pavement management with dynamic traffic and ann: a case

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Draft Pavement Management with dynamic traffic and ANN: a case study of Montreal Journal: Canadian Journal of Civil Engineering Manuscript ID cjce-2015-0299.R1 Manuscript Type: Article Date Submitted by the Author: 02-Dec-2015 Complete List of Authors: Amin, Md Shohel; Concordia University, Building, civil & Environmental Engineering Amador-Jiménez, Luis; Concordia University, Building, Civil and Environmental Engineering Keyword: transp. & urban planning < MANUSCRIPT CLASSIFICATION, computational methods < type of paper to review, systems analysis < Transportation, transportation structures < Construction, transportation < Computer Applications https://mc06.manuscriptcentral.com/cjce-pubs Canadian Journal of Civil Engineering

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Page 1: Pavement Management with dynamic traffic and ANN: a case

Draft

Pavement Management with dynamic traffic and ANN: a

case study of Montreal

Journal: Canadian Journal of Civil Engineering

Manuscript ID cjce-2015-0299.R1

Manuscript Type: Article

Date Submitted by the Author: 02-Dec-2015

Complete List of Authors: Amin, Md Shohel; Concordia University, Building, civil & Environmental Engineering Amador-Jiménez, Luis; Concordia University, Building, Civil and Environmental Engineering

Keyword:

transp. & urban planning < MANUSCRIPT CLASSIFICATION, computational methods < type of paper to review, systems analysis < Transportation, transportation structures < Construction, transportation < Computer Applications

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Pavement Management with dynamic traffic and ANN: a case study of

Montreal

Md. Shohel Reza Amin

Research Assistant, Dept. of Building, Civil and Environmental Engineering,

Concordia University, 1515 St. Catherine Ouest

Montreal, QC H3G1M8, Canada

Tel: +14389364119. Fax: +1-514-848-7965.

Email: [email protected]

(Corresponding Author)

Luis E. Amador-Jiménez

Associate Professor, Dept. of Building, Civil and Environmental Engineering,

Concordia University, 1515 St. Catherine Ouest

Montreal, QC H3G1M8, Canada

Tel: +1-514-848-2424 (ext. 5783). Fax: +1-514-848-7965.

Email: [email protected]

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Pavement Management with dynamic traffic and ANN: a case study of

Montreal

Abstract

This study improves pavement management system developing a linear programming

optimization for the road network of the city of Montreal with simulated traffic for a period of 50

years and deals with the uncertainty of pavement performance modeling. Travel demand models

are applied to simulate annual average daily traffic (AADT) every 5 years. A Backpropagation

Neural Network (BPN) with a Generalized Delta Rule (GDR) learning algorithm is applied to

develop pavement performance models without uncertainties. Linear programming of lifecycle

optimization is applied to develop maintenance and rehabilitation strategies to ensure the

achievement of good levels of pavement condition subject to a given maintenance budget. The

BPN network estimated that PCI values were predominantly determined by the differences in

PCI, AADT and ESALs. Dynamic linear programming optimization estimated that CAD 150

million is the minimum annual budget to achieve most of the arterial and local roads in good

condition in Montreal.

Keywords: Pavement management; traffic simulation; backpropagation neural network;

performance modeling; uncertainties; linear programming; lifecycle optimization.

Introduction

The aging road network in Montreal City is at an advanced state of deterioration. Inappropriate

maintenance, low priority on infrastructure maintenance, and inadequate funding are the main

factors for this state of deterioration. Lack of comprehensive pavement management system

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(PMS) and a long-term plan are responsible for observing an increase in the budget for the City

of Montreal of more than 560% since 2001 (Amin and Amador-Jiménez 2014). The City needs a

holistic model of PMS to predict the response and performance of its pavements under predicted

dynamic traffic loads that optimizes the allocation of treatment operations.

Life-cycle cost analysis (LCCA) for PMS has been applied in a number of studies (Chan et al.

