SP-024 Manual for Condition Rating of Flexible Pavements … · 2020-02-07 · Acknowledgement The Manual for Condition Rating of Flexible Pavement was originally developed by George

SP-024 Manual for Condition Rating of Flexible Pavements

Distress Manifestations

Ontario

Ministry of Transportation Highway Standards Branch

Materials and Engineering Research Office

Materials Engineering and Research Office

Crown Copyright © 2016 Ministry of Transportation

Technical Report Documentation Page

Number: SP - 024 ISBN 978-1-4606-8019-3 (Print) ISBN 978-1-4606-8020-9 (PDF)

Ministry Contact:

Materials and Engineering Office Highway Standard Branch Provincial Highway Management Division (416) 235-3733

Abstract: Most highway infrastructure authorities use pavement condition rating to assess the service life of a pavement and its ability to meet the needs of the travelling public. The Ministry of Transportation Ontario uses two interrelated measures, ride quality and distress manifestations, as the basis of its pavement condition rating scheme. Pavement condition rating is an essential component of the Ministry’s pavement management system. This manual provides the what, why, and how of pavement condition rating for flexible pavements.

Key Words: Pavement condition rating, ride condition, distress manifestations

Manual for Condition Rating of Flexible Pavements


Revision Committee: Becca Lane Manager

Materials Engineering & Research Office

Brij Sharma Pavement Management Engineer Betty Bennett Senior Pavement Design Engineer Sam Cui Pavement Management Analyst Materials Engineering and Research Office Highway Standards Branch Dave Harris Pavement Design and Evaluation Officer

Geotechnical Section, Engineering Office, West Region Selva Reginold Project Soils Engineer

Geotechnical Section, Engineering Office, Central Region Mike Baird Pavement Design and Evaluation Officer

Geotechnical Section, Engineering Office, Eastern Region Derek Thompson Geotechnical Engineer Geotechnical Section, Engineering Office, Northeast Region Gary Dorval Pavement Design and Evaluation Officer

Geotechnical Office, Engineering Office, Northwest Region

John McDonald Technical Services Supervisor

Operational Services, West Region March 2016

SP-024 Manual for Condition Rating of Flexible Pavements


Acknowledgement

The Manual for Condition Rating of Flexible Pavement was originally developed by George J.

Chong, Research Engineer, William A. Phang, Principal Research Engineer and Gerry A. Wrong, Head

of Design Evaluation and Pavement Section in 1989. The manual has served its purpose very well in

the Ministry’s pavement management practice.

This edition is updated based on field experience and input from pavement evaluation experts to

improve the clarity of distress identification and the rating scheme. It takes into consideration of

consolidating certain specifications, advancements in surveying technology and a wider application of

the manual.

Becca Lane, Manager of Materials Engineering and Research Office, initiated the manual update in

2010 and has steered the edition since then.

Technical guidance was provided by the Heads of MTO Regional Geotechnical Sections: Nick Gilbert,

West Region; Susanne Chan, Acting, Central Region; Frank Vanderlaan, East Region; Jason Wright,

Northeast Region; and Dick Dykstra, Northwest Region.

Thanks to Fazal Mabood, Gem Jiang, and Carolina Cautillo who provided additional photos to

supplement the visual examples of pavement distress manifestation.

Special thanks to all Pavement Design and Evaluation Officers from the five regions that have provided

valuable comments and suggestions to the manual through their routine experiences.

Table of Contents

1. Introduction ............................................................................................................................ 1

2. Pavement Surface Condition Rating Scheme ....................................................................... 2

3. Procedure for Pavement Evaluation ...................................................................................... 5

4. Riding Quality (Ride Condition Rating) .................................................................................. 6

5. Distress Manifestations .......................................................................................................... 7

5.1 Surface Defects ........................................................................................................... 11

5.1.1 Loss of Coarse Aggregates and Ravelling ........................................................ 12

5.1.2 Segregation ........................................................................................................ 17

5.1.3 Flushing .............................................................................................................. 21

5.2 Distortion or Permanent Deformation Surface Defects ............................................... 26

5.2.1 Rippling and Shoving ......................................................................................... 27

5.2.2 Wheel Track Rutting .......................................................................................... 33

5.2.3 Distortion ............................................................................................................ 38

5.3 Cracking ....................................................................................................................... 43

5.3.1 Longitudinal Wheel-Track Cracking ................................................................... 44

5.3.2 Centreline Cracking ........................................................................................... 50

5.3.3 Pavement Edge Cracking .................................................................................. 54

5.3.4 Transverse Cracking .......................................................................................... 59

5.3.5 Longitudinal Meander and Mid-lane Cracking ................................................... 64

5.3.6 Random / Map Cracking .................................................................................... 68

5.3.7 Alligator Crack .................................................................................................... 73

5.3.8 Miscellaneous .................................................................................................... 78

6. Paved Shoulder Distress Manifestations ............................................................................. 81

6.1 Paved Shoulder Cracking ............................................................................................ 82

6.2 Pavement Edge, Paved Shoulder (or Curb) Separation ............................................. 83

6.3 Paved Shoulder Break-up............................................................................................ 84

6.4 Paved Shoulder Distortion ........................................................................................... 85

References… ............................................................................................................................... 86

Appendix A.. ................................................................................................................................ 87

Appendix B ………………………………………………………………………………… ………….90

Appendix C…………. ................................................................................................................... 95

Appendix D.. ................................................................................................................................ 96

Appendix E.. ................................................................................................................................ 97

1

Introduction

Rating of pavement surface condition is used in one form or another by most highway authorities as

a measure of the ability of the pavement to continue to provide service to the public. Condition

ratings are used in determining deficiencies, inadequacies, remedial measures, fiscal needs, and in

programming. The surface condition rating scheme used in Ontario is based on two interrelated

measures - ride quality and distress manifestations.

Ride quality, is a subjective measure of the smoothness of the pavement surface profile. Since the

subjective measure may depend on personal opinion, regional bias, and observer experience, the

ride quality can be measured quantitatively by mechanical devices. Distress manifestations have

not previously been quantified, but quantification is necessary if more meaningful use is to be made

of condition ratings.

In this manual, distress manifestations are categorized, and illustrations of each category are

provided to lend uniformity to reporting and interpretation. In addition, descriptions of the density of

occurrence and the severity of each type of distress manifestation are made to conform to standard

words which precisely express the relative density or severity on a scale of 1 to 5. For example, in

the description "slight multiple longitudinal wheel-track cracks occurring at frequent intervals over

the section," the words slight and frequent are the standard words that correspond to Numbers 2

and 3, respectively, on the severity and density scales. Guidelines and photographs are provided to

control the use of standard words.

Probable causes of each distress manifestation are presented, together with comments on

progressive deterioration or other behaviour that might affect remedial treatment.

Although the purpose of this manual is to describe distress manifestations, possible remedial

measures are included under each distress manifestation. However, the remedial measures listed

against a deficiency are not necessarily the most effective maintenance alternative; nor will these

measures necessarily effectively correct the cause or causes of the distress. The listed remedial

measure may be only an expedient maintenance treatment to slow deterioration.

2

Pavement Surface Condition Rating Scheme

The rating scheme devised and currently used in Ontario is shown in Table B-1 of Appendix B. It

presents a rating scale of 0 to 100. The ranges on this scale are used for separating and

determining timing and types of remedial action to be taken and show corresponding descriptions of

surface condition in terms of riding quality, distortion, and the severity, extent and type of cracking

distress. The scheme is valid; however, more value can be obtained from Condition Reports if a for-

malized and uniformly-worded description of each distress manifestation is implemented. Such

descriptions are a decision-aid in choosing the remedial treatment with the best probable chance of

success. Standard descriptions also assist in performance evaluation of different pavement

designs, they allow identification of specific problems or weaknesses, and they permit quantitative

analysis of the type, extent, and location of distress manifestations. To do a condition rating, the rater evaluates two physical parameters:

• The ride quality of the pavement surface (the indicator for pavement functional condition);and

• The extent and severity of pavement surface distress manifestations (the indicator of pavement structural condition).

