Goran Mladenovic

Use of key performance indicators for PPP transport projects to meet stakeholders’ performance objectives

Purpose – The need for more efficient and effective public-private partnership (PPP) projects makes performance management of increasing importance, especially with respect to stakeholder expectations. This paper seeks to examine the use of key performances indicators (KPI) based on the analysis of critical success factors (CSF) for monitoring of PPP transport projects from the perspective of different stakeholders. Design/methodology/approach – The list of stakeholders’ performance objectives including CSF was defined using the brainstorming technique applied to group of experts in PPP transport sectors and refined through literature review. Input of the expert group was validated against a feedback from a respective survey. Three main groups of stakeholders were identified: public sector, private sector, and users. Finally, the review and comparative analysis of existing KPIs in PPP transport projects was performed based on stakeholders’ objectives and project attributes using the “frequency of mention”...

ESTIMATION OF PAVEMENT LAYER THICKNESS VARIABILITY FOR RELIABILITY-BASED DESIGN

Estimating the variability of key pavement design inputs is essential to reliability-based pavement design. The thickness of most pavement layers has a great impact on the outcome of practically all analyses of pavement performance. The within-section layer thickness variability is investigated here, as is the extent of the mean layer thickness deviation from its design thickness. Pavement layer thickness data (elevation and core measurements) from a large number of newly constructed flexible and rigid pavement sections in the Long-Term Pavement Performance (LTPP) program were examined. To determine the distribution type of the thickness data, a combined statistical test for skewness and kurtosis showed that (a) thickness variations within a layer indicate a normal distribution for 86% of 1,034 layers and (b) the mean thickness deviations from the design values may be assumed to be normally distributed for a layer having a given type and design thickness. The estimated thickness-within-layer variability values and the estimated typical thickness deviations derived from LTPP data may serve as benchmarks for use in pavement design reliability, construction quality assurance specifications, and other research studies. In addition, statistical comparisons of layer thickness variability indicators were made between the elevation and core layer thickness data to determine whether there are systematic differences between these two measuring methods. These results will be very useful to both researchers and practitioners who develop or use reliability-based pavement design procedures.

NATIONAL PARK SERVICE ROAD INVENTORY PROGRAM: QUALITY ASSURANCE SAMPLING CONSIDERATIONS FOR AUTOMATED COLLECTION AND PROCESSING OF DISTRESS DATA

The National Park Service Road Inventory Program (RIP) uses automated collection and processing of pavement-condition data. The study examines various approaches to quality assurance (QA) sampling used to evaluate those data. The RIP includes automated collection and processing of pavement-condition and roadside-inventory-feature data at 258 national parks, covering over 5,000 mi of paved roads. Evaluating the quality of some data elements requires manual data assessment conducted by trained data analysts. Because of the high volume of the collected and processed data, it is economically impractical to check quality of all data manually. To overcome this difficulty, a search for an appropriate QA data sampling methodology was conducted. The goal of the investigation was to determine appropriate statistical procedures and required sample sizes so that conclusions based on QA sample testing could be extrapolated to the whole data set with a certain level of confidence. Evaluation of QA sampling approaches, including the selection of statistical procedures for QA testing, determination of QA sample sizes, and development of the procedures for evaluating the QA testing results applicable to the RIP, is presented. The results will be of interest to practitioners involved in automated collection of pavement data and to researchers involved in the design of statistical testing procedures for engineering QA applications.

