement condition survey

vendors use to analyze the images to determine the type, severity, and extent of the requested pavement

distresses. A third purpose became apparent during the course of the project: to find gaps in the

definitions of distress developed by the UCPRC that were given to the equipment vendors.


UCPRC-TM-2008-13 5

Because the new PMS will be starting with little or no transferable historical data from the manual PCS, it

is desired that as much of the complete network (15,000 centerline miles and 50,000 lane-miles) as

possible be surveyed on an annual basis for the first few years in order to quickly build up a

comprehensive picture of the trends in network performance. In order to rate the entire network in an

economical and timely manner, it is envisaged that the successful vendor will need to (a) capture images

of the pavement surface at highway speeds, and (b) utilize some degree of automation in the post-

processing of the data.


UCPRC-TM-2008-13 6


UCPRC-TM-2008-13 7

2 PAVEMENT DISTRESS DEFINITIONS

Prior to 2008, Caltrans used a series of distress categories or elements to rate pavement. These distress

elements had been selected and defined to aid in the prioritization of sections requiring maintenance

and/or rehabilitation. The type and severity of distress elements included in the PCS were also intended to

aid in the selection of appropriate maintenance treatments. As part of previous efforts by the UCPRC in

the area of PMS research, changes to the existing Caltrans distress elements were recommended to

provide a more comprehensive, detailed picture of pavement condition. The suggested changes to the

distress definitions were also designed to track the various mechanisms of pavement deterioration and to

have the capacity to provide pavement performance feedback for the Mechanistic-Empirical (ME)

pavement design process that Caltrans is currently moving towards implementing. As part of the current

PMS project, Caltrans reviewed these suggested changes to the distress element definitions, and this

review resulted in a revised set of distress elements that will be used by both the manual PCS crews in

2008 and 2009 and by the automated PCS that will begin in 2009.

There were thirty-one separate distress elements in the PCS prior to the revisions, with some related to

ride quality that apply to all pavement types, and others that were specific to flexible, rigid, or composite

pavements, as well as some related to shoulders and on-pavement items. The distresses are listed in Table

2.1. A subset of these elements were adapted for use in the 2008 and 2009 manual survey, with the

intention that this data can be used to start a time-series trend of pavement performance.

Categories to define the severity and extent of each distress were established. Some distresses are rated by

number/area/length per survey length and others are rated by percentage of survey length or percent of

wheelpath length. For cracks that are defined by an area, assignment of a pseudo area to a length of single

crack is required so that an area can be calculated. The pseudo area was assigned a value of one square

foot per linear foot of crack. It is intended that the future surveys will be reported by the vendor(s) in SI

units (since many vendors are already set up that way), but that the PMS will convert them and produce

reports in U.S. standard units.

It is recognized that some of the distress elements may not be measurable using current semi- or fully-

automated image analysis systems. One purpose of the rodeo was to identify such elements and either to

eliminate them or flag them as needing attention in the future as the state-of-the practice advances.


UCPRC-TM-2008-13 8

Table 2.1: Distress Descriptions in PCS Manual for 2008 Used for Rodeo Distress ID Condition Description Severity Extent “Visual Image Analysis”–Type Measurements Rigid Pavements 1 Rigid Cracking (Longitudinal) Cracks/slab %slabs # cracks 2 Rigid Cracking (Transverse) cracks/slab %slabs # cracks 3 Rigid Cracking (Corner) cracks/slab %slabs # cracks 4 Rigid Cracking (Misaligned Joint -

Transverse) cracks/slab %slabs # cracks

5 Rigid Cracking (Combination of above) # combinations/slab %slabs # types of cracking

6 Crack edges spalling length/depth/width across/along slab

%cracks

7 Joint spalling length/depth/width across slab %joints 8 Cracks filled with sealant 9 Joints sealed 10 CRC Crack Spacing Average spacing (m) 11 CRC Punchouts # punchouts/segment # 12 CRC Crack Sealed 13 Surface spalling found % area Flexible Pavements 14 Alligator A cracking in wheelpaths Crack width (mm) % wp area 15 Alligator B cracking in wheelpaths Crack width (mm) %wp area 16 Alligator C cracking in lane Crack width (mm) %area outside wp 31 Short transverse cracks outside wp Crack width (mm) Area (m2) 17 Transverse cracking Crack width (mm) # 18 Longitudinal cracks outside wp Crack width (mm) Total crack length

(m) 19 Asphalt pavement binder bleeding Presence % wp area 20 Asphalt pavement has been dug out and

replaced Area (m²) Area

21 Patched (potholed) pavement in this location Area (m²) Area 22 Shoulder joint sealed No joint /open/ sealed %segment length Composite Pavements 23 Corner Reflective Cracking (AC/PCC or

AC/CTB) Crack width (mm) #

24 Longitudinal Reflective Cracking (AC/PCC or AC/CTB)

Crack width (mm) %segment length

25 Transverse Reflective Cracking (AC/PCC or AC/CTB)

Crack width (mm) #

Flexible and Composite Pavements 26 Block cracking Vendors were asked to rate

cracks separately as per distresses 14–18 & 21.

Roughness / Ride Quality measurements 27 Rigid pavement slabs faulted Height (mm) <1.2, 1.2-2.5, 2.5-

6.4, 6.4-12.5, >12.5 %joints and cracks

28 Rutting in wheel paths Height (mm) <2.5, 2.5-6.4, 6.4-12.5, 12.5-19, >19

%wp

29 IRI IRI value 30 Texture MPD (mm) %

Notes: CRC is continuously reinforced concrete pavements; wp is wheelpath; # is number; MPD is mean profile depth measured using a high-speed laser in the wheelpath; IRI is International Roughness Index.


UCPRC-TM-2008-13 9

3 PAVEMENT CONDITION RODEO

It must be noted that the rodeo was planned and completed in a time span of just a few months. This left

the participating vendors little time to make any changes for the data collection, which was intentional so

that UCPRC/Caltrans might see what current technology could deliver. The vendors also had little time to

analyze the data according to the distress elements as defined for the 2008 PCS. They therefore had

difficulty changing automated or semiautomated distress analysis software and processes to match the

Caltrans distress definitions, and they had no time to go through a normal iterative process to be sure that

they understood all the distress definitions as UCPRC/Caltrans meant them. They were also not

compensated to make major changes in any software used for image analysis, or to spend much time

training their staff in the manual interpretation of distresses from the images.

It is certain that the schedule caused differing interpretations of the PCS distress definitions among the

different vendors, and this resulted in differences in the reported distresses for the test sections.

3.1 Rodeo Details

The route for the rodeo was chosen so that vendors would be required to survey a range of surface types

and conditions. The route included eleven 500-ft long sites chosen by UCPRC personnel. There were four

rigid and seven flexible or composite sites, described in Table 3.1 and shown in Figure 3.1.

A list of eighteen pavement condition survey service providers was compiled and an invitation was issued

to participate in the rodeo. Vendors were compensated by Caltrans for coming with a fixed fee. Six

vendors elected to participate (Table 3.2). The vendors completed the rodeo at their convenience between

mid-April and early June. The vendors were supplied with a detailed description of the route and the

locations of the sections. The vendors also had the opportunity to make a presentation and to demonstrate

their equipment to interested personnel from Caltrans and the UCPRC. The vendors completed the rodeo

circuit with only their own personnel in the survey vehicle. The equipment that each vendor used in the

rodeo is listed in Table 3.3.

The vendors were required to submit their results in a standard format, which five of the six vendors did.

The sixth vendor was unable to meet this requirement in the six months following the rodeo. This vendor

did submit detailed reports of its analysis but the cracking measurements were not in a form that could be

parsed into the standard format. The roughness and rutting measurements from this vendor were in a

format that enabled them to be incorporated into the results.


UCPRC-TM-2008-13 10

Brief descriptions of the distress definitions were given to the vendors; as the data analysis progressed,

UCPRC received specific questions from the vendors and their answers were distributed to the other

vendors. However, it is likely that the time frame was insufficient for Caltrans/UCPRC and the different

vendors to arrive at complete agreement in understanding the definitions.

Images from the same pavement from four vendors are shown in Figure 3.2 and Figure 3.3 for flexible

and rigid pavements, respectively. It can be seen that distresses are readily visible in the images. One

vendor reported unhappiness with the aperture settings on its equipment and that the images were not

typical of its equipment.

Table 3.1: Site Locations

Site # Route Direction Lane Pavement Surface PM 1 CA 113 NB Old Davis Rd to Woodland

onramp NB 2 HMA or possibly

semi-rigid (HMA on CTB)

-

2 113 NB 3 (of 4) HMA (Composite) 0.0 3 113 NB 2 PCC 4.30 4 113 NB 2 PCC 7.50 51 16 WB 1 HMA 37.62 6 16 WB 1 HMA 36.4 7 505 SB 2 HMA (Composite) 9.5 8 80 EB 3 PCC 32.48 9 80 EB 3 PCC 33.2 10 80 EB 3 HMA 40.2 11 80 EB 4 HMA 42.4 1 Site was eliminated from rodeo due to rehabilitation between the first and second vendors completing their surveys.


