bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Semiautomated and Automated Pavement Distress Collection for Network-Level Pavement Management
Authors: Tighe Susan L. , Ningyuan Li , Kazmierowski Tom
Published: January 2009

The Ministry of Transportation Ontario (MTO) and the University of Waterloo examined the feasibility of using automated pavement distress collection techniques in addition to data collected through manual surveys. Test sections including surface-treated, asphalt concrete, composite, and portland cement concrete pavement structures in 37 locations in southern Ontario, Canada, were evaluated. Distress manifestation index (DMI) values were computed for each section by MTO pavement design and evaluation officers using the manual evaluation data collected. DMI values were then computed for each section by using automated distress evaluation data. Before DMI values could be computed, the relevant data had to be extracted and verified, and the distress data had to be categorized. DMI values computed from data collected manually and by using automated systems were compared. Finally, a repeatability analysis was performed on both the manual and the automated techniques. Results indicate no significant differences among sensor-based equipment; however, there are significant differences among measurements obtained from digital image-based technology. The implications of such outcomes are discussed, including the specifics regarding methodology implementation in order to encourage practitioners to benefit from the preliminary investigation. Current available techniques can provide MTO with valuable information for pavement management purposes. The automated results are comparable with manual surveys. However, these surveys should be supplemented with manual surveys, especially for design purposes, because some of the pavement distresses were difficult to identify with the automated methods.
Hybrid Multiobjective Optimization Model for Regional Pavement-Preservation Resource Allocation
Authors: Wu Zheng , Flintsch Gerardo W. , Chowdhury Tanveer
Published: January 2009

Because of a lack of reliable performance prediction models, many state departments of transportation (DOTs) use a needs-based budgeting process, namely, annual budget requests. Allocations of funding across maintenance activities and districts are developed on the basis of pavement maintenance needs derived from pavement inventory and annual or biannual condition data. This allocation of funding across maintenance activities and districts is challenging and often involves negotiation and balancing. A decision support model is proposed for the optimization of short-term pavement preservation budgeting based on two proven operations research techniques: goal programming for handling multiple objectives and an analytic hierarchy process for priority setting under multiple criteria. The model simultaneously considers two incommensurable and conflicting objectives: maximization of the preservation effectiveness in terms of extended service life and minimization of the total preservation cost. Application of the model is demonstrated with a short-term pavement preservation budgeting problem for a decentralized state DOT with nine maintenance districts. The illustrative example reveals that the proposed model is practical for supporting needs-based budgeting.
Probabilistic Analysis of Pavement Distress Ratings with the Clusterwise Regression Method
Authors: Luo Zairen , Yin Huiming
Published: January 2009

A mixture clusterwise regression method is proposed to analyze pavement distress ratings and predict the future performance of pavements. Rather than using a single equation as the ordinary least-squares regression method, a clusterwise regression uses several regression equations (clusters) to fit a data set with a large variation. Each cluster indicates a portion or a percentage of a data set that follows a uniform tendency. A weighted regression function consisting of all clusters is introduced to take into account current and historical observations of pavement distresses and to predict future pavement conditions. An example using the existing database is provided to compare the proposed model with the conventional Markov probabilistic model. The results show that at the network level the proposed model provides much more accurate predictions than the conventional Markov model does; at the project level, the proposed model correctly predicted five of seven ratings for an example pavement, but the conventional Markov model predicted none of them. This model, if integrated into a pavement management system, can significantly improve the accuracy and applicability of the system, especially for a complex highway system.
Robust Optimization for Managing Pavement Maintenance and Rehabilitation
Authors: Gao Lu , Zhang Zhanmin
Published: January 2009

A pavement management system should help a decision maker to select the best preservation program, decide which preservation treatment to use, and where and when to apply it to maximize the use of the available resources. One of the essential roles of pavement management is to provide a rational, cost-effective optimal funding planning and allocation strategy for highway agencies. Researchers have previously developed deterministic optimization methods for programming pavement maintenance and rehabilitation strategies. However, pavement infrastructure deterioration is a dynamic, complicated, and stochastic process affected by a variety of factors such as traffic loading, environmental conditions, and structural capacities, as well as certain unobserved factors. Ignoring these fundamental characteristics may limit the usefulness of an optimal solution. To take the uncertainties into consideration, some researchers have introduced stochastic programming techniques into pavement maintenance management. However, difficulties in characterizing the distribution of data and the substantial computational challenge have compromised the practical application of those techniques. A project-level robust optimization method for maintenance budget planning to overcome these difficulties is presented. The solutions from this proposed method are computationally tractable and not overly sensitive to any specific realization of the uncertainties. An application of this method is demonstrated by using long-term pavement performance data collected during the past 20 years, yielding promising preliminary results.
Bituminous Surface Treatment Protocol for the Washington State Department of Transportation
Authors: Li Jianhua , Mahoney Joe P. , Muench Stephen T. , Pierce Linda M.
Published: January 2009