Developing Cost Estimation Models for Road Rehabilitation and Reconstruction: Case Study of Projects in Europe and Central Asia

The average unit costs of road works vary substantially between countries, and even between projects in the same country, due to a number of factors. In this paper an effort is made to develop prediction models for the unit costs of road works that could be applied for a wide range of conditions in different countries. A specialized dataset was used, which was generated under a World Bank study that included road works contracts from 14 countries in Europe and Central Asia (ECA). Two techniques were used for model development: multiple regression analysis and artificial neural networks. As the major problem found with the data set was missing or incomplete data, classification trees were used as an intermediate step to evaluate the correctness of the selected parameters. Three models were developed using regression analysis, two for the unit cost of asphalt concrete and one for the cost per km of rehabilitation and reconstruction works. The models include as independent variables the price of diesel fuel, country Gross National Income, World Governance Index, Transparency International Corruption Perception Index, percent of local bidders participating in the tender, and climate conditions. The analysis using classification trees confirmed the appropriateness of the variables selected in the regression analysis. The models developed using artificial neural networks were superior compared to the regression models, using mostly the same parameters. The resulting models could be particularly useful at the strategic level, for planning and optimization of works on road networks in ECA countries.

COMPARISON OF AS-CONSTRUCTED AND AS-DESIGNED FLEXIBLE PAVEMENT LAYER THICKNESSES

Sound pavement design is important for improving pavement performance, but construction is equally critical. Because of variations in pavement construction, the as-constructed pavement layer thickness varies spatially within a pavement section, and the mean constructed pavement layer thickness often deviates from the designed values. The as-constructed pavement layer thicknesses are compared to their design values by using data from the newly constructed flexible pavement sections in the Long-Term Pavement Performance program. First, the distribution type of the mean layer thickness deviation was investigated, and a combined statistical test for skewness and kurtosis showed that the mean thickness deviations may be assumed to be normally distributed for a given layer type and target thickness. Typical thickness deviation summary statistics values were derived to estimate the extent of deviations from the design thicknesses. Second, the analysis showed that elevation thickness data differ from the core examination data. Furthermore, as-constructed layer thickness values were compared to their design values by looking into the percentage of the individual measurements falling into specified ranges from the design values and by using two-sided and one-sided t-tests to compare the mean constructed thicknesses and the design values. The analyses showed that the mean constructed layer thicknesses tend to be above the design value for the thinner layers and below the design value for the thicker layers for the same layer and material type. Results from the study will be useful as inputs for reliability-based design procedures.

Assessing the Financial Feasibility of Availability Payment PPP Projects

Over the last couple of decades there has been an increased contribution of the private sector to finance infrastructure projects. However, in view of the current global financial crisis, it has become more difficult for governments, particularly in transition and developing economies, to attract private financing for infrastructure, which may affect negatively the capacity of many countries to expand, and even keep up their infrastructure. While this is an observed short-term phenomenon, it is still not clear what will be the medium to long term effect of the crisis. It may well be that governments may be willing to increase their financial support to infrastructure projects so as to make them more attractive to potential private investors. This paper focuses on availability payment (AP), which has been increasingly used to undertake critical infrastructure projects in both developing and developed countries. It presents the development of a user-friendly tool for financial assessments of availability payment PPP projects. The model is suitable for preliminary assessment and screening of potential PPP projects. The applicability of the tool is demonstrated through a numerical example of a potential road PPP project. The model can also be applied to any other mode of transport or infrastructure. The model can be used to carry out sensitivity analyses. The user can change the value of an input parameter (e.g., construction cost) and obtain the resulting impact, for example, on the project financial internal rate of return.

Implementation of Preventive Maintenance in Network-Level Optimization

Application of appropriate preventive maintenance treatments, at the right time, extends the service life of pavements, resulting in benefits to road users through increased ride comfort and safety and to road agencies through the reduction of future maintenance costs and improvement of the network condition. Preventive maintenance treatments usually have been applied on the highly trafficked sections of the Serbian national road network, but they have not been applied on the low-volume part of the network. This study used the Serbian low-volume roads network as a case study to identify appropriate preventive maintenance treatments for low-volume roads, model these into a pavement management system, and assess the potential benefits of their application compared with the current practice. The World Banks RONET (road network evaluation tools) model, designed to assess the current characteristics of road networks and their future performance according to various levels of interventions (and budgets), was selected for this study. The model was modified for the study to incorporate use of preventive maintenance treatments. Modifications included adjustment of the pavement deterioration curves to incorporate a slower deterioration rate resulting from the application of crack sealing and pothole patching and surface dressings or thin overlays while the pavement was still in good condition. The results indicate that the use of preventive maintenance treatments would result in increased net benefits and a substantial reduction in future road agency costs compared with the maintenance scenario without preventive maintenance.

