Pavement Deterioration

Reports addressing pavement deterioration and its modelling.

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Gravel loss is the change in thickness i.e. reduction in thickness of gravel roads surfacing over a period of time. For effective maintenance management of gravel road, a gravel loss prediction model works as a tool in selecting the optimal re-gravelling schedule. As gravel loss can be caused by many factors, for formulating a prediction model here average daily traffic (ADT) representing Traffic, absolute gradient (G) representing geometric design feature, mean monthly precipitation (MMP) representing climatic factors, plasticity index (PI), gradation of the aggregate (P20) representing surface material quality and the duration of observation in terms of day (D) are used as the model independent variable. The dependent variable of the model, gravel loss, are collected by observing the selected gravel roads in six month interval and the independent variables included in the model are gathered using standard procedures and methods. The selected roads for the study are NuwakotAsurkot-Pyuthan Road (Arghakhanchi district), Argha-Dharampani-Maidan Road (Arghakhanchi district), Sahid BasudevMarg,Ambhanjyang Road(Makawanpur district), Kabahigodh-Piparadi-Patarhati Road(Bara district), SonbarsaGadi-Sakhuwa-Parsauni– Mahuwan-Ramnagari Road (Parsa district), Bindawasni-Bairia-Birta Road (Parsa district), Bahurwabhatta-Pokharia, Padam Road (Parsa district). In each road a 60m of longitudinal grid are considered which are further divided into 10 m interval where elevation across the width of the road are observed using auto level. Model is developed using SPSS which will be helpful to find the residual life and appropriate time for re-gravelling.

The World Bank HDM 4 model is adopted in many countries worldwide. It is consisted of the developed models for almost all types of deformation on the pavement structures, but it can’t be used as it is developed everywhere in the world without proper adjustments to local conditions such as traffic load, climate, construction specificities, maintenance level etc. This paper presents the results of the researches carried out in Macedonia for determining calibration coefficient of the rutting model in HDM 4.

Pavement roughness is one of essential performance indicators that are used in road maintenance. A model was developed in this study to obtain roughness value from easily measurable distress values, namely cracking and potholes, for low-volume roads in India. The data collected at 173 in-service flexible pavements were utilised for model development. Using the model developed in this study, a satisfactory roughness value can indirectly be obtained from the cracking and potholing data, even without the use of a roughness measuring device.

This paper presents comparisons of the environmental impacts and life cycle costs of various alternative strategies for a portland cement concrete (PCC) pavement project in Manitoba to demonstrate the opportunity to optimize the cost, pavement performance and environmental impacts. A matrix of 10 different strategies that include alternative PCC mix, pavement design, and maintenance and rehabilitation (M&R) treatments have been used to contrast both the life cycle costs and environmental impacts with MI’s past practice (base case). The presented analysis is expected to assist highway agencies to better understand and weigh not only the economics of alternative strategies, but also the environmental implications of alternative roadway materials, design, construction, and maintenance and rehabilitation practices.

The aim of this project was to clarify the effectiveness of pavement maintenance (preservation) activities, in the form of periodic maintenance and rehabilitation, on pavement condition and distress (roughness, rutting and cracking) deterioration rates. This was addressed by estimating trends in pavement deterioration in three jurisdictions (New South Wales, Queensland and Victoria) from a time series of observational data (supplied by the jurisdictions) using mostly iPave condition and deflection data. In order to assess the effectiveness of the various pavement maintenance treatments, a comparison of these observational trends with historical and predicted rates of deterioration was made.

The main findings of the study were as follows:

  • A comparison between the observed deterioration rates derived from the time series of observational data with historically-derived rates and the Austroads RD model estimates suggested that the three approaches produced comparable results in terms of roughness and rutting deterioration, but not for cracking.
  • Based on the historical rates of roughness and rutting deterioration representing pre-treatment deterioration, the post-treatment roughness deterioration rates in NSW and Victoria were reduced by a range of between 8% (seals) and 58% (OGA), demonstrating the effectiveness of the surface treatments.

Comparisons of functional condition parameters (roughness, rutting and cracking) against the mean maximum deflection found that their deterioration rates were significantly influenced by pavement strength. The effect of traffic and climate on deterioration was not as strong as pavement strength.

This is a very interesting and important report which presents the results of a major study looking into the impact of vehicle loading on pavement deterioration, in particular, the '4th power law' damage factor relevance for lower standard pavements. Highly recommended.