The two physical parameters are interrelated by reason that some distress manifestations result in

surface distortion and unevenness that, in turn, cause a reduction in riding quality. A prime example

is transverse crack lipping or cupping which results in a rough ride for road users. Rougher

pavements, in turn, cause vehicles to produce higher dynamic wheel loads, thereby increasing

stresses, strains, and deflections and hastening pavement deterioration. However, not all distress

manifestations are accompanied by distortion or unevenness. The type of distress and the extent

and severity of occurrence are all very useful indicators of structural inadequacy, materials

deficiency, and probable rate of subsequent deterioration.

Riding quality is a perceived measure, although it is practical for the experienced rater to evaluate

ride quality and provide reliable measurements, to improve the accuracy, consistence and

efficiency the ride quality evaluation, mechanical measurements using automated roughness

devices such as Road Analyzer (ARAN) may be made in lieu of the subjective riding comfort rating;

however, the numerical value measured by these mechanical devices (e.g., International

Roughness Index) must be equated to the same subjectively-derived riding comfort rating scale.

Distress manifestations of pavement surface may be grouped under three main headings:

• Surface defects • Surface deformation • Cracking

The different distress manifestations are listed in Table 2.1. For each type of distress, a description

of physical appearance and an array of possible causes are given (Section 5). Each distress is

3

evaluated in terms of the extent or density of occurrence and in terms of severity. Uniform

descriptions are given to correspond to each category of density or severity.

Table 2.1 Pavement Distress Manifestations

Type Pavement Distress Code No.

SURFACE DEFECTS

Coarse Aggregates Loss, Ravelling Segregation

1

Flushing 2

SURFACE DEFORMATION

Rippling and Shoving 3

Wheel Track Rutting 4

Distortion 5

CRACKING

Longitudinal Wheel Track Single and Multiple 6

Alligator 7

Centreline Single and Multiple 8

Alligator 9

Pavement Edge Single and Multiple 10

Alligator 11

Transverse Half, Full and Multiple 12

Alligator 13

Longitudinal Meander and Mid-lane 14

Random/Map 15

A pavement condition rating based on the two physical parameters should reflect the average

condition of the pavement section rated. This requires that roads be divided into sections exhibiting

relatively uniform performance. In general, sections should start and end at major intersections or

contract limits. A preliminary evaluation of riding quality should enable the rater to identify sections

with substantially different qualities, and the project may be subdivided according to these

variations. However, it is suggested that in rural areas the subsection should not be less than 1.6

km and, in the case of urban streets, not less than the distance between two intersections (if

uniform in performance and appearance). Intersections should be included as part of the evaluation

section in both rural and urban situations.

Pavement condition ratings are to be carried out between late spring and early fall ensuring there is

no frost in the ground, and to allow the pavement to stabilize.

Pavement shoulder distresses, although not directly affecting the pavement surface condition, do

contribute to overall pavement performance. Therefore, evaluations should round out the total

4

performance picture. For practical purposes, only paved shoulders are considered, and the

distresses are grouped under the following headings:

Fully paved or partially paved shoulder • Cracking Pavement edge/Curb separation • Distortion

Maintenance treatments carried out on the pavement surface contribute directly to overall

pavement performance Pavement serviceability and function are directly affected by the riding

quality of the pavement surface. Therefore, reporting on the type and extent of maintenance

treatment carried out on the pavement is both desirable and necessary.

Complete and uniform condition reports lead to increased confidence in identifying pavement

deficiencies. Pavement condition ratings should be completed at regular time intervals to document

changing conditions. The information is critical for planning the most appropriate maintenance,

pavement preservation, rehabilitation and/or reconstruction strategies for that pavement section.

The preferred interval is one year but, if this is not feasible or economical, the maximum interval is

two years.

5

Procedure for Pavement Evaluation Step 1 To carry out the pavement condition evaluation, drive slowly over the pavement to

visually inspect its overall surface condition for uniformity in appearance. If distinct differences are observed, then the pavement should be subdivided into two (or more) appropriate sections for evaluation. However, each evaluation section should have a minimum length of 1.6 km for rural roads, and the distance between two intersections (regardless of length) for urban streets. This minimum length requirement is strictly for economic reasons.

Step 2 After establishing the evaluation section, assess the pavement functional condition by

obtaining the Ride Condition Rating (RCR), refer to Table 4.1. This rating is obtained by averaging the ride quality of both directions of the pavement. Drive over the pavement at the posted speed limit. However, if it is not possible to maintain the posted speed limit safely, the pavement should be rated at a safe speed and that speed should be noted. For an urban situation where the evaluation section covers more than one block with intervening stops, traffic regulations must be observed, but the RCR should be obtained by averaging the whole evaluation section.

Step 3 After determining the RCR, assess the pavement structural condition by driving over

the shoulder slowly to assess distress manifestations. Multiple stops per section should be made to examine distress type and severity, particularly with respect to surface defects and structural defects.

Step 4 Complete the Pavement Condition Rating Form by recording the Ride Condition Rating

and all observed distress manifestations, shoulder distress manifestations, and maintenance treatments in their appropriate places (Figure A-l, Appendix A).

Step 5 Assign a Pavement Condition Rating (PCR) according to the guide for the estimation of

pavement condition rating for Flexible Pavements (Table B-1) given in Appendix B.

6

Riding Quality (Ride Condition Rating)

The riding quality of pavement is the degree of riding comfort that the pavement provides to the

travelling public. The rater should drive over the pavement section at the posted speed and, having

done so, classify the pavement's ride condition according to the descriptions given in Table 4.1.

Perhaps surprisingly, the type of passenger vehicle used to perform a Ride Condition Rating has no

significant influence on the evaluation. This finding was reported in an experimental study

conducted by MTO in 1968, in which over 100 individual raters used different types and sizes of

automobiles [1]

. Therefore, it is not necessary to specify any particular vehicle for assessment of the

riding quality (Ride Condition Rating) of the pavement surface.

When rating ride condition, it is important that the rater not be influenced by the appearance of the

pavement surface - only the riding quality the pavement provides to the rater should be considered

relevant.

Table 4.1 Ride Condition Rating Guide

RCR Uniform Description of Ride Condition at Posted Speed (RCR)

Guidelines

9 – 10 Excellent A very smooth ride.

7 – 9 Good A smooth ride with just a few bumps or depressions.

5 – 7 Fair A comfortable ride with intermittent bumps or depressions.

2 – 5 Poor An uncomfortable ride with frequent to extensive bumps or depressions. Cannot maintain the posted speed at lower end of the scale.

0 – 2 Very Poor A very uncomfortable ride with constant jarring bumps and depressions. Cannot maintain the posted speed and must steer constantly to avoid bumps and depressions.

7


Distress manifestations are visible signs of pavement structural condition. These distresses are

indicators of problems due to material deficiencies, construction deficiencies, environmental and

climatic conditions, traffic loading, or other causes. The degree of severity (How bad?) and density

or extent of occurrence (How big?) of these distresses are good indicators of the problem.

Severity

The term "severity" simply indicates how bad the problem is. It is a scale based on past engineering

experience. It has five levels – Very Slight, Slight, Moderate, Severe and Very Severe. These

Guidelines give a verbal description of each stage, along with pictorial representations.

Density (Extent of Occurrence)

The term "density" simply describes how big the problem is. It, too, is based on past engineering

experience. It has five levels - Few, Intermittent, Frequent, Extensive and Throughout. Density is

based on the percentage of surface area affected or, in the case of transverse cracking, it is based

on spacing (Table 5.1). Table 5.1 Pavement Distress Density

Density Rating Scale

Percentage of Surface Area Affected

All Distresses Except Transverse Cracking

Density Based on Crack Spacing

Transverse Cracks Only

Few 1 0-10% More than 40 m apart

Intermittent 2 10-20% About 30 to 40 m apart

Frequent 3 20-50% About 20 to 30 m apart

Extensive 4 50-80% About 10 to 20 m apart

Throughout 5 80-100% Less than 10 m apart

8

For example, the rater may encounter a situation where there are some incidences of longitudinal

wheel track cracking within the evaluation section. The method for evaluating the density of such

distress is presented in Figure 5.1 through Figure 5.6. The percentage of affected area is calculated

based on each driving lane and then averaged across the entire pavement section.