2008; Salem et al. 2003; Li and Madanu 2009). Chan et al. (2008) assessed LCCA practices in

the Michigan Department of Transportation and analyzed its accuracy in projecting the actual

costs and choosing the best alternatives for the treatments operations during the lifespan of the

pavement. Salem et al. (2003) applied risk-based life-cycle cost model that reflects the time to

failure of each treatment alternative and informs about the uncertainty levels that accompany the

estimated life-cycle costs. Li and Madanu (2009) developed an uncertainty-based method for

highway project-level LCCA to deal with computational uncertainty that inherited with input

factors. Zhang et al. (2013) applied life-cycle optimization model to develop a new network-

level pavement asset management system (PAMS) from historical values of pavement distress.

Traditional PMS tools such as PAVER and HDM3 are based on cost-benefit analysis that are

incapable of trading-off decisions between asset types and modes of transportation (Moazami et

al. 2011; Jain et al. 2005; Amin and Amador- Jiménez 2014; Humphries 2012). The linear

programming and other optimization techniques for PMS are capable of finding the optimal

solution of cost-effectiveness of maintenance and rehabilitation (M&R) operations and the

benefits of advancing or deferring a certain treatment (Hudson et al. 1997).

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The Arizona Department of Transportation (ADOT) has applied Markovian chain–based

pavement management systems (PMS) to support its pavement design, construction, and

preservation activities (Li et al. 2006). Several other researchers also applied Markov decision

process (MDP) as a PMS tool (Abaza et al. 2004; Golabi and Pereira 2003; Gao and Zhang

2008). The MDP models optimize the M&R strategies based on the steady-state probabilities. In

reality, the pavements under a given maintenance policy usually takes many years to reach the

steady state and the proportion of the pavements are deteriorating or upgrading year-by-year

(Amin and Amador-Jiménez 2014).

Prediction of pavement deterioration, a crucial part of PMS, is explicitly complicated since the

pavement performance depends on a large number of dynamic and static attributes. Deterministic

and stochastic models are applied to predict the pavement deterioration. Deterministic models

are mechanistic, mechanistic-empirical and regression models (Archilla 2006; Yu et al. 2007;

Santos and Ferreira 2013; Sathaye et al. 2010). Stochastic models apply Markov transition

matrices that predict the ‘after’ condition of pavement knowing the ‘before’ condition (Ferreira

et al. 2011; Ortiz-García et al. 2006; Kobayashi et al. 2010). Deterministic and stochastic models

cannot properly address the uncertainties associated with data collection and computation. In

addition, MDP models suffer from somewhat unrealistic assumptions of discrete transition time

intervals and dependence of the future facility condition only on the current condition (Morcous

2002; Li et al. 2006). The MDP models lack the flexibility to consider the distinct conditions

associated with individual pavement projects or sections (Li et al. 2006).

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Ben-Akiva et al. (1993) developed the latent performance approach dealing with forecasting

uncertainties during condition data collection. This latent model had computational limitations

because number of outcomes, probabilities and computational effort to obtain M&R policies

increase exponentially with the number of distresses being measured. Attoh-Okine (1999)

proposed the Artificial Neural Network (ANN) for predicting the roughness progression in

flexible pavements. However, some built-in functions of ANN such as learning rate and

momentum term of ANN algorithm were not investigated properly. Several researchers also

applied ANN as a tool of PMS (Shekharan 1999; Yang et al. 2006). These models have not yet

overcome the functional limitations of neural network algorithms. This study accommodates the

simulated traffic and addresses the model uncertainties of pavement performance function.

This study develops the linear programming of PMS for the road network of Montreal City that

accommodates the simulated traffic during 50 years design period and deals with the uncertainty

of the pavement performance modeling.

Methodology

This study has been executed in three main steps: first the simulation of traffic (volumes and

truck loads), second the development of pavement performance models and third the

optimization of long term budget allocation and scheduling of interventions (Figure 1).

Figure 1: Flow chart of methodology

Simulation of traffic

Traffic volume, on each segment of the road network, has been simulated every five years for a

period of 50 years (between 2009 and 2058) through a travel demand model. A discrete choice

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model estimates the trip generations from different Traffic Analysis Zones (TAZs) using

disaggregate household or individual level data. Trip generation is the function of gender, age,

personal and household income, occupation, family size, auto ownership, number of children in

the household, land use, and residential density. The model aggregates individual probabilities

(of individual trip making decisions) to predict the total number of trips produced in the TAZs

(Caliper 2005). The predicted trips are spatially distributed among TAZs by applying a doubly-

constrained gravity model (Equation 1) (Mozalin et al. 2000).