Pavement management at a network level requires reliable accurate performance prediction models to help road agencies make useful complex decisions about highways maintenance and rehabilitating activities. The purpose of this paper is to report the approach adopted for model development and validation for heavy duty flexible pavements representing by seven rural freeways segments. Hierarchical generalized linear modelling approach has been applied to predict multilevel model to capture the effect of variations among time series data, among road sections and among highways with same duty pavements. The estimation of pavement cracking progression has been based on longitudinal dataset contain cracking data (reported as a percent of the affected area) as dependent variable and cumulative traffic loading, pavement strength and environmental conditions as independent variables. The study illustrates how panel data can be nested to predict the probability of crack progression to capture the effect of significant unobserved heterogeneity. The significance of relevant contributing factors in predicting crack progression were presented and elucidated.The validation results indicate that the model replicates the pavement behavior well, and that the inclusion of additional factors in addition to time is improving the model prediction.

In this research paper, prediction model is developed for the progression of roughness, which is the most important performance indicator of flexible pavements. Since many stretches of flexible pavements in village roads in India are not exposed to routine maintenance for years together due to the paucity of the funds and models are not available for predicting the performance of the pavements under such conditions, this research is focused to develop prediction model for the roughness of flexible pavements exposed to least or nil routine maintenance. Roughness data were collected from the selected in- service pavements (171 stretches in Tamil Nadu state in India) and model is developed using stepwise regression analysis. The model has been validated with independent field data. The versatile roughness prediction model developed in this study will be useful for practicing engineers in managing the flexible pavements in low volume roads exposed to least or nil routine maintenance.

Bituminous surfacing seals are used on a high percentage of the southern African road network to protect the mostly granular pavement base layers and to provide wet weather skid resistance, appropriate for the conditions at hand. A study has been designed to empirically model crack initiation and texture loss to assist with the development and calibration of a Finite Element Model (FEM) for seals. Thirty five road sections have been selected throughout South Africa covering different seal and binder types (Single seals, multiple stone seals and Cape seals), age of seal, traffic volume and climatic region for performance investigation. Two samples were taken from each site (In the wheel-path and outside the wheelpath) to also evaluate the effect of traffic on ageing of the binder. In addition to this the performance of different seals on more than six hundred road sections, over a period of fourteen years, has been evaluated to quantify the effect of binder type and film thickness on crack reflection. A synthesis of the key performance variables has led to the development of survivor curves for different seal types, which is a strategic output of the study This paper provides an overview of findings related to the long term performance of seals in the South African environment. Conclusions are drawn regarding the contribution of different factors influencing crack initiation and texture loss.

Report addressing the impacts dust emissions from unsealed roads have on people, and identifying environmentally sustainable and financially cost effective mitigation measures likely to be effective at reducing those impacts.

 

This report describes a two-year study designed to quantify the immediate and longer-term maintenance impact of grader blading and surface re-sheeting on unsealed roads.  The project assembled and analysed roughness data collected by Cassowary Coast Regional Council in Queensland, Blayney Shire Council in New South Wales and Moorabool Shire Council in central Victoria to expand the current works effects (WE) models to cover a wider range of traffic and climatic conditions and to validate the existing unsealed road roughness deterioration (RD) model. WE models were developed for light blading, medium blading and granular re-sheeting maintenance works and a RD model was developed for roughness progression between maintenance activities.  The suggested modifications to the RD and WE models should assist local government asset managers in their management of unsealed roads. It is expected that the models could be adapted to the varying local conditions of unsealed roads in other locations.

The objectives of this study are to: (1) prediction of pavement distress such as low temperature cracking, (2) estimate different types of user costs incurred by pavement roughness resulting from distresses, (3) compare agency investments for different maintenance and rehabilitation strategies and associated roughness-related user costs, (4) analyze environmental impacts of construction, maintenance, and rehabilitation (CMR) activities used in pavement engineering, (5) estimate and compare agency costs, user costs due to roughness, and emission costs due to CMR activities, and; (6) estimate emission costs associated with pavement roughness. By considering the cost associated with the environmental impact of CMR activities, a more realistic estimate of the ROI associated with maintaining relatively smooth pavement throughout its service life was assessed.

It is quite essential to investigate the causes of pavement deterioration in order to select the proper maintenance technique. The objective of this study was to identify factors cause deterioration of recently constructed roads in Khartoum state. A comprehensive literature concerning the factors of road deterioration, common road defects and their causes were reviewed. Three major road projects with different deterioration reasons were selected for this study. The investigation involved field survey and laboratory testing on those projects to examine the existing pavement conditions. The results revealed that the roads investigated experienced severe failures in the forms of cracks, potholes, and rutting in the wheel path. The causes of those failures were found mainly linked to poor drainage, traffic overloading, expansive subgrade soils, and the use of low quality materials in construction. Based on the results, recommendations were provided to help highway engineers in selecting the most effective repair techniques for specific kinds of distresses.