UCPRC-TM-2008-13 11

Figure 3.1: Map of rodeo circuit.

Table 3.2: Alphabetical List of Participating Vendors

Vendor Applied Research Associates Inc.

EBA Engineering Consultants Ltd. Dynatest Consulting Inc.

Mandli Communications Inc. Pathway Services Inc. Roadware Group Inc.

3.2 Manual Survey and Desktop Survey

In order to provide an indication of the relationship of the reduced manual distress matrix and the full

automated matrix, the Caltrans PCS crew manually surveyed the sections in the rodeo. In addition, the

UCPRC performed a “desktop” survey to measure the cracking and other distresses that were visible in

the images provided by the vendors. The UCPRC survey was used as the baseline to provide a point of

reference for assessing the automated technologies.


UCPRC-TM-2008-13 12

3.3 North Carolina DOT Data Collection Rodeo and Workshop

The North Carolina Department of Transport (NCDOT) conducted an exercise similar to the one

described in this technical memorandum in the summer of 2008. The NCDOT was assessing the available

technologies with a view to automating their current manual evaluation methods. The NCDOT manages

the complete road network in North Carolina, approximately 80,000 centerline miles, hence its desire to

move toward an automated system for both safety and logistical reasons. The NCDOT required the

automated outputs to follow the same format and style as its current manual rating system (0 to

100 overall score) as the department wished to maintain continuity with historical data.

The main findings from the NCDOT exercise were:

• Only two vendors participated in the rodeo.

• The four experienced manual raters who provided the “ground truth” had considerable

variation in their individual ratings. “Ground truth” is defined as the base measurement

against which all other measurements are compared. It was found that as the extent/severity of

distress increased, the variability in the ratings increased. This was due to a rater having to

make more complex interpretations and decisions about distress type and severity.

• There were difficulties in translating the output from the automated systems to match that

required by the historical overall rating score.

• There was considerable variation between the vendor and ground truth results. This could be

attributed partly to the fact that neither training nor feedback was given to the vendors, apart

from the NCDOT rating manual.


UCPRC-TM-2008-13 13

Table 3.3: Detailed Descriptions of Vendor Equipment

ARA* Dynatest* EBA Mandli Communication*

Pathway* Fugro-Roadware

Profiling Systems

Rutting Laser, 5-sensor Dynatest Mk III – 7 sensor

11 point laser INO LRMS1 INO LRMS1 INO LRMS1

Roughness Laser Dynatest Mk III Yes (Selcom) Dynatest Mk IV Yes Yes Texture 32kHz Lasers No texture sensor in

this profilometer Yes (Selcom) Optional Optional Optional

Imaging Systems

System ICC INO LRIS2 integrated by Dynatest

In-house INO LRIS2 In-house In-house

Image type Line scan Line scan Line scan Line scan Line scan Area scan No. of cameras 1 2 1 2 1 2 Illumination Visible (white)

Lighting Infra-red Laser Infra-red Laser Infra-red Laser Infra-red Laser Visible Strobe

Transverse resolution

1.0 mm cracks visible

4000 pixels per 4000mm of pavement (width) = 1.0 mm/pixel

4000 pixels per 4000 mm of pavement (width) = 1.0 mm/pixel

4000 pixels per 4000 mm of pavement (width) = 1.0 mm/pixel

4000 or 6000 pixels per 4000 mm of pavement (width) = 1.0 or 0.67 mm/pixel

2784 pixels per 3600mm of pavement (width) = 1.3 mm/pixel

Longitudinal resolution

1.0 mm cracks visible

1.0 mm/pixel 1.5 mm Continuous, 100% coverage

2 mm, 1 mm optional

Location system DMI, DGPS & Applanix INS

Trimble AG-132 receiver + Applanix POS LV 220

Applanix POS LV

Applanix POS LV DMI/GPS Applanix POS LV420

Digital imaging ROW

3 Cameras (ICC) currently 1300 x 1028 pixels each. Upgrading soon.

Panasonic HVX-200 high-resolution, digital, color camera

Single camera 1600 x 1200 pixels, 2 cameras

Up to 3 cameras Single high definition camera, 1920 x 1080 pixel resolution


UCPRC-TM-2008-13 14

Table 3.4: Detailed Descriptions of Vendor Equipment (con’t.)

ARA* Dynatest* EBA Mandli Communication*

Pathway* Fugro-Roadware

Data Management In-vehicle data management/control software

ICC WinPro Dynatest RSP (Road Surface Profiler)

NS Mandli’s DVX data collection software, developed in-house

PathRunnerXP including Database/GPS Navigation/VoiceFeedback

ARAN 3

Image/post-processing software

ICC WinRP, ICC Work Station Software & Others depending upon client criteria

Waylink Crack-scope Semi-automatic 20% auto 80% manual

PathView II WiseCrax, D/V-Rate, Step3 (Data compiling software)

Data turnaround time

Depends upon criteria and data being produced

16 days NS 2 weeks 2 weeks 6 weeks

*Information confirmed with vendor NS Information not supplied ICC International Cybernetics Corporation INO Canadian optics/photonics development and manufacturing institute INS Inertial Navigation System LRMS Laser Rut Measurement System – 2-laser illumination with line scan camera, 1280 points/lane, up to 4000 mm wide LRIS Laser Road Imaging System ROW Right of Way Line Scan camera Takes a picture with a resolution of one pixel by n pixels. Area Scan camera Takes a picture with a resolution of n pixels by m pixels. The same a regular camera


UCPRC-TM-2008-13 15

Note: The upper right image is in reverse order with respect to the other images due to the way the vendor’s software arranges the line scans for viewing (For three of the vendors, the images show increasing distance as going from the bottom to the top of the image. The fourth vendor shows

increasing distance from the top to the bottom of the image). Figure 3.2: Downward pavement images of a flexible pavement.


UCPRC-TM-2008-13 16

Note: The upper left image is in reverse order with respect to the other images due to the way the vendor’s software orders the line scans for viewing.

Figure 3.3: Downward pavement images of a rigid pavement.


UCPRC-TM-2008-13 17

4 SURVEY RESULTS

The results of the survey are presented separately for each of the eleven sections. The vendors are only

identified by a number, which remains the same throughout all the results. It was decided to use blind

reporting of the results as the vendors were not given feedback on their submitted data, and as such, there

may have been discrepancies between the UCPRC and vendor interpretations of distresses and the

reporting format. In a formal contracting environment, the vendor would be asked to submit a test set of

data at the beginning of the contract and this would be reviewed by the client and vendor to ensure that

both parties were “seeing” the same distresses in the pavement.

The vendors were asked to rate each section as a series of 100-ft subsections and to present the results

separately for each subsection. Only data for the distresses that were present in each section are given in

this document. During the analysis of the rigid sections it was found that the vendors had assigned

differing numbers of slabs to each subsection, thus affecting the percentages reported for each subsection

and making vendor-to-vendor comparisons difficult. By analyzing the reported percentages, the number

of cracks per section could be estimated using the assumption that the distress counts were integer

quantities. For example if a vendor reported 14 percent for a distress, it could be assumed that there were

7 distress counts in the subsection (100 / 14 = 7.14 ≈ 7). Once the number of cracks for each subsection

was known, the totals for each subsection were summed to give a total for the complete section and the

totals were then reported.

4.1 Section 1: Old Davis Road On-Ramp to NB SR113

This section was a flexible pavement with cracking. The majority of the cracks were sealed, with some

locations being completely covered by sealant. The types of distress present in this section could create

difficulty for a rating process because it could be argued that the cracks are a series of longitudinal and

transverse cracks rather than Alligator A, B, and C cracks. Figure 4.1 shows a photo of Section 1.

The feedback from the results from Section 1 is that it is important to have more detailed definitions of

the various crack types, e.g., the minimum separation distance between isolated cracks, and what

constitutes a wheelpath-related crack. The definitions in the 2008 PCS manual provided to the vendors do

not have that level of detail.


UCPRC-TM-2008-13 18

Figure 4.1: Photo of Section 1, Old Davis Road On-Ramp to NB SR 113.

4.1.1 Alligator A and B Cracks

The vendor and manual results are shown in Table 4.1 for Alligator A cracks and in Table 4.2 for

Alligator B cracks. Because the cracks tended to meander in this section, a crack could drift in and out of

the defined wheelpath, thus moving a crack between Alligator A and C or Alligator A and Short

Transverse. For the Alligator A cracks, two vendors over-reported cracking when compared to the manual

measurements and one vendor was closer to the manual results. For the Alligator B cracks, the vendor

results were lower than the manual measurements, with only one vendor close to the manual results. The

PCS manual shows that Alligator A and B cracking are mutually exclusive, i.e., the combined percentage

should not exceed 100 percent. The sum of Alligator A and B for Vendor 1 is greater than 100 percent,

indicating a misinterpretation of the definitions. The combined totals for Alligator A and B cracks

appearing in Table 4.3 show that Vendors 3 and 4 are closest to the manual totals, but still with up to a

20 percent difference. Vendor 2 appears to have used a different interpretation of distress definitions for

asphalt surfaced sections than the other vendors, including Section 1.


