city of saskatoon's pavement management system: …docs.trb.org/prp/12-1369.pdf · city of...

City of Saskatoon’s Pavement Management System: Network Level Structural Evaluation

Colin Prang, P.Eng.

City of Saskatoon

222 – 3rd Avenue North

Saskatoon, SK, Canada, S7K 0J5

Phone: (306) 975-2487

Email: [email protected]

Diana Podborochynski, E.I.T

PSI Technologies Inc.

221 Jessop Avenue

Saskatoon, SK, Canada, S7N 1Y3

Phone: (306) 477-4090


Roanne Kelln, E.I.T

PSI Technologies Inc.

221 Jessop Avenue

Saskatoon, SK, Canada, S7N 1Y3

Phone: (306) 477-4090


Curtis Berthelot, Ph.D., P.Eng.

Professor, Department of Civil and Geological Engineering

University of Saskatchewan

57 Campus Drive, Saskatoon, Saskatchewan

Canada, S7N 5A9

(306) 966-7009


Word Count: 5330

Table and Figures: 8 x 250 = 2000 word equivalents

Total Words: 7330 words

Submitted To:

Transportation Research Board

Transportation Research Record

November 8, 2011

TRB 2012 Annual Meeting Paper revised from original submittal.

Prang, Podborochynski, Kelln, Berthelot 2

ABSTRACT: Pavement management systems (PMS) combine economics and engineering to derive cost-effective

solutions for road maintenance and reconstruction. Since 1993, the City of Saskatoon (COS) has

employed a PMS that focuses on pavement surface deterioration and ride quality to measure the

performance of the city‟s road network. However, reliably predicting the structural condition of roads

based on surface distress information can be very difficult; furthermore, structural road issues are the

most intensive and costly to rehabilitate. The COS started using heavy weight deflectometer (HWD)

measurements to assess the structural condition of the COS road network in 2006.

Since it is difficult to distinguish between certain surface distresses, like top down cracking, from

structural distresses, such as fatigue cracking, HWD structural information may be beneficial in assessing

the condition of the road structure and the corresponding treatment needed. Therefore, using COS

network level PMS surface distress data and condition ratings, the effect of using structural data as

measured by HWD is examined in this paper. Two neighborhoods in Saskatoon were analyzed using

typical COS PMS surface distresses and HWD deflection measurements.

The results of structural condition assessments complement and enhance the findings of surface

condition assessments. The risks posed by using surface condition assessments can be mitigated by using

structural condition assessments in addition to surface condition assessments. Ultimately, the use of

structural asset management will reduce the risk of a significant road failure and subsequent high

expenditures to fix such a failure.



INTRODUCTION

The American Association of State Highway and Transportation Officials (AASHTO) defines Pavement

Management Systems (PMS) as a “set of tools or methods that assist decision-makers in finding optimum

strategies for providing, evaluating, and maintaining pavements in a serviceable condition over a period

of time” (1). Generally, PMS have components of data collection and condition monitoring, data and

condition state analysis, treatment implementation, cost analysis, and feedback. PMS can improve the

efficiency of decisions and provide cost effective treatment strategies; this is turn improves the pavement

network and allows for funds to be properly allocated (1,2). PMS integrate economics with engineering

to optimize road decisions in a cost-efficient manner.

Since their development in the 1960‟s, PMS have used surface distresses to make decisions

regarding maintenance and rehabilitation treatment timing and scope (1,2). Agencies have come to

realize limitations of using surface distresses to quantify the structural capacity of pavements (3). Often,

by the time surface distress measures indicate that a road has structurally failed, the structural

deterioration has reached such a severe state that the road usually requires full rehabilitation or

reconstruction, preventing the optimization of maintenance and rehabilitation treatments. Structural

condition assessments based on surface condition often result in reactive as opposed to preventative

preservation treatments (3,4).