This paper describes briefly the state-of-the-art in terms of rutting models. Some of the
models are analysed by comparing rutting evolution prediction for a set of representative
Portuguese pavements structures and traffic conditions. HDM-4 deterioration model was
considered to be the most promising to implement in a new Portuguese Maintenance
Optimisation System (MOS).

This paper describes the development of a cracking prediction model for Portuguese conditions which is expected to integrate the Pavement Management System (PMS) of Estradas de Portugal. The World Bank’s highway development and management (versions III and 4) and PARIS models are used as reference for the development of a deterministic (mechanistic-empirical) model, using pavement condition data from sections of the main road network. A two-phase distress evolution model is proposed where the initiation of cracking (1st phase) is ruled by a different equation than the progression of cracking (2nd phase). Cracking initiation is predicted on a traffic basis, from the annual traffic load and the structural capacity of the pavement. An absolute model is presented and recommended for the maintenance and rehabilitation (M&R) programming in the long-term and for the analysis of non-cracked segments. Absolute and relative type models were obtained for cracking progression. The relative model shows better agreement to data and is proposed for short- to medium-term analysis on segments with cracking history, while the absolute model is proposed for the M&R programming in the long-term and the analysis of non-cracked segments. Finally, the recommended model is evaluated based on the application to a set of pavement structures defined in the Portuguese pavement design guide.

Flushing is the process whereby chipseal texture depth is lost over time, resulting in a loss of skid resistance. It is the single most important reason for resealing on New Zealand state highways.


This report details research carried out from 2012 to 2015. In the first part of the work the aim was to identify and investigate the physical mechanisms causing flushing. The aim of the second part of the project, undertaken by researchers at the University of Auckland, was to use pavement condition data to develop a model to predict the rate of flushing progression in chipseals.

 

Factors making a major contribution to flushing are:


• aggregate abrasion and breakdown
• compaction and reorientation of the seal layer under traffic
• water venting and sub-surface stripping in seal layers.

Factors having no or making only a minor contribution to flushing are:


• thermal expansion of the bitumen
• excess bitumen application
• binder viscosity.

 

Further work is needed to quantify the significance of chip embedment into the basecourse.


A two-part model using parameters in the NZ Transport Agency Long-Term Pavement Performance database was developed. The first part uses a logistic model to predict the onset of flushing and an accuracy of 74% when used to predict the initiation of flushing on a separate data set.

The second part uses a linear model to predict the rate of flushing progression. First-coat seals, and second and higher generation seals were modelled separately.

The linear model was statistically strong (R2 of 0.445 for first-coat seals and 0.628 for second and higher generation seals).

Flushing is the process whereby chipseal texture depth is lost over time, resulting in a loss of skid resistance. It is the single most important reason for resealing on New Zealand state highways.  This report details research carried out from 2012 to 2015. In the first part of the work the aim was to identify and investigate the physical mechanisms causing flushing. The aim of the second part of the project, undertaken by researchers at the University of Auckland, was to use pavement condition data to develop a model to predict the rate of flushing progression in chipseals.

Flushing is a defect which has a damaging effect on the functional performance of sprayed seal (chipseal) pavements. Accurate understanding of flushing can have a significant impact when predicting the future performance and maintenance needs of pavements. The reported study was conducted to develop a prediction model to effectively identify, asses and manage flushed pavements. The study also aimed to develop a decision-making tool for treating flushed pavements. This study utilised pavement data from New Zealand’s Long-Term Pavement Performance programme and data analysis was conducted to develop a model to predict the flushing potential of chipseal pavements. Additionally, the study conducted laboratory testing on pavement samples from flushed chipseal pavements. The conducted tests included wheel tracking and rutting measurements, air void volume measurements, as well as computed tomography scanning and image analysis. The laboratory test results were used to supplement the outputs of the performance prediction model in detecting the mechanisms that were causing flushing. The outcomes of this study included a model that was able to predict a) the probability of flushing initiation, and b) the quantity of flushing on a pavement. This model was statistically robust where the flushing initiation model had an accuracy of 76%. The flushing prediction model and the laboratory results were incorporated into an overall pavement assessment guideline for flushed pavements. This assessment guideline will aid pavement practitioners with accurate identification of flushing on a pavement network as well as with selecting the best method of maintenance treatment for flushed chipseal pavements.

The fatigue cracking behaviour of laboratory prepared chipseal beams and beams cut from field samples was studied using a four-point bending test method. Preliminary results indicate that chipseal fatigue lives at 5ºC are up to eight times greater than those of estimated values for asphalt mix under the same loading conditions. The results suggest binder oxidation was not the dominant factor in seal cracking and that cracking in the field may be primarily due to very high, localised deformations. Such deformations may arise through weak basecourse patches formed during construction or more likely, from water damage (to both the basecourse and seal structure itself) arising from leaking seals.