UCPRC-TM-2008-13 19

Considering this section’s extensive and complex cracking in and between the wheelpaths (possibly

including reflective cracking from a shrinkage-cracked cement-treated base), it is clear that the responsive

vendors (Vendors 1, 3, 4, and 5) all identified extensive Alligator cracking in the section (as shown in

Table 4.3), and that the definitions of Alligator A and B need to be more precise in the PCS manual.

Table 4.1: Section 1, Alligator A Cracking

Vendor 0-100' 100-200' 200-300' 300-400' 400-500' % of wheelpath

1 54 67 36 36 26 2 0 0 0 0 0 3 67 55 71 49 42 4 6 34 8 22 18 5 0 5 0 0 0 6 - - - - -

UCPRC/CT PCS* 0 21 7 13 18 * UCPRC from images considering Caltrans PCS crew manual evaluations.

Table 4.2: Section 1, Alligator B Cracking


1 100 100 90 57 77 2 0 0 0 0 0 3 12 36 3 45 18 4 76 54 71 28 31 5 55 64 49 38 23 6 - - - - -

UCPRC/CT PCS 100 78 71 58 62

Table 4.3: Section 1, Combined Total for Alligator A and B Cracking Vendor 0-100' 100-200' 200-300' 300-400' 400-500'

% of wheelpath 1** 154 167 126 93 103 2 0 0 0 0 0 3 79 91 74 94 60 4 82 88 78 49 49 5 55 69 49 38 23 6 - - - - -

UCPRC/CT PCS 100 99 78 71 80 ** Misinterpretating PCS definition, Vendor 1 counted both Alligator A and B in the same locations in the wheelpath if both were present, whereas in the intended definition there can only be one type of Alligator cracking in the same location.

4.1.2 Cracks Between and Outside the Wheelpaths

Because of potential misinterpretation of the crack definitions, the results for percent of area with the

different types of cracking outside the wheelpaths defined in the manual—Alligator C, Short Cracks


UCPRC-TM-2008-13 20

Outside the Wheelpath, Transverse, and Longitudinal cracks—are shown back-to-back in this technical

memorandum. The results appear in Table 4.4 through to Table 4.7. As there was no clear trend regarding

whether the vendors over- or underreported when compared to the manual results, this reinforces the

feedback from the rodeo that the definitions provided in the 2008 PCS manual need more detail. Because

vendors overreported transverse cracks, this would explain the underreporting for the other categories.

These results also suggest that an option is to simplify many of the outside-the-wheelpath cracking

categories, since the mechanisms for some are not clear. For example, Alligator C and Short Cracks

Outside the Wheelpath do not have clear connections to pavement damage mechanisms, and are most

likely the result of advanced aging and cracking, and/or reflection of shrinkage cracks from underlying

cemented layers. In addition, the maintenance strategies for this cracking are essentially the same.

Longitudinal cracks may be due to asphalt construction joints or to reflection from underlying PCC joints.

Transverse cracks, on the other hand, are clearly tied to either low-temperature cracking or to reflective

cracking of transverse joints in underlying PCC. Therefore, both of these types of cracking can be

assigned to a particular mechanism from information regarding the pavement structure.

In general it can also be concluded that the analysis systems that the vendors use are able to detect and

rate cracks that have been sealed.

Table 4.4: Section 1, Alligator C Cracking

Vendor 0-100' 100-200' 200-300' 300-400' 400-500' % of area between wheelpaths

1 63 53 59 16 16 2 0 0 0 0 0 3 5 5 5 2 8 4 65 42 48 35 15 5 37 58 68 96 72 6 - - - - -

UCPRC/CT PCS 100 35 47 25 39


UCPRC-TM-2008-13 21

Table 4.5: Section 1, Short Transverse Cracks Outside the Wheelpath

Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Area outside the wheelpaths (m2)

1 6 5 7 4 2 2 0 0 0 0 0 3 0 0 0 0 0 4 4 4 8 3 1 5 4 3 4 2 2 6 - - - - -

UCPRC/CT PCS 10 15 17 11 10

Table 4.6: Section 1, Transverse Cracks

Vendor 0-100' 100-200' 200-300' 300-400' 400-500' (Number)

1 1 1 2 4 5 2 0 0 0 0 0 3 8 8 10 9 9 4 6 5 3 3 6 5 0 1 0 0 0 6 - - - - -

UCPRC/CT PCS 1 1 0 1 0

Table 4.7: Section 1, Longitudinal Cracks

Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Length (m)

1 17 31 62 50 31 2 0 0 0 21 7 3 7 3 26 2 0 4 19 28 44 37 38 5 0 0 0 0 0 6 - - - - -


4.1.3 Roughness and Rutting

All vendors reported rutting in Section 1, however the vendors did not agree on the rut depth defnitions

stated in the 2008 PCS manual. One vendor reported a maximum rut depth of 6.4 mm, four vendors

reported a maximum rut depth of 12.5 mm, and one vendor reported rutting greater than 19 mm. This

indicates that a more precise definition of rut depth must be included in the PCS manual. Currently,

different states use several definitions, which are partly dependent on equipment. The number of lasers is

one issue, and the use of single point versus continuous transverse laser is another. A clear definition of

rut depth that explicitly states whether the uplift at the sides of the wheelpath will be considered and

which plane is used as reference (the projected original surface or the tops of the humps at the sides of the

rut are typically used) for measuring rut depth need to be included in the next version of the PCS manual.


UCPRC-TM-2008-13 22

The roughness values are summarized in Section 4.12.

4.2 Section 2: NB SR113

Section 2 was a flexible pavement with some block or reflective cracking (presence of underlying PCC is

uncertain). A photo of the section is shown in Figure 4.2. The vendors were asked to rate this section as

flexible, i.e., to rate cracks as alligator/transverse/longitudinal, etc. The cracks were not sealed. It is

surmised that the hot-mix asphalt (HMA) is overlying a cracked cement-treated base (CTB) layer.

Figure 4.2: Photo of Section 2, NB SR113.


The vendor and manual results are shown in Table 4.8 for the Alligator A cracks and in Table 4.9 for the

Alligator B cracks. For the Alligator A cracks, Vendors 1, 3, and 5 reported extensive cracking, similar to

the UCPRC/CT PCS results. Vendors 2 and 4 appeared to not be able to identify the cracking seen by the

other vendors and the manual survey. For the Alligator B cracks, Vendors 3 and 5 had results in the same


UCPRC-TM-2008-13 23

range as the manual survey. Vendor 1 identified much more Alligator B cracking, and also counted

Alligator A and B in the same locations, as with the other asphalt surfaced sections. The combined totals

for Alligator A and B cracks are shown in Table 4.10 and show that Vendor 3 was closest to the manual

totals and that Vendor 5 reported values about half of the manual total extents.

It is highly likely that there is a cement-treated base layer below the asphalt concrete and that the cracking

on the surface is due to reflection of shrinkage cracks in the CTB up through the asphalt. This is not

“true” Alligator cracking but the 2008 PCS survey does not separate this type of cracking from cracking

in the wheelpaths caused by flexure as occurs when there is a granular base, and condition surveyors

cannot often cannot discern the difference without knowledge of the pavement structure.



1 81 38 80 41 29 2 0 0 0 0 0 3 78 60 67 72 30 4 0 0 0 0 0 5 39 11 18 23 8 6

UCPRC/CT PCS 54 47 60 61 21



1 68 80 88 92 55 2 0 0 0 0 0 3 4 0 0 0 0 4 0 0 0 0 0 5 19 15 4 6


Table 4.10: Section 2, Combined Total for Alligator A and B Cracking


1 149 118 168 133 84 2 0 0 0 0 0 3 82 60 67 72 30 4 0 0 0 0 0 5 39 30 18 38 12 6 0 0 0 0 0

UCPRC/CT PCS 66 52 67 66 23


UCPRC-TM-2008-13 24


The results for cracks between and outside the wheelpaths are shown in Table 4.11 through to Table 4.14.

Vendors 1, 3, and 5 generally showed extents similar to the manual survey for all crack types. The results

for the transverse cracks were within one or two counts of the manual counts. Vendors 2 and 4 had

difficulty identifying many of these cracks. In general, it can be concluded that the analysis systems the

vendors used were able to detect and rate cracks that have not been sealed.