PMS are conducted at the network level or project level depending on the detail of information

required. Project level PMS are detailed and include information such as soil conditions and structural

capacity, in addition to surface distresses. Network level PMS are less detailed and are often limited to

surface distresses only. Network level PMS prioritize projects based on the needs, benefits, and costs of

the whole system (5).

Since PMS can have a great effect on agency budgets and fund allocations, PMS can be an

important component of an asset management system. Asset management systems value an agency‟s

infrastructure over its lifetime (6). For managing road infrastructure, estimates of the condition of the

road network are used to allocate limited funds for maintenance and rehabilitation treatments within the

network. An agency‟s PMS needs to adequately measure the structural integrity of its roads to achieve an

optimized road maintenance and rehabilitation strategy.

City of Saskatoon PMS Background

Prior to 1993, the City of Saskatoon (COS) did not employ a Pavement Management System (PMS).

Maintenance treatments were conducted on a reactive basis, often following a citizen‟s complaint (7).

Maintenance and rehabilitation treatments were not planned and were instead completed on roads with the

most severe surface distresses first (7). A “worst first” scenario was developed (3).

In 1993, the COS initiated a PMS that focused on pavement surface deterioration and ride quality

to allocate intermediate treatments and to measure the performance of the city‟s road network. Since

1993, the COS-employed PMS has evolved in terms of distresses and condition rating system. COS PMS

relies on surface deterioration and ride quality to measure road network performance (4). The COS road

network is divided into four road classifications: local, collector, arterial, and expressway. Road

classifications are determined based on estimates made at the time of construction of the road‟s future

traffic volumes and function. Budget funding is allocated amongst these classes.

Local roads are low volume roads with less than 1,500 vehicles per day and very few large trucks.

Local roads are used for accessibility and are constructed with thinner pavement structures typically

consisting of 50 mm hot mix asphalt concrete (HMAC), 125 mm granular base, 150 mm subbase, and 150

mm subgrade compaction. The local road class also includes industrial local roads that carry over 10

percent truck traffic in industrial areas of Saskatoon. Industrial local roads are subject to heavy, slow

truck traffic and are typically construction with 80 mm of HMAC, 150 granular base, 350 subbase, and

300 mm of prepared subgrade.

Collector roads move traffic from local roads to arterial roads and carry up to 12,000 vehicles per

day. Collector roads have less than two percent truck traffic but carry the majority of COS transit routes.



Collector roads are typically built with 80 mm of HMAC with 150 mm granular base, 225 mm subbase,

and 300 mm of prepared subgrade.

Arterial roads carry up to 30,000 vehicles per day and move traffic from housing subdivisions to

their day-time destinations. Arterial roads carry less than five percent truck traffic. Arterial roads are

typically constructed with 100 mm HMAC, 150 mm granular base, 300 mm subbase, and 300 mm of

prepared subgrade.

Expressway roads are high volume, high speed, and provide limited access. These roadways

carry traffic within the city and through the city. Traffic volumes on expressways typically exceed 30,000

vehicles per day and truck traffic can exceed ten percent. There are no standard pavement structures for

expressways. Expressways are designed specifically based on soil investigation data.

Presently, the COS PMS uses three visual surface distresses to determine the pavement condition

of the road network: International Roughness Index (IRI), rutting, and cracking (4). At the network level,

COS collects surface distress data every three years on its entire roadway network. Local and collector

roads surface distress data is collected on a third of the network annually. Arterial roads and expressways

surface distress data is collected every three years. Surface distress data is used to rate the condition of

each road to select maintenance and rehabilitation treatments across the network. If additional

information is required, project level data is collected for verification and structural design.

Table 1 describes the COS PMS condition states for minor and major roads. Condition state 1

represents a good condition state; condition state 8 represents a poor condition state. Raveling,

depression area, and cracking distress data is collected for local and collector roads; eight condition states

result based on the combinations and severity of these distresses. IRI and rutting distress data is collected

for arterial roads; four condition states result based on the combinations and severity of these distresses,

with IRI being the primary treatment indicator.

TABLE 1 City of Saskatoon PMS condition states.