A multinomial Logit (MNL) model is applied to estimate the choice of modes by commuters,

assuming that the utility of an alternative is a function of the choice determinants, unknown

parameters and an i.i.d Gumbel-distribution error term. Choice determinants are travel time and

cost. Finally, a deterministic User Equilibrium (UE) model is applied to simulate the annual

average daily traffic (AADT) on each road segment of the network. The deterministic UE

method applies an iterative process to achieve a convergent solution so that no travelers can

improve their travel times (or cost) by shifting routes (Prashker and Bekhor 2004).

Pavement performance modeling

This study applies a Backpropagation Neural Network (BPN) method with a Generalized Delta

Rule (GDR) as a learning algorithm that minimizes uncertainty of pavements performance

modeling. The GDR learning algorithm is applied to the neural network because the relationship

is nonlinear and multidimensional (Freeman and Skapura 1991).The BPN network has two forms

of activation functions chosen from either the hyperbolic tangent or the logistic function. This

research uses the logistic function given that the output of the model (e.g. pavement condition) is

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a positive value (Freeman and Skapura 1991) and the logistic function results in positive outputs

in the unitary range (0, 1). Rather the hyperbolic tangent function in the range of (-1, 1). The

errors, estimated from the difference between calculated and observed outputs, are transferred

backward from the output layer in the ANN to each unit in the intermediate layer. Each unit in

the intermediate layer receives only a portion of the total error based roughly on the relative

contribution the unit made to the estimated output (Freeman and Skapura 1991). This process is

repeated layer-by-layer until each node in the network has received a proportion of error that

represents its relative contribution to the total error. The connection weights are updated based

on the error received by each unit (Freeman and Skapura 1991).

Pavement performance curves are estimated for four categories of roads based on the road

characteristics and the type of pavement: from now on arterial-flexible refers to an arterial road

with asphalt concrete pavement, in a similar fashion a local-flexible, arterial-rigid and local-rigid

refer to other combinations of either rigid or flexible pavements and road’s functional

classification. A Pavement Condition Index (PCI) was used in this research, in practical

applications it is advisable to replicate the work herein developed with independent indicators of

damage such as cracking and rutting, that can be easily correlated to available interventions, such

information was unfortunately not available.

For pavement deterioration, the input variables of the ANN for flexible pavements were: traffic

volume in the form of AADT and equivalent single axle loads (ESALs), structural number (SN),

pavement’s age (N) and difference of PCI between current and preceding year (∆PCI = PCI2009

– PCI2010). The ∆PCI helps to track the application of treatment operations during the preceding

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year, and separate deterioration of intervened roads. Weather was constant across all road

segments and hence ignored on the case study, however, climate must be included when dealing

with roads traversing through various climate regions. The input variables for the rigid

pavements were AADT, ESALs, slab thickness (T), N and ∆PCI. Since AADT and ESALs are

log-linearly related to PCI, Log10 (AADT) and Log10 (ESALs) are taken as input variables of

PCI.

Data on pavement condition, age, thickness and road characteristics was collected from the City

of Montreal. From a total of 19826 segments in the network, the city counts with pavement

condition for 6868 segments in the year 2009 and 10842 segment in 2010. The AADT was

converted to 80-KN ESALs and only considers the total damage to the pavement caused by

commercial vehicles. The ESALs were calculated based on simulated AADT and traffic mixture

(number, type and distribution of commercial vehicles). Data on type and distribution of vehicles

on the road network of Montreal City are adopted from the report prepared by the Cement

Association of Canada (Cement Association of Canada 2012). The SN of the flexible pavements

is calculated from the thickness of pavement layers and climate condition of Montreal City

following the 1993 AASHTO Guide basic design equation.

Linear programming of pavement management system (PMS)

Lifecycle optimization to achieve and sustain acceptable mean network condition ( Q ) at a

minimum cost is used to find required levels of funding for Montreal road network (Equation 2

and 3). The maximization of total network condition under such a budget is then used to find

optimal strategic results for pavement management (Equation 4 and 5). This formulation relied

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on a decision tree containing all possible paths of pavement condition across time, after

hypothetically receiving available treatments (Amin and Amador 2014). This tree is based upon

a transfer function used to estimate condition (Qti) as a convex combination based on the decision

variable and the effectiveness or deterioration of the specific link on time t (Equation 6).

