Zhibo Zhang

Modeling Deterioration of Bridge Components with Binary Probit Techniques with Random Effects

Highway agencies use deterioration models to monitor the performance of bridge components (deck, superstructure, and substructure) and to predict their remaining service lives on the basis of the attributes of the bridges and their operating environments. Most bridge deterioration models are deterministic in nature. However, as a result of recent federal legislation, agencies are paying more attention to risk-based performance evaluation and decision making and are seeking models that incorporate stochastic elements. Probabilistic models provide more robust predictions of conditions. This paper describes the development of ordered binary probit (BP) models that duly account for observation-specific effects. The models describe the bridge component deterioration trends, specifically the probability that the component condition will drop from one state to another. This paper also acknowledges past similar or related efforts in this area of research but presents new insights and simplifies the complexity associated with BP models. To demonstrate the application of the models, data from over 5,000 in-service bridges were accessed; included were component age, superstructure material type, type of service under bridge, highway functional class, truck traffic, climate severity, rehabilitation history, condition switching state in last inspection period, and current condition rating. With the use of the developed BP models, a simulation was conducted to predict the probability of the component condition dropping from one state to another, where the predicted future condition is based on simulation involving the predicted probability and the current condition. The paper also presents visualizations of the deterioration trend simulation for each bridge component.

General Framework for Evaluating Long-Term Leasing of Toll Roads: Case Study of Indiana I-90 Highway

The long-term leasing of toll roads, a type of public–private partnership (PPP), has been attracting the attention of state governments since the two landmark cases of the Chicago Skyway in Illinois and the Indiana Toll Road in 2005 and 2006, respectively. To assist public agencies in making appropriate decisions to enter PPP agreements that are in the best interest of taxpayers, this paper presents a general framework for evaluating the long-term leasing of toll roads and investigates the two main criteria in the decision-making process: economic efficiency of privatization and the protection of public interest. The economic efficiency of PPPs is also analyzed with an uncertainty-based net present value method, which is demonstrated with a case study of the lease of the Indiana Toll Road. The analysis with Monte Carlo simulation demonstrates that over the analysis period, a public agency is not likely to gain as much benefit from the up-front payment lease amount as from that of continued in-house management of the toll road. The following analyses are conducted: a sensitivity analysis of revenue and cost factors and a break-even analysis to examine and establish the conditions under which the public agency could obtain as much benefit from continued in-house management of the toll road as the agency received from the privatization of the toll road. Finally, the actions taken by Indiana officials to protect the interest of its citizens and toll road users are discussed.

Statistical Assessment of the Cost Effectiveness of Highway Pavement Warranty Contracts

AbstractThe evaluation of warranty contracts is of great interest to highway agencies that seek innovative ways to manage their assets in the most cost-effective way. This paper demonstrates a statistical approach for evaluating the long-term performance and cost effectiveness of pavement warranties via comparison with similar traditional contracts. This is in contrast to past studies that used descriptive statistics and one-to-one comparisons to evaluate the performance of these two contracting approaches. In this study, random-parameter regression models that account for unobserved heterogeneity were developed to evaluate the performance of warranty and traditional contracts for similar projects on the basis of resulting pavement service life. The projects studied involved structural hot-mix asphalt overlay of crack-and-seat rigid pavements. The warranty projects in the study data sample were found to be 10% more effective in terms of average service life compared with traditional contract projects. Add...

Efficiency Measurement of Bridge Management with Data Envelopment Analysis

This study explored the feasibility of data envelopment analysis (DEA) to measure objectively the efficiency of Interstate bridge replacement and rehabilitation programs of the state highway agencies in the United States. Past applications of DEA indicated that this method showed promise for such assessments because of the ability to take into account the effect of uncontrollable factors and scale efficiency. The current study developed a modified input-oriented variable returns to scale model that treated the uncontrollable variables as uncontrollable. The two variables selected as outputs were (a) the change in area of structurally deficient bridges and (b) the change in area of functionally obsolete bridges between two consecutive years. The six variables selected as inputs were (a) expenditures on Interstate bridge replacement and rehabilitation, (b) average daily traffic on Interstate bridges per deck area, (c) proportion of Interstate truck vehicle miles traveled (VMT) to Interstate total VMT, (d) average age of Interstate bridges, (e) annual precipitation, and (f) annual freeze–thaw cycles. For each state, the DEA efficiency score and the corresponding target states were identified. The performances of the states and the possible reasons for inefficiencies were assessed. The Malmquist productivity index model was applied to calculate the technical efficiency change (catch-up effect) and the technological change (frontier shift). Over the analysis period, an overall improvement was observed in the frontier of the studied industry; this improvement suggested within this period a general improvement in the efficiencies of the Interstate highway bridge replacement and rehabilitation programs at highway agencies in the United States.

Indiana State Highway Cost Allocation and Revenue Attribution Study and Estimation of Travel by Out-of-State Vehicles on Indiana Highways

This study was commissioned by Indiana Department of Transportation (INDOT) to investigate the cost responsibility and the revenue contribution of highway users with regard to the upkeep of Indiana’s state and local highway infrastructure (pavements, bridges, safety assets, and mobility assets). The costs consisted of expenditures on construction, preservation, maintenance, and operations of the highway infrastructure. For revenues, user and non‐user sources were considered. The highway users were represented by the 13 Federal Highway Administration (FHWA) vehicle classes, and the study was based on 2009‐2012 data on expenditures and revenues. The study framework duly recognized the dichotomy between attributable and common costs. For allocating the attributable costs to the vehicle classes, equivalent single axle loads (ESALs), American Association of State Highway and Transportation Officials (AASHTO) loading equivalents, and passenger car equivalents (PCEs) were used; for allocating common costs, vehicle miles traveled (VMT) was used. For each vehicle class, the share of revenue contribution was compared to the share of cost responsibility to determine respective equity ratios and thus to ascertain the extent to which vehicles in each class may be underpaying or overpaying their cost responsibilities at the current time. The study also determined the distribution of fuel purchases and travel by out‐of‐state vehicles on Indiana’s highways; this analysis was required to further refine the results of the cost allocation and also to quantify the magnitude of any imbalance between the out‐of‐state travel and share of consumption on Indiana’s infrastructure and the revenue from such out‐of‐state vehicles. The outcome of this research is a systematic documentation of the sources and extents of highway revenues and the areas of expenditures at the local and state levels in Indiana. Pavement and bridge expenditures were found to have a dominant share of the overall expenditures on Indiana’s highway system. Classes 2 (automobiles) and 9 (5‐axle combination trucks) were found to have a dominant share of the cost responsibilities. It was determined that the user revenue sources contributed approximately 63.5% of the total state funding for highway expenditures and 36.5% were from non‐user revenue sources. The inability of user revenue sources to cover the total highway expenditure and the consequent partial reliance on non‐user sources seem to constitute a rather unstable funding situation particularly because the non‐user sources are characterized by significant variability. On the basis of the expenditures and revenues associated with the various user groups (vehicle classes) over the analysis period, this study found that inequities exist, albeit in varying degrees, among the highway user groups. Of the 13 vehicle classes, classes 1–4 were found to be overpaying their cost responsibilities while classes 5–13 are underpaying. For example, vehicle class 2 is overpaying its cost responsibility by 10% while vehicle class 9 is underpaying by 19%. The results of the equity analysis are generally consistent with those of studies carried out at other states. Also, it was estimated that the travel by out‐of‐state vehicles on Indiana’s interstates, national highway system (NHS) non‐interstates, non‐NHS and local roads are 21%, 10%, 9%, and 7% respectively, of the total travel as a percentage of VMT on those families of highway systems.