Condition State Local and Collector Roads Arterial Roads

1 No defects meeting thresholds No defects meeting thresholds

2 Ravel threshold exceeded IRI threshold exceeded

3 Depression threshold exceeded Rutting threshold exceeded

4 Poor raveling and depression Poor IRI and rutting

5 Cracking threshold exceeded -

6 Poor cracking and raveling -

7 Poor cracking and depression -

8 Poor cracking, depression, and raveling -

Maintenance and Rehabilitation Treatments

The COS recently developed four treatment categories for the city‟s roads, based on their condition and

the effort required to improve their condition. The four conditions are:

1. Maintenance – roads that do not require any planned treatment, other than pothole patching, spray

patching, or sand crack sealing if necessary,

2. Preservation – roads starting to exhibit degradation (although not necessarily visible to the public),

where treatment will extend the time until a more extensive treatment is needed,

3. Restoration – roads with profile problems and rough sections, where treatments will improve

drainage and ride without enhancing the road‟s structural capacity, and

4. Rehabilitation – roads with structural failures as evidenced by shear failures, potholes, and

significant cracking, where treatments improve the structural capacity of the road.



While the costs of preservation treatments range from $1 to $10 per m2 in the COS and the costs of

restoration treatments range from $12 to $35 per m2, the costs of rehabilitation treatments is far more

expensive, ranging from $50 to $130 per m2.

Limitations of Current PMS

The American Association of State Highways Officials (AASHO) performance prediction model

developed during the AASHO Road Test in the 1960‟s illustrates how public opinion determines the way

agencies manage pavement. Although public opinion is of great importance for COS, it should not be the

primary deciding factor for when a treatment is applied to a pavement. While surface deterioration and

ride quality are the road characteristics most recognized by the public, these characteristics do not

accurately assess the causes of pavement distress or the resulting structural condition of the road. Using

historical performance models based on public opinion to derive long term pavement preservation

allocations does not address the physical performance of the road structure itself in real time.

The current visual surface distresses measured in COS PMS are limiting. Using roughness

ratings to measure road network performance stems from the AASHO Road Test conducted in the 1960s

and does not reflect the structural capacity of the pavement structure (1). Although cracking is estimated

during surface distress data collection, information on the cause of cracking is not collected. For example,

on arterial roads, IRI and rutting are the primary indicators of condition state; cracking is only detected by

IRI measures when the road‟s lateral and transverse variations become too high and the ride

correspondingly becomes too rough. Therefore, moderate cracking often goes unnoticed and structural

damage, moisture infiltration, and permanent deformation can occur. Fatigue cracking can increase

rapidly once it develops and it has been found that a road structure can fail without exceeding the

treatment thresholds for IRI and rutting measurements. Even low severity fatigue cracking is an indicator

of structural deterioration.

While recommended treatments vary depending on surface distress condition threshold

differences, the actual condition state of a road can be overlooked, either rated to be in a good condition

state when it is performing poorly or vice versa. However, lowering the thresholds would result in

treatments that are untimely and not cost effective. Figure 1 illustrates a COS road that was rated as good

by the PMS; further inspection shows significant fatigue cracking and structural failure.

FIGURE 1 City of Saskatoon PMS rated road in good condition state.



With regards to road classification, there is currently no separate analysis for industrial local

roads. Industrial local roads are lumped in with local roads, despite the significant difference in load

spectra. While local roads carry little more than personal vehicles, industrial local roads carry slow

moving, heavy truck traffic. As such, the loading on Industrial local roads are substantially more than the

loading on residential local roads.

Furthermore, current PMS do not accurately reflect the structural performance of a pavement with

respect to applied load spectra. For example, the current PMS condition state of a road does not reflect

whether a road has adequate structural capacity to accommodate a bus route, detour, or additional heavy

truck traffic (8). In Saskatoon, unscheduled detours have resulted in the structural failure of local and

collector roads. Figure 2 illustrates the pavement surface of a COS road that was subjected to a detoured

bus route. Substantial surface distresses resulted and the road structure had to be reconstructed.