Figure 5.1 Density Evaluation

Few Longitudinal Wheel Track Cracking (0 - 10% Pavement Area Affected)

Density evaluation: Affected pavement area in West Bound Lane (WBL) = 10.0% Affected pavement area in East Bound Lane (EBL) = 5.0% Total affected pavement area = (10.0% +5.0%) / 2 = 7.5%

Figure 5.2 Density Evaluation

Intermittent Longitudinal Wheel Track Cracking (10 - 20% Pavement Area Affected)

Density evaluation: Affected pavement area in West Bound Lane (WBL) = 15.0% Affected pavement area in East Bound Lane (EBL) = 20.0% Total affected pavement area = (15.0% +20.0%) / 2 = 17.5%

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15.0%

15.0%

5.0%

9

Figure 5.3 Density Evaluation Frequent Longitudinal Wheel Track Cracking

(20 - 50% Pavement Area Affected)

Density evaluation: Affected pavement area in West Bound Lane (WBL) = 45.0% Affected pavement area in East Bound Lane (EBL) = 40.0% Total affected pavement area = (45.0% + 40.0%) / 2 = 42.5%

Figure 5.4 Density Evaluation Extensive Longitudinal Wheel Track Cracking


Density evaluation: Affected pavement area in West Bound Lane (WBL = 75.0% Affected pavement area in East Bound Lane (EBL) = 45.0% Total affected pavement area = (75.0% +45.0%) / 2 = 60.0%

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10

Figure 5.5 Density Evaluation Throughout Longitudinal Wheel Track Cracking


Density evaluation: Affected pavement area in West Bound Lane (WBL = 100.0% Affected pavement area in East Bound Lane (EBL) = 80.0% Total affected pavement area = (100.0% + 80.0%) / 2 = 90.0%

Figure 5.6 Density Evaluation Illustration of 100% Pavement Area Affected by

Longitudinal Wheel Track Cracking

Density evaluation: Affected pavement area in West Bound Lane (WBL = 100.0% Affected pavement area in East Bound Lane (EBL) = 100.0% Total affected pavement area = (100.0% + 100.0%) / 2 = 100.0%

These illustrations are presented for longitudinal wheel track cracking; however, the procedure

generally applies to all distress manifestations except transverse cracking. Transverse crack

density is determined based on the parameters provided in Table 5.1.

500 m

475 m

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11

1.1 Surface Defects

Loss of Coarse Aggregates and Ravelling

Segregation

Flushing

12

1.1.1 Loss of Coarse Aggregates and Ravelling

Description:

Loss of Coarse Aggregates: Pavement surface is breaking up into small pock-marks as coarse aggregate particles are lost from the surface; Ravelling: progressive loss of pavement materials (coarse or fine aggregates, or both) from surface downward results in a pock-marked appearance;

Possible Causes:

1. Lack of bond between particles and mortar due to inadequate coating or to

stripping under the action of water.

2. Fracture of the particles through load or natural causes, allowing the

loosened pieces to be picked out by traffic action.

3. Disintegration of particles, such as chert, that are highly absorptive, and

fracture and disintegrate upon repeated freezing and thawing.

4. Delamination of chert or shale particles.

5. Clay-coated aggregate particles.

6. Insufficient asphalt content.

7. High air voids.

8. Poor adhesion of asphalt cement to aggregate particles due to wet aggregate

or lack of anti-stripping agent.

9. Poor compaction especially cold weather paving permits infiltration of water

and salts which promote stripping of asphalt.

10. Asphalt hardening due to aging or impurities in the AC.

11. Segregation during paving.

Surface Defects

13

Severity Guidelines

Very Slight

Barely noticeable loss/lack of pavement materials.

Slight Noticeable loss/lack of pavement materials.

Moderate Having pock-marked appearance, fairly well spaced between pock-marks. Shallow disintegration of pavement surface, an open-textured look.

Severe Having pock-marked appearance, pock-marks are closely spaced. Disintegration with low severity potholes*.

Very Severe Surface has a ravelled appearance and is disintegrated into moderate or high severity potholes*.

* Reference:

The severity of pothole is based on the Federal Highway Administration (FHWA) Distress Identification Manual for the LTPP (5

th Edition, 2014) where three severity levels are

specified based on the depth of the potholes, regardless the diameter: Low Severity <25mm Moderate 25mm to 50mm High Severity >50mm

Density Guidelines (Based on Percent of Surface Area in the Pavement Section affected by the Defect)

Few Less than 10% of pavement surface area affected.

Intermittent 10 to 20% of pavement surface area affected.

Frequent 20 to 50% of pavement surface area affected.

Extensive 50 to 80% of pavement surface area affected.

Throughout 80 to 100% of pavement surface area affected.

14

Figure 5.1.1 (a) Very Slight Coarse Aggregate Loss

Figure 5.1.1 (b) Very Slight Coarse Aggregate Loss

15

Figure 5.1.1 (c) Slight Coarse Aggregate Loss

Figure 5.1.1 (d) Moderate Coarse Aggregate Loss

16

Figure 5.1.1 (e) Severe Ravelling

Figure 5.1.1 (f) Very Severe Ravelling

17

1.1.2 Segregation

Description:

A construction-related deficiency resulting in areas of the pavement surface having comparatively coarser or finer texture than that of the surrounding surface; a non-uniform distribution of aggregate sizes through the mat.

Possible Causes:

1. Poor construction practices such as improper storage bins, loading of truck, paving equipment trains, end load segregation.

2. Placement of segregated hot mix.

3. Temperature differences within material during placement (thermal segregation).

Severity Guidelines

Slight A pavement matrix is in place between the coarse aggregate particles; however, there are slightly more coarse aggregate particles in comparison with the surrounding acceptable mix.

Medium The pavement has significantly more coarse aggregate particles than the surrounding acceptable mat and usually exhibits some lack of surface matrix.

Severe The pavement appears very coarse, with coarse aggregate particle against coarse aggregate particle and the pavement has little or no matrix.

Surface Defects

18







19

Figure 5.1.2 (a) Slight Segregation

Figure 5.1.2 (b) Slight Segregation

20

Figure 5.1.2 (c) Medium Segregation

Figure 5.1.2 (d) Severe Segregation

21

1.1.3 Flushing

Description:

The presence of free asphalt cement on the pavement surface. Most likely to occur in the wheel tracks during hot weather.

Possible Causes:

1. High asphalt cement content relative to void content in mineral aggregate. On hot days, asphalt cement expands into air voids; if air voids are too low, continued expansion results in lower stability of the mix, with the consequence that traffic loading causes excess asphalt cement to migrate to the surface.

2. Paving over excessively primed surfaces.

Severity Guidelines

Very Slight

Very faint colouring (veining).

Slight Colouring visible (interconnected veining).

Moderate Distinctive appearance of excess asphalt cement on the pavement surface.

Severe Areas of free asphalt cement giving the pavement surface area a wet look.

Very Severe Excess asphalt cement giving the affected pavement surface area a wet look, and wheel noise comparable to that when driving over a wet surface.

Surface Defects

22







23

Figure 5.1.3 (a) Very Slight Flushing

Figure 5.1.3 (b) Slight Flushing

24

Figure 5.1.3 (c) Slight Flushing

Figure 5.1.3 (d) Moderate Flushing

25

Figure 5.1.3 (e) Severe Flushing

Figure 5.1.3 (f) Very Severe Flushing

26

1.2 Distortion or Permanent Deformation Surface Defects Rippling and Shoving

Wheel Track Rutting

Distortion

27

1.2.1 Rippling and Shoving

Description:

Rippling: Regular transverse undulations in the surface of the pavement,

consisting of closely spaced, alternate valleys and crests (Washboard Effect).