The objective function is to minimize cost (Z) and maximize pavement condition of the road

network [∑∑= =

T

t

a

i

tiiQL1 1

)( ].

ZT

1 1 1

i

t

a

i

o

j

tijtj LXCMINIMIZE ∑∑∑= = =

= (2)

( )∑∑∑== =

≥a

i

i

T

t

a

i

tii LQQL11 1

:Subject to

(3)

∑∑= =

T

t

a

i

tiiQLMAXIMIZE1 1

)(

(4)

t

T

1 1 1

B Z:ubject to ≤=∑∑∑= = =

i

t

a

i

k

j

tijtj LXCS

(5)

0 ≤ Qt,i ≤ 100 and ∑∈

≤tiJj

tijX 1 {for all times t and for each asset i}

Qtij = Xtij (Q(t-1)ij + Eij)+ (1-Xtij) (Q(t-1)ij + Dit) (6)

Where Xtij is 1 if treatment j is applied on road segment i at year t, zero otherwise; Qti is condition

Index for road segment i at year t; Qtij is condition Index of road segment i at year t for treatment

j; Q(t-1)ij is condition Index of road segment i at year (t-1) for treatment j; Ctj is cost ($) of

treatment j at year t; Li is length of road (km) for road segment i; Eij is improvement (+) on road

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segment i from treatment j, Dit is deterioration (-) on road segment i at time t, Bt is budget at year

t.

Data Analysis

Travel demand modeling and simulation of traffic volumes and loads

Traffic volume (AADT) is simulated for each road segment of Montreal road network at 5-years

interval during the fifty years analysis period by applying four-step travel demand model. Figure

2 shows the projected average AADT for four types of road categories during the analysis period.

It is estimated that the average traffic volume on arterial-flexible roads will increase from 8955

to 17069 during the period of 2009-2058 (Figure 2). The AADT will be increase to 4808, 11812

and 7684 on arterial-rigid, local-flexible and local-rigid roads during the same period,

respectively (Figure 2). Travel demand model at urban level is validated with original data of the

year 2008. Comparative evaluation of original and calibrated AADT shows that the overall

AADT on the road network of Montreal will be increased by only a 1.68% when applying the

travel demand model. In particular the model overestimates AADT for arterial-rigid and arterial-

flexible roads: 9.05% and 7.88% more, respectively. Conversely, the model underestimates

AADT for local-rigid and local-flexible roads: 5.13% and 4.40% less, respectively. The DUE

model assign traffic on a road segment based on the performance function (travel time) that is the

function of free-flow travel time, volume and capacity of road segment and calibration

parameters. This is why; increment of AADT is observed on the arterial roads applying the travel

demand model.

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The compounding effect from the traffic growth rate (1.01% annual growth) was removed from

predicted traffic in order to measure the accuracy of the model. The comparative analyses shown

that simulated traffic increases from 7.88% to 26.23% when compared to the AADT levels

calculated by the compound traffic growth rate on arterial-flexible roads during the period of

2009-2058. Figure 2 illustrates the other cases.

Figure 2: Simulated 50-percentile AADT for different road categories during the period of 2009-

2058

Accumulated traffic loads in the form of Equivalent Single Axles Loads (ESALs) were

calculated from predicted AADT and locally observed truck distributions combined with truck

factors (FHWA 2011). The model estimated 39.38, 11.56, 27.35 and 17.71 million ESALs for

arterial-flexible, arterial-rigid, local-flexible and local-rigid roads, for the period between 2009

and 2058 (Figure 3). During this period of 50 years, the simulated traffic explains otherwise non-

accounted increases of 26.80%, 18.32%, 13.59% and 6.80% of additional traffic loads (ESALs)

for the arterial-flexible, arterial-rigid, local-flexible and local-rigid roads (Figure 3). These

unaccounted differences could result in faster damage and inadequate timing of road

interventions.

