bluuebunny/crossref_metadata_2025 huggingface dataset:
Costs and Benefits of Using Intelligent Transportation Systems as an Alternative Data Source: Case Study
Authors: Hu Pat S. , Goeltz Richard T. , Schmoyer Richard L.
Published: April 2007

Intelligent transportation systems (ITSs) are an alternative data source that could lead to win–win situations: this source will not only benefit the transportation operations and planning communities by allowing them to access more and better data, but it will also enhance the appeal of ITS deployment by significantly broadening its originally intended benefits. Use of ITS-generated data as an alternative data resource is reflected in the archived data user services (ADUS) in the national ITS architecture. Usually, an agency will evaluate the costs and the benefits of ADUS before it decides whether to deploy ADUS. The costs and benefits of ADUS are examined on the basis of results from a case study in which ITS-generated traffic data were analyzed to determine whether they can help meet such traffic data needs as estimating the total travel volume and the total vehicle miles traveled. The cost is measured in terms of the effort needed to archive and reformat the data, revamp the software, and address data quality and data integration issues. The benefits are measured in terms of the value added by the ITS-generated data. Although the costs are high to use ITS-generated data for purposes other than the originally intended use, the research has proved that ITS-generated data can improve transportation decisions by, in this case, improving traffic estimates.
Monte Carlo Simulation in Sampling Techniques of Traffic Data Collection
Authors: Williamson Derek G. , Yao Maosheng , McFadden John
Published: April 2007

Traffic volume counts are used in transportation planning, design, operation, and safety analyses. A new methodology establishes a statistical basis for comparing traffic volumes generated from different samples. Monte Carlo simulation was used to generate a cumulative probability function (CPF) of traffic volumes based on the fit-of-Weibull probability distribution to a particular traffic sample. A 90% confidence interval of the traffic volumes from a given traffic sample was obtained from the CPF and was used to compare different traffic samples. A case study was performed by using this methodology to determine if shorter time-frame data may be used to represent longer-time traffic. Results from the case study show that traffic at 20-min intervals may be used to represent 1-h traffic when moderate to high traffic volumes are considered. It was observed that subsamples failed to represent the 1-h traffic data for lower traffic volumes of selected vehicle types.
Measuring Variability in Traffic Conditions by Using Archived Traffic Data
Authors: Turochy Rod E. , Smith Brian L.
Published: April 2007

The predictability of transportation service is of great importance to travelers. Whereas most transportation performance measures deal more directly with congestion, such as through delay measures, few quantify the level of predictability of travel. A new measure that effectively measures predictability of transportation service, the variability index, was developed and demonstrated. The variability index is a good example of the application of data mining in large transportation databases. Conceptually based on multivariate statistical quality control (MSQC), the variability index is computed by measuring the size (spatial volume) of the confidence regions defined by MSQC by using large sets of archived traffic data. In other words, experience (archived traffic data) is mined to measure the level of variability experienced by time and location. A case study application of this procedure demonstrates how this measure can clearly identify times of day and days of the week that experience relatively high degrees of variability in traffic conditions—or less predictable service for the traveler.
Comparison of Distance Estimates for Commodity Flow Survey: Great Circle Distances Versus Network-Based Distances
Authors: Qureshi Mohammad A. , Hwang Ho-Ling , Chin Shih-Miao
Published: April 2007

A study was conducted to compare distance estimates derived from great circle distances (GCD) with distance estimates derived from a network-based model. The study used a sample of shipments from the 1993 commodity flow survey (CFS). For each shipment in the sample, the distance from the zip code of origin to the zip code of destination was calculated by using the Oak Ridge National Laboratories National Highway Network and assuming that the minimum impedance path was utilized. For each of these origin–destination pairs, the GCD and several variations of the GCD also were estimated. Finally, the network-based estimates and the GCD-based estimates were statistically compared. As expected, distance estimates based on GCD were found to be different from network-based estimates. However, applying a constant circuity factor of 1.22 or using variable circuity factors based on distance category did not result in a statistical bias in these distance estimates. Examination of distance estimates at the level of origin–destination pair revealed that distance estimates could vary as much as 75%. A comparison of published values for the 1997 CFS with values derived from GCD-based distance estimates shows that approximately 5% to 35% of the GCD-based values for the 1997 CFS would fall outside a two standard error interval. Although GCD-based estimates, under some conditions, may produce unbiased estimates of the mean distance, this does not eliminate the need for network-based estimates.
Prediction of Recreational Travel Using Genetically Designed Regression and Time-Delay Neural Network Models
Authors: Lingras Pawan , Sharma Satish , Zhong Ming
Published: April 2007

