Adelino Ferreira

Life-cycle cost analysis system for pavement management at project level

Despite the fact that it considers a design period of 20 years for flexible pavements, the Portuguese manual of pavement structures states the importance of making a life-cycle cost analysis (LCCA) for a period of no less than 40 years, called project analysis period, in order to compare different pavement solutions in terms of global costs for the final choice of the pavement structure for a national road or a highway. The problem is that until now this analysis has never been done in Portugal. This paper presents a new LCCA system based on an optimisation model considering pavement performance, called OPTIPAV, developed and programmed to help pavement designers to choose the best pavement structure for a road or a highway. The LCCA system considers the serviceability concept adopted by the American Association of State Highway and Transportation Officials for use in the design of flexible pavements. The results obtained by the application of the new LCCA system clearly indicate that it is a valuable addition to the road engineers toolbox.

Selection of pavement performance models for use in the Portuguese PMS

This paper compares different pavement performance models (PPMs) from around the world and recommends one for use in the Portuguese pavement management systems (PMS). The paper is divided into three complementary sections. The first section describes several PPMs used around the world. The models analysed are (or come from) the Highway Development and Management System, the American Association of State Highway and Transportation Officials, the Nevada PMS, the Collop–Cebon whole-life pavement performance, the Swedish PMS and the Spanish PMS. The second section compares the results obtained for a case study with those of the two most promising PPMs and presents the advantages and disadvantages of using these models. The models were tested using the strategies evaluation tool, one of the components of the PMS utilised by the main Portuguese concessionaire. The final section of the paper presents the conclusions of the study on the use of the PPM evaluated and recommends one model to be used for managing the Portuguese highway network.

A segment-linked optimization model for deterministic pavement management systems

This paper presents a segment-linked optimization model to be used within deterministic pavement management systems. The model is aimed at determining the least-cost maintenance and rehabilitation strategy to be implemented in a road network, taking into account the applicable technical and budgetary constraints. The evolution of pavements with regard to cracking, rutting, surface disintegration, and longitudinal roughness is estimated with deterministic performance models. The overall quality of pavements is assessed through a modified version of the Present Serviceability Index (PSI). The method developed to solve the model is based on genetic algorithm principles. The application of the model is illustrated for a case study involving the road network of Coimbra, the third-largest Portuguese city. The results obtained for this case study indicate that the model is a valuable addition to the road engineers toolbox.

A life cycle assessment model for pavement management: methodology and computational framework

Despite the general consensus among stakeholders on how useful the life cycle assessment (LCA) methodology can be in helping to reduce the environmental burdens of a road pavement, very few pavement LCA models have considered the entire pavement life cycle. This paper presents the development of a highly customisable LCA tool that provides an integrated, project-level approach that includes all six pavement life cycle phases. The developed tool encompasses six main modules, including extraction of raw materials and production; construction, maintenance and rehabilitation; transportation of materials; work-zone traffic management; usage; and end-of-life. Data regarding the Portuguese practise of pavement construction and management have been collected on site with certified Portuguese construction companies and complemented using published literature and databases. The research described in this paper provides a widely applicable pavement LCA model that will enable highway agencies, private companies and the construction industry to estimate emissions and environmental impacts during the project analysis period for road pavement. The use of the proposed tool for benchmarking current practises in pavement construction and management enhances the scientific basis for understanding where further efforts can be undertaken to promote sustainable pavement investment decisions.

A life cycle assessment of in-place recycling and conventional pavement construction and maintenance practices

The application of in-place recycling techniques has emerged as a practical and effective way to enhance the sustainability of agency pavement management decisions for asphalt-surfaced pavements. However, the potential environmental benefits resulting from applying in-place recycling techniques have not been fully documented in the literature. This paper presents a comprehensive pavement life cycle assessment (LCA) model that extends the typical pavement LCAs system boundaries to include the environmental impacts resulting from the usage phase and the production of the energy sources. The results of the application of the pavement LCA model to a specific highway rehabilitation project in the state of Virginia showed that in-place recycling practices and an effective control of the pavement roughness can improve significantly the life cycle environmental performance of a pavement system.