1 11 4 7 9 3 2 0 0 0 0 0 3 5 3 3 3 3 4 0 0 0 0 0 5 17 4 0 1 4 6




1 3 3 2 3 3 2 0 0 0 0 0.3 3 0 0.1 0 0 0.3 4 0 0 0 0 0 5 0.6 0.6 0.7 0.5 0.3 6

UCPRC/CT PCS 1 0.5 0.8 0.7 0.1


Vendor 0-100' 100-200' 200-300' 300-400' 400-500' (Number)

1 6 5 6 6 5 2 0 0 2 1 2 3 8 6 6 7 6 4 0 0 0 0 0 5 3 6 8 5 4 6



UCPRC-TM-2008-13 25


Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Length (m)

1 33 22 28 16 20 2 0 0 8 6 15 3 6 2 8 3 6 4 26 10 17 11 20 5 11 10 32 33 27 6

UCPRC/CT PCS 21 17 21 17 18


All vendors reported rutting in the section, however there was no consensus from them on its magnitude,

in part due to interpretation of the distress definition for rutting. Four vendors reported a maximum rut

depth of 6.4 mm with a random distribution between less than 1.2 mm and between 1.2 and 6.4 mm, the

other two vendors reported distributions in the 1.2-to-6.4 mm and 6.4-to-12.5 mm categories described in

the PCS manual. Three vendors measured higher rut depths in the first subsection than the remaining four

subsections.



This is a rigid section with a burlap drag surface texture. The section was in good condition and the only

distress present was a number of transverse cracks in the second half (from 250 to 500 feet) of the section.

All of the transverse joints and most of the transverse cracks were sealed in this section. One vendor did

not supply data in the requested format; however the pavement images that the vendor supplied showed

the results of the automatic processing as an overlay on the images. This system classified the transverse

joints as cracks and detected a number of phantom cracks. That vendor’s results are not shown in the

tables.

A photo of the section is shown in Figure 4.3.


UCPRC-TM-2008-13 26


4.3.1 Rigid Transverse Cracks

The UCPRC/CT PCS survey counted eight slabs with one transverse crack and one slab with two

transverse cracks. Three vendors matched these counts, one vendor missed one of the single transverse

cracks, and another vendor missed five of the cracks. The results are shown in Table 4.15.


UCPRC-TM-2008-13 27

Table 4.15: Section 3, Rigid Transverse Cracks

Vendor No. Slabs with 1 Crack No. Slabs with 2 Cracks 1 8 1 2 8 1 3 4 0 4 8 1 5 7 1

UCPRC/CT PCS 8 1

4.3.2 Rigid Joints and Cracks Filled with Sealant

Two vendors were able to distinguish between cracks with and without sealant. Because of the issue with

the number of slabs per subsection, it was not possible to compare these two vendors’ results as they were

expressed as percentages. However, it is promising that at least two vendors were able to make a

distinction between sealed and open cracks.

4.3.3 Rigid Faulting, Roughness, and Rutting

Four of the six vendors reported faulting of the joints, and the levels of faulting were mostly less than

1.3 mm, which is the smallest-sized category in the 2008 PCS manual and indicates little or no faulting.

There were a small number of joints or cracks (three to six per vendor) that had faulting in the 1.3-to-

2.5 mm range.

Four vendors reported rutting in the section, which is inappropriate for this section since there should be

no rutting in a rigid pavement, especially in an area that has not been subjected to tire chain use.



This section is a rigid pavement with a longitudinal tining texture on the surface. The section showed no

signs of visible distress other than one corner crack, and was chosen because of the surface texture. All of

the section’s transverse joints were sealed. One vendor did not supply data in the requested format;

however the pavement images that the vendor supplied showed the results of the automatic processing

that classified the transverse joints as cracks and detected a number of phantom cracks, as for Section 3.

This vendor’s results are not included in the tables.

A photo of Section 4 is shown in Figure 4.4.


UCPRC-TM-2008-13 28


4.4.1 Rigid Corner Cracks

The UCPRC/CT PCS survey counted one slab with one sealed corner crack. Four vendors matched this

count and one vendor missed the crack. The results are shown in Table 4.16.

Table 4.16: Section 4, Rigid Corner Cracks

Vendor No. Slabs with 1 Crack No. Slabs with 2 Cracks 1 1 0 2 1 0 3 0 0 4 1 0 5 1 0

UCPRC/CT PCS 1 0


UCPRC-TM-2008-13 29



the number of slabs per subsection, it was not possible to compare the results of these two vendors as

their results were expressed as percentages. However it is promising that at least two vendors were able to

make a distinction between sealed and open cracks.


Three of the six vendors reported measurable faulting of the joints, which was greater than 1.3 mm. The

maximum reported amount of joint faulting occurred at two locations.

Three vendors reported rutting in the section, which is inappropriate since there should be no rutting in a

rigid pavement, especially in an area that has not been subjected to tire chain use. The influence of the

longitudinal tining on reporting of rutting on a rigid pavement is uncertain.


4.5 Section 5: WB SR16

This was a section of flexible pavement with a number of distresses. However, the section was

rehabilitated in the period between the assessments by the first and second vendors and therefore no data

is reported for it.

4.6 Section 6: WB SR16

The section is a two-lane rural flexible pavement with no shoulders. The pavement has some cracking. A

photo of the section is shown in Figure 4.5.


UCPRC-TM-2008-13 30

Figure 4.5: Photo of Section 6, WB SR16.


The vendor and manual results for Alligator A cracks are shown in Table 4.17 and for Alligator B cracks

in Table 4.18. For the Alligator A cracks, all the vendors who reported measurements overreported the

cracking compared to the manual measurements. For Alligator B cracks, the vendors were generally

closer to the manual survey. Vendor 1 double counted the two types of alligator cracking, as on all other

asphalt sections, indicating misinterpretations of the definitions. Vendor 2 could not identify much

cracking on asphalt surfaces, as with all other asphalt sections. The combined totals for Alligator A and B

cracks appear in Table 4.19, and show that Vendors 3, 4, and 5 generally had cracking in ranges similar to

those of the manual survey. This indicates that they can identify cracking and that further refinement of

definitions is needed.


UCPRC-TM-2008-13 31



1 27 28 21 0 0 2 0 0 0 0 0 3 9 42 21 0 0 4 11 3 0 0 0 5 2 6 2 1 3 6




1 29 97 44 22 43 2 0 0 0 0 0 3 1 12 1 0 0 4 36 21 5 7 2 5 9 7 9 0 3 6




1 56 125 65 22 43 2 0 0 0 0 0 3 10 54 22 0 0 4 47 24 5 7 2 5 11 13 11 1 6 6



The results for cracks between and outside the wheelpaths are shown in Table 4.20 through to Table 4.23.

The vendors generally overreported the partial and full lane–width cracks (Alligator C, Short Transverse

Outside the Wheelpath, and Transverse) when compared to the manual results. This would indicate a

more relaxed criterion was used by the vendors for selecting these types of cracks than was used by the

manual survey. These results show that the vendors are able to identify cracks, but that more precise

definitions are needed. In particular, this section again indicates that the number of cracking types outside

the wheelpath should be reduced, and that overall crack lengths outside the wheelpath, other than

transverse cracking and potentially longitudinal cracks, may be the best solution.


UCPRC-TM-2008-13 32



1 11 18 24 4 31 2 3 1 4 1 0 1 4 51 16 0 2 0 5 10 20 14 0 2 6




1 3 12 4 2 3 2 3 0 0.3 0.5 0.9 0.1 4 6 2 0.8 0.5 0.1 5 0.2 2 0.7 0.9 0.9 6

UCPRC/CT PCS 2 8 2 0.9 0.7


Vendor 0-100' 100-200' 200-300' 300-400' 400-500' (Number)

1 3 0 0 1 0 2 4 4 11 5 6 3 4 5 1 1 0 4 1 1 1 0 0 5 3 0 1 1 0 6



Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Length (m)

1 24 1 1 3 0 2 16 7 7 0 0 3 3 2 0.9 0.6 0 4 8 2 0 0 0 5 6



UCPRC-TM-2008-13 33


All vendors reported rutting in the section, although there was variability as to the rut depth measurement

category that was partially attributable to differences in equipment and in definitions of rut depth. Four

vendors reported a maximum rut depth of 6.4 mm with a random distribution between less than 1.2 mm

and between 1.2 and 6.4 mm rut depth categories; the other vendor reported distributions in all of the rut

depth categories.


4.7 Section 7: SB I505

Section 7 was a rigid pavement that had recently been overlaid with an open-graded asphalt concrete and

was in excellent condition. The vendors reported no cracking, which agreed with the manual

measurements.

A photo of the section is shown in Figure 4.6.

Figure 4.6: Photo of Section 7, SB I505.


UCPRC-TM-2008-13 34


All vendors reported rutting in this section. Four vendors reported a maximum rut depth of 6.4 mm with

the majority of rutting having a depth of less than 1.2 mm. One vendor reported a maximum rut depth of

1.2 mm and the other vendor reported rut depth distributions up to a maximum of 12.5 mm.