Data from long-term pavement performance sites show that overall, the average number of cracks initiated per site increased approximately linearly from the time of crack initiation. The average annual increase in crack length is approximately half the crack length, so as the crack grows the rate of crack growth in mm/year increases. A brief analysis was carried out for two sites that showed an approximately three-year lag between crack initiation and pothole formation.

The report proposes practice guidelines and the outline of a performance-based specification for the crack repair of chipseals.

This report details research carried out from 2012 to 2015 into chipseal flushing. The physical mechanisms causing flushing were investigated and a model was developed to predict the growth of flushing over the New Zealand state highway network. Factors making a major contribution to flushing are: • aggregate abrasion and breakdown • compaction and reorientation of the seal layer under traffic • water venting and sub-surface stripping in seal layers. Factors having no or making only a minor contribution to flushing are: • thermal expansion of the bitumen • excess bitumen application • binder viscosity. Further work is needed to quantify the significance of chip embedment into the basecourse. A two-part model using parameters in the NZ Transport Agency Long-Term Pavement Performance database was developed. The first part uses a logistic model to predict the onset of flushing and an accuracy of 74% when used to predict the initiation of flushing on a separate data set. The second part uses a linear model to predict the rate of flushing progression. First-coat seals, and second and higher generation seals were modelled separately.

Prediction models for low volume village roads in India are developed to evaluate the progression of different types of distress such as roughness, cracking, and potholes. Even though the Government of India is investing huge quantum of money on road construction every year, poor control over the quality of road construction and its subsequent maintenance is leading to the faster road deterioration. In this regard, it is essential that scientific maintenance procedures are to be evolved on the basis of performance of low volume flexible pavements. Considering the above, an attempt has beenmade in this research endeavor to develop prediction models to understand the progression of roughness, cracking, and potholes in flexible pavements exposed to least or nil routine maintenance. Distress data were collected from the low volume rural roads covering about 173 stretches spread across Tamil Nadu state in India. Based on the above collected data, distress prediction models have been developed using multiple linear regression analysis. Further, the models have been validated using independent field data. It can be concluded that the models developed in this study can serve as useful tools for the practicing engineers maintaining flexible pavements on low volume roads.

Thermal cracking of pavements may occur due to the top of the pavement being exposed to cold atmospheric conditions. The formation of cracks may cause a deterioration of ride quality and ingress of water to the base. Developing of capabilities to model thermal cracking of pavements is beneficial because it will allow the assessment of susceptibility of pavement materials and geometries to thermal cracking. Fracture resistant asphalt mixtures can then be identified. A methodology is proposed by which numerical modelling of thermal cracking of pavements is carried out using the distinct element method and cohesive cracks. The distinct element method efficiently handles the subdivision of the originally intact material. The cohesive crack method allows the inclusion of experimentally determinable fracture properties into the formulation. Results obtained were consistent with an analytical model available in literature. Thermal cracking observed in a field experiment could then be numerically replicated.

This report documents research to further develop probabilistic modelling work undertaken in 2012 and demonstrate the impact the variations in predictions of the main dependent variable, roughness, has on road agency costs (RAC) and vehicle operating costs (VOC) in a pavement life-cycle costing analysis.

This phase of work used a pilot application of a three road network with each road having different levels of traffic and pavement performance outcomes. The pilot study showed that the RAC estimates are highly sensitive to the percentile roughness estimates compared to the VOC estimates because during the pavement life-cycle costing analysis the roughness levels are contained to within 4 IRI by the intervention of rehabilitation.

The current Austroads approach to assess the relative damaging effects of different axle groups on road pavements is by comparison of the peak static pavement deflection response under the axle groups. The assumption that deflection is the most appropriate indicator of pavement damage is open to question and is not consistent with the use of strains to calculate the performance of pavement materials.

In response, research conducted has determined that, with regard to the fatigue damage of asphalt and cemented materials, the standard load for an axle group type is dependent upon the thickness and modulus of the asphalt and the underlying pavement structure.

As a result, it is proposed that the mechanistic design procedure for flexible pavements not use the concept of standard loads, but rather that the procedure determines the pavement damage resulting from each axle load and each axle group within a traffic load distribution. An examination of the implications of pavement design outcomes in using this method determined that in general, reductions in both asphalt and cemented material thicknesses of up to 50 mm would result.

The research also determined that the currently used standard loads for tandem, triaxle and quad-axle were appropriate for use with the current empirical procedures for the design of granular pavements with thin bituminous surfacings.