FIGURE 2 City of Saskatoon road after application of a bus route detour.

Several neighborhoods in the COS are subject to subsurface moisture problems that are not

quantified in surface distress surveys. In addition to poor draining and moisture susceptible subgrades,

some areas of Saskatoon are subject to high water tables. Subsurface moisture can weaken pavement

structural layers and cause structural failures (9).

COS PMS identifies preservation treatments well, but is limited in the ability to correctly identify

locations requiring rehabilitation treatments.

Determining the Structural Capacity of a Road

Reliably predicting structural condition based on surface distress information can be very difficult. There

are testing methods available to quantitatively characterize a pavement structure and determine structural

capacity of the road (10,11). The structural capacity of a road can be determined using both destructive

and non-destructive methods.

The most commonly used destructive test method is coring the pavement structure. Coring

determines the layer thicknesses of the road structure and the physical properties of the road materials.

Cores can be tested in the laboratory to determine stiffness and strength. Coring is expensive and time

consuming. Due to its destructive nature, coring is not applicable at the network level for PMS.



Two common non-destructive methods are the Benkleman beam test and the heavy weight

deflectometer (HWD) test. The Benkleman beam test is conducted on a pavement surface and measures

the deflection of the pavement structure under one fixed load (11). The Benkleman beam test is common

for highways and urban road tests. One of its drawbacks is that only one load can be applied at a fixed

load rate; varying loads and load rates cannot be applied.

Like the Benkleman beam, the HWD measures the deflection of a pavement structure when a

load is applied. However, the HWD is capable of testing the deflection of a pavement under varying load

spectra, thus better representing field state conditions and realistic truck traffic loads. HWD measurement

have been used in road engineering applications to assess the structural integrity of pavement structures

across typical commercial truck loads (3,4,9,11,12,13). Resultant pavement deflection profiles are used

to determine the structural condition of the road beyond the surface of the road. Using deflections to

characterize pavement structure responses, as measured by HWD, have been shown to be a good indicator

of structural performance (14,15,16). Aggregate course deterioration and the resulting potential damage

can be identified by HWD measurements (16). The deflection profiles can also be used to calculate

pavement structure layer stiffness and to determine the deflection sensitivity across load spectra (13).

The COS has collected network level HWD data since 2006 and has built a database of over

4,000 individual drop locations with information under load spectra of typical commercial truck loadings

experienced in Saskatoon from secondary legal load limits to primary legal load limits. Figure 3

illustrates the drop locations in Saskatoon.

FIGURE 3 City of Saskatoon HWD drop locations.

Since it is difficult to distinguish between surface distresses and structural distresses, HWD

structural information may be beneficial in assessing the condition state of the road structure and the

corresponding treatment. Therefore, using COS network level PMS surface distress data and condition



ratings, the effect of using structural data as measured by HWD is examined in this paper. Two

neighborhoods in Saskatoon were analyzed using typical COS PMS surface distresses and HWD

deflection measurements.

OBJECTIVE & SCOPE

The objective of this study was to compare surface and structural distress measurements for two

Saskatoon neighborhoods. The end goal was to determine if pavement structure performance data

contributed to the PMS; it is hypothesized that structural information would be beneficial in COS PMS.

The two neighborhoods examined in this study are Briarwood and Parkridge. Roads measured in

these neighborhoods include local and collector roads. HWD and surface distress data was collected in

the same year, for each neighborhood, at the network level. The individual deflection drop values for

primary highway weights were averaged over roadway segments. The segments were assigned good, fair,

and poor structural values.

Local roads were considered in a poor structural condition state if the average HWD segment

deflections exceeded 1.75 mm. The segment was considered fair if the average HWD deflection was

between 0.95 mm and 1.75 mm. If the HWD deflections averaged less than 0.95 mm, the segment was

rated good. Collector roads were considered in poor structural condition state if the average HWD

segment deflections exceeded 0.95 mm. The segment was considered fair if the average HWD deflection

was between 0.65 mm and 0.95 mm. If the HWD deflections averaged less than 0.65 mm, the segment

was rated good.