4.8 Section 8: EB I80

This section is a rigid pavement with an unknown type of original surface texture. The section was in

poor condition and a number of its slabs had multiple cracks. All of the section’s the longitudinal cracks

and all of its transverse joints and cracks but one were sealed. One vendor did not supply data in the

requested format; however the pavement images that the vendor supplied showed the results of the

automatic processing, which classified the transverse joints as cracks and detected a number of phantom

cracks as for Section 3. This vendor’s results are not included in the tables.


Figure 4.7: Photo of Section 8, EB I80.


UCPRC-TM-2008-13 35

4.8.1 Rigid Longitudinal Cracks

The UCPRC/CT PCS survey counted eleven slabs with one longitudinal crack, and only one of the

longitudinal cracks was not sealed. Three vendors matched the manual count and one vendor counted an

additional two cracks; this vendor may have classified a transverse crack as a joint, thus double counting a

single crack. The other vendor only reported one longitudinal crack.


The UCPRC/CT PCS survey counted 27 slabs with one transverse crack and two slabs with two

transverse cracks. Only one transverse crack was not sealed. One vendor missed one crack, one vendor

missed two cracks, and one vendor missed three cracks. The other two vendors reported 15 and 5 cracks.

The results are shown in Table 4.24.


Vendor No. Slabs with 1

Crack No. Slabs with 2

Cracks 1 25 2 2 25 1 3 5 0 4 26 0 5 15 1

UCPRC/CT PCS 27 2





make a distinction between sealed and open cracks.

4.8.4 Rigid Faulting, Roughness and Rutting

Five of the six vendors reported faulting of the joints, with levels of faulting mostly less than 1.3 mm,

which is the smallest fault height category, indicating little or no faulting. There were a small number of

joints or cracks (15 to 20 percent of total joints and cracks per vendor) that had faulting in the 1.3-to-

6.4 mm range.


UCPRC-TM-2008-13 36

Four vendors reported rutting in the section, which is inappropriate for this since there should be no

rutting in a rigid pavement, especially in an area that has not been subjected to tire chain use.



This is a rigid section with an unknown original surface texture. The section was in poor condition and six

out of 32 slabs had multiple cracks. Some of the section’s transverse joints and cracks and longitudinal

cracks were sealed. One vendor did not supply data in the requested format; however the pavement

images that the vendor supplied showed the results of automatic processing that classified the transverse

joints as cracks and detected a number of phantom cracks, as for Section 3. This vendor’s results are not

included in the tables.




UCPRC-TM-2008-13 37

4.9.1 Rigid Longitudinal Cracks

The UCPRC/CT PCS survey counted four slabs that each had one unsealed longitudinal crack. Four

vendors matched the manual count and the other vendor only reported no longitudinal cracks.


The UCPRC/CT PCS survey counted nineteen slabs with one transverse crack, two slabs with two

transverse cracks, and one slab with four transverse cracks. There was a mixture of sealed and unsealed

cracks. Three vendors were within one crack of the manual count, one vendor missed approximately 20

percent of the cracks, and the other vendor only reported eight cracks. Vendor 3 reported a significant

number of combination cracks in the slabs, which explains the low count on the total of transverse cracks.

The results are shown in Table 4.25.


Vendor No. Slabs with 1

Crack No. Slabs with 2

Cracks No. Slabs with 4

Cracks 1 20 3 2 19 5 3 8 0 4 20 2 5 15 4

UCPRC/CT PCS 19 2 2

4.9.3 Rigid Joints and Cracks Filled with Sealant and Joint/Crack Spalling




make a distinction between sealed and open cracks. Four vendors reported joint or crack spalling;

examination of the downward-looking images from the vendors confirmed spalling of some joints and

cracks. This indicates that spalling can potentially be identified from images.


Five of the six vendors reported faulting of the joints; the levels of faulting were mostly between 1.3 and

6.4 mm. Two vendors reported a small number of faults that were greater than 12.5 mm.

Four vendors reported rutting in the section, which is inappropriate since there should be no rutting in a

rigid pavement, especially in an area that has not been subjected to tire chain use.


UCPRC-TM-2008-13 38



The section is a divided four-lane rural flexible pavement with shoulders. The pavement has some

cracking and continuous patching in the right wheelpath. There are some patches that are the full lane-

width. A photo of the section is shown in Figure 4.9 (cracking is difficult to see in the photo).



The vendor and UCPRC/CT PCS results are shown for Alligator A cracks in Table 4.26 and for Alligator

B cracks in Table 4.27. The reported vendor measurements for the Alligator A cracks were generally

inconsistent with the manual measurements. Alligator B results were also generally inconsistent with the

manual survey. In terms of combined Alligator A and B cracking extents shown in Table 4.28, Vendor 4

had results similar to those of the manual survey. As with the other sections with asphalt surfaces,

Vendor 1 misinterpreted the definitions of extent, and also appeared to greatly over-report the amount of

alligator cracking.


UCPRC-TM-2008-13 39



1 9 9 62 0 13 2 0 1 12 19 15 3 2 0 3 5 13 4 1 0 3 20 13 5 2 1 7 8 4 6




1 14 32 81 67 70 2 0 0 0 0 0 3 0 5 7 2 2 4 3 8 25 18 20 5 0 6 4 0 3 6

UCPRC/CT PCS 8 14 13 25 19



1 23 41 143 67 83 2 0 1 12 19 15 3 2 5 10 7 15 4 4 8 28 38 33 5 2 7 11 9 6 6

UCPRC/CT PCS 10 14 36 34 26


The results for cracks between and outside the wheelpaths are shown in Table 4.29 through Table 4.32.

The vendors’ results for the partial lane-width cracks (Alligator C, Short Transverse Outside the

Wheelpath) generally had low levels similar to the manual survey, except for Vendor 1 who showed high

levels of Alligator C, and Vendor 2 who showed little or no cracking, as in other sections. Transverse

cracking results from the vendors were similar to those in the manual survey (little or no cracking), except

for Vendor 2 who showed higher levels. Low levels of longitudinal cracking where found by the vendors

and the manual survey except for a few subsections. Discerning whether the edges of patches and digouts

are longitudinal cracks when they begin to open up is not clear in the 2008 PCS manual.


UCPRC-TM-2008-13 40



1 12 42 25 30 20 2 0 0 0 0 0 3 1 5 1 2 1 4 0 2 6 2 2 5 1 5 3 5 5 6




1 2 2 1 3 2 2 0 0 0 0 0 3 0 0 0 0 0 4 0.1 0.3 0.3 0 1 5 0.5 0.3 0 0 0 6

UCPRC/CT PCS 2 2 0.5 0.7 0.3


Vendor 0-100' 100-200' 200-300' 300-400' 400-500' (Number)

1 0 0 0 0 1 2 4 7 5 7 3 3 0 0 1 1 0 4 0 0 0 0 1 5 0 2 0 0 0 6



Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Length (m)

1 3 2 4 0 0 2 3 0 0 0 0 3 0 0 0 0 0 4 0 1 8 1 0 5 0 0 13 0.8 0 6



UCPRC-TM-2008-13 41

4.10.3 Digouts and Patches

This section contained a significant length of pavement digout and repair in the right wheelpath. The five

vendors who submitted compliant data consistently rated the same amount of digout for the first 300 feet

of the section as the manual survey. There were larger variations in the last 200 feet, although the orders

of magnitude are similar. The reported values are shown in Table 4.33. The variations could be due to the

problems with the vendors having difficulty scaling their images in the longitudinal direction.

There was one pothole in the first 100-ft subsection. Four of the five vendors reported the pothole.

Table 4.33: Section 10, Digouts

Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Area (m2)

1 35 32 32 8 21 2 29 33 35 19 14 3 34 32 32 20 15 4 33 33 33 22 22 5 30 31 34 13 19 6

UCPRC/CT PCS 30 30 30 7 28


All vendors reported rutting in the section. Four vendors reported a maximum rut depth of 6.4 mm with a

random distribution between the rut depths categories of less than 1.2 mm, and 1.2 to 6.4 mm, while the

fifth vendor reported distributions in all of the rut depth categories.



The section is a divided four-lane rural asphalt-surfaced pavement with shoulders. The pavement has

some block cracking and extensive cracking in the wheelpaths. This pavement is probably an overlay of a

cracked concrete pavement, or semi-rigid pavement (asphalt on cement-treated base) and the cracking is

likely reflection of cracking in the underlying layers. Some of the cracking in the wheelpath may be

longitudinal cracks in PCC reflecting up through the asphalt, not true Alligator cracking. Figure 4.10

shows a photo of the section (cracking is difficult to see in the photo).


