Journal of Infrastructure Systems

Performance-based maintenance contracts are becoming an increasingly popular method of outsourcing pavement maintenance work. These contracts transfer performance-related risks to contractors with the objective of reducing the total cost of maintenance over the pavement life cycle by leveraging on the efficiencies of private sector management. In such contractual settings, transportation agencies hedge their exposure to poorly performing pavements that require frequent attention. However, this comes with a price. Contractors price in their bids a premium to account for such scenarios. This paper presents a model for contractors to determine optimal management strategies by taking into account the inherent spatial variability in pavement’s structural characteristics. The model considers a tradeoff between economies of scale associated with managing longer pavement sections and the risk reduction benefits with managing relatively smaller, e.g., more homogeneous sections. The results indicate that the length of optimal management sections depends not only on the expected contract penalty costs (disincentive costs), but also the ability of the contractor to explore economies of scale. The model is illustrated using typical data available to transportation agencies.

The development of highway infrastructure has increasingly been shifting toward the use of public-private partnerships (PPP) and alternative methods of project financing. In such schemes, the evaluation of their financial viability is the most commonly used industry practice for assessing the potential of the project to achieve the financial targets of its various stakeholders and ultimately affects its selection for implementation. In this study, a methodological framework for the evaluation of the financial viability of revenue-generating transportation infrastructure projects is presented in terms of their investment risk, using the method of moments. The investment risk is defined as the risk of not achieving the expected infrastructure-generated profit and thus not being able to service the financing debt outstanding and/or obtain an adequate return on the investment. The framework leads to a probabilistic assessment of the financial viability which can be achieved by performing various sensitivity and scenario analyses. To illustrate the application of the proposed methodology, a comparison of various alternative scenarios of financing is undertaken coupled with a few additional sensitivity analyses, for the case of a highway project developed as a typical PPP concession.

Highway agencies around the world are undergoing major changes in their traditional maintenance practices, including the privatization of entire sections of highway routine maintenance activities. Performance-based contracts (PBC) are an option in such privatizing efforts. This paper presents a methodology to estimate the likelihood and amount of cost savings associated with the application of PBC for highway maintenance operations. Using data on maintenance contracts from around the world, we develop models that can be used to compare several contracting methods and include variables such as contract duration, activity type, and contract size. We find that large projects with strong competition, long duration and extension periods, long outsourced road sections that incorporate crack sealing, pothole repair, illumination repair/maintenance, and mowing activities, favor outsourcing under PBC. Our methodology can be useful to transportation agencies for making decisions about the use of PBC and other methods of maintenance outsourcing at the preplanning phase.

This paper describes the New York City water supply performance and suppression of fire during the World Trade Center (WTC) disaster. The water losses sustained by damaged water distribution pipelines are discussed and their impacts on emergency response and telecommunications and transportation infrastructure are noted. The results of hydraulic network analyses are presented to quantify the performance of hose and engine relay systems from fireboats to the WTC site. The results of an analytical study of firefighting relay systems are summarized to provide guidance on the most effective selection of hose size, number of hose lines, and engines for future use of fireboats for landside fire protection. The fire department response to the WTC disaster is compared with similar response to the 1989 Loma Prieta earthquake. Drawing on lessons from both events, recommendations are made for improved emergency planning and services.

The flow capacity of municipal sewer lines often diminishes over time due to root intrusion and debris accumulation. As a consequence, many wastewater agencies use high-velocity jets to scour sewer pipes and restore the discharge capacity of the collection lines. Occasionally, jetting operations expel fluid from the sewer through connecting laterals to plumbing fixtures in adjacent homes and businesses. While rare, these hydraulic blowouts pose health problems, damage private property, and strain public relations. This paper investigates the conditions under which sewer line blowouts occur in order to predict and reduce their occurrence. Statistical analyses of field data gathered over a 10-year period by the Metropolitan Sewer District of Greater Cincinnati revealed that, among many competing factors, the incidence of sewer blowouts was highest in pipes with the smallest flow capacity. Based on this finding, a simple formula was developed to identify service zones with high blowout risks. Two computational flow models, FLUENT and SWMM, were used to simulate and corroborate the sewer blowout phenomenon.

In this paper, a time-dependent deterioration forecasting model is presented. In the model the deterioration process is described by transition probabilities, which are conditional upon actual in-service duration. The model is formulated by the multistage Weibull hazard model defined by using multiple Weibull hazard functions. The model can be estimated based upon inspection data that are obtained at discrete points in time. The applicability of the model and the estimation methodology presented in this paper are investigated against an empirical data set of highway utilities in the real world.

We present the development of an empirical pavement overlay crack progression model using condition survey data for the highway system in the state of Washington. The crack progression model uses random-effect panel data regression techniques, with correction for incidental truncation, endogeneity bias, and unobserved heterogeneity. The parameter estimation results show that existing cracking prior to the overlay, traffic loading, overlay thickness and materials, and some environmental factors play important roles in explaining crack progression. The model developed in this paper is used jointly with a probabilistic model of overlay crack initiation as inputs to a Monte Carlo simulation of overlay cracking trends over time. These trends are realistic for overlays in the estimation database, but caution should be used when applying the model to other states. Specifically, it should only be used in situations where the maintenance policy used is similar to that used by the Washington DOT.