Network-Level Pavement Management: Case of Serbian Low-Volume Roads

This paper presents the application of the World Banks Road Network Evaluation Tools (RONET) model to strategic network-level analysis of the Serbian state low-volume road (LVR) network. This network condition deteriorated considerably during the 1990s as a result of the under-financing of its operations and maintenance. In recent years, financing for the road sector has gradually increased and focuses on the most hazardous and highly trafficked parts of the network. However, the overall budget allocated to the sector remains inadequate to maintain the entire state road network in stable condition. The goals of the presented study are to obtain the optimum maintenance and rehabilitation (M&R) strategy and related budget, estimate the impact of different funding levels on future quality, and estimate the economic consequences of budget constraints for the M&R of the LVR network. Application of the RONET model to the prevailing conditions on the Serbian LVR network led to an optimal M&R strategy with a good balance between rehabilitation and periodic and recurrent maintenance. Implementation of the optimal M&R strategy would cause major improvement compared with the current condition of the LVR network. Implementation of higher M&R standards would lead to substantially higher road agency costs and, consequently, lower net benefits, whereas the implementation of lower M&R standards would lead to considerably worse network condition for approximately the same or slightly lower agency costs. This situation means that even minor budget constraints would result in considerably worse network condition and much higher total road transport costs.

IMPROVING RELIABILITY OF PAVEMENT LOADING ESTIMATES WITH PAVEMENT LOADING GUIDE

The development of the Long-Term Pavement Performance (LTPP) Pavement Loading Guide (PLG) was initiated to improve the reliability of traffic load estimates for the LTPP sections that do not have measured axle load data. The PLG contains extensive traffic data obtained from the LTPP database that may constitute the best available source of traffic data at the national level, a user-friendly graphical interface, and guidelines intended to help the user with the development of axle load spectra. Because of these features, the PLG will also facilitate traffic projections for general pavement design and management purposes. The uncertainty associated with estimating annual axle load spectra was quantified by assuming that the measured data do not exist and must be estimated. The estimated data were obtained by using axle load spectra obtained at similar sites in the same jurisdiction and utilized prototype PLG software. The difference between the estimated and the measured traffic loads was quantified by expressing axle load spectra in terms of equivalent single-axle loads. The results show that reasonable traffic load estimates can be obtained by judiciously selecting replacement traffic data. Although the PLG can reduce uncertainty of traffic forecasts and facilitate traffic forecasting, surrogate data can never replace site-specific data.

Experimental Dimensional Accuracy Analysis of Reformer Prototype Model Produced by FDM and SLA 3D Printing Technology

The subject of this paper is the evaluation of the dimensional accuracy of FDM and SLA 3D printing technologies in comparison with developed reformer polymer electrolyte membrane (PEM) fuel cell CAD model. 3D printing technologies allow a bottom-up approach to manufacturing, by depositing material in layers to final shape. Dimensional inaccuracy is still a problem in 3D printing technologies due to material shrinking and residual stress. Materials used in this research are PLA (Polylactic Acid) for FDM technology and the standard white resin material for SLA technology. Both materials are commonly used for 3D printing. PLA material is printed in three different height resolutions: 0.3 mm, 0.2 mm and 0.1 mm. White resin is printed in 0.1 mm height resolution. The aim of this paper is to show how layer height affects the dimensional accuracy of FDM models and to compare the dimensional accuracy of FDM and SLA printed reformer models with the same height resolution.