This report details a study conducted using detailed roughness measurements on a panel of unsealed local roads located in Moorabool Shire Council at both the pre- and post-works effect (WE) treatment stages. The aim of the study was to develop interim WE models and validate any existing interim WE models, as well as validate current road deterioration (RD) models for roughness. Simple WE models were developed with the independent variable, IRIb, the roughness before treatment, which explained 59% to 91% of the dependent variable, IRIa, the roughness after treatment, depending on the type of works effect being modelled. No validation of any existing RD roughness model was possible due to the limited material and environmental variations.

Paper describing statistical analysis of road condition data using machine learning methods.

Over the lifetime of an asphalt concrete (AC) pavement, the roadway requires periodic resurfacing and rehabilitation to provide acceptable performance. The most popular resurfacing method is an asphalt overlay over the existing roadway. In the design of asphalt overlays, the thickness is related to the structural strength of the existing pavement. As the layers are overlaid their stru ctural
characteristics change due to aging of asphalt. However, currently there is no method to determine the effect of aging on the strength of existing pavement layers. 


This study examined structural characterization of six pavement test sections in Kansas using three different test methods: Falling Weight Deflectometer (FWD), Portable Seismic Property Analyzer (PSPA), and Indirect Tensile (IDT) tests. The results were analyzed to determine how the modulus of an AC pavement layer changes over time. The results indicate that as the AC pavement ages, its modulus decreases due to pavement deterioration. The most prominent cause for AC pavement deterioration was observed to be stripping. Two of the test sections on US-169 and K-4 showed little signs of stripping and had a minimal reduction or even an increase in AC moduli. 


The analyzed results from different test methods for moduli were inconclusive as far as any correlation among the methods is concerned. While the correlation between various test methods studied was mostly consistent for a particular roadway, no universal correlation was found for all pavement sections tested.


Fatigue test results show that older pavement layers have a higher propensity for fatigue failure than the newer layers. However, some older pavement layers showed excellent fatigue life. Fatigue results correlated well with the condition of the cores as assessed by visual observation.

Pavement deterioration is a serious problem for road and traffic highway sector in Jordan. The allocated cost for construction of new roads, replacement and rehabilitation, and maintenance was 292.1 M JD in the implementation program (2007-2009) and 192. 2 M JD in (2011-2013). The current research aims to describe the most affecting causes for road deterioration in Jordan by a questionnaire designed and directed to contractors in road construction and maintenance. A list of causes was prepared through conducting literature review, consulting and interviewing a group of 15 managers from contractors and experts in the field, they advised to study 51 of expected causes for road deterioration. Then a questionnaire was prepared and directed to 150 of contractors in road construction and maintenance. The mission was involving to give a scale (rank) from 1
(strongly disagree), 2 (disagree), 3 (do not know), 4 (agree), and 5 (strongly agree) to the expected causes. 38 (25.33%) responses were received and analyzed. The criterion (defects caused during construction due to poor construction quality) takes the highest rank of 4.15, while the lowest factor is (Inadequate resistance to polishing of surface aggregate) of 2.73. Also, the causes for deterioration were reorganized into 11 consistent groups of relevant causes. The first group (Effect of Cracks and Structural Failure) ranks 3.96 and the last group (Effect of Pavement Width) ranks 2.93 in group comparison. The research is helpful in highlighting the causes for road deterioration in Jordan, and in avoiding of these causes or mitigating their effect during design, construction, and
maintenance through operation.

Maintenance and repair of the highway network system are major expenses in the state budget. For this reason various concerned organizations are pointing out the need for developing an intelligent and efficient pavement performance model that can prioritize pavement maintenance and rehabilitation works. Such models can forecast the remaining pavement service life and pavement
rehabilitation needs, and can help in the formulation of pavement maintenance and strengthening programmes which will reduce the road agency and road user costs. The flexible pavement performance or deterioration models involve the complex interaction between vehicles and the environment, and the structure and surface of the pavement. Performance models relating to the pavement distress conditions like, cracking, raveling, potholing, and roughness are analyzed and developed by various researchers. But most of these models are found applicable to a particular set of traffic or environment conditions, thus highlighting the need of model(s) that can work in varied conditions satisfactorily. The paper presents a detailed review of various pavement performance models to examine the role of factors related to pavement materials, environmental conditions, type of traffic and volume of traffic, and to identify the limitations and gaps in the present knowledge on such models.

Deterioration models allow predicting pavement condition and the development of maintenance programs. Normally, when evaluating pavement performance through model deterioration, the forecast given is a determinist value. However, pavement engineering projects, as any engineering poject, have a degree of uncertainty. This implies that an adequate performance of the engineering solution cannot be absolutely guaranteed.