Pavement systems provide critical infrastructure services to society but also pose significant impacts related to large material consumption, energy inputs, and capital investment. A life-cycle model was developed to estimate environmental impacts resulting from material production and distribution, overlay construction and preservation, construction-related traffic congestion, overlay usage, and end of life management. To improve sustainability in pavement design, a promising alternative material, engineered cementitious composites (ECC) was explored. Compared to conventional concrete and hot-mixed asphalt overlay systems, the ECC overlay system reduces life-cycle energy consumption by 15 and 72%, greenhouse gas emissions by 32 and 37%, and costs by 40 and 47%, respectively. Material, construction-related traffic congestion, and pavement surface roughness effects were identified as the greatest contributors to environmental impacts throughout the overlay life cycle. The sensitivity analysis indicated that traffic growth has much greater impact on the life-cycle energy consumption and environmental impacts of overlay systems compared to fuel economy improvements.

Preservation (maintenance and rehabilitation) strategy is the critical factor controlling pavement performance. A life-cycle optimization (LCO) model was developed to determine an optimal preservation strategy for a pavement overlay system and to minimize the total life-cycle energy consumption, greenhouse gas (GHG) emissions, and costs within an analysis period. Using dynamic programming optimization techniques, the LCO model integrates dynamic life-cycle assessment and life-cycle cost analysis models with an autoregressive pavement overlay deterioration model. To improve sustainability in pavement design, a promising alternative material for pavement overlays, engineered cementitious composites (ECCs), was studied. The LCO model was applied to an ECC overlay system, a concrete overlay system, and a hot mixed asphalt (HMA) overlay system. The LCO results show that the optimal preservation strategies will reduce the total life-cycle energy consumption by 5–30%, GHG emissions by 4–40%, and costs by 0.4–12% for the concrete, ECC, and HMA overlay systems compared to the current Michigan Department of Transportation preservation strategies, respectively. The impact of traffic growth on the optimal preservation strategies was also explored.

The selection of appropriate type of contract for a highway maintenance project can be influenced by project attributes such as the expected cost and duration. However, the expected project cost and planned duration depend on other project attributes and also depend on each other. These simultaneous relationships complicate the identification of the appropriate contract for a highway maintenance project. While previous research has provided insight into the factors that affect project cost and duration, the validity of the findings may have been stymied by a lack of explicit consideration of the simultaneous relationships between project duration and cost. In this paper, we develop a framework based on a three-stage least-squares model to identify the most appropriate type of contract given the project’s attributes while explicitly accounting for the simultaneity between project cost and duration. The framework can also be used to estimate the expected contract duration and cost on the basis of the project type, constituent work activities, physical size (length) of the project, and contract type. The results suggest that the choice of the appropriate contract type for a highway maintenance project is influenced by characteristics such as the number of constituent maintenance activities in the contract, the expected or specified contract characteristics (contract duration, cost, and length), and the type of highway asset in question.

This paper evaluates regulation by contract in public-private partnerships (PPPs) in infrastructure services. Although the benefits of competition for the market and of regulatory contracts are widely acknowledged, the literature identifies several failures in their design. These “flaws” are present in both developed and developing countries and arise in all types of contracts. This study analyzes both contractual PPPs and institutionalized PPPs (mixed companies). The evidence suggests that for all kinds of contracts, the major problems tend to arise in the preparation of public tender documents: the “best” bidder is not often the winner. The likely results include redistribution in favor of the private partner, weak incentives for high performance, and renegotiation of contracts. Moreover, risks are not allocated correctly nor is effective monitoring ensured. This review of contract procedures and design allows us to draw several implications for policy makers and to present suggestions and recommendations for improving regulatory contracts.

It is important for the public and private sectors to establish effective risk allocation strategies for public-private partnership (PPP) projects in order to achieve a more efficient process of contract negotiation and reduce the occurrence of dispute during the concession period. This paper aims first to identify the preferred risk allocation in PPP projects of mainland China and the Hong Kong Special Administrative Region (referred to as China and Hong Kong from here onward) and then to compare these preferences to those in the U.K. and Greece by a questionnaire survey based on the same risk register. The results in China and Hong Kong show that the public sector preferred to retain most political, legal, and social risks, and share most microlevel risks and force majeure risk; while the majority of mesolevel risks were preferred to be allocated to the private sector. The comparative analyses of risk allocation preference among these four countries/jurisdictions indicate that the public sector in the U.K. was most able to transfer the PPP risks to the private sector, followed by Greece, Hong Kong, and China. Respondents from Greece exhibited the greatest degree of support for the public sector to retain the macrolevel risks. All respondents agreed that private investors should take a more active role in managing the mesolevel risks. Respondents from China and Hong Kong considered that majority of the microlevel risks should be shared equally between the public and private sectors, while respondents from Greece indicated that the private sector should take a more active role in managing the microlevel risks. The comparative study provides international investors a better understanding of risk preferences in different countries/jurisdictions so that they could adjust their strategies according to the specific situation and achieve better value for money in running their PPP projects.