Figure 3: Simulated 50-percentile ESALs (million) for different road categories during the period

of 2009-2058

Backpropagation Neural Network (BPN) for modeling of pavement performance

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A Multi-Layer Perceptron (MLP) network was used to minimize the prediction error. The MLP

procedure computes the minimum and maximum values of the range and find the best number of

hidden layers to distribute the error term (IBM 2010). The MLP estimates the number of hidden

layers based on the minimum error in the testing data and the smallest Bayesian information

criterion (BIC) in the training data (IBM 2010). The logistic activation function is used for the

hidden layers so that the activation of the hidden unit is a Gaussian ‘bump’ as a function of input

units (IBM 2010).

The BPN network estimates that PCI values for arterial-flexible roads are predominantly

determined by ∆PCI and pavement’s age (Table 1). Other input variable such as log10 (AADT),

log10 (ESALs) and SN have 13.8 percent, 12 percent and 1.5 percent contributions in

determining the PCI value (Table 1). The ∆PCI also significantly influence the PCI values of

arterial-rigid, local-flexible and local-rigid roads by 33.1 percent, 33 percent and 32.9 percent

respectively (Table 1). However, pavement’s age does not significantly influence the PCI values

of arterial-rigid, local-flexible and local-rigid roads (Table 1).

[Table 1]

The log10 (AADT) and log10 (ESALs) have considerable importance to estimate the PCI values in

BPN models for arterial-rigid, local-flexible and local-rigid roads. For example, the log10

(AADT) has 23 percent importance to estimate PCI values of arterial-rigid with similar values

for the other categories (Table 1). The log10 (ESALs) variable contributes 24.8 percent of PCI

values for local-rigid roads (Table 1). The structural characteristics of pavement such as SN and

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slab thickness of flexible and rigid pavements do not have significant influence in determining

the PCI values respectively (Table 1). The reason is that the categorical values of thickness of

pavement’s layers for broader categories of AADT are applied in this study both for flexible and

rigid pavements from the report prepared by the Cement Association of Canada (2012). There is

a strong potential that the BPN models might estimate the significant or considerable influences

of SN and slab thickness on the PCI for flexible and rigid pavements respectively, if the actual

data on thickness of pavement’s layers for each road segment can be accommodated into the

BPN network.

The PCI value of each road segment is estimated based on the estimated relationship between

the PCI values and input variables applying BPN, and simulated traffic applying travel demand

modelling. The estimated PCI values are averaged for each road category for each period to

determine the average PCI value of arterial flexible, arterial rigid, local flexible and local rigid

roads. The average PCI values of the four road categories are plotted and fitted in the different

curves in the Figure 4 to show how the performance curves of the four road categories look like

during the 50 years analysis period. This study finds out that the polynomial and exponential

curves better represent the pattern of PCI curves for the selected four road categories.

Figure 4: Pavement performance curves for different road categories during the period of 2009-

2058

The original and estimated PCI values of Montreal road network for the year 2009 were

compared to validate the accuracy of the estimated PCI values using BPN model. The

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comparison shows that the BPN models estimate on an average 3.26% less PCI values

compared to the original values. The lower estimation of PCI values is associated with the

higher estimation of AADT (1.68%) predicted by the travel demand model. The BPN models

estimate 3.23% and 4.48% lower PCI values comparing to the original PCI values for arterial-

rigid and arterial-flexible roads since these categories of roads observe 9.05% and 7.88%

increases of AADT, respectively. On the other hand, the BPN models estimate 3.74% and

1.61% lower PCI values comparing to the original PCI values for local-rigid and local-flexible

roads since these roads observe 5.13% and 4.40% decreases of AADT, respectively. Both the

original and estimated PCI values show that the overall structural quality of rigid pavements is

poor comparing to flexible pavements in Montreal Island.

Pavement treatment operations

Table 2 presents the criteria employed to identify the type of intervention that is applicable to

every segment at different points of time and following several possible paths (deteriorated or

improved). The criteria includes cost, effectiveness and range of applicability, these criteria came

from the Cement Association of Canada (2012). The timing of the intervention is modeled as a

binary decision variable (Equations 2 and 3) and the overall optimization algorithm takes care of

identifying the optimal set of interventions for the whole network during the analysis term (50

years in this case) within a complex structure with time dependencies that link the repercussions

of decisions through time. The aggregation of individual annual interventions found at the

solution return the minimum maintenance budget to achieve and sustain good pavement

condition. The computational time to find a global maximum was 48 seconds. It was found that

CAD 150 million is the minimum annual budget that ensures having good average roads

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condition (Figure 5). This research qualitatively defined pavement condition in four categories

such as excellent (PCI ≥80), good (80 > PCI ≥ 70), fair (70 > PCI ≥ 50) and poor (PCI<50).