UCPRC-TM-2008-13 42



The vendor and manual results for Alligator A cracking are shown in Table 4.34 and for Alligator B

cracking in Table 4.35. The combined totals for Alligator A and B cracks appear in Table 4.36. Vendors 1,

3, 4, and 5 showed extensive cracking in the wheelpaths, which compares well with the manual

measurements. However, it is clear that there is difficulty in separating Alligator A from Alligator B

cracking when the pattern is probably not caused by the mechanism that causes “true” alligator cracking,

bending of the asphalt layers, but is instead actually reflection of cracking from the layer beneath that

appears in the wheelpath. Knowledge of the underlying layer type (granular or cemented) is necessary to

clearly assign alligator cracking in the wheelpath as opposed to reflective cracking in the wheelpath. This

suggests that once the pavement structural inventory is completed, cracking on pavements with PCC or

CTB below should be classified as “in the wheelpath” cracking, and that alligator cracking should only be

identified on asphalt-surfaced pavements with granular layers below where the mechanism causing

alligator cracking occurs.


UCPRC-TM-2008-13 43

As with the other sections with asphalt surfaces, Vendor 1 misinterpreted the definitions of extent, and

also appeared to greatly over-report the amount of alligator cracking. Vendor 2 appeared to not be able to

identify wheelpath cracking, as was the case on all other sections.



1 61 58 18 80 100 2 0 0 1 0 0 3 62 82 66 70 91 4 17 25 41 22 59 5 37 49 31 36 36 6

UCPRC/CT PCS 68 54 43 56 74



1 100 100 100 98 87 2 0 0 0 0 0 3 0 4 9 6 2 4 14 56 51 63 20 5 0 9 10 1 9 6

UCPRC/CT PCS 23 25 25 29 14



1 161 158 118 178 187 2 0 0 1 0 0 3 62 86 75 76 93 4 31 81 92 85 79 5 37 58 41 37 45 6

UCPRC/CT PCS 91 79 68 85 88


UCPRC-TM-2008-13 44


The results are shown in Table 4.37 to Table 4.40. Vendors 1, 3, 4, and 5 generally reported similar orders

of magnitude for the partial lane-width cracks (Alligator C, Short Transverse Outside the Wheelpath)

when compared to the manual results, except that Vendor 1 generally over-reported Alligator C cracking

and Vendor 3 over-reported Alligator C in some subsections. All vendors except Vendor 2 showed

transverse cracking results similar to the manual survey. Similar ranges of longitudinal cracking were

reported by all vendors.



1 20 39 51 35 30 2 0 0 0 0 0 3 4 4 2 5 7 4 20 30 9 8 43 5 9 10 5 12 9 6




1 2 2 1 3 2

2 0 0 0 0 0

3 0 0 0 0 0

4 0.1 0.3 0.3 0 1

5 0.5 0.3 0 0 0

6



Vendor 0-100' 100-200' 200-300' 300-400' 400-500' (Number)

1 6 3 3 4 4 2 0 0 0 0 0 3 3 4 4 4 5 4 0 2 4 3 2 5 4 2 3 3 2 6



UCPRC-TM-2008-13 45


Vendor 0-100' 100-200' 200-300' 300-400' 400-500' Length (m)

1 2 7 13 14 7

2 6 10 21 0 0

3 0 0 22 15 9

4 0 0.9 24 23 0

5 0 3 20 11 0

6



All vendors reported rutting in the section, however there was variability as to the rut depth measurement

category. Four vendors reported a maximum rut depth of 6.4 mm with a random distribution between the

rut depths categories of less than 1.2 mm, and 1.2 to 6.4 mm; the other vendor reported rut depth

distributions in these categories, plus the next more severe category (12.5-to-19 mm).


4.12 Roughness Results

A table showing the roughness measures (IRI) for all vendors and all subsections is included in the

Appendix. The table shows the mean, standard deviation, and total range (maximum minus minimum) of

IRI for each section and subsection across the different vendors, the mean of IRI for each vendor across

all of the subsections in each section, and the mean and standard deviation of all the vendor’s means for

each section is included in the Appendix.

Trellis graphs show the data in Figure 4.11 and Figure 4.12 for each section and each vendor. Each

column in Figure 4.11 shows measured IRI for all six vendors for the same section with each subsection

shown as an individual circle from left to right. Figure 4.12 shows the values for each vendor, with all

values for each of the subsections (circles) stacked on top of each other in each of the 11 sections and a

mean trend line between them. It can be seen that the trends for IRI values follow same patterns and have

similar values across the vendors. The results also show that even within the short 500-ft sections, there is

considerable variation between the 100-ft subsections.

Because IRI is an average value, shorter reporting lengths tend to have a higher variability due to the

influence of individual profile perturbations. The effect of isolated perturbations is attenuated over longer

section lengths as a result of the averaging process.


UCPRC-TM-2008-13 46

1

2

3

4

5

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1vendor1

2vendor1

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2

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11vendor6

IRI (

m/k

m)

Figure 4.11: Summary of IRI (m/km) values for all vendors, all sections, and all subsections.


UCPRC-TM-2008-13 47

Section

IRI (

m/k

m)

1

2

3

4

5

2 4 6 8 10

vendor4 vendor3

2 4 6 8 10

vendor5

vendor2

2 4 6 8 10

vendor6

1

2

3

4

5

vendor1

Section

IRI (

m/k

m)

1

2

3

4

5

2 4 6 8 10

vendor4 vendor3

2 4 6 8 10

vendor5

vendor2

2 4 6 8 10

vendor6

1

2

3

4

5

vendor1

Figure 4.12: Summary of IRI (m/km) values for all vendors and all subsections (with mean-trend lines).


UCPRC-TM-2008-13 48

The standard deviation between vendors’ means for each very short 100-ft subsection is somewhat

correlated with the mean roughness for the subsection, as can be seen in Figure 4.13, with rougher

subsections having greater variation between vendors. Comparison of Figure 4.14 (asphalt surfaces) with

Figure 4.15 (PCC surfaces) indicates that the variation between vendors is somewhat greater on the

subsections with asphalt surfaces than on the subsections with PCC surfaces.

The results in the appendix also show that the vendor outliers are well distributed across all test sections.

These results indicate that there is randomness across sections, but half the vendors are responsible for

most of the outliers. The results in the table also indicate that there is no pattern of one vendor being high

or low relative to the mean.

Each subsection was short and had its own specific roughness, and each test car may have followed a

slightly different line along the wheelpath. It must be remembered that IRI is being used as a network-

level measure, not to find precise measures of roughness for sections that are 100 ft long. This is borne

out by comparison of the overall IRI summed across the ten sections (IRI is linearly cumulative1), each

500 ft long, as if it were one section with a total length of 5,000 ft (nearly a mile) and a wide range of

roughness within each of the section’s 100-ft subsections, shown below. These results indicate that when

summed across longer sections, the differences in measured IRI on are lower than those indicated by

individual subsection values; the vendors generally show similar variability. A large part of this may be

the averaging of the drivers’ lines through the wheelpaths over longer sections.

Vendor 1 2 3 4 5 6

Mean IRI (m/km) 2.14 2.10 1.92 2.12 2.02 2.07

Mean IRI (inches/mile) 136 133 122 135 128 132

Std Dev IRI (m/km) 1.03 1.03 0.83 0.99 0.89 1.08

Maximum (m/km) 5.48 5.12 4.47 4.27 4.89 5.22

Minimum (m/km) 0.69 0.64 0.65 0.69 0.63 0.69

A normal plot (QQ-plot) of the Studentized residuals is used to check for outliers. If there are vertical

jumps near either end of such a plot, or even if the plot turns sharply upward or downward near the ends,

we might have points that should be flagged for further investigation.”2 Figure 4.16 plots the IRI

1 Sayers, M., and S. Karamihas. 1998. The Little Book of Profiling. University of Michigan. 2 Sen, A., and Srivastava, M. 1990. Regression Analysis: Theory, Methods, and Applications. Springer-Verlag, New

York.


UCPRC-TM-2008-13 49

distributions of all the vendors across all the sections in terms of histogram and QQ-plot. The IRI value is

expressed in natural logarithm. The plots indicate that the distribution of IRI of each vendor seems to be

lognormal distribution. All of the vendors have similar QQ plots. Table 4.41 summarizes the means and

standard deviations of all the vendors across all the sections.

Table 4.41: Summary of the Means and Standard Deviations of Ln(IRI).

Vendor Mean Standard Deviation

1 0.6517 0.4801

2 0.6243 0.4973

3 0.5633 0.4308

4 0.6422 0.4821

5 0.6079 0.4537

6 0.6059 0.4982

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00

Mean IRI across vendors

Stan

dard

Dev

iatio

n IR

I of m

eans

acr

oss

vend

ors

m/km = in/mile0.5 = 321.0 = 631.5 = 952.0 = 1272.5 = 1583.0 = 1904.0 = 2535.0 = 317

Figure 4.13: Mean IRI (m/km) versus mean standard deviation across vendors for each subsection.