To help the Washington State Department of Transportation (WSDOT) enhance its pavement preservation program through an improved understanding of the use of bituminous surface treatment (BST), the Highway Development and Management System was used as an analytical tool to test the average annual daily traffic and equivalent single-axle load levels appropriate as criteria for selecting the application of BST resurfacings to WSDOT pavements. It verified the feasibility of using BSTs to maintain pavements with higher traffic levels than have been applied in the past. Results also suggested that alternating the application of BST resurfacings and 45-mm hot-mix asphalt overlays is an effective rehabilitation strategy. Finally, the study results were used to estimate the impacts that increased use of BST surfaces would have on the performance of the state-owned route system.
Application of Rolling Dynamic Deflectometer to Forensic Studies and Pavement Rehabilitation Projects
Authors: Chen Dar-Hao , Nam Boo Hyun , Stokoe Kenneth H.
Published: January 2009

Characterization of the load transfer of jointed plain concrete pavements requires proper tools. The rolling dynamic deflectometer (RDD) has been used successfully on many Texas Department of Transportation projects for this purpose. Applications of the RDD in forensic studies and pavement rehabilitation projects are presented. RDD deflection profiles were used to assist in diagnosing the causes of reflective cracks on SH87a, where a reflective crack relief interlayer was placed in a rehabilitation project to minimize reflective cracking. However, frequent and severe reflective cracks still occurred on SH87a in the turning and inside lanes, where traffic is lighter than in the outside lane. It was concluded that poor load transfer at joints (indicated by high relative vertical movements) was one of the main contributing factors to the reflective cracking in these two lanes. Two rehabilitation projects are also presented to show how continuous RDD deflection profiles were critical to the success of the projects. In the BU287 project, RDD profiles were used to identify successfully locations for full-depth repair in Subsection 1 and recommend a different rehabilitation strategy (remove and reconstruct) in Subsection 2 because of the significant number of joints that have a severe potential for reflective cracking. In the SH87b rehabilitation project, the RDD was employed to identify locations that need dowel bar retrofit and other locations that need full-depth repair. It is concluded that RDD data not only are able to provide 100% coverage but also offer quantifiable and objective information for forensic and rehabilitation studies in terms of relative movements at joints and cracks.
Sustainable Pavements
Authors: Alkins Andrew E. , Lane Becca , Kazmierowski Tom
Published: January 2009

The Ministry of Transportation Ontario, Canada, is committed to using technologies to help build a more sustainable transportation system that supports today's needs while protecting the environment for future generations. Cold in-place recycling (CIR) is an established pavement rehabilitation technology that processes an existing asphalt pavement, sizes it, mixes in additional asphalt cement, and lays it back down without off-site hauling and processing. The added asphalt cement is typically emulsified asphalt. A recent development in CIR technology is the use of expanded (foamed) asphalt, rather than emulsified asphalt, to bind the mix. This combination of CIR and expanded asphalt technologies is termed cold in-place recycled expanded asphalt mix (CIREAM). Both CIR and CIREAM technologies support the philosophy of a sustainable transportation system. More specifically, CIR and CIREAM meet the criteria for a sustainable pavement: safe, efficient, economic, environmentally friendly pavement that meets the needs of present-day users without compromising those of future generations.
In Situ Assessment of Interlayer Systems to Abate Reflective Cracking in Hot-Mix Asphalt Overlays
Authors: Baek Jongeun , Al-Qadi Imad L. , Xie Wei , Buttlar William G.
Published: January 2009

A method to investigate the effectiveness of interlay systems in hot-mix asphalt (HMA) overlays to retard reflective cracking is introduced. Significant research has been conducted on developing techniques to reduce reflective cracking in HMA overlays. Many interlayer systems have been used in the field; some showed no structural or economical benefits, while others could reduce reflective cracking in the short term. However, long-term and quantitative benefits for many of these techniques have not been realized. Hence, this research fulfills the need to quantify the effectiveness of interlayer systems in delaying or abating reflective cracking–it proposes a systematic approach to identify reflective cracking and a conceptual index to evaluate interlayer systems. Ground-penetrating radar and a video integration system are used to detect surface cracks in overlays as well as joint opening and dowel bars in existing portland cement concrete pavements. Transverse cracks that exist over a joint are classified as joint-associated reflective cracks. Other transverse cracks are categorized as non-joint-associated transverse cracks. These cracks are not considered reflective cracks. A weight function is introduced to incorporate crack severity. Finally, two performance indices are introduced: reflective cracking appearance ratio and transverse cracking appearance ratio. By means of these new indices, the effectiveness of four interlayer system types used in Illinois is quantified: nonwoven reinforcing fabric with asphalt binder, sand antifracture, interlayer stress-absorbing composite, and modified leveling binder.
Simultaneous Perturbation Stochastic Approximation Algorithm for Solving Stochastic Problems of Transportation Network Analysis
Authors: Ozguven Eren Erman , Ozbay Kaan
Published: January 2009