Framework for Multiobjective Optimization of Physical Highway Assets Investments

AbstractOptimization-based tools have been included in many engineering management systems for individual infrastructure asset classes such as pavement management systems (PMS) and bridge management systems (BMS). These tools typically include single-objective optimization analyses. However, real-world decisions concerning asset preservation and renewal often involve more than one objective reflecting the various goals of the agency and need to evaluate possible alternatives according to multiple criteria. Traditional single-objective optimization approaches for handling such situations optimize a selected most important objective while either neglecting the less important competing objectives or imposing them as known constraints in the optimization formulation. This approach often does not provide truly optimal solutions. Multiobjective optimization formulations have clear theoretical advantages but increase the complexity of the mathematical formulation. This paper presents a review of the application ...

Road network pavement maintenance optimisation using the HDM-4 pavement performance prediction models

This paper presents a new maintenance optimisation system (MOS), called GENEPAV-HDM4, which was developed to integrate the pavement management system (PMS) of the municipality of Viseu (Portugal). At the same time, it was also developed for possible application to other existing PMS that need an upgrade due to recent Portuguese legislation. This is the case of the PMS used by the main Portuguese concessionaire Estradas de Portugal, SA. Currently, the MOS of this PMS uses a global deterministic pavement performance prediction model which makes part of the AASHTO flexible pavement design method. The new MOS (GENEPAV-HDM4) uses a similar optimisation model but the AASHTO pavement performance prediction model was substituted by the highway development and management (HDM-4) pavement performance prediction models to take into account recent Portuguese legislation. The results obtained by the application of the new MOS to the main road network of Viseu clearly indicate that it is a valuable addition to the road engineers toolbox.

Life-cycle cost analysis system for pavement management at project level: sensitivity analysis to the discount rate

The Portuguese manual of pavement structures, despite the fact it uses a design period of 20 years for flexible pavements, states the importance of making a life-cycle cost analysis (LCCA) for a period of no less than 40 years. This paper presents a sensitivity analysis to the discount rate that was carried out on the application of a new LCCA system, called OPTIPAV, developed and programmed to help pavement designers to choose the best pavement structure for a road or highway. The OPTIPAV system uses the serviceability concept adopted by the American Association of State Highway and Transportation Officials (AASHTO) for use in the design of flexible pavements. The results obtained by the application of the new LCCA system clearly indicate that, for any combination between traffic and pavement foundation, the optimum pavement structure always remains the same or decreases in terms of structural capacity with the increase of the discount rate value.

Pavement maintenance programming considering two objectives: maintenance costs and user costs

This paper presents the development and implementation of a Multi-Objective Decision-Aid Tool (MODAT) tested with data from the Estradas de Portugals Pavement Management System. The MODAT uses a multi-objective deterministic section-linked optimisation model with different possible goals: minimisation of agency costs, minimisation of user costs, maximisation of the residual value of pavements, etc. The MODAT also uses the deterministic pavement performance model used in the AASHTO flexible pavement design method. The application of the new Decision-Aid Tool is illustrated with a case study involving the main road network of Castelo Branco, a district of Portugal. In this application, the Knee point, that represents the most interesting solution of the Pareto frontier, corresponds to an agency costs weight value of 4% and an user costs weight value of 96%, demonstrating that user costs, which are generally much higher than agency costs, dominate the decision process.

A life cycle assessment model for pavement management: road pavement construction and management in Portugal

Improving the sustainability of road pavements requires road agencies and construction companies to identify, by means of appropriate methodologies and tools, the priority areas of action. The life cycle assessment method has gradually become a versatile tool capable of informing decisions on resource and process selection to better understand, measure and reduce the environmental impacts of a system. This article presents the results of a study aimed at estimating and comparing the life cycle impacts of the flexible pavement structures defined in the Portuguese pavement design catalogue. The analysis assessed the functional units over a 40-year project analysis period (PAP), considering all pavement life cycle phases: extraction of raw materials and production; transportation of materials; construction, maintenance and rehabilitation; work zone traffic management; usage and end-of-life. The results of the case study showed that for the less demanding traffic classes the materials phase is the main contributor to the road pavements overall life cycle environmental impact. However, if the road pavement is expected to carry significant volumes of traffic over its PAP, then the usage phase dominates the road pavements overall environmental performance. The analysis also showed that, as expected, the foundation class impacts the environmental performance of the pavement under high traffic volumes. Stronger pavement foundations require thinner pavement, resulting in lower overall environmental burdens.