The aim of this research is to incorporate probability in the output of a structural cracking model. To achieve this objective the model of crack initiation and progression of HDM-4 was used under several scenarios defined based on geographic location, type of traffic and structural capacity of 86 roads located in Chile. The input data for each scenario were obtained from the Ministry of Public Works of Chile and calibration studies of deterioration models to local conditions. To incorporate probability in the structural cracking models, a simulation model that reproduced the deterioration due to cracking for a lifecycle of 25 years was developed, based on random input data sets. With the set of outputs of the simulation, probability density functions that represent the probabilistic response of the deterioration model were developed.

The main output of this research is a set of probability density functions of cracking initiation and cracking progression of all structural cracks and wide cracks of 14 groups of Chilean roads. Although the research was carried out using Chilean data, the methodology presented could be applied to other states or countries.

This study was undertaken to establish whether various pavement deterioration models incorporated into the New Zealand – Deighton’s Total Infrastructure Management System (NZ-dTIMS) and Highway Design and Maintenance Model 4 (HDM-4) pavement management systems could be modified to reliably predict the condition of a pavement after it had been exposed to sudden extreme traffic loading, which can occur with the commencement of forestry logging, mining or enforced detours. Specifically, the deterioration models considered were for roughness progression (both the NZ-dTIMS and HDM-4 models) and rutting progression (NZ-dTIMS model only).

The objective of this research (undertaken 2008–2011) was the development of an improved method of modelling the decision to rehabilitate a typical New Zealand thin-surfaced unbound granular pavement. This was driven by previous research that had found a poor correlation between the data recorded in the road asset maintenance management (RAMM) database and the decision to rehabilitate. It had been hoped that by talking to local engineers and examining pavements proposed for rehabilitation, distress not currently recorded may be identified. This would have then driven the development of better models and may also have expanded the detail collected in the visual surveys. The research found, however, that the drivers are not obvious and that the decision maybe being based on factors such as the engineers’ assessment of the risk of rapid failure.

The conclusions from this research are:

According to a visual engineering inspection, many pavement sections require rehabilitation.

In many cases, a significant quantum of deferred maintenance needs to be performed for the do-minimum option. This maintenance is not necessarily obvious from the data in RAMM or visual observations of the high-speed data videos.

The methods used to determine future maintenance costs vary widely. This ranges from including the deferred maintenance cost into one year and extrapolating from this cost, to ignoring the deferred maintenance cost in the analysis.

The timeframe for assessing maintenance cost history is variable.

The net present value (NPV) calculation can be very sensitive to assumptions made on future maintenance and seal lives. This includes assuming that higher priced polymer-modified seals need to be used.

Rutting and flushing at 88% and 80% of the surveyed pavements are the two most commonly quoted distress mechanisms. These do not appear in a proposed rehabilitation algorithm.

Digouts are a factor mentioned in 55% of justifications.

The inspection length associated with the visual pavement inspection did not reflect the treatment section length in 40% of sites.

The influence of non-engineering factors, such as concerns over ‘consuming the asset’ and fears of rapid pavement failure, need to be investigated.

The difference in condition between the typical pavements in a network and those chosen for rehabilitation can often be minor and thus very difficult to quantify.

Better guidelines should be developed to assist and standardise the decision process. These guidelines need to be based on a risk and consequence approach, which, it is believed, will better reflect the engineers’ approach.

Report on the establishment of pavement deterioration models for Norway.

Pavement surface performances have a great influence on road functionality and can affect user’s safety, vehicle operational costs, environmental sustainability. The assessment of evolution of pavement surface performance plays a fundamental role in road pavement management and is useful in order to allocation of maintenance resources.

In the light of the above, Authors introduced the first results carried out from a two-year monitoring of an experimental road section. Four different dense graded wearing courses were designed with different aggregates: limestone, basalt and expanded clay. Several surface performances were measured by different devices (Skid Tester, Sand Patch Test, Laser Profilometer).

In the life-cycle prediction of road pavement, it needs the model that should be able to predict the expected change of condition in the future. The model should consider current condition, pavement strength and age characteristics, environment, incremental time and incremental traffic. The aim of this study is to application the traffic simulation model for predicting initiation and progression of crack on road pavement. The aim of the study can be achieved by developing a computer simulation model that can predict road deterioration. The research develop coefficient of each models that agree with local condition based on observed data that collected for 1.5 years. These models are able to predict progression of cracking with R2=0.5925 to 0.8765 more appropriate than the existing model (R2=0.304 to 0.314). The coefficient of crack initiation model has difference with the existing models that are 5.7% to 20% for asphalt mix on asphalt pavement, 2.8% to 14% for asphalt mix on stabilized base, 1.6% to 2.2% for asphalt mix on granular base. While progression of cracking are 5.7% to 20% for asphalt mix on asphalt pavement, 2.8% up to 14% for asphalt mix on stabilized base, 1.6% to 2.2% for asphalt mix on granular base. In addition, the cracking model can be used as guidance for maintenance intervention criteria.