Stochastic optimization has become one of the important modeling approaches in transportation network analysis. For example, for traffic assignment problems based on stochastic simulation, it is necessary to use a mathematical algorithm that iteratively seeks out the optimal, the suboptimal solution, or both, because an analytical (closed-form) objective function is not available. Therefore, efficient stochastic approximation algorithms that can find optimal or suboptimal solutions to these problems are needed. The method of successive averages (MSA), a well-known algorithm, is used to solve both deterministic and stochastic equilibrium assignment problems. As found in previous studies, the MSA has questionable convergence characteristics, especially when the number of iterations is not sufficiently large. In fact, the stochastic approximation algorithm is of little practical use if the number of iterations to reduce the errors to within reasonable bounds is arbitrarily large. An efficient method to solve stochastic approximation problems is the simultaneous perturbation stochastic approximation (SPSA), which can be a viable alternative to the MSA because of its proven power to converge to sub-optimal solutions in the presence of stochasticities and its ease of implementation. The performance of MSA and SPSA algorithms is compared for solving traffic assignment problems with varying levels of stochastic-ities on a small network. The utmost importance is given to comparison of the convergence characteristics of the two algorithms as well as to the computational times. A worst-case scenario is also studied to check the efficiency and practicality of both algorithms in terms of computational times and accuracy of results.
Dynamic Origin-Destination Demand Estimation Using Turning Movement Counts
Authors: Alibabai Hamed , Mahmassani Hani S.
Published: January 2009

A dynamic origin-destination (O-D) demand estimation model is presented that uses turning movement counts as observations. Based on an iterative bilevel estimation framework, the upper-level problem is to minimize a weighted objective function of the deviation between simulated link flows and real-time link counts and the deviation between estimated time-dependent demand and an a priori historical O-D table, where the weighting value is determined by an interactive approach to obtain the best compromise solution. A case study was performed on the US-29 network in Maryland to compare the estimated tables of this approach with the one obtained from the traditional method, which uses only approach link volume counts. The application illustrates considerable benefits of using turning movements instead of approach volumes in matching observed counts.
Generalized Wardrop Principle and Its Application in Regional Transportation
Authors: He Shengxue , Fan Bingquan
Published: January 2009

Regional transportation can be regarded as a complex system consisting of many subsystems. If it is assumed that the decisions of others are known, one of the subsystems, such as a manufacturer, will make decisions from the viewpoint of individual optimal. But among these subsystems, there are noncooperative interactions. The first Wardrop principle can be used to explain the interplay between the subsystems and the second Wardrop principle to explain the internal decision making of one subsystem. To capture the feature of hierarchical behavior, classical Wardrop principles need to be generalized. The new behavior principle is named the generalized Wardrop principle. With the substitution of actual path sets for the simple links in a spatial price equilibrium network and constructing the generalized transportation cost functions, the regional transportation network equilibrium model is formulated. The new model combines the spatial price equilibrium model with the network optimization model. It can be explained by the generalized Wardrop principle and reflects the multicommodity, multimodal characteristics of regional transportation. The modified projection algorithm is used to solve the model. One numerical example is given to show the efficiency of the algorithm.
Stochastic Multiclass Traffic Assignment with Consideration of Risk-Taking Behaviors
Authors: Di Shan , Pan Changxuan , Ran Bin
Published: January 2009

A study of the problem of predicting traffic flows under traffic equilibrium in a stochastic transportation network is presented. Travelers’ risk-taking behaviors are explicitly modeled with respect to probabilistic travel times. Traveling risks are quantified from the travel time distributions directly and are embedded in the route choice conditions. The classification of risk-neutral, risk-averse, and risk-prone travelers is based on their preferred traveling risks. The formulation of the model clarifies that travelers with different risk preferences have the same objective–to save travel time cost–though they may make different route choices. The proposed solution algorithm is applicable for networks with normal distribution link travel times theoretically. Further simulation analysis shows that it can also be applied to approximate the equilibrium network flows for other frequently used travel time distribution families: gamma, Weibull, and log-normal. The proposed model was applied to a test network and a medium-sized transportation network. The results demonstrate that the model captures travelers’ risk-taking behaviors more realistically and flexibly compared with existing stochastic traffic equilibrium models.
Adaptive Route Choice Models in Stochastic Time-Dependent Networks
Authors: Gao Song , Frejinger Emma , Ben-Akiva Moshe
Published: January 2009