Shoving: Singular and multiple waves or humps located transversely or

longitudinally on the pavement surface. Possible Causes:

1. Poor construction practices.

2. Heavy traffic on steep downgrade or upgrade, or pavement with too thick tack

coat or too thick soft waterproofing membranes on bridge decks.

3. Low stability in asphalt mix.

4. Braking, acceleration and turning movements at intersections.

5. Lack of bond between asphalt surface and underlying layer -may be caused

by excess tack coat acting as a lubricant.

6. Unstable granular base reflecting through the surface.

Severity Guidelines

Very Slight Barely noticeable washboard effect, not always visible.

Slight Noticeable washboard effect.

Moderate Bumpy with washboard appearance or ridges and valleys.

Severe Very bumpy with pronounced washboarding or large humps on pavement surface.

Very Severe Washboarding or large humps that cause vehicles to drift sideways and may cause loss of control of vehicles.

Distortion / Deformation

28







29

Figure 5.2.1 (a) Very Slight Shoving

Figure 5.2.1 (b) Slight Shoving

30

Figure 5.2.1 (c) Moderate Rippling

Figure 5.2.1 (d) Moderate Shoving

31

Figure 5.2.1 (e) Moderate Rippling and Shoving

Figure 5.2.1 (f) Severe Shoving

32

Figure 5.2.1 (g) Very Severe Shoving

33

1.2.2 Wheel Track Rutting

Description:

Longitudinal depressions taking the form of a single or double rut in the wheel tracks after repeated load application. Wheel track rutting results from densification and permanent deformation under the load, combined with displacement of pavement materials. Deep ruts are often accompanied by longitudinal cracking in the wheel tracks. The rut depth is measured by placing a 1.8m straight edge across the rut area perpendicular to the driving direction and vertically placing a gauge, with minimum 1mm graduation or finer, to measure the greatest distance between the pavement and the bottom of the straight edge.

Possible Causes:

1. Poorly-compacted structural layers.

2. Unstable granular bases or sub bases created by positive pore water

pressures under loads at times of near-saturation.

3. Unstable asphalt mixes (due to high temperatures, high asphalt content, low air

voids, or low viscosity of asphalt).

4. Unstable shoulder material; does not provide adequate lateral support.

5. Overstressed subgrade.

6. Allowing traffic on to a hot mat before letting it cool.

7. Wear from studded tires.


Rut Depth

Measure Gauge

1.8m Straight Edge

Pavement

34

Severity Guidelines

Very Slight Barely noticeable, the rut depth is 3 to 6 mm.

Slight Rut depth is between 7 to 12 mm.

Moderate Rut depth is between 13 to 19 mm or double rutting begins to develop.

Severe Rut depth is between 20 to 25 mm or double rutting developed.

Very Severe Rut depth is greater than 25 mm, with single or double rutting.







35

Figure 5.2.2 (a) Very Slight Wheel Track Rutting

Figure 5.2.2 (b) Slight Wheel Track Rutting

36

Figure 5.2.2(c) Moderate Wheel Track Rutting

Figure 5.2.2(d) Moderate to Severe Wheel Track Rutting

37

Figure 5.2.2(e) Severe Wheel Track Rutting

Figure 5.2.2(f) Very Severe Wheel Track Rutting

38

1.2.3 Distortion

Description:

Any deviation (other than described for rippling, shoving, and rutting) of the

pavement surface from its original shape. Generally, distortions result from

settlement, slope failure, volume changes due to moisture changes or frost

heaving, and from residual effects of frost heaving accumulating after each winter.

Distortion may take the form of dishing, bumps, dips (do not include the bumps

associated with cupped or tented cracks), all of which give rise to pitch, roll, and

jarring drop in a moving vehicle. Possible Causes:

1. Differential frost heave in poorly-drained cuts and transitions.

2. Differential frost heave at pavement edges, road centre, or pavement cracks.

3. Reverse differential frost heave at culverts.

4. Differential settlement of subgrade or base material.

5. Lack of subgrade support.

6. Embankment slope failure.

7. Improper maintenance.

8. Culvert failures

9. Loss of granular into rock fill

Severity Guidelines

Very Slight

Barely noticeable swaying of vehicle while in motion.

Slight Fairly noticeable pitch and roll, and jarring bump or drop. Good control of vehicle.

Moderate Noticeable pitch and roll, and harsh bump or jarring drop. Good/fair control of vehicle.

Severe Continuous pitch and roll, and hard jarring bump or drop; driver always has to anticipate distortion ahead. Fair control of vehicle.

Very Severe Continuous distortion, making the driver feel it is necessary to reduce speed from the posted speed. Poor control of vehicle.


39







40

Figure 5.2.3 (a) Very Slight Distortion

Figure 5.2.3 (b) Slight Distortion

41

Figure 5.2.3 (c) Moderate Distortion

Figure 5.2.3 (d) Severe Distortion

42

Figure 5.2.3 (e) Very Severe Distortion

43

1.3 Cracking

Longitudinal Wheel-Track Cracking

Centre Line Cracking

Pavement Edge Cracking

Transverse Cracking

Longitudinal Meander and Mid-lane Cracking

Map Cracking

Alligator Cracking

44

1.3.1 Longitudinal Wheel-Track Cracking

Description:

Cracks that follow a course approximately parallel to the centre line of the

pavement and are situated at or near the centre of the wheel tracks.

Possible Causes:

1. Overloaded vehicles at the weakest pavement period, in the early spring. 2. Fatigue failure of thin asphalt surfacing is initiated in this manner.

Severity Guidelines

Very Slight Single crack less than 3 mm.

Slight Single crack from 3 mm to 12 mm.

Moderate 13 mm to 19 mm width for single cracks, or multiple cracks starting.

Severe 20-25 mm width for single cracks, or multiple cracks, spalling begins to develop.

Very Severe Greater than 25 mm wide for single cracks, or multiple cracks with spalling developed. May begin to alligator.







Cracking

45

Figure 5.3.1 (a) Very Slight Wheel Track Cracking

Figure 5.3.1 (b) Slight Wheel Track Cracking

46

Figure 5.3.1 (c) Slight Wheel Track Cracking

47

Figure 5.3.1 (d) Moderate Wheel Track Cracking

Figure 5.3.1 (e) Moderate Wheel Track Cracking (Multiple Slight Cracks)

48

Figure 5.3.1 (f) Severe Wheel Track Cracking

Figure 5.3.1 (g) Severe Wheel Track Cracking

49

Figure 5.3.1 (e) Very Severe Wheel Track Cracking

50

1.3.2 Centreline Cracking

Description:

Crack(s) that run(s) along or near the road centre line. Possible Causes:

1. Poor longitudinal joint construction. 2. Frost action- variable granular depths due to constructing lanes separately;

differential frost heave along centre line due to insulating value of snow along pavement edges.

3. Moisture changes (swelling/shrinkage).

Severity Guidelines


Slight Single crack from 3 mm to 12 mm.

Moderate Single or multiple cracks. Single crack from 13 mm to 19 mm. Multiple cracks even if less than 13 mm.

Severe Single or multiple cracks. Single crack 20 mm to 25 mm wide with initial signs of spalling. Multiple cracks >13mm and <20 mm wide, with initial signs of spalling.

Very Severe Single or multiple cracks. Single crack greater than 25 mm, with or without spalling. Multiple cracks >20 mm and < 25 mm wide, with or without spalling.