Selection of appropriate input variables is a crucial step in developing the statistical or neural network model for short-term traffic prediction. Recently, genetic algorithms have provided some success in input variable selection. Extensive experimentation with recreational traffic volume projections from Banff National Park in Alberta, Canada, is reported. Genetic algorithms (GAs) were used to select a set of historical traffic volumes that had higher correlation to the next hourly traffic volume. Universal models developed using GAs were accurate within 10%, on average. Separation of time series for individual hours revealed a linear trend in traffic volumes. Genetically designed regression submodels for individual hours had average prediction errors of less than 1% for the training sets. Even the 95th-percentile errors for the test sets were between 2% and 8%. Many highway agencies expect to deploy an advanced traveler information system (ATIS) for all highway categories. On the basis of such accurate predictions of traffic conditions from an ATIS, recreational drivers will be able to reschedule their travel time as well as routes. Such rescheduling will alleviate stress caused by traffic congestion during recreational travel.
Automobile Ownership Analysis Using Ordered Probit Models
Authors: Chu You-Lian
Published: April 2007

A mathematical model developed to predict automobile ownership for individual households residing in New York City is presented. This effort is distinguished from previous disaggregate household-level automobile ownership models primarily by the use of ordered probit models rather than the commonly used multinominal logit (MNL) and sequential logit (SL) models. When the dependent variable involves ordinal categorical data (in this case, automobile ownership level—zero automobiles, one automobile, two automobiles, and three or more automobiles), the ordered probit model will discern unequal differences between ordinal categories in the dependent variable, the MNL model will treat categories as independent choice alternatives, and the SL model (a product of binary logits) will assume independence of the error terms across all binary choices. The modeling approach was based on a behavioral analysis that explained the factors influencing household automobile ownership decisions in a highly urbanized environment. In addition to socioeconomic variables, transportation and land use–related measures were developed and used to test the sensitivity of household automobile ownership choice to transit accessibility, traffic congestion, parking cost and availability, and levels of access to opportunity sites through nonmotorized transportation. The estimation results uncover important interactions between socioeconomic- and location-related elements and automobile ownership. Findings provide exploratory methodological and empirical evidence that could lead to an approach to predicting the change in household automobile ownership as a result of changes in future socioeconomic conditions and transportation and land use scenarios.
Flexible Modeling Strategies for Assessing the Influence of Transportation on Accessibility
Authors: Vadali Sharada R.
Published: April 2007

Despite advances in statistical modeling and estimation, policy modeling and infrastructure impact assessments in the transportation area are almost always conducted by assuming linearity. The focus is on the assessment of location premiums associated with accessibility variables that are key policy variables, estimated via hedonic methods. These variables are invaluable for assessing effects of transportation projects on nearby land uses. Most hedonic studies hypothesize a parametric functional relation between accessibility and the dependent variable in estimating premiums. Unfortunately, common parametric approaches cannot control for functional form misspecification of individual variables. That line of research is extended to investigate and explore these issues with a flexible modeling strategy using a cross-section sample of housing sales. The analysis indicates the presence of significant nonlinearities that have implications for impact assessment approaches and for the assessment of accessibility influences on price premiums. The methods suggested can be extended to other areas as well, areas in which theory does not provide any a priori bounds on behavior of variables included in an analysis.
Temperature Correction of Multiload-Level Falling Weight Deflectometer Deflections
Authors: Mun Park Hee , Kim Y. Richard , Park Sunwoo
Published: April 2007

A new temperature correction procedure was developed for multiload-level falling weight deflectometer (FWD) deflections for flexible pavements in North Carolina. In this procedure, temperature correction factors were dependent on the radial offset distance from the FWD load plate. Temperature and FWD multiload-level deflection data used in developing this procedure were collected from 11 pavements in three different climatic regions of North Carolina. The effect of the FWD load level on this temperature correction procedure was investigated. Research efforts focused on improving the accuracy of the current temperature correction procedure of the North Carolina Department of Transportation. The measured deflection and temperature data were also used to validate the long-term pavement performance (LTPP) temperature correction procedure. It was found that the effective pavement temperature prediction algorithm in the LTPP procedure is relatively accurate and that the temperature-deflection correction procedure undercorrects the deflections at higher temperatures in pavements with an asphalt concrete layer thicker than 242 mm. The main reason for this deficiency is that the LTPP procedure was developed from the national database and cannot fully consider the local variation in mixture characteristics.
Pavement Response to Dual Tires and New Wide-Base Tires at Same Tire Pressure
Authors: Al-Qadi Imad L. , Loulizi Amara , Janajreh Ibrahim , Freeman Thomas E.
Published: April 2007