Figure 6 shows that pavement condition will rapidly deteriorate after 31st year of the analysis

period under annual maintenance budget of CAD 125 million. Additional investment in

maintenance budget on the top of CAD 150 million will not significantly improve the pavement

condition rather the proportion of roads in good condition will be upgraded to excellent

condition. Figure 7 shows that the overall pavement condition of Montreal road network will not

be improved under the annual maintenance budget of CAD 175 million.

[Table 2]

Figure 5: Predicted conditions of roads after treatment operations under annual maintenance

budget of CAD 150 million

Figure 6: Predicted conditions of roads after treatment operations under annual maintenance

budget of CAD 125 million

Figure 7: Predicted conditions of roads after treatment operations under annual maintenance

budget of CAD 175 million

The predicted annual budget of CAD 150 million will almost equally be distributed for the

treatment operations of flexible and rigid pavements during first 20 years, but flexible pavements

will require more maintenance budget during the period of 2029 -2045 (Figure 8). Considerably

higher maintenance budget will be invested for treating rigid pavements after 36th design period

(Figure 8). The majority of the maintenance budget for flexible pavements will be invested in

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reconstruction (RC), resurfacing (RS), repair and overlay during the first 6 years of the analysis

period. For the remaining of the analysis period, annual budget for flexible pavements will be

invested in rout and sealing (CS) treatment (Figure 9). Similar pattern of budget distribution is

found in treatment operations for rigid pavements (Figure 10).

Figure 8: Distribution of annual maintenance budget (CAD $150 million) among rigid and

flexible pavements

Figure 9: Distribution of annual maintenance budget for different treatment operations of flexible

pavements

Figure 10: Distribution of annual maintenance budget for different treatment operations of rigid

pavements

It is worthwhile mentioning that the herein proposed model improves over the conventional PMS.

Firstly, it bases performance on dynamic traffic. Traditional methods use deterioration curves

that are based on the historical traffic (volume and growth). But traffic volume and distribution is

related to land use, economy, employment opportunities, and travel behavior. This study predicts

dynamic traffic volume and loads by applying travel demand modeling. Secondly, this proposed

model deals with the uncertainties of developing pavement performance curves. Traditional

deterministic and stochastic methods for predicting pavement deterioration are not only unable to

address dynamic traffic loads, but also have drawbacks of model uncertainty, subjective

evaluations of pavement condition and steady-state probabilities for transition of pavement

condition from one state to another. This model helps the transportation authorities to manage

continuous aggregate behavior of the transportation system, estimate more accurate pavement

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deterioration and solve lifecycle optimization problems of pavement management at any time

interval during the lifespan of pavement.

Conclusion

Traditional PMS methods are limited to a static traffic prediction and inaccurate deterioration

models, erroneously biasing investment decisions of pavement interventions. This study

develops a linear programming approach for PMS that accommodates simulated traffic during a

long term analysis period. Even if dynamic traffic is considered, PMS models still do not address

the uncertainty of the predictions. This research proposes a method to address uncertainty on

pavement deterioration predictions. A case study of Montreal road network is used to illustrate

the proposed method. Arterial roads of Montreal City, mostly constructed in 1950’s, were found

at an advanced state of deterioration. Linear programming was applied to develop M&R

strategies ensuring the good pavement condition of roads at a minimum maintenance budget.

Lifecycle optimization of PMS estimated that CAD 150 million is the minimum annual budget to

achieve most of arterial and local roads are at least in good condition in Montreal City. The

developed model of PMS has two-fold improvement on the conventional methods of PMS.

Firstly, this study predicts dynamic traffic volumes and loads during the fifty-year analysis

period by applying travel demand models. Secondly, this model deals with the computational

errors of developing the pavement performance curves. This proposed model will help the

transportation authorities to manage continuous aggregate behavior of transportation system,

estimate more accurate pavement deterioration and solve lifecycle optimization problems of

pavement management at any time interval during the lifespan of pavement.