For surface distress assessments, streets that did not meet any treatment threshold were

considered good. Streets that met the thresholds for preservation or rehabilitation treatments were

considered fair. Streets that met the threshold for rehabilitation were considered poor.



NETWORK LEVEL SURFACE AND STRUCTURAL ASSESSMENT

Parkridge Neighborhood

Located on the south west side of Saskatoon, the Parkridge neighborhood was constructed mainly from

1979 to 1983, with some additional construction in the late 1990s and early 2000s. The Parkridge area

has a till subgrade and a low water table, although the neighborhood directly north of Parkridge has

certain areas with high water table issues. No roads in the Parkridge area have been reconstructed since

their initial construction, and the expected service life of Parkridge roads is in excess of 70 years.

Figure 4 presents the surface and structural ratings of local (Figure 4a) and collector (Figure 4b)

roads in Parkridge. As shown in Figure 4, the surface condition rating of Parkridge‟s local roads was

overall good, with 95.6 percent of local roads rated good and only 3.7 percent rated poor. The surface

condition ratings of Parkridge‟s collector streets was also good, with 85.1 percent rated good, 14.9

percent rated fair, and no roads rated poor. As seen in Figure 4, the structural ratings for Parkridge

coincided relatively well with the surface ratings. The majority of local and collector roads rated good

structurally, and no roads of either category were considered structurally poor. In Parkridge, 68.4 percent

of local roads and 88.3 percent of collector roads rated good structurally.

Figure 5 presents geographic maps of Parkridge, showing the surface condition and structural

condition ratings. Roads in good, fair, and poor conditions are shown in green, yellow, and red

respectively. For various road segments in Parkridge, the surface rating condition coincides relatively

closely with the structural rating condition. For roads where there was a difference between surface and

structural ratings, the difference was from good to fair.

Based on the surface and structural ratings, there are some local and collector roads in need of

surface treatments, as shown by the surface ratings, but structural issues are not the foremost concern for

the roads in Parkridge.

a) Local roads

b) Collector roads

FIGURE 4 Parkridge surface and structural condition class.

95.6%

0.7% 3.7%

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

urf

ace

Rati

ng

Surface Rating

68.4%

31.6%

0.0% 0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

tru

ctu

ral

Rati

ng

Structural Rating

85.1%

14.9%

0.0% 0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

urf

ace

Rati

ng

Surface Rating

88.3%

11.7% 0.0%

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

tru

ctu

ral

Rati

ng

Structural Rating



a) Surface condition rating

b) Structural condition rating

FIGURE 5 Parkridge condition rating maps.

Hart Rd

11th St W

22nd St W

McCormack Rd

Forrest

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Pendygrasse Rd

Sm

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Highway 7

Fairlig

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Caldwell Cres

Wri

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Batoche Cres

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Needham Way

Barb

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Cooper Way

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Blue P

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Hart Rd

22nd St W

McCormack Rd

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Forrest

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Pendygrasse Rd

Fairlig

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Sm

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Highway 7

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Sherry Cres

Shill

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Cre

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Poth C

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Sherry Way

Bow

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Heise Cres

Priel P

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Smith

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Olm

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Gro

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White

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Peeling A

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Wri

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Batoche C

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Needham Way

Barb

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Cooper Way

Galbraith Cres

Arrand C

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Cooper C

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Lo

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Barr P

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Nea

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Blue P

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Postn

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Kinloch Cres

Priel Way

Barber Pl

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Fu

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Briarwood Neighborhood

The Briarwood neighborhood is located in the south-east section of the COS. The local and collector

roads in Briarwood were constructed over an 11 year span from 1989 to 2010. The Briarwood area has a

clay subgrade and a high water table. In total, Briarwood has 139,239 m2 and 31,901 m

2 of local and

collector streets respectively.