Cracking

51

Figure 5.3.2 (a) Very Slight Centreline Cracking

Figure 5.3.2 (b) Slight Centreline Cracking

52

Figure 5.3.2 (c) Moderate Centreline Cracking

Figure 5.3.2 (d) Severe Centreline Cracking

53

Figure 5.3.2 (e) Very Severe Centreline Cracking

54

1.3.3 Pavement Edge Cracking

Description:

Crack parallel to extending out from the pavement lane edge, and is either a fairly continuous "straight" crack or consists of crescent-shaped cracks in a wave forma-tion. On some thin asphalt surfaces, pavement edge cracking progressively encroaches onto the outer wheel tracks through the middle of the lane, and may even progress to the centre line.

Possible Causes:

1. Frost action.

2. Insufficient bearing support and/or excessive traffic loading at the pavement edge.

3. Poor drainage at pavement edge and shoulder.

4. Inadequate pavement width results in forcing traffic too close to pavement edge.

5. The pavement edge line is painted in the wrong place allowing traffic passing on to the partially paved shoulder.

6. Core construction (earth shoulders).

Severity Guidelines

Very Slight Single longitudinal crack or single wave-formation crack less than 3 mm wide and no more than 150 mm from pavement edge.

Slight Single crack or two parallel cracks 3 mm to 12 mm wide and less than 300 mm from pavement edge.

Moderate Extending over 300 mm but less than 600 mm from pavement edge. Multiple cracks begin to interweave with connecting cracks.

Severe Extending over 600 mm but under 1500 mm from pavement edge. Outermost area near edge cracks begins to develop connecting cracks to give appearance of alligatoring.

Very Severe Progressive multiple cracks extend over 1500 mm from pavement edge. Outermost area near edge is alligatored.

Cracking

55







56

Figure 5.3.3 (a) Very Slight Pavement Edge Cracking

Figure 5.3.3 (b) Slight Pavement Edge Cracking

57

Figure 5.3.3 (c) Moderate Pavement Edge Cracking

Figure 5.3.3 (d) Severe Pavement Edge Cracking

58

Figure 5.3.3 (e) Very Severe Pavement Edge Cracking

59

1.3.4 Transverse Cracking

Description:

Crack follows a course approximately at right angles to the pavement centre line. Full transverse cracks tend to be regularly spaced along the length of the road, while half transverse and partial transverse occur at shorter, intermediate distances.

Possible Causes:

1. Natural shrinkage caused by very low temperatures.

2. Low temperature susceptibility of asphalt cement in asphalt mixes.

3. Frost action.

4. Reflection cracks.

Severity Guidelines

Very Slight Less than 3 mm single crack.

Slight Single crack 3 mm to 12 mm.

Moderate 13 mm to 19 mm single crack, or multiple cracks even if crack opening is less than 13mm. Cracks starting to develop cupping or lipping, barely noticeable bump.

Severe 20 mm to 25 mm single crack, or multiple cracks even if crack opening is less than 20 mm but greater than 13 mm. Cracks have developed cupping or lipping with noticeable bump.

Very Severe Greater than 25 mm single crack, or multiple cracks even if crack opening is less than 25 mm but greater than 20 mm. Cracks have fully developed cupping or lipping, and spalling has occurred. Bump or thump.

Cracking

60

Density Guidelines

Few Cracks (full or partial width) are more than about 40 m apart.

Intermittent No set pattern. Cracks are about 30 to 40 m apart.

Frequent A set pattern. Cracks are about 20 to 30 m apart.

Extensive Rather regular pattern. Cracks are about 10 to 20 m apart.

Throughout Regular pattern. Cracks are less than about 10 m apart.

61

Figure 5.3.4 (a) Very Slight Transverse Crack

Figure 5.3.4 (b) Slight Transverse Crack

62

Figure 5.3.4 (c1) Moderate Transverse Crack

Figure 5.3.4 (c2) Moderate Transverse Crack (multiple slight cracks)

63

Figure 5.3.4 (d) Severe Transverse Crack

Figure 5.3.4 (e) Very Severe Transverse Crack

64

1.3.5 Longitudinal Meander and Mid-lane Cracking

Description:

Crack, usually quite long, that wanders from edge to edge of the pavement, or

crack that is usually straight and parallel to the centre line, at or near the middle of

the lane. These types of cracks are usually single cracks, but occasionally

secondary cracks do develop parallel to them. Possible Causes:

1. Frost action - greater heave at pavement centre than at edges. More prevalent in mixes where asphalt stripping is extensive.

2. Poor construction practices.

3. Faulty construction equipment resulting in weak plane that then fails due to thermal shrinkage.

Severity Guidelines


Slight Single crack from 3 mm to 12 mm wide.

Moderate 13-19 mm width for single cracks or development of multiple cracks.

Severe 20-25 mm width for single cracks or multiple cracks; spalling begins to develop.

Very Severe Greater than 25 mm wide for single cracks or multiple cracks with spalling developed. May begin to alligator.







Cracking

65

Figure 5.3.5 (a) Very Slight Mid-lane Cracking

Figure 5.3.5 (b) Slight Mid-lane / Meandering Cracking

66

Figure 5.3.5 (c) Moderate Mid-lane Cracking

Figure 5.3.5 (d) Severe Mid-lane Cracking

67

Figure 5.3.5 (e) Very Severe Mid-lane Cracking

Figure 5.3.5 (f) Very Severe Meandering Cracking

68

1.3.6 Random / Map Cracking

Description:

Interconnected cracks forming a series of large polygons that resemble a map. The cracking appears to combine transverse and longitudinal cracks.

Possible Causes:

1. Swelling or shrinkage.

2. Frost action.

3. Hardening and shrinkage of the asphalt due to age.

Severity Guidelines

Very Slight Single cracks less than 3 mm and of short length, developed randomly between transverse cracks.

Slight Single cracks 3 mm to 12 mm, well-spaced but interconnected to form map-like appearance.

Moderate Interconnected cracks begin to develop multiple cracks. First sign of spalling. Single crack width 13 mm to 19 mm.

Severe Multiple interconnected cracks, some with spalling. Single crack width 20 mm to 25 mm.

Very Severe Multiple interconnected cracks, many with spalling or even potholes. Single cracks width more than 25 mm.







Cracking

69

Figure 5.3.6 (a) Very Slight Map Crack

Figure 5.3.6 (b) Very Slight Map Crack

70

Figure 5.3.6 (c) Slight Map Crack

71

Figure 5.3.6 (d) Moderate Map Crack

Figure 5.3.6 (e) Severe Map Crack

72

Figure 5.3.6 (f) Very Severe Map Crack

73

1.3.7 Alligator Crack

Description:

Cracks that form a network of polygon blocks resembling the skin of an alligator. The

block size, ranging in diameter from a few millimetres to about a metre, is indicative

of the level (depth) at which failure is taking place. Small block sizes (100 mm to 150

mm) indicate that movement is occurring in the upper (granular base) layer. This type

of alligatoring is mostly observed on "thin" (less than 75 mm) asphalt surfacings,

accompanied at times by slight depressions (perhaps 12 mm). Large block sizes (300

mm and more) indicate that movement is occurring in the deep granular layers and

subgrade. This type of alligatoring is accompanied by large depressions (perhaps as

much as 50 mm), together with lateral movement of the pavement edge outwards

(and upwards); the pavement forms a "bird-bath" during rains.

Alligator cracking is a consequence of the inability of a part of the structure to support

the repeated loads, due to a "softening" of the underlying material. Softening is

normally associated with an increase in moisture content. Cracks such as transverse,

centre line, and longitudinal, that are left unsealed, will allow surface water to infiltrate

the pavement structure and cause softening. Alligatoring will be the final stage of

crack development.

Alligator-type failures that are deep-seated in the subbase or subgrade are progressive (that is, under traffic and high moisture conditions they tend to spread rapidly) and traffic causes blocks of surfacing to be displaced and broken up.

Alligator failures in the upper layers normally appear in the very early spring. They do

not generally progress after warmer weather appears, probably because drainage of

the wet granular bases has increased pavement strength. Possible Causes:

1. Insufficient bearing support.

2. Poor base drainage and stiff or brittle asphalt mixes at cold temperatures.

Cracking

74

Severity Guidelines

Very Slight Multiple cracks begin to develop short interconnecting cracks and cause alligator pattern forming. May include depression up to 6 mm. Crack width is up to 3mm.