Adaptive route choice models are studied that explicitly capture travelers’ route choice adjustments according to information on realized network conditions in stochastic time-dependent networks. Two types of adaptive route choice models are explored: an adaptive path model in which a sequence of path choice models are applied at intermediate decision nodes and a routing policy choice model in which the alternatives correspond to routing policies rather than paths at the origin. A routing policy in this study is a decision rule that maps from all possible pairs (e.g., node, time) to the next links out of the node. Existing route choice models that can be estimated on disaggregate revealed preferences assume a deterministic network setting from the traveler's perspective and cannot capture the traveler's proactive adaptive behavior under uncertain traffic conditions. The literature includes a number of algorithmic studies of optimal routing policy problems, but the estimation of a routing policy choice model is a new research area. The specifications of estimating the two adaptive route choice models are established and the feasibility of estimation from path observations is demonstrated on an illustrative network. Prediction results from three models–nonadaptive path model, adaptive path model, and routing policy model–are compared. The routing policy model is shown to better capture the option value of diversion than the adaptive path model. The difference between the two adaptive models and the nonadaptive model is larger in terms of expected travel time if the network is more stochastic, indicating that the benefit of adaptivity is more significant in a more unpredictable network.
Strain and Pulse Duration Considerations for Extended-Life Hot-Mix Asphalt Pavement Design
Authors: Garcia Gabriel , Thompson Marshall R.
Published: January 2009

In the design of extended-life hot-mix asphalt pavements (ELHMAP or perpetual pavements), the fatigue endurance limit is the key element. Thus, horizontal tensile strain at the bottom of the hot-mix asphalt layer is the critical design parameter. This paper presents results of a study performed at the University of Illinois test facility that focused on the evaluation of the most critical pavements responses for ELHMAP design. Longitudinal and transverse tensile strain pulses were measured in four sections tested with the accelerated pavement testing machine. A very strong relationship between the longitudinal and transverse pulse durations was found. In general, the transverse pulse durations were about three times those in the longitudinal direction. A relationship between longitudinal and transverse tensile strains was also found. Generally speaking, the transverse tensile strains were about 1.5 times greater than those in the longitudinal direction. The haversine function was the best representation for the longitudinal and the transverse strain pulses. The transverse pulse is very sensitive to the lateral position of the moving load. As the offset of the moving load increases, the rate at which the transverse tensile strain decreases is considerably greater than that of the longitudinal tensile strain. Moreover, if the moving load passes far enough from the strain gauge location, the transverse strain pulse reverses from tension to compression.
Benefits of the Minnesota Road Research Project
Authors: Tompkins Derek M. , Khazanovich Lev , Johnson David M.
Published: January 2009

The Minnesota Department of Transportation began construction on the Minnesota Road Research Project (MnROAD) in 1991 and opened the full-scale pavement research facility to live traffic in 1994. Since the time of its construction, MnROAD, the first major test track since the AASHO Road Test of the 1950s and 1960s, has provided many lessons in pavement testing and pavement engineering on behalf of the greater pavement community. Researchers at the University of Minnesota reviewed these lessons from the first phase of MnROAD (the facility's first 10 years of operation) for a project titled MnROAD Lessons Learned. The Lessons Learned project involved more than 50 interviews; 300 published and unpublished reports, papers, and briefs; and an online survey of pavement professionals. This paper, based on the Lessons Learned project, presents a sample of the lasting benefits of MnROAD at the local, state, and national levels. Furthermore, the paper provides extensive references for these benefits in the hope of increasing awareness of this pavement test facility's underpublicized contributions to pavement engineering.
Dynamic Analysis and in Situ Validation of Perpetual Pavement Response to Vehicular Loading
Authors: Al-Qadi Imad L. , Wang Hao , Yoo Pyeong Jun , Dessouky Samer H.
Published: January 2009

A three-dimensional (3-D) finite element (FE) model was developed to predict pavement responses to vehicular loading. The model incorporates measured tire-pavement contact stresses, continuous moving wheel loading, and hot-mix asphalt (HMA) viscoelastic characteristics. The model was fine-tuned using implicit-dynamic analysis and validated using pavement response from accelerated loading. Two tire configurations (dual-tire assembly and wide-base 455 tire) and three full-depth flexible pavement designs (HMA 152 mm, 254 mm, and 420 mm) were used in both FE modeling and accelerated loading tests. The predicted and calculated strain responses at the bottom of HMA were in agreement. Most important, the study shows that vertical shear strain in the upper 76 to 100 mm of the pavement surface is critical for thick pavement and is influenced by the 3-D tire-pavement contact stresses under each tire rib. However, the tensile strain at the bottom of HMA is affected mainly by the total wheel load. The vertical shear strain is responsible for near-surface fatigue cracking as well as HMA primary rutting. Top-down cracking could result from the local vertical shear strain in the upper 25 mm of the HMA where the effect of tire-pavement tangential stresses are the highest. In addition, the study concluded that wide-base tires cause higher longitudinal tensile strain at the bottom of HMA and compressive strain at the top of subgrade, where those responses are highly affected by the total wheel load. However, wide-base tires were found to cause less vertical shear strains near the surface than dual-tire assembly loading regardless of HMA thicknesses.
Repeatability of Asphalt Strain Measurements under Full-Scale Dynamic Loading
Authors: Willis J. Richard , Timm David H.
Published: January 2009