Figure 6 presents the surface and structural ratings of local (Figure 6a) and collector (Figure 6b)

roads in Briarwood. As shown in Figure 6, the surface condition rating of Briarwood‟s local roads was

overall good, with 94.3 percent of the local roads rating good and 0.0 percent rating poor. The surface

condition rating of Briarwood‟s collector roads indicate that treatments are needed for some roads, since

33.8 percent of roads rated fair and 7.8 percent of roads rated poor. However, the surface ratings for

Briarwood are not indicative of the overall structural condition of the local and collector roads in

Briarwood. With regards to structural condition, Briarwood was the most poorly rated subdivision of

eleven surveyed in the COS. As shown in Figure 6, 82.7 percent of all local roads are in poor condition

structurally, even though 0 percent were classified as „poor‟ under the surface distress assessment.

Similarly, 72.7 percent of Briarwood‟s collector streets were classified as structurally fair and 27.3

percent were classified as structurally poor, despite the results of the surface distress survey indicating the

majority of Briarwood collectors are rated good.

Figure 7 presents geographic maps of Briarwood, showing the surface condition and structural

condition ratings. Roads in good, fair, and poor conditions are shown in green, yellow, and red

respectively. Notably, only three road segments in Briarwood had surface ratings that coincided with

structural ratings. For many road segments, the difference between surface and structural ratings was not

a difference between good and fair, but between good and poor.

While the surface network level survey may suggest that a series of maintenance treatments will

be needed in Briarwood, the structural network level survey shows that significant work and funding will

be required in the near future to maintain a reasonable level of service for these roads.

a) Local roads

b) Collector roads

FIGURE 6 Briarwood surface and structural condition class.

94.3%

5.7% 0.0%

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

urf

ace

Rati

ng

Surface Rating

0.0%

17.3%

82.7%

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

tru

ctu

ral

Rati

ng

Structural Rating

58.4%

33.8%

7.8%

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

urf

ace

Rati

ng

Surface Rating

0.0%

72.7%

27.3%

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

Good Fair Poor

Per

cen

tag

e of

Road

s of

Giv

en S

tru

ctu

ral

Rati

ng

Structural Rating



a) Surface condition rating

b) Structural condition rating

FIGURE 7 Briarwood condition rating maps.

8th St E

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Taylor St E

Boych

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Bra

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Brookhurst C

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Beechm

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Bla

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Bro

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Bellmont Cres

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Braeburn Cres

Bayview Cres

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8th St E

<Incorrect>

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Taylor St E

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Brookhurst Cres

Banyan C

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Blackburn Cres

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Brookmore Cres

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Beechm

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Bayfield C

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Bla

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Brookh

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Bro

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Bellmont Cres

Bla

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Briarvale Rd

Brookdale C

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Braeburn C

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Bayview Cres

Braeshire Lane

Brookmore Lane

Heritage Cres

Beechdale

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Beechw

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Bellmont Crt

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Bee

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Beechm

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Herold Rd

Bayfield Pl



DISCUSSION

As the goal of PMS is to optimize the maintenance and rehabilitation treatments applied across a road

network with regard to budgetary constraints, performance and life cycle predictions of road

infrastructure are necessary for network-level decision-making, both to determine expected treatments

and expected timelines for the treatments of all roads in the network. The findings of this study clearly

show that surface condition assessments do not provide information adequate for assessing the life cycle

and performance of road structures.

Although the surface condition assessments of Briarwood and Parkridge indicate relatively

similar conditions for both subdivisions, the structural condition assessments show drastic differences

between the conditions of the two subdivisions. While the structural condition ratings of the majority of

roads in Briarwood indicate that significant rehabilitation and reconstruction are needed in the near future,

the surface condition ratings only indicate that surface treatments will likely be needed for a number of

Briarwood‟s collector roads. In contrast, for the Parkridge local and collector roads, both the surfacing

and structural condition ratings show that Parkridge roads are generally in good condition, and will not

require major structural treatments in the near future. Also, while Parkridge is performing structurally

good after as much as 30 years of service, Briarwood is performing structurally fair or poor after 5 to 20

years of service. The ability of the HWD to assess structural performance of Briarwood roads provides

insight into upcoming maintenance and rehabilitation requirements. By evaluating structural conditions

of roads, the cost liabilities for the COS can be identified.