Series of reports from the NordFoU project which developed deterioration models for nordic countries.

Report presenting the results of extended pavement performance trials including various types of bitumen seal, clay and concrete bricks and unreinforced concrete, using TRL and Austroads design standards.

This research project is the second report detailing findings from the NZ Long Term Pavement Performance (LTPP) programme. This programme includes the monitoring of 63 sections on the State Highways and 82 sections on local authority roads. This report details all work related to developing a rutting model for New Zealand conditions. Previous work highlighted some data limitations in the LTTP programme – some of this development work relied on the Transit CAPTIF accelerated pavement testing programme.

This research project also investigated a total new method of predicting rut changes over time including:

• a simplified model proposed for the initial rut/initial densification of the pavement;

• model formats considered for the prediction of the annual change in rutting progression; and

• an additional component to the rutting model added to predict the probable point when the accelerated rut stage starts.

A practical method for predicting the performance of unbound granular materials, including alternative, industrial by-products and recycled materials has been proposed. It is recommended that this method replace the existing laboratory repeated load triaxial (RLT) method adopted in the Transit New Zealand specification TNZ M/22 (2000) to determine the suitability of the alternative road material for use as a base or sub-base material for thin-surfaced granular pavements in the New Zealand context.

Report on how the modelling of roughness progression can supplement pavement design.

Models for predicting pavement deterioration developed in Nordic countries.

Report describing the HDM-4 models for predicting pavement deterioration and mainteance effects.

How the HDM-4 pavement deterioration model was calibrated to Chile (in Spanish)

Road agencies in Australia are adapting HDM-4 technology to the strategic management of their road
networks. There is a need to develop HDM-4 technology road deterioration (RD) models for sealed granular
pavements as they comprise 95% of Australia’s rural arterial roads. Austroads has funded ARRB Transport
Research (ARRB) since 1994 to adapt HDM-4 technology to Australian conditions.
Since 1994 ARRB has monitored long term pavement performance (LTPP) sites to observe road
deterioration with traffic loading, climate and pavement type. From 1998 onwards, ARRB has also
monitored the influence of maintenance on sealed granular pavement performance using long term
pavement performance maintenance (LTPPM) sites on Australia’s arterial roads, specifically varying surface
maintenance treatments at each site. In addition, ARRB, in an independent consulting capacity, has
performed field data-driven RD model calibrations for a number of States.
Accelerated load testing (ALT) of experimental sealed granular pavements commenced in 1999 to quantify
the influence of maintenance on relative pavement performance, under controlled conditions of loading,
climate and maintenance. In 2003 ALT was used to quantify the influence of increased axle mass loading
on pavement deterioration.
Historical Australian seal life and binder hardening data was available to ARRB to develop a refined binder
hardening model using variables for environmental conditions, elapsed time, binder characteristics and the
nominal seal size. This refined model, in conjunction with an existing distress viscosity model, allowed the
development of an explicit seal life model to predict the expected life of different nominal seal sizes in
different climates throughout Australia.
This paper presents the current state-of-the-art characteristics, by means of re-calibrated default coefficients,
for the RD models for roughness and rutting progression which were shown to vary with the environment
and surface maintenance treatments. The RD model re-calibration used the observational data from the
LTPP and LTPPM sites in conjunction with the relative performance factors estimated for various surface
maintenance treatments from the ALT data. The current imitations of these revised models with the above
sealed granular pavement data are stated, including those for the seal life model. As a result, the RD
models are more responsive to changes in maintenance under a range of Australian climatic conditions.
It was not possible to predict the impact of surface maintenance treatments, time and traffic on the structural
deterioration of sealed granular pavements. Consequently, the HDM-4 structural deterioration model for
sealed granular pavements could not be re-calibrated. This outcome suggests that modifications to the
HDM-4 structural deterioration model are needed for sealed granular pavements.

Details on the modelling approach in HDM-4 and the Swedish PMS

The design of new pavements in New Zealand and rehabilitation treatments are currently performed in accordance with the Austroads Pavement Design Guide and its New Zealand supplement. New Zealand is also adopting pavement deterioration modeling based on the World Bank HDM models. This paper demonstrates how the modeling of roughness progression can supplement pavement design. It also demonstrates that the long life >50 years of many NZ pavements without significant roughness is not unexpected. It concludes that a combination of deterioration modeling and mechanistic design can be a powerful tool and that the rehabilitation of most of the network is associated with failure other than the classic roughness and rutting.