Embedded instrumentation has become an important tool at accelerated load facilities as states begin implementing mechanistic-empirical pavement design and analysis methodologies. Instrumentation can provide valuable information to help validate mechanistic models and develop a deeper understanding of pavement response under a wide range of conditions. Before such investigations are conducted, however, it is critical to determine whether the response measurements are accurate and precise. Although both accuracy and precision are important, this investigation centers on establishing the practical level of between-gauge precision for asphalt strain measurements made at the National Center for Asphalt Technology Pavement Test Track. Eleven test sections, each containing six paired gauges, were included in this study. Absolute differences between paired strain readings were computed on a per-truck and per-axle basis during 8 months of testing that included approximately 80,000 strain readings. It was found that longitudinal strain was slightly less variable between gauges than transverse strain. Steer axles had the least differences in strain between gauges, followed by the tandem and trailing single axles. The condition of the pavement (i.e., extent of cracking) was found to be very important to the measured differences between gauges. Overall, 80% of strain readings with differences less than 30 μ∈ were set as a practical benchmark for the test track
Coefficient of Thermal Expansion of Concrete Materials
Authors: Tran Nam H. , Hall Kevin D. , James Mainey
Published: January 2009

The new Mechanistic-Empirical Pavement Design Guide (MEPDG) requires the coefficient of thermal expansion (CTE) of concrete materials as a direct input to determine critical pavement distresses. The CTE can be determined using AASHTO TP 60. For this study, a CTE measuring device in compliance with AASHTO TP 60 was acquired. Three replicate specimens were prepared for each of 24 concrete and cement paste mixtures and tested at 7 and 28 days. The range of CTE determined in this study was in agreement with the range of values reported by other studies, and the variability of test results was favorably comparable. Analysis of variance and sensitivity analyses were performed to evaluate the influence of mixture properties on the CTE and the effect on pavement performance predictions of using Level 1- and 3-CTE inputs. It was concluded that the type of coarse aggregate used in portland cement concrete (PCC) mixtures significantly influenced the CTE and pavement performance predictions. The proportion of coarse aggregates in the PCC mixture could significantly affect the CTE depending on the types of aggregates used in the mixture. In addition, recommendations for Level-3 CTE input can be used for PCC mixtures with limestones and sandstones. However, CTE recommendations for PCC mixtures with gravels were not available for comparisons. It is recommended that a future CTE testing program for supporting implementation of the MEPDG include primary local aggregate types and that CTE recommendations for Level-3 CTE input in the design software be updated to include more aggregate types, especially gravels.
Accuracy of Current Complex Modulus Selection Procedure from Vehicular Load Pulse
Authors: Al-Qadi Imad L. , Elseifi Mostafa A. , Yoo Pyeong Jun , Dessouky Samer H. , Gibson Nelson , Harman Tom , D'Angelo John , Petros Katherine
Published: January 2009

The Mechanistic-Empirical Pavement Design Guide (MEPDG) uses the complex modulus to simulate the time and temperature dependency of hot-mix asphalt (HMA). To account for the time dependency of HMA, MEPDG recommends calculation of the frequency of the applied load as a function of the vehicle speed and the pavement structure. By this approach, the Odemark method of thickness equivalency is first used to transform the pavement structure into a single-layer system, and it is then assumed that the stress distribution occurs at a constant slope of 45° in the equivalent pavement structure. Concerns were raised that the current MEPDG methodology may be overestimating the frequency, which would result in underconservative distress predictions. Therefore, to evaluate the MEPDG methodology for calculation of the loading time, the results of the MEPDG procedure were compared with those of an advanced three-dimensional (3-D) finite element (FE) approach that simulates the approaching-leaving rolling wheel at a specific speed. The model developed accurately simulated actual tire rib sizes and the applicable contact pressure for each rib. In addition, laboratory-measured viscoelastic properties were incorporated into the FE model to describe the constitutive behavior of HMA. Comparison of these two methods shows that the frequencies calculated on the basis of the MEPDG procedure are greater than the ones determined by the 3-D FE method, which indicates that the loading time determined from MEPDG is not conservative. Ultimately, this would result in underestimation of the pavement response to a load and, therefore, greater errors in calibrations of the pavement response to field distress. Correction factors are thus presented to ensure the correctness of the loading time calculation in MEPDG. Adoption of the proposed factors within the MEPDG software does necessitate a recalibration of the performance models.
Conversion of Testing Frequency to Loading Time Applied to the Mechanistic-Empirical Pavement Design Guide
Authors: Katicha Samer , Flintsch Gerardo W. , Loulizi Amara , Wang Linbing
Published: January 2009