UCPRC-TM-2008-13 50

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00


Stan

dard

Dev

iatio

n IR

I of m

eans

acr

oss

vend

ors

m/km = in/mile0.5 = 321.0 = 631.5 = 952.0 = 1272.5 = 1583.0 = 1904.0 = 2535.0 = 317

Figure 4.14: Mean IRI (m/km) versus mean standard deviation across vendors for each asphalt-

surfaced subsection.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00


Stan

dard

Dev

iatio

n IR

I of m

eans

acr

oss

vend

ors m/km = in/mile

0.5 = 321.0 = 631.5 = 952.0 = 1272.5 = 1583.0 = 1904.0 = 2535.0 = 317

Figure 4.15: Mean IRI (m/km) versus mean standard deviation across vendors for each PCC-

surfaced subsection.


UCPRC-TM-2008-13 51

-0.5

0.0

0.5

1.0

1.5

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iri)

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30vendor6

Ln(IRI)

Per

cent

of T

otal

(a) Histogram

(b) QQ plot

-0.5

0.0

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1.0

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vendor1 vendor2

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vendor3

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iri)

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-0.5 0.0 0.5 1.0 1.5

vendor1 vendor2

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5

10

15

20

25

30vendor6

Ln(IRI)

Per

cent

of T

otal

(a) Histogram

(b) QQ plot

Figure 4.16: IRI distributions of all the vendors across all the sections: (a) Histogram and (b) QQ-plot.


UCPRC-TM-2008-13 52


UCPRC-TM-2008-13 53

5 FINDINGS AND CONCLUSIONS

The first purpose of this equipment rodeo was to evaluate the current state of the practice for

equipment/technologies that capture pavement surface images. Its second purpose was to evaluate the

various technologies/systems that pavement condition survey vendors use to analyze the images to

determine the type, severity, and extent of the requested pavement distresses. A third purpose became

apparent during the course of the project: to find gaps in the definitions of distress developed by the

University of California Pavement Research Center/Caltrans Pavement Condition Survey (UCPRC/CT

PCS) that were given to the equipment vendors.

It is recognized that some distress elements may not be measurable using current semi- or fully-automated

image analysis systems. One purpose of the rodeo was to identify these elements and either to eliminate

them or flag them as needing attention in the future as the state-of-the-practice advances.

In addition to pavement surface images and analysis, the vendors participating in the rodeo provided

measures of International Roughness Index (IRI) for each test section, which provided insight into the

state-of-the-practice for this parameter.

The findings and conclusions for the evaluation exercise are presented below. The findings and

conclusions are presented in four parts: image capture, image analysis, distress definitions, IRI

measurements, and items for consideration for the RFQ/vendor selection process.

5.1 Image Capture

Prior to 2006, vendors around the world had spent considerable time and effort developing systems to

capture images of pavement surfaces that would show cracks. These systems tended to be cumbersome

and somewhat problematic in their operation, due either to the required lighting conditions or to the

consistency of their results. With the development of the infrared illumination and line-scan cameras that

have been available since 2006, vendors finally have a way to record the crack patterns on a pavement

surface under uniform lighting conditions at highway speeds. The rodeo discussed in this memorandum

showed that vendors who still use visible lighting and area cameras are able to collect pavement images

that are comparable to those from line-scan technology and that these images can successfully be used in

analysis systems. Both types of images had minor problems: the area images had occasional shadows,

while the line-scan images were prone to banding—although it is not known how this banding affects the

image processing.


UCPRC-TM-2008-13 54

The current resolution of the systems is a pixel size of one millimeter by one millimeter, which means

that the effective minimum crack width that can be detected is about 1.5 mm. Under ideal lighting and

stationary conditions, the human eye can detect finer cracks than this, but these seldom occur in the field.

In general, the quality of images from all of the vendors was sufficient to allow manual desktop analysis

of the crack patterns by a human eye. This would result in eliminating the need for personnel to manually

rate pavements from the shoulder of a highway, thus improving worker safety and substantially increasing

productivity.

All six vendors had the capability to capture high-quality right-of-way images for later viewing.

5.2 Image Analysis

Due to a lack of precise distress definitions and the time constraint for this one-time event, some vendors

made their own interpretations of the distresses supplied; other vendors sought and received feedback on

definitions. This made an overall comparison somewhat difficult. In addition, the UCPRC/CT PCS

measurements used for comparison were also based on interpretation of images and roadside assessment.

Communication with several vendors showed that they would prefer to work in a feedback environment

with an agency, particularly in the early stages of a contract, so that the vendor is working to the same

definition and intent as the agency engineers and systems. This would be the situation once a contract is

awarded, but it could not be replicated in the rodeo.

No one vendor was consistently “better” or “worse” than the manual results, and in most cases there was

no clear consensus among all seven data sets. This highlighted the need for better distress definitions.

No vendor used a 100 percent automatic analysis system; the degree of automation appeared to range

from zero to about eighty percent. Several vendors said that their processing rate was about twenty

percent of the collection rate for a single rater, that is, it would take five person-hours to rate one hour of

data collection at highway speeds (50 to 65 mph).

Because of the relative complexity of the proposed distress matrix, compared to something relatively

simple such as the AASHTO P44 specification, the cost per lane-mile is unknown. A factor in Caltrans’

favor is the rapid improvement of this technology, and thus by the time a contractor starts the actual

survey in late 2009 (at the earliest), the degree of automation and consistency should be improved.


UCPRC-TM-2008-13 55

5.3 Recommended Changes to the Distress Definitions

Based on the feedback received from the vendors during the data analysis period and findings from the in-

depth analysis of the vendor data, the following changes are recommended to the distress definitions:

• All Pavements

o Cracks/joints that have been sealed should be rated, assuming there is a crack beneath the

sealant.

o Sealed cracks should be an additional “bin” (category) option alongside the crack width

bins since it would be difficult or impossible to determine the width of a crack that has

been sealed.

o These two criteria should guide the decision about whether to call out specific types of

cracking or just to measure the amount of cracking without classifying the type:

Is the type of cracking tied to a specific damage mechanism causing it? For

example, Alligator C cracking cannot be tied to any specific mechanism, but

transverse cracking in asphalt pavements can be clearly tied to low temperatures

where there is a granular base or to the reflection of transverse joints/cracks

where there are underlying PCC slabs,.

Does the type of cracking change the maintenance or rehabilitation treatment?

• Rigid Pavements

o Switch from reporting percentage of slabs with a distress to reporting the total number of

slabs in the survey length and the actual number of slabs with each distress.

o Rate faulting in each wheelpath, and report the number of faults per size bin. The

maximum number of reported faults will be the twice the sum of the number of slabs and

the number of transverse cracks in the survey section.

• Flexible Pavements

o The results warrant simplifying many of the outside-the-wheelpath cracking categories

since the mechanisms causing some of them are unclear. For example, neither Alligator C

nor Short Cracks Outside the Wheelpath have clear connections to pavement damage

mechanisms, and most likely result from advanced aging and cracking, and/or reflection

of shrinkage cracks in underlying cemented layers. In addition, the maintenance

maintenance strategies for these types of cracking are essentially the same. Similarly,

longitudinal cracks may be due to asphalt construction joints or to reflection from

underlying PCC joints. On the other hand, transverse cracks that extend across the lane

are clearly tied to either low-temperature cracking or to reflective cracking of transverse


UCPRC-TM-2008-13 56

joints in underlying PCC. Therefore, both of these types of cracking can be assigned to a

particular mechanism from information regarding the pavement structure.

o Transverse cracks plus other cracks: If a transverse crack is located in an area with other

cracks, then the transverse crack length/pseudo-area should be ignored for the calculation

of the length/pseudo area of the other crack type.

o Transverse cracks should be a straight line rather than a meandering line. A limit on the

deviation from a straight line should be implemented to ensure that transverse cracks

caused by low-temperature cracking are separated from transverse cracks from other

causes.

o Crack metrics should be consistent, particularly for cracking outside the wheelpaths other

than transverse cracks that extend all the way across the lane, preferably using summed

crack lengths rather than percentages of area.

o Cracks that are in the shoulder but within 0.25 m of the lane edge should be included in

the lane analysis, depending on whether this area is included in the required imaging (see

next bullet).

o Include shoulder widths of less than 0.25 m in the lane definition.

o Alligator A cracks, which are single isolated cracks, should be rated as Alligator B if they

are joined to other crack(s).

o A simple, clear definition separating Alligator A and B cracking is required. This should

be based on either a summed crack length within short subsections of the wheelpath or on

a simple geometrical definition with regard to intersections of cracks.

o Clarification is required on how to discern whether or not the edges of patches and

digouts that begin to open up are longitudinal cracks. The 2008 PCS manual is unclear

about this.

o Once the pavement structural inventory is completed, cracking on pavements with PCC

or CTB below should be classified as “in the wheelpath” cracking, and alligator cracking

should only be identified on asphalt-surfaced pavements with granular layers below the

HMA, where the mechanism causing alligator cracking occurs.