Results of a study to calibrate the HDM-4 rut depth model to Japan
Paper from LVR Conference on HDM calibration to Chile.
Results of pavement performance study in Indonesia and suitability of modelling with HDM-4 approach
Identifies the sensitive input data for pavement deterioration modelling. Although focused on dTIMS, the models were based on HDM
Report describing various techniques for establishing pavement strength and how they were implemented in New Zealand.
Draft Final Report. The main objective of this Transfund funded research project is to identify the sensitive parameters which will affect the output of the analysis using NZ dTIMS system. This will help the user on deciding which data item should be given higher priority in terms of accuracy level with which data are to be acquired.
Memo on different methods for calculating the SNP from FWD data. Includes a workbook which applies the different methods.
Report summarizing a workshop held to address issues in the HDM-4 pavement deterioration modelling.
Report describing issues with the HDM-4 pavement deterioration models and proposed alternatives
Report describing outcome of presentations at 1999 RDWE workshop
The World Bank's Deterioration of Unpaved Roads Model (DETOUR) implements in MS-Excel the road deterioration relationships for unpaved roads of the Highway Design and Maintenance Standards Model (HDM-III), which are the same as the forthcoming Highway Development and Management Model (HDM-4). DETOUR was developed for the World Bank Rural Transport Thematic Group and is designed primarily for engineered unpaved roads, of either gravel or earth surfacing, because the empirical models are based on a variety of such roads. When necessary it is possible to use the relationships also for tracks as a first estimate, but the user needs to be aware that the environmental effects of drainage and rainfall may be poorly represented. For more information regarding roughness and the economic aspects of low volume roads, visit the Design & Appraisal of Rural Transport Infrastructure Web page maintained by the World Bank Rural Transport Thematic Group.
ARRB calibration of HDM-4's surface dressing model to Australia.
This paper presents a proposal for modelling work zones in HDM-4. A worked example of the calculations is also given. It is an update of Bennett (1996) and Bennett (1998) with corrections to several equations and modifications to reflect the current version of the work zone effects software.
Worked Examples of calculating work zone costs.
ARRB initial calibration of HDM-4's surface dressing model to Australia.
ARRB evaluation of HDM-4's surface dressing predictions for Australia.
Report by Mike Riley on the examination of the effects of maintenance surfacings on retarding crack initiation and the effect of previous cracking on the performance of the new surfacing.

Realistic prediction of pavement performance is a critical component of asset management. Performance in terms of structural capacity is generally measured by the Adjusted Structural Number (SNP), hence a review has been carried out testing alternative methods for deriving this parameter for unbound granular pavements. Simplified methods may work reasonably well when calibrated to typical local conditions, but they are less likely to provide the same reliability in different regions or with different pavement structures. The rigorous methods (which can be readily applied) are recommended wherever deflection bowl information has been recorded. However, it is important to note that the standard equations are based on isotropic moduli for each layer, rather than anisotropic moduli, which the Austroads Pavement Design Guide has adopted for mechanistic analysis. Typical field measured moduli for unbound granular pavements are presented and appropriate calculation procedures suggested. Calibration or correction of SNP may also be required in a range of circumstances when refining the structural capacity for use in long-term pavement performance prediction. Where representative benchmark sites are set up and actual performance is monitored, appropriate calibration factors, based on specific modes of distress can be developed. These result in effective SNP values for a given network, giving due regard to the local range of materials and construction techniques.

Report on pavement deterioration models approached for Indonesia's low-volume Kabupaten roads.
Report describing how the FICEM concrete models were incorporated into HDM-4
Working paper from HDM-4 study on the impact of seals and thin overlays on crack initiation and progression.
Meeting Minutes. Objective of the meeting was to resolve the outstanding techinical issues with respect to Road Deterioration and Work Effects modelling in HDM-4.
This is the second paper reviewing the Road Deterioration and Maintenance Effects (RDME) relationships proposed for HDM-4.
This paper details an initial review of the Final Report. The review focuses on the first eight chapters which cover the proposed road deterioration relationships for HDM-4.
Paper looking at the HDM probabilistic cracking model and LTPP data.
Original specification and associated files for how HDM-4 handles maintenance works effects.
Program for predicting pavement deterioration rates
Memo describing proposed HDM-4 transverse thermal cracking model

Report on road deterioration and maintenance effects modelling.

This report is the original NDLI report describing the HDM-4 pavement deterioration and works effects models. Some of the models were refined, but it provides a lot of the background to the final HDM-4 models. It also includes models that were not included in HDM-4, such as for block pavements.
A review of how HDM-III was used in studies in different countries.
Default parameters for when using aggregate data inputs in HDM-4
 

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