Slight Alligator pattern established with block corners fracturing. May include depression 7-12 mm. Crack width is between 3 and 12mm.

Moderate Alligator pattern established with spalling of blocks. May include depression 13-19 mm. Crack width is between 13 and 19mm.

Severe Blocks begin to lift. Small potholes from missing blocks. May include depression 20-25 mm. Crack width is between 20 and 25mm.

Very Severe Polygon blocks lifting. Potholes from missing blocks. May include depression greater than 25 mm. Crack width is greater 25mm.







75

Figure 5.3.7 (a) Very Slight Alligator Crack

Figure 5.3.7 (b) Slight Alligator Crack

76

Figure 5.3.7 (c) Moderate Alligator Crack

Figure 5.3.7 (d) Severe Alligator Crack

77

Figure 5.3.7 (e) Very Severe Alligator Crack

78

1.3.8 Miscellaneous

There are types of cracks that are not specifically described in the above subsections because they

are either uncommon or restricted to local areas. In all cases of reporting such cracks, the crack

should be named or described briefly, and estimates given of its severity and density of occurrence

on the "Distress Comments" space provided on the "Flexible Pavement Condition Evaluation

Form". Some examples of these miscellaneous cracks are:

Slippage Crack

Tearing Crack

Elephant Crack.

Distress Manifestation Description and Possible Cause

Slippage Crack

Crack that outlines the edge of a fill settlement. It generally takes the form of a large crescent. The enclosed side of the crescent is depressed, or may have been filled in with surfacing material. Slippage cracks are usually caused by embankment slope instability or indicative of potential slope failure.

Tearing Crack Crescent-shape tearing of the surfacing, likely caused by horizontal forces at a spot where the bond with the underlying layer is very poor.

Elephant Crack

"Elephant footprint" cracks appear on thin pavement design (single course asphalt pavement less than 45 mm over granular grade). There may be a series of these cracks down the centre line of the road, and there may be a slight depression at the centre of the area. Possible causes are a combination of the winter snow removal practice of centre-bare blowing and salting, and porous mix due to either lack of compaction or mix design of the asphalt pavement.

Cracking

79

Figure 5.3.8 (a) Slippage Crack

Figure 5.3.8 (b) Tearing Crack

80

Figure 5.3.8 (c) Elephant Crack

81

Paved Shoulder Distress Manifestations

Paved Shoulder Cracking

Pavement Edge, Shoulder (or Curb) Separation

Paved Shoulder Break-up

Paved Shoulder Distortion

82

1.4 Paved Shoulder Cracking

Description:

Cracking distresses occur in paved shoulders in the same way as in pavement of

similar type. Therefore, the same descriptions are applicable. Possible Causes:

1. Differential frost action.

2. Settlement.

3. Traffic loads.

Severity: See descriptions for various cracking distresses.

Density: See descriptions for various cracking distresses.

Paved Shoulder Distress

83

1.5 Pavement Edge, Paved Shoulder (or Curb) Separation Description:

The longitudinal joint between the pavement lane and the paved shoulder (or curb/ gutter) is opened or separated.

Possible Causes:

1. Movement due to differential frost action and settlement.

2. Contraction of asphalt pavement in low temperatures is not fully recovered

when pavement warms up, resulting in a gap between curb/gutter and

pavement surface, that grows wider year after year.

3. Failure of sealant material used in the longitudinal joint of pavement lane and

paved shoulder, or curb and gutter.

4. Cracking.

Severity Guidelines

Slight Less than 12 mm single cracking.

Moderate 13 mm to 19 mm opening with or without multiple cracking.

Severe Greater than 19 mm opening with or without multiple cracking.

Density Guidelines

Intermittent Less than 20% of pavement surface affected.

Frequent 20 to 50% of pavement surface affected.

Throughout Greater than 50% of pavement surface affected.


84

1.6 Paved Shoulder Break-up

Description:

These distresses occur in paved shoulders in the same way as in pavement of

similar type. Therefore, the same descriptions are applicable.

Possible Causes:

See descriptions for Pavement Edge Break.

Severity: See descriptions for Pavement Edge Break.

Density: See descriptions for Pavement Edge Break.


85

1.7 Paved Shoulder Distortion Description:

Any deviation of the surface from its original shape. Generally, these distortions result from settlement, from volume changes due to moisture and frost heaving, or from residual effects of frost heaving accumulating after each winter.

Possible Causes:

1. Differential frost action between pavement lane and paved shoulder or curb. 2. Differential settlement of subgrade or materials between pavement lane and

paved shoulder or curb, 3. Traffic loading.

Severity: See description for various distortion distresses.

Density: See description for various distortion distresses.


86

References

This "Manual for Condition Rating of Flexible Pavements – Distress Manifestations" was the first

(1975) of a series of manuals for pavement condition evaluation published by this Ministry.

Therefore, all other manuals and publications related to this subject matter made reference to this

particular manual. However, as a matter of reference interest, the following is a list of these related

documents:

[1] Chong, G.J., "A Rideability Rating Experiment," Report IR-19, Ministry of Transportation

and Communications, Ontario, Canada, 1968.

[2] Chong, G.J., Phang, W.A., Wrong, G.A., "Manual for Condition Rating of Rigid Pavements

-Distress Manifestations," Ministry of Transportation and Communications, Ontario,

Canada, 1977.

[3] Chong, G.J., Jewer, F.W., Macey, K., "Pavement Maintenance Guidelines -Distresses,

Maintenance Alternatives and Performance Standards," Report SP-001, Ministry of

Transportation and Communications, Ontario, Canada, 1980.

[4] Chong, G.J., Phang, W.A., Jewer, F.W., "Choosing Cost-Effective Maintenance," Report

PAV-8003, Ministry of Transportation and Communications, Ontario, Canada, 1980

[5] Blum, W.E., Phang, W.A., "Preventive Pavement Maintenance Concepts," Report PAV-

80-04, Ministry of Transportation and Communications, Ontario, Canada, 1981.

[6] Phang, W.A., Chong, G.J., "Ontario Flexible Pavement Distress Assessment for Use in

Pavement Management," Report PAV-81-01, Ministry of Transportation and

Communications, Ontario, Canada, 1981.

[7] Phang, W.A., Lefevre, R.N., James, H.H., Matthews, J.D., Nicholls, W., Pattison, H., She-

f1in, M.J., "Pavement Management Systems -Guidelines for Municipalities," Report PAV-

83-05, Ministry of Transportation and Communications, Ontario, Canada, 1983.

[8] Hajek, J.J., Phang, W.A., Wrong, G.A., Prakash, A., Stott, G.M., "Pavement Condition

Index (PCI) for Flexible Pavements," Report PAV-86-02, Ministry of Transportation and

Communications, Ontario, Canada, 1986.

[9] Chong, G.J., Phang, W.A., Wrong, G.A., "Manual for Condition Rating of Surface Treated

Pavements -Distress Manifestations," Ministry of Transportation, Ontario, Canada, 1989.

[10] Chong, G.J., Phang, W.A., Wrong, G.A., "Manual for Condition Rating of Flexible

Pavements Guidelines for Municipalities," Report SP-022, Ministry of Transportation, Ontario, Canada, 1989.

[11] FHWA, Distress Identification Manual for the Long-Term Pavement Performance Program

Publication No. FHWA-HRT-13-092 (Revised May 2014).

87

Appendix A

A Guide for Completing the "Flexible Pavement Condition Evaluation Form" Pavement Identification Pavement sections under evaluation must be identified by completing the following (refer also to Figure A-1).