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The fast rate of deterioration of Montreal roads is confirmed by the estimations from the model:

even though overall vehicle traffic is expected to double within 50 years, truck traffic is expected

to suffer a much faster increase; doubling the number of ESALs every 15 years, this is a direct

result from economic activity and some traffic could be regional. A backpropagation Neural

Network (BPN) of the type multilayer perceptron combined with a Generalized Delta Rule

(GDR) was able to improve the estimation of future deterioration of pavements. Both rigid and

flexible pavements deteriorated at a similar rate, no big differences were observed. A budget of

at least CAN$150 million is required to sustain arterial and local roads of Montreal in good

condition.

Roads in the island of Montreal need to undergo through a stabilization period for about 25

years, a steady state seems to be reached after that and only preventive maintenance treatments

are applied after that. Future research should study more complex maintenance rules regarding

the limited back-to-back application of certain interventions, per instance limiting the number of

consecutive crack sealing before enforcing an overlay. Future research can study alternate

methods for traffic prediction. Future research should use individual distress indicators of

pavement damage instead of PCI.

References

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Data Input

• Simulated AADT

• Distribution of commercial vehicles

• Load Equivalency Factor (LEF)

• Directional split and lane distribution factor

• Number of Commercial Trucking Days per Year

• Design periods – 50 years

Equivalent Single Axle loads (ESALs)

Data Input • Simulated AADT and

ESALs

• Structural number (SN)

• Pavement’s age (N)

• Slab thickness (T)

• Difference of PCI between current and preceding year, ∆PCI

Traffic Loads

Pavement Performance

Modeling (Backpropagation Neural Network)

Data Input

• Predicted PCI

• Treatment operations

• Unit cost of treatment operations

• Length of road segments

• Annual maintenance budget

Linear programing of life-cycle optimization

Pavement management

system

Data Input • Disaggregate household data

on demographic and socio-economic characteristics of commuter

• Auto ownership

• Land use and residential density

• Total number of travelers in different income groups

• Travel time and cost

Simulated

Annual

Average Daily

Traffic (AADT)

Travel demand modelling

• Trip generation – Discrete choice model

• Trip distribution - Doubly-constrained gravity model

• Mode choice - Multinomial Logit (MNL) model

• Traffic assignment – Deterministic User

Fle

xib

le p

ave

me

nt

Rig

id p

av

em

en

t

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0

2000

4000

6000

8000

10000

12000

14000

16000

18000

2008 2013 2018 2023 2028 2033 2038 2043 2048 2053 2058

Arterial-flexible Arterial-flexible Arterial-rigid

Arterial-rigid Local-Flexible Local-Flexible

Local-rigid Local-rigid Traffic growth rate

AADT

Years

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0

5

10

15

20

25

30

35

40

2008 2013 2018 2023 2028 2033 2038 2043 2048 2053 2058

Arterial-flexible Arterial-flexible Arterial-rigid Arterial-rigid

Local-Flexible Local-Flexible Local-rigid Local-rigid

CumulativeESALs (m

illion)

Years

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77

30

74

27

70

28

67

25

R² = 0.9644

R² = 0.9937

R² = 0.9921

R² = 0.9642

20

25

30

35

40

45

50

55

60

65

70

75

2008 2013 2018 2023 2028 2033 2038 2043 2048 2053 2058

Arterial Flexible

Arterial Rigid

Local Flexible

Local Rigid

Expon. (Arterial Flexible)

Poly. (Arterial Rigid)

Expon. (Local Flexible)

Expon. (Local Rigid)

PCI

Years

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Length (meters)

Periods

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Length (meters)

Periods

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Length (meters)

Periods

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Periods

Maintenance budget (CAD)

Total cost

Total costs for rigid pavements

Total cost for flexible pavements

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Periods

Maintenance budget (CAD)

Rout and seal (Arterial)

Rout and seal (Local)

Spot repairs, mill 40 mm/ patch 40 mm

(Arterial)

Spot repairs, mill 40 mm/ patch 40 mm

(Local)

Mill HMA (Arterial)

Mill HMA (Local)

Resurface with ESG 10 (Arterial)

Resurface with ESG 10 (Local)