Flexible pavements in Saskatoon are highly dependent on subgrade type for their life cycle

performance. Due to the relatively thin layers of asphalt concrete and granular base used for typical COS

pavement designs, the material properties of the subgrade largely dictate the performance of roads. The

importance of subgrade type is evident in the comparison between Briarwood and Parkridge. While the

traffic loading and climatic conditions are similar for both subdivisions, Briarwood has a clay subgrade

prone to moisture problems while Parkridge has a till subgrade not subject to high moisture conditions.

The effect of subgrade type is clearly reflected in the structural assessment results found, as the local and

collector roads in the „high-and-dry‟ Parkridge area are predominantly classified as good structurally

while the roads in the low lying and wet Briarwood area are predominantly classified as poor or fair

structurally. The surface condition assessment was not sensitive to the subgrade of the road structure.

Even though Parkridge‟s local and collector roads exhibited less discrepancies between the surface and

structural condition ratings, structural condition assessments are still important for optimizing

maintenance treatments within the subdivision and within the city as a whole.

Although surface assessments provide valuable information about what maintenance or

preservation treatments are needed for each road, surface assessments are limited because they do not

address the mechanisms of road distresses or failures. While symptomatic treatment is effective for

maintenance and preservation issues with roads, further assessment is needed to diagnose structural issues

and to arrive at a timely and cost-effective rehabilitation strategy. Using only surface assessments poses

the risk to road agencies that structural issues may go undetected until the condition of the road reaches a

point where complete removal and replacement is the only treatment option, an intensive and costly

endeavor. For Saskatoon in particular, the greatest concern in road infrastructure is structural failure,

given the thin local and collector structures, the high moisture conditions becoming increasingly prevalent,

and the subgrade dependence of road designs.

CONCLUSIONS The results of structural condition assessments complement and enhance the findings of surface

condition assessments. The risks posed by using surface condition assessments can be mitigated by using

structural condition assessments in addition to surface condition assessments. Ultimately, the use of

structural asset management will reduce the risk of a significant road failure and subsequent high

expenditures to fix such a failure.

In looking at the surface and structural condition assessment for both Briarwood and Parkridge, a

greater disparity can be seen between the surface and structural condition assessments for the local roads



than for the collector roads. The thicker collector structures tend to „bridge‟ the poor subgrades more than

the local structures. Due to heavy traffic, structurally poor collectors are discovered sooner by surface

ratings as severe fatigue cracking becomes quite noticeable.

As the city continues to expand, structural condition assessments will become increasingly more

important, as limited budgets for road maintenance and rehabilitation must be stretched across an

expanding network. Urban expansion in Saskatoon is predominantly into low-lying areas with potentially

high water tables, similar to Briarwood.

The applicability of structural assessment extends beyond predicting performance to optimize

road treatments to being a valuable source of feedback for the structural design of roads in these areas.

Structural assessments can also be used at the project level to evaluate alternative road structural designs.

For instance, the use of recycled aggregates like reclaimed asphalt pavement (RAP) or crushed Portland

cement concrete (PCC) as base materials can be evaluated, even though these materials are not used in

conventional road structures. Also, the structural performance of roads with a drainage system, including

PCC or virgin crushed rock, weeping tiles, wick drains, geotextiles, or other materials or designs, can be

assessed. Over time, structural assessment can validate the long-term performance of these alternative

road structures, providing field-validation for future work.

ACKNOWLEDGMENTS

The authors would like to thank the City of Saskatoon and the University of Saskatchewan Centre in

Excellence for Transportation and Infrastructure for funding this project as well as for their assistance in

this research.