This paper investigates the issue of converting testing frequency in a dynamic modulus test of hot-mix asphalt (HMA) to loading time for implementation in the proposed mechanistic-empirical pavement design guide. Two methods have been proposed in the literature. The first is to convert the test frequency (f; in hertz) to loading time (t; in seconds) by using t = 1/f. The second method is to convert the test angular frequency (to) to the loading time (in seconds) by using t = 1/ω = 1/2πf. An exact interconversion based on the representation of dynamic modulus results by using a generalized Kelvin model and a generalized Maxwell model is presented. The exact interconversion is compared with the two debated methods of converting the dynamic modulus or the storage modulus to a stiffness (inverse of creep compliance) and relaxation modulus. It is shown that both methods result in error in determining either the relaxation modulus or stiffness. On the other hand, it is shown that the resilient modulus can be adequately approximated by the dynamic modulus taken at a frequency of 1/t.
Integrating Equity Objectives in a Road Network Design Model
Authors: Santos Bruno , Antunes António , Miller Eric J.
Published: January 2009

The traditional approach to the road network design problem focuses on the optimization of network efficiency under a given budget. Generally, this leads to the improvement of roads next to the largest population centers, where travel demand is higher. Such results are not consistent with sustainable development principles, since the dissimilarities between the welfare of large and small centers will tend to increase. Nevertheless, equity issues were rarely taken into account in road network design. Moreover, all existing studies rely on a single equity measure. In this paper equity concerns in transportation planning are reviewed briefly, and a comparison of alternative equity measures is presented. Three equity measures were selected and incorporated into an accessibility-maximization road network design model. The three equity measures reflect different perspectives on equity: accessibility to low-accessibility centers, the dispersion of accessibility values across all centers (Gini coefficient), and the dispersion of accessibility values across all centers and across centers in the same region (Theil index). The implications of adopting each of these equity measures are illustrated through application of the optimization model to three random networks.
Equity and Efficiency Analysis of Pricing Strategies in a Bimodal Network with Heterogeneous User Groups
Authors: Wu Z. X. , Lam W. H. K. , Huang Hai-Jun
Published: January 2009

This paper investigates the equity and efficiency of pricing strategies in a bimodal transport network with elastic demand and heterogeneous users on the basis of logit-based discrete choice models. The network consists of a railway line and a parallel highway with a bottleneck that provide daily commuting services between a residential area and a workplace. On the basis of two user groups differing in values of time, first-best pricing is shown to remain possible through the use of anonymous charges under the stochastic user equilibrium condition. Second-best pricing is also examined, in which an equity constraint is introduced to ensure that some users, if not all, are at least not worse off from implementing the pricing at expectation level. The efficiency, equity, demand realization, and modal split resulting from various pricing strategies are investigated and numerically validated in a simplified real network connecting the Kowloon urban area to Hong Kong, China, International Airport. It was found that the equity-constrained second-best pricing can result in a win-win situation for society and users. The efficiency and welfare gains depend heavily on the values of time of user groups and the number of users in each group.
Incorporating Environmental Justice Measures into Equilibrium-Based Network Design
Authors: Duthie Jennifer , Waller S. Travis
Published: January 2009

A new variation of the user equilibrium-discrete network design problem (UE-DNDP) is proposed for achieving environmental justice (EJ) or equity among population groups. This research is motivated by the federal requirement that transportation plans using federal money include an evaluation of EJ and that the planning agency mitigate, where feasible, any disproportionate impacts on protected populations (i.e., minority and low-income groups). Eight potential objective functions focused on maximizing equity of congestion and travel time are developed and discussed with regard to their applicability for the upper level of this bilevel problem. On the basis of assumed knowledge of the origin-destination travel matrices by population group, numerical analysis is conducted to assess the performance of each proposed formulation. The lower-level UE problem is solved by using the Frank-Wolfe method, and because of the hard combinatorial nature of EJ-UE-DNDP, a selectorecombinative genetic algorithm is implemented to search the solution space for feasible network improvement strategies efficiently. The results of numerical analysis suggest that Pareto-optimal approaches can be successfully applied and that the most effective formulations minimize the difference between the change in congestion or travel time across population groups due to the selected improvement projects.
Solution Algorithm for Long-Haul Freight Network Design Using Shipper-Carrier Freight Flow Prediction with Explicit Capacity Constraints
Authors: Apivatanagul Pruttipong (Palm) , Regan Amelia C.
Published: January 2009

Freight transportation has long been recognized as an important foundation of economic strength. Previous studies used traditional methods such as cost-benefit analysis to examine a set of scenarios. However, because of the complexity of transportation projects that can have substitution or complementary effects in a network, more scenarios may result than can be examined on a case-by-case basis. To realize optimal network design, a branch and bound method is applied to examine all possible scenarios. The work described in this paper focuses on developing public infrastructure investment decisions to improve freight movements. A freight flow prediction model that focuses on the relationship between shippers, who select types of services, and carriers, who decide how to route vehicles, is used to represent freight route choice behaviors. In addition, explicit capacity constraints are used to divert traffic volume from congested links. The benefits and limitations of the method are discussed, its computational efficiency is examined, and a numerical example is provided. The results indicate that project selection by the traditional case-by-case analysis cannot capture the complexity of freight transportation network improvements and yields a suboptimal solution.
New Methodology for Optimizing Transit Priority at the Network Level
Authors: Mesbah Mahmoud , Sarvi Majid , Currie Graham
Published: January 2009