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Periods

Maintenance budget (CAD)

Reseal joints (Arterial)

Reseal joints (Local)

Partial depth PCC repair (Arterial)

Partial depth PCC repair (Local)

Full depth PCC repair (Arterial)

Full depth PCC repair (Local)

Reconstruction (Arterial)

Reconstruction (Local)

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Table 1 Importance of input variables to estimate PCI values in BPN networks

Input variables Arterial Collector

Flexible Rigid Flexible Rigid

∆PCI .364 .331 .330 .329

Log10(AADT) .138 .230 .226 .201

Log10(ESALs) .120 .194 .221 .248

Pavement’s Age (N) .363 .162 .123 .211

Structural Number (SN) .015 .100

Slab Thickness (mm), T .083 .012

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Table 2: Treatment and Operational Windows Used in Network-Level Trade-Off Analysis

Pavement Type Treatments Operational window

Unit cost (CAD$)

Arterial Local

Rigid

Reseal joints, % length (m)

AGE ≤ 5

10 10 80 ≥ PCI (Arterial) ≥ 77; 80 ≥ PCI (Local) ≥ 73

Partial depth PCC repair, % area, (sq. m.)

5 ≤ AGE ≤ 12

150 150 76 ≥ PCI (Arterial) ≥ 68; 72 ≥ PCI (Local) ≥ 55

Full depth PCC repair, % area, (sq. m.)

12 ≤ AGE ≤ 25

125 125 67 ≥ PCI (Arterial) ≥ 56; 54 ≥ PCI (Local) ≥ 44

Reconstruction - Arterial 200 mm PCC pavement, 25.4mm dowels (m²) Base - MG 20, mm (t) Subbase - MG 112, mm (t) AGE ≥ 26; PCI (Arterial) < 55

108

64

23

21

Reconstruction - Local 175 mm PCC pavement, no dowels (m²) Base - MG 20, mm (t) Subbase - MG 112, mm (t)

AGE ≥ 26; PCI (Local) < 43

98.75

54.75

23

21

Flexible

Rout and seal, m/km (m)

AGE ≤ 5

5 5 80 ≥ PCI (Arterial) ≥ 76; 80 ≥ PCI (Local) ≥ 72

Spot repairs, mill 40 mm/ patch 40 mm, % area (sq. m.)

5 ≤ AGE ≤ 10

20 20 74 ≥ PCI (Arterial) ≥ 69; 70 ≥ PCI (Local) ≥ 65

Mill HMA, mm (t)

10 ≤ AGE ≤ 15

10.4 10.4 68 ≥ PCI (Arterial) ≥ 64; 64 ≥ PCI (Local) ≥ 59

Resurface with ESG 10, mm (t)

15 ≤ AGE ≤ 25

135 135 63 ≥ PCI (Arterial) ≥ 58; 58 ≥ PCI (Local) ≥ 46

Reconstruction - Arterial HMA - ESG 10, mm (t) 70-28 Base - MG 20, mm (t) Subbase - MG 112, mm (t) AGE ≥ 26; PCI (Arterial) < 58

179

135

23

21

Reconstruction - Local HMA - ESG 10, mm (t) 64-28 Base - MG 20, mm (t) Subbase - MG 112, mm (t) AGE ≥ 26; PCI (Local) < 46

173

129

23

21

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List of figures

Figure 1: Flow chart of methodology

Figure 2: Simulated 50-percentile AADT for different road categories during the period of 2009-

2058

Figure 3: Simulated 50-percentile ESALs (million) for different road categories during the period

of 2009-2058

Figure 4: Pavement performance curves for different road categories during the period of 2009-

2058

Figure 5: Predicted conditions of roads after treatment operations under annual maintenance

budget of CAD 150 million

Figure 6: Predicted conditions of roads after treatment operations under annual maintenance

budget of CAD 125 million

Figure 7: Predicted conditions of roads after treatment operations under annual maintenance

budget of CAD 175 million

Figure 8: Distribution of annual maintenance budget (CAD $150 million) among rigid and

flexible pavements

Figure 9: Distribution of annual maintenance budget for different treatment operations of flexible

pavements

Figure 10: Distribution of annual maintenance budget for different treatment operations of rigid

pavements

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