1. Location: tie into the nearest town or city, major highway interchange, or any prominent landmarks.

2. Linear Highway Referencing System (LHRS) numbers for evaluation section.

3. Offset distance for evaluation section as related to LHRS point.

4. Evaluation section's length in kilometres.

5. District: number of district.

6. Date of survey: time evaluation took place.

7. Highway: number of highway.

8. Contract number.

9. Work project number.

10. Traffic direction of survey.

11. Facility of pavement lane surveyed.

12. Class of Highway

Riding Quality (RCR) The riding quality rating of an evaluation section is made by driving over the pavement at the

posted speed. The rating is recorded in the proper column on the evaluation form (Figure A-1).

Pavement Surface Distress Manifestations Pavement surface distress manifestations are evaluated by the rater walking and/or driving very

slowly over the evaluation section, and checking off all the pavement distress manifestations in their

appropriate spaces (Figure A-1).

The pavement distresses are listed under three subgroups.

88

1. Surface distress

loss of coarse aggregate/ravelling/segregation

flushing

2. Surface distortion or deformation

Rippling and shoving

Wheel track rutting

Distortion

3. Cracking

Longitudinal wheel track

Centre line

Pavement edge

Transverse

Longitudinal meander and mid-lane

Map

Alligator

Miscellaneous (for any type of cracking that is not specifically described by the above).

Shoulders

Shoulder type should be reported. Distresses, if any, should be evaluated and their density and

severity of occurrence reported by checking off the appropriate spaces (Figure A-l).

Maintenance

Maintenance should be reported by its type and density of occurrence, by checking off the

appropriate spaces (Figure A-l).

Comments

Items not covered or other significant factors that might influence pavement performance should be

reported in their appropriate spaces (Figure A-l).

Pavement Condition Rating (PCR)

Pavement Condition Rating is a subjectively derived rating of serviceability based on an evaluation

of pavement riding comfort and of pavement surface distresses such as distortion, cracking,

alligatoring, and so on. PCR is an assessment of overall pavement performance, both functionally

and structurally, as related to actual observable pavement characteristics -roughness and various

distress manifestations.

The Pavement Condition Rating is assigned according to the guidelines provided in Table B-1. The

guidelines also suggest the type and timing of maintenance activities or rehabilitation appropriate

for the Pavement Condition Rating.

89

Figure A.1 Pavement Condition Rating Form (Screenshot of PDDC)

90

Appendix B A Guide for Completing "Pavement Condition Report Forms"

District No. Number of district: the district code assigned to each district. Hwy. No. If highway location has more than one number, list all, with the lowest number

first (e.g., 7, 15, and 29).

W.P. No. List the current work project number, if applicable. Length Indicate the length in kilometres. If there is a discrepancy between the distance

table or map distance and the actual car distance, use the actual car distance ~ the odometer reads correctly.

Location

The location should be given in reference to the junction of highways or secondary highways, or

to city or town limits. Do not refer to small villages, rivers, municipal boundaries, or other

landmarks that are not readily identifiable on an official road map.

The sections should run from east to west or from south to north. The current MTO Reference

System number of the closest numbered location to the east or south of each end of the project

should be given, together with the offset distance (if any) from this location.

Last Contract No.

Indicate the number or numbers of previous contracts on the section of highway.

RCR (Ride Condition Rating)

Indicate the Ride Condition Rating to one decimal place (e.g., 6.4), based on an assessment of

the ride at posted speed. The RCR scale in Table 4.1 should be used.

Pavement

Type: Indicate surface type only – gravel surface, surface treated, hot–mix, concrete, etc.

Width: Measure with tape at the time of survey. If variable, show minimum widths.

Shoulders: Estimate width or, if variable, show minimum and maximum widths.

91

Traffic

Indicate the year of the traffic count, the AADT and SADT, and the percentage of truck traffic if

known.

Soils Data

Indicate the topography and soil types. This information may be supplemented by reference to

Putnam and Chapman or to regional soil maps, if necessary.

Pavement Structure Data

Indicate any spray patching, hot-mix patching, joint sealing, or other maintenance repair work

carried out, and the approximate year the work was done.

Performance and Condition

Provide a detailed summary of riding quality, surface defects, distortion, and cracking. The

Manual for Condition Rating of Flexible Pavements describes riding quality and various forms of

pavement distress, and details the terminology to be used to describe them. The descriptive

terms used in the manual have been standardized, and should be strictly followed to allow

accurate comparison of information from various sources.

Remarks

This section should include general comments on points such as the following:

type of W.P., if this has been assigned

possible changes in type or volume of traffic

frost heaves

ditching

safety features

alignment

possible combination with other projects

If deflection or rebound measurements have been made to assess the strength of the pavement,

the results should be indicated here. The type of measurement (i.e., FWD, Dynaflect, Benkelman

Beam, etc) should be noted. The data should be presented in standard form (i.e., values.

The time of the survey should be noted, to indicate whether the data represents the maximum

spring rebound values or whether it was taken from a single survey at some other time of year.

Roughness measurements, if any, should be indicated, showing the type of machine used and

the data, usually in millimetres per kilometre.

Skid resistance measurements should be shown, indicating skid number values and the speed at

which the skid number was assessed. The method of measurement (i.e. brake force trailer or

stereo photographs) should be indicated.

Proposed Remedial Measures

Indicate if patching or other maintenance measures will be adequate, and indicate the year when

these should be carried out. If resurfacing is proposed, indicate the type and thickness of courses

required and the extent of any padding.

2_

x

92

Program Year

Indicate the present program year, if any, and any suggested changes. If work is required within a

5-year period, indicate the year. If no work is required at present, estimate whether work will be

required in 5 to10 years, or after 10 years. This estimate is of value to the Highway Program

Administration Office.

Date of Survey

Indicate the day, month, and year.

Condition Rating

Table B-1 is a guide to assessing condition rating and proposed treatments. The

recommendations may be varied according to the class of highway considered.

Distribution

Distribution is made to Regional Staff. Copies should be sent to the District Office and to the

appropriate Head Office staff in the following sections:

Design Evaluation and Pavement Section

Reference and Inventory Systems Section

Highway Project Control Section

93

Figure B – 1 Pavement Condition Report

94

Table B – 1

PCR A Guide for the Estimation of Pavement Condition Rating for Flexible Pavements

90 - 100

Pavement is in excellent condition with few cracks. The Ride Condition Rating is excellent with few areas of very slight to slight distortion.

75 - 90 The pavement is in good condition with frequent very slight or slight cracking. The Ride Condition Rating is good with a few slightly rough and uneven sections.

65 - 75

The pavement is in fairly good condition with slight cracking, slight or very slight distortion and a few areas of slight alligatoring. The Ride Condition Rating is fairly good with intermittent rough and uneven sections.

50 - 65

The pavement is in fair condition with intermittent moderate and frequent slight cracking, and with intermittent slight or moderate alligatoring and distortion. The Ride Condition Rating is fair and the surface is slightly rough and uneven.

40 - 50

The pavement is in poor to fair condition with frequent moderate cracking and distortion, and intermittent moderate alligatoring. The Ride Condition Rating is poor to fair and the surface is moderately rough and uneven.

30 - 40

The pavement is in poor to fair condition with frequent moderate alligatoring and extensive moderate cracking and distortion. The Ride Condition Rating is poor to fair and the surface is moderately rough and uneven.

20 - 30

The pavement is in poor condition with moderate alligatoring and extensive severe cracking and distortion. The Ride Condition Rating is poor and the surface is very rough and uneven.

0 - 20

The pavement is in poor to very poor condition with extensive severe cracking, alligatoring and distortion. The Ride Condition Rating is very poor and the surface is very rough and uneven.

95

Appendix C

Tips for New Raters

1. Do not double count distresses - for example the area where alligator centre line cracking

exists is not also single & multiple cracking. It would be impossible to have severe single

and multiple centre line cracking throughout along with extensive slight alligator centre line

cracking.

2. The severity rating for a crack is based on the predominant width of the crack. The

occurrence of crack in one severity exceeds 80% of the total length of the same crack type.

3. The crack at the joint between edge of pavement and paved shoulder is not a pavement

edge crack.