REFERENCES

(1) American Association of State Highway and Transportation Officials (AASHTO). AASHTO

Guide for Design of Pavement Structures. AASHTO, Washington, D.C., 1993.

(2) Haas, R., Hudson, W.R., and J.P. Zaniewski. Modern Pavement Management. Krieger

Publishing Company, Malabar, Florida, 1994.

(3) Berthelot, C., Podborochynski, D., Stuber, E., Prang, C., and B. Marjerison. Saskatchewan Case

Studies of Network and Project Level Applications of Structural Asset Management. In 7th

International Conference on Managing Pavement Assets Proceedings. CDROM. International

Conference on Managing Pavement Assets, Calgary, Canada, 2008.

(4) Prang, C., Berthelot, C., Stuber, E., and J. Fair. Development of a Structural Asset Management

System for Urban Pavements. In Transportation Association of Canada (TAC) 2007 Annual

Conference Proceedings. CDROM. TAC, Ottawa, Ontario, 2007.

(5) Federal Highway Administration (FHWA). Asset Management Primer. U.S. Department of

Transportation, FHWA, Office of Asset Management, Washington D.C, 1999.

(6) Prang, C., and C. Berthelot. Performance Valuation Model for Urban Pavements. In

Transportation Research Board of the National Academies 2009 Annual Meeting Compendium.

CDROM. Transportation Research Board, Washington, D.C., 2009.

(7) Chartier, G.P. An Asset Management Framework for Urban Local Roads. M.Sc. Thesis,

Department of Civil and Geological Engineering, University of Saskatchewan, 1996.

(8) Thomas, Lee. Mechanistic-Empirical Equivalent Single Axle Loads for Urban Pavement. M.Sc.

Thesis, Department of Civil and Geological Engineering, University of Saskatchewan, 2008.



(9) Berthelot, C., Taylor, B., Stuber, E., Prang, C., Marjerison, B., and M. Campbell. Use of

Structural Asset Management to Evaluate Road Substructure Drainage Systems. In

Transportation Research Record: Journal of the Transportation Research Board of the National

Academies, No. 2101, Transportation Research Board of the National Academies, Washington,

D.C., 2009, pp. 44-52.

(10) Transportation Association of Canada. Pavement Design and Management Guide.

Transportation Association of Canada, Ottawa, 1997.

(11) Huang, Y.H. Pavement Analysis and Design (2nd

edition). Pearson Prentice Hall, Upper Saddle

River, N.J., 2004.

(12) Anthony, A., and C. Berthelot. Preliminary findings from Saskatchewan‟s asphalt rubber project.

In Canadian Technical Asphalt Association Proceedings 2008. Canadian Technical Asphalt

Association, Victoria, B.C., 2008, pp. 289-311.

(13) Noureldin, A.S., Zhu, K., Li, S., and D. Harris. Network Pavement Evaluation Using Falling

Weight Deflectometer and Ground Penetrating Radar. Presented at the 2003 Transportation

Research Board Annual Meeting, Washington, D.C, 2003.

(14) Bing Xu, Ranjithan, R., and Y.R. Kim. New Relationships Between Falling Weight

Deflectometer Deflections and Asphalt Pavement Layer Condition Indicators. In Transportation

Research Record: Journal of the Transportation Research Board of the National Academies, No.

1806, Transportation Research Board of the National Academies, Washington, D.C., 2002, pp.

48-56.

(15) Garg, N., and M.R. Thompson. Structural Response of LVR Flexible Pavements at Mn/Road

Project. Journal of Transportation Engineering, Vol. 125, No. 3, May/June 1999, 238-244.

(16) Donovan, P., and E. Tutumluer. Falling Weight Deflectometer Testing to Determine Relative

Damage in Asphalt Pavement Unbound Aggregate Layers. In Transportation Research Record:

Journal of the Transportation Research Board of the National Academies, No. 2104,

Transportation Research Board of the National Academies, Washington, D.C., 2009, pp. 12-23.


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