5.4 Recommended Changes Regarding Quality Assurance for IRI Measurements

The results showed that there is considerable variability when looking at short subsections of 100 ft

length; however, when IRI is calculated for longer sections there is less variability between vendors. The

results indicate that vendor outliers are well distributed across all test sections. These results indicate that


UCPRC-TM-2008-13 57

there is randomness across sections, but half the vendors are responsible for most of the outliers. Based on

these results it is recommended that some quality assurance of IRI measurements be included in the

contract

5.5 Recommendations for the Vendor Evaluation Part of the RFQ Process

• Potential vendors should be required to rate rigid pavements with unsealed cracks.

• Include the ability to rate white cracks on HMA pavements. The white cracks can caused by

cement dust rising through cracks from cement-treated bases or by the accumulation of dust

during the dry California summers.

• Vendors should rate multiple passes of the same section, using different human raters if

applicable, to check the consistency of their systems.

• Vendors should be given time to capture and rate a pretrial section and receive feedback on

their results using the Caltrans distress matrix before starting the actual evaluation exercise.

• IRI measurement should be part of the vendor evaluation RFQ process.

5.6 Overall Recommendations

It is the opinion of the authors that the current state of the practice would allow the detailed distress

matrix to be used to conduct a pavement condition survey of the entire Caltrans network. However,

potential vendors may see a risk in the unknown time required to rate the pavement using a detailed

distress matrix and price their bids accordingly.

The technology and business practices of vendors is continuously improving and therefore by the time a

vendor is selected, sufficient advances should have been made to reduce or to quantify the risk to both the

vendor and the agency.

Concurrent work on the overall PMS, which is developing a technical specification for generating a

baseline pavement structure inventory, has given Caltrans and the UCPRC valuable experience in

developing a comprehensive technical scope of work that will result in few or no surprises to either the

vendor or the agency.

In the event that the received bid prices are too high per unit distance, a more generalized or smaller

distress matrix should be prepared. This alternative matrix should be compatible with the proposed matrix,

since technology is expected to advance sufficiently to enable the complete matrix to be used in the not-

to-distant future. Some recommendations for simplifying the distress recommendation are already

provided in this chapter.


UCPRC-TM-2008-13 58

APPENDIX: SUMMARY OF IRI (M/KM) VALUES FOR ALL VENDORS AND ALL SECTIONS

Vendor 1 2 3 4 5 6 Mean Std Dev Range Section 1 0-100' 3.25 3.28 2.13 2.95 3.16 2.14 2.82 0.54 1.15

100-200' 3.17 3.18 1.94 2.88 2.51 3.00 2.78 0.48 1.24

200-300' 3.24 3.52 2.47 4.07 3.11 2.77 3.20 0.56 1.60

300-400' 4.10 3.72 2.23 4.27 3.35 3.09 3.46 0.75 2.04

400-500' 4.15 3.99 2.21 4.05 3.06 3.54 3.50 0.75 1.94

Mean 3.58 3.54 2.20 3.64 3.04 2.91 3.15 0.56

Section 2 0-100' 3.60 3.45 3.40 3.69 2.95 5.08 3.70 0.73 2.13

100-200' 0.98 0.98 1.09 1.23 0.90 2.58 1.29 0.64 1.68

200-300' 0.99 0.95 1.48 1.01 1.34 0.91 1.11 0.24 0.57

300-400' 0.98 1.17 1.46 0.94 1.03 1.01 1.10 0.19 0.52

400-500' 1.09 1.61 1.08 1.69 0.90 0.94 1.22 0.34 0.79

Mean 1.53 1.63 1.70 1.71 1.42 2.10 1.68 0.23

Section 3 0-100' 2.38 1.80 1.51 1.85 2.02 1.50 1.84 0.33 0.88

100-200' 2.02 1.79 1.53 1.75 1.99 1.53 1.77 0.21 0.49

200-300' 1.86 1.80 1.55 1.79 1.86 1.47 1.72 0.17 0.39

300-400' 2.02 1.70 1.63 1.78 1.99 1.54 1.78 0.19 0.48

400-500' 2.02 1.86 1.88 2.08 2.08 2.04 1.99 0.10 0.22

Mean 2.06 1.79 1.62 1.85 1.99 1.62 1.82 0.18

Section 4 0-100' 1.66 1.23 1.40 1.64 1.40 1.08 1.40 0.23 0.58

100-200' 1.47 1.19 1.15 1.33 1.29 1.25 1.28 0.11 0.32

200-300' 1.33 1.01 1.07 1.45 1.20 1.03 1.18 0.18 0.44

300-400' 1.42 1.15 1.13 1.15 1.36 1.14 1.23 0.13 0.29

400-500' 1.53 1.26 1.07 1.40 1.26 1.27 1.30 0.15 0.46

Mean 1.48 1.17 1.16 1.39 1.30 1.15 1.28 0.14


UCPRC-TM-2008-13 59

Vendor

1 2 3 4 5 6 Mean Std Dev Range Section 6 0-100' 1.47 1.41 1.27 1.36 1.40 1.44 1.39 0.07 0.20

100-200' 2.15 2.02 2.26 2.00 2.05 1.79 2.05 0.16 0.47

200-300' 2.13 1.94 2.09 1.86 2.24 1.66 1.99 0.21 0.58

300-400' 2.26 2.62 2.32 2.40 2.26 2.41 2.38 0.14 0.36

400-500' 1.66 1.74 1.66 1.92 1.78 2.02 1.80 0.15 0.36

Mean 1.93 1.95 1.92 1.91 1.95 1.86 1.92 0.03

Section 7 0-100' 0.71 0.64 0.75 0.69 0.74 0.73 0.71 0.04 0.10

100-200' 0.87 0.74 0.78 0.69 0.88 0.84 0.80 0.08 0.20

200-300' 0.69 0.69 0.65 0.78 0.63 0.69 0.69 0.05 0.15

300-400' 0.96 1.09 1.04 0.79 1.06 1.04 1.00 0.11 0.30

400-500' 0.88 0.88 0.86 1.00 0.93 0.88 0.91 0.05 0.15

Mean 0.82 0.81 0.82 0.79 0.85 0.84 0.82 0.02

Section 8 0-100' 1.86 1.58 1.58 1.78 1.40 1.67 1.65 0.16 0.46

100-200' 1.86 1.84 2.00 1.71 1.96 1.68 1.84 0.13 0.32

200-300' 1.58 1.53 1.55 1.76 1.53 1.68 1.61 0.09 0.23

300-400' 1.86 1.96 1.96 1.71 2.02 1.56 1.85 0.18 0.46

400-500' 1.89 1.91 2.00 1.96 1.97 2.00 1.96 0.05 0.11

Mean 1.81 1.76 1.82 1.78 1.78 1.72 1.78 0.04

Section 9 0-100' 2.00 2.01 2.11 2.03 2.24 1.91 2.05 0.11 0.33

100-200' 2.11 2.07 2.30 2.09 2.51 2.02 2.18 0.19 0.49

200-300' 5.48 5.12 4.47 4.10 4.89 5.22 4.88 0.51 1.38

300-400' 3.55 4.43 3.63 4.27 3.80 3.53 3.87 0.39 0.90

400-500' 2.13 2.09 2.00 2.17 2.07 2.10 2.09 0.06 0.16

Mean 3.05 3.14 2.90 2.93 3.10 2.96 3.02 0.10


UCPRC-TM-2008-13 60

Vendor 1 2 3 4 5 6 Mean Std Dev Range Section 10 0-100' 4.45 4.07 3.95 1.65 3.87 4.97 3.83 1.14 3.32

100-200' 3.11 3.07 3.05 1.79 3.22 3.42 2.94 0.58 1.63

200-300' 2.49 2.64 2.66 1.54 2.35 3.17 2.48 0.54 1.63

300-400' 2.90 3.00 2.75 2.79 2.68 3.08 2.87 0.15 0.40

400-500' 2.57 2.30 2.82 3.13 2.67 2.33 2.64 0.31 0.83

Mean 3.10 3.02 3.05 2.18 2.96 3.39 2.95 0.41

Section 11 0-100' 2.32 2.54 2.92 2.79 2.16 2.61 2.56 0.28 0.76

100-200' 1.94 2.58 1.64 3.60 1.85 1.76 2.23 0.75 1.96

200-300' 1.74 1.61 2.03 3.35 1.83 2.40 2.16 0.64 1.74

300-400' 1.67 2.04 1.70 2.44 1.63 2.25 1.96 0.34 0.82

400-500' 2.53 2.19 1.76 2.87 1.75 1.80 2.15 0.47 1.12

Mean 2.04 2.19 2.01 3.01 1.84 2.16 2.21 0.41

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