A new methodology for optimizing transit road space priority at the network level is proposed. Transit vehicles carry large numbers of passengers within congested road space efficiently. This aids justification of transit priority. Almost all studies that have investigated transit priority lanes focus at a link or an arterial road level, and no study has investigated road space allocation for priority from a network perspective. The aim of the proposed approach is to find the optimum combination of exclusive lanes in an existing operational transport network. Mode share is assumed variable, and an assignment is performed for both private and transit traffic. The problem is formulated by using bilevel programming, which minimizes the total travel time. The approach is applied to an example network and the results are discussed. The approach can identify the optimal combination of transit priority lanes and achieve the global optimum of the objective function. Areas for further development are discussed.
Optimizing Distance-Based Fares and Headway of an Intercity Transportation System with Elastic Demand and Trip Length Differentiation
Authors: Tsai Feng-Ming , Chien Steven I-Jy , Spasovic Lazar N.
Published: January 2009

An efficient fare structure combined with good service quality can stimulate demand and increase revenue. This paper presents an optimization approach for an intercity transportation system where demand is sensitive to fare and wait time and the fare sensitivity further varies with trip length. The approach jointly optimizes service headway and distance-based fare structure to maximize total profit, subject to service capacity and fleet size constraints. The optimal fares are also differentiated on the basis of trip length. An efficient solution method is developed and applied to solve the profit maximization problem. The model is applied to a case study of the Taiwan High-Speed Rail System. Numerical results, including optimal solutions and sensitivity analyses, are presented. Insights that may lead to managerial decisions are discussed.
The continued burden of spine fractures after motor vehicle crashes
Authors: Wang Marjorie C. , Pintar Frank , Yoganandan Narayan , Maiman Dennis J.
Published: January 2009

Object

Spine fractures are a significant cause of morbidity and mortality after motor vehicle crashes (MVCs). Public health interventions, such as the National Highway Traffic Safety Administration's Federal Motor Vehicle Safety Standards, have led to an increase in automobiles with air bags and the increased use of seat belts to lessen injuries sustained from MVCs. The purpose of this study was to evaluate secular trends in the occurrence of spine fractures associated with MVCs and evaluate the association between air bag and seat belt use with spine fractures.

Methods

Using the Crash Outcome Data Evaluation System, a database of the police reports of all MVCs in Wisconsin linked to hospital records, the authors studied the occurrence of spine fractures and seat belt and air bag use from 1994 to 2002. Demographic information and crash characteristics were obtained from the police reports. Injury characteristics were determined using International Classification of Disease, 9th Revision, Clinical Modification (ICD-9-CM) hospital discharge codes.

Results

From 1994 to 2002, there were 29,860 hospital admissions associated with automobile or truck crashes. There were 20,276 drivers or front-seat passengers 16 years of age and older who were not missing ICD-9-CM discharge codes, seat belt or air bag data, and who had not been ejected from the vehicle. Of these, 2530 (12.5%) sustained a spine fracture. The occurrence of spine fractures increased over the study period, and the use of a seat belt plus air bag, and of air bags alone also increased during this period. However, the occurrence of severe spine fractures (Abbreviated Injury Scale Score ≥3) did not significantly increase over the study period. The use of both seat belt and air bag was associated with decreased odds of a spine fracture. Use of an air bag alone was associated with increased odds of a severe thoracic, but not cervical spine fracture.

Conclusions

Among drivers and front-seat passengers admitted to the hospital after MVCs, the occurrence of spine fractures increased from 1994 to 2002 despite concomitant increases in seat belt and air bag use. However, the occurrence of severe spine fractures did not increase over the study period. The use of both seat belt and air bag is protective against spine fractures. Although the overall increased occurrence of spine fractures may appear contrary to the increased use of seat belts and air bags in general, it is possible that improved imaging technology may be associated with an increase in the diagnosis of relatively minor fractures. However, given the significant protective effects of both seat belt and air bag use against spine fractures, resources should continue to be dedicated toward increasing their use to mitigate the effects of MVCs.
Comparative Serological Responses and Protection Conferred by Vaccination with V4HR and BCRDV in Chickens
Authors: Kafi MA , Rahman MB , Amin MM , Islam MR , Rahman MM , Rahman MK
Published: January 2009