4. If you are choosing between severities and densities only one apart on scale e.g. severe

frequent and moderate extensive choose the higher severity. If in addition, there is a very

severe distress that is only few in density remain with the severe frequent and note the

very severe in the comments.

5. Routed & sealed cracks that are functioning properly are not counted.

6. The term intermittent in practical terms means “noticeable” as compared to rarely seen.

7. Multiple or cupped cracks automatically move the severity of transverse cracking to

moderate. There are similar rules for the existence of spalling and for dual wheel track

rutting that could be noted.

8. Cupped or tented transverse cracks are not evaluated as distortion; cupping and tenting is

captured in the RCR or RCI.

9. Alligator cracking extending from the edge of pavement out to the midlane without wheel

track rutting is considered pavement edge alligator cracking; with wheel track rutting it is a

combination of pavement edge and longitudinal wheel track alligator cracking.

10. Very slight distresses can be seen better after a light rain where the pavement has had a

chance to dry, as well, distresses can be seen better in the early morning and evening light

when on multiple lane highways.

11. Distortion and rutting can be seen after it has rained and ponding water has formed on the

driving surface.

96

Appendix D Glossary

DMI (Distress Manifestation Index): Based on a scale of 0-10 (extremely distressed to distress-free), this index represents the aggregate effect of various distresses manifested over a given pavement surface. It is purely subjective as it is only based on rater’s ability to identify a distress and quantify it in terms of its severity and extent.

IRI (International Roughness Index): Based on a scale of 0 to infinity (perfectly smooth to infinitely rough), it is an international standard for measuring pavement roughness based on a quarter-car model and a standard sprung mass.

PCI (Pavement Condition Index): Based on a scale of 0-100 (failed to perfect pavement), PCI is MTO’s overall measurement of pavement condition. It is obtained by combining the DMI (subjective) and RCI (objective) values in a linear model. PCI is a more objective version of PCR.

PCR (Pavement Condition Rating): On a scale of 0-100 (failed to perfect pavement), it is based on the rater’s perception of the combined effects of RCR and DMI.

RCI (Ride Condition Index): On a scale of 0-10 (very poor - excellent), RCI is similar to RCR except it is objectively obtained. Specialized equipment is driven over the pavement section to gather data and obtain a rating. From 1985 to 1996, MTO used the PURD (Portable Universal Roughness Device, a trailer-mounted response-type measuring device) to measure RCI values. Since 1997, MTO has measured ride using International Roughness Index (IRI). IRI values are based on the actual pavement profile of the roadway. RCI values are derived from IRI measurements using an exponential regression model.

RCR (Ride Condition Rating): On a scale of 0 -10 (very poor to excellent), it is the subjective assessment of pavement ride condition and may vary based on the perception of the rater.

97

Appendix E

Guide for Describing Severity of Distresses

98

ASPHALTIC CONCRETE PAVEMENTS - Guide for Describing Severity of Distresses

Distress Type

S e v e r i t y o f D i s t r e s s 1 Very Slight

2 Slight

3 Moderate

4 Severe

5 Very Severe

Su

rface

Def

ects

1 Ravelling and

Coarse Agg. Loss, Segregation and Potholes

Barely noticeable loss.

Noticeable loss.

Pockmarks well-spaced, shallow disintegration, open- textured look.

Pockmarks closely-spaced, disintegration with small potholes.

Disintegration with large potholes.

2 Flushing

Very faint colouring (veining).

Colouring visible (interconnected veining).

Distinctive appearance with free asphalt.

Free asphalt on surface; has wet look.

Wet look with tire noise like driving on wet pavement surface.

Su

rface

Def

orm

ati

on

s

3 Rippling and

Shoving

Barely noticeable. Washboard effect.

Noticeable. Washboard effect.

Bumpy. Washboard effect.

Very bumpy. Pronounced washboard effect.

Large humps may cause poor control of car.

4 Wheel Track

Rutting

3-6 mm

Usually no longitudinal cracks.

7-12 mm

May include single longitudinal cracks.

13-19 mm

May include starting multiple longitudinal cracks. Dual rutting may begin to be visible.

20-25 mm

May include multiple longitudinal cracks. May include dual rutting.

> 25 mm

May include multiple longitudinal cracks. Usually with dual rutting.

5 Distortion

Barely noticeable swaying motion.

Fairly noticeable bump or drop. Good control of car.

Noticeable bump or drop.

Good/fair control of car.

Significant bounce.

Fair control of car.

Excessive and harsh bounce.

Poor control of car.

Cra

ckin

g

Sin

gle

an

d M

ult

iple

6 Longitudinal Wheel

Track

Width <3 mm. Single hairline cracks. Transverse cracks may be partial or full width.

3-12 mm width. Single cracks. Transverse cracks may be partial or full width.

13-19 mm width for single cracks or multiple cracks starting. Transverse cracks may also have slight cupping or lipping. (Barely noticeable bump.)

20-25 mm width for single cracks or multiple cracks; spalling begins to develop. Transverse cracks may also have moderate cupping or lipping. (Noticeable bump.)

> 25 mm wide for single cracks or multiple cracks with spalling developed. May begin to alligator. Transverse cracks may also have severe cupping or lipping. (Bump or thump.)

8 Centre Line 12 Transverse (half, full

& multiple) 14 Meander & Midlane 15 Random / Map 10 Pavement Edge

Width <3 mm. Single crack or single wave formation.

3-12 mm width. Single crack or two parallel cracks up to 0.3 m from edge.

Multiple cracks extend up to 0.6 m from edge.

Multiple cracks extend up to 1.5 m from edge.

Multiple cracks extend over 1.5 m from edge. Alligator pattern forming.

All

igato

r

7 Longitudinal Wheel

Track

Alligator pattern forming. May include depression up to 6 mm.

Alligator pattern established with block corners fracturing. May include depression 7-12 mm.

Alligator pattern established with spalling of blocks. May include depression 13-19 mm.

Blocks begin to lift. Small potholes from missing blocks. May include depression 20-25 mm.

Polygon blocks lifting. Potholes from missing blocks. May include depression >25 mm.

9 Centre Line 11 Pavement Edge 13 Transverse

Note: Crack width should be determined during the period from May to October. Do not report routed and sealed cracks; these will be reported as Maintenance Treatment.

99

ASPHALTIC CONCRETE PAVEMENTS

Pavement Distresses

Guide for Describing Extent of Pavement Distresses

Class

All Distresses

Except Transverse

Cracking* Transverse Cracking Only

1 Few

<10%

Cracks (full and/or half

cracks) are more than about

40 m apart.

2 Intermittent

10-20%

No set pattern. Cracks (full

and/or half) are about 30 to

40 m apart. 3 Frequent

20-50%

A set pattern. Cracks (full

and/or half) are about 20 to

30 m apart.

4 Extensive

50-80%

Rather regular pattern.

Cracks (full and/or half are

about 10 to 20 m apart). 5 Throughout

80-100%

Regular pattern. Cracks (full

and/or half) are less than

about 10 m apart.

* Based on percent of surface area within the PMS section affected by

distress

Shoulder Distresses Guide for Describing Severity of Shoulder Distresses

Type of Distress

Severity of Distress

1 Moderate

2 Severe

Cracking

Multiple slight to

moderate cracks

developed.

Multiple moderate to

severe cracks developed.

Pavement Edge -

Shoulder (Curb)

Separation

Single cracks.

Width: 13-19 mm.

Single crack width over

20 mm or multiple

cracks.

Distortion

Noticeable edge curling,

depression or heaving.

No major cracks.

Obvious edge curling,

depression or heaving.

Multiple cracks.

Breakup

Disintegration with small

potholes up to 150 mm.

Disintegration with

potholes >150 mm.

Edge Break

Edge cracks with some

loss of material.

Edge breaking with

extensive loss of

material.

Documents

SP-024 Manual for Condition Rating of Flexible Pavements … · 2020-02-07 · Acknowledgement The Manual for Condition Rating of Flexible Pavement was originally developed by George