The serological responses and protection of Sonali breed chickens with Australian Newcastle disease V4 heat resistant (NDV4HR) live freeze-dried vaccine (Australian Webster Pvt. Ltd., Sydney) was compared with that of locally produced conventional Lentogenic F-strain Baby Chick Ranikhet Disease vaccine (BCRDV, DLS, Dhaka) of Bangladesh. Thirty day-old chicks were purchased from Mirpur Govt. Poultry Farm, Dhaka and maintained hygienically with commercial feed and water supply ad libitum during the experimental period from November 2002 to January 2003. These birds were divided into three groups (A, B and C), each consisting of 10 birds. Each birds of group A was vaccinated with NDV4HR and group B with BCRDV intraocularly, primary vaccination at 7 days and booster vaccination at 28 days of age, whereas the birds of group C kept as control. Sera samples of each of the bird of all the three groups were collected at 14 days of post-vaccination following each of the primary and booster vaccination at 23 and 44 days of age of birds. Each of the serum sample of all the three groups of birds was titrated by using haemagglutination inhibition (HI) test and results recorded that both the NDV4HR (32.49 Â± 23.94) and BCRDV (28.28 Â± 10.54) produced more or less similar serological response at two weeks after booster vaccination. The results of challenged experiment showed that the NDV4HR vaccine ( 80% ) apparently conferred higher protection to birds than the BCRDV vaccine (70%). Therefore both the vaccines may be recommended to control ND in commercial chickens but NDV4HR vaccine could provide a practical method of control ND in rural scavenging chickens. Key words: Serological responses, F-strain (BCRDV) NDV4HR vaccine, HI antibody titre, protection, chickens DOI = 10.3329/bjvm.v1i1.1913 Bangl. J. Vet. Med. ( 2003 ). 1 (1) : 25 - 27
Haemato-biochemical Changes and Antibiotic Sensitivity to Eschericia coli Associated with Concurrent Enteric and Septicaemic Infection in Calves
Authors: Samad MA , Islam MA , Hossain KA , Islam MT , Saha S
Published: January 2009

Concurrent enteric and septicaemic Escherichia coli infection was recorded in six local calves aged between 8 to 12 months old for the first time in Bangladesh during the period from May to June 2002. Bacteriologic examination of both the faecal and blood samples of six febrile calves showed positive for E. coli of all the six faecal (100%) and only two blood (33.33%) samples. Clinical examination revealed significantly (p < 0.01) high rectal temperature at peak febrile stage which varied from 103.5 to 106Â°F with a mean of 104.7 Â± 0.85Â°F. The fever associated signs and clinical anaemia were recorded in all these calves. Haematological examination showed significantly (p < 0.01) decreased haemoglobin (5.58 Â± 0.45 g%), packed cell volume (19.83 Â± 1.95 %), total erythrocytic count (3.52 Â± 0.58Â  106/ mm3) and total leukocytic count (6.68 Â± 0.44Â  103 / mm3) which indicates anaemia and leukopenia at the peak febrile stage of the disease. Biochemical studies showed significantly (p < 0.05) increased that serum magnesium and iron values were at fever stage, whereas serum phosphorus significantly (p < 0.01) decreased at the 4th day (convalescent stage) but no significant (p > 0.05) change was observed with the serum calcium, sodium, potassium and chloride values between prefever and fever stage. Antibiotic sensitivity pattern of E. coli isolated from faecal and blood samples revealed that these isolates were found to be resistant to penicillin, ampicillin and amoxycillin, moderately sensitive to gentamicin and streptomycin but highly sensitive to tetracycline. This indicates that tetracycline could be the drug of choice for both the septicaemic and enteric E. coli infection in calves. Key words: Haematobiochemical; Escherichia coli; enteric; septicemic; infection; calves DOI = 10.3329/bjvm.v1i1.1916 Bangl. J. Vet. Med.Â  (2003). 1(1) : 39 - 43
What is the Minimum EROI that a Sustainable Society Must Have?
Authors: Hall Charles  A. S. , Balogh Stephen , Murphy David  J.R.
Published: January 2009

Economic production and, more generally, most global societies, are overwhelmingly dependant upon depleting supplies of fossil fuels. There is considerable concern amongst resource scientists, if not most economists, as to whether market signals or cost benefit analysis based on today’s prices are sufficient to guide our decisions about our energy future. These suspicions and concerns were escalated during the oil price increase from 2005 – 2008 and the subsequent but probably related market collapse of 2008. We believe that Energy Return On Investment (EROI) analysis provides a useful approach for examining disadvantages and advantages of different fuels and also offers the possibility to look into the future in ways that markets seem unable to do. The goal of this paper is to review the application of EROI theory to both natural and economic realms, and to assess preliminarily the minimum EROI that a society must attain from its energy exploitation to support continued economic activity and social function. In doing so we calculate herein a basic first attempt at the minimum EROI for current society and some of the consequences when that minimum is approached. The theory of the minimum EROI discussed here, which describes the somewhat obvious but nonetheless important idea that for any being or system to survive or grow it must gain substantially more energy than it uses in obtaining that energy, may be especially important. Thus any particular being or system must abide by a “Law of Minimum EROI”, which we calculate for both oil and corn-based ethanol as about 3:1 at the mine-mouth/farm-gate. Since most biofuels have EROI’s of less than 3:1 they must be subsidized by fossil fuels to be useful.