Although concern was raised about the introduction of radial tires due to their higher inflation pressure compared with that of bias tires, radial tires have been proven to reduce the strain at the bottom of the hot-mix asphalt (HMA) layer. However, conventional wide-base single tires have been shown to be more damaging to pavement than dual tires. The damage mainly depends on the tire tread width and inflation pressure. It has been suggested that wide-base tires may produce damage equivalent to that of dual tires if the maximum load per tire is limited to 11.6 kg/mm of tire tread width. Recent advances in tire design and material have led to the design of a new wide-base tire that is wider and flatter in the crown area to provide a uniform contact stress distribution. It operates at an inflation pressure of 690 kPa for 151-kN tandem axle load. An experimental program studied the effects of the newly developed wide-base tire on a flexible pavement section at the Virginia Smart Road under different loading and environmental conditions. Testing results have shown that the newly developed wide-base tires induce approximately the same horizontal tensile strains under the HMA layer as do equivalent dual tires. Hence, the fatigue damage expected from these newly developed wide-base tires is the same as that produced by dual tires. However, the vertical compressive stresses induced by the wide-base tire are greater on the upper HMA layers of the pavement. The difference in stresses diminishes with depth and becomes negligible at the bottom of the subbase layer.
Ride Quality Assessment with Pavement Profiling Devices
Authors: El-Korchi Tahar , Bacon Jason , Turo Matthew , Ecmecian Michael
Published: April 2007

In its pursuit for providing smooth pavements, the Massachusetts Highway Department (MHD) is developing and implementing ride quality specifications as part of its construction quality assurance program. To achieve its goal, MHD, in cooperation with FHWA, sponsored a research project to identify suitable profiling devices with adequate precision and bias for implementing construction quality assurance specifications. The purpose was to evaluate precision and bias of profiling devices based on ASTM E950-94. In 1999, the study was conducted, wherein 16 profiling devices, including high-speed, lightweight, and walking profiling devices, performed 10 repeat runs on eight sites each. Analysis of precision (repeatability) with the international roughness index (IRI) shows that approximately 75% of all tests have an average standard deviation in IRI units below 0.05 mm/m (3 in./mi). The high-speed devices produce better results compared to the lightweight profilers with almost 90% of all tests producing a standard deviation below 0.05 mm/m (3 in./mi) IRI units. Analysis of bias (profiling device, Walking Profiler) with the IRI statistic shows that for all devices, 80% of the left wheelpath tests fall below a bias range of ±0.09 mm/m (6 in./mi) IRI units. Profile analysis and profile lead-in effect were also determined.
Patricia: Predicting Activity-Travel Interdependencies with a Suite of Choice-Based, Interlinked Analyses
Authors: Borgers Aloys , Timmermans Harry , van der Waerden Peter
Published: April 2007

The development and performance of Patricia, a suite of (choice) models that can be used to analyze and predict activity-travel patterns, is reported. This suite of models, which differs from similar sequential utility-maximizing models of activity-travel patterns in that it incorporates a larger number of choice facets and choice options, was sequentially estimated with activity-travel data collected in the region of South Rotterdam, the Netherlands. The results of the estimation are satisfactory at the level of aggregated origin-destination matrices and individual activity patterns.
Factors Affecting Determination of Subgrade Water Content from Multisegment Time Domain Reflectometry Probes
Authors: Zuo Gang , Wright Wesley C. , Rainwater N. Randy , Drumm Eric C. , Yoder Ronald E.
Published: April 2007

Multisegment time domain reflectometry (TDR) probes are an attractive alternative to single-segment probes when used for the in situ measurement of water content changes in pavement systems. Because several independent measurements are made along the length of the multi-segment probe, these instruments offer several advantages over the more traditional TDR probes. These include the ability to obtain measurements over a greater volume of soil, the ability to install the probe into relatively undisturbed soils, and the redundancy provided by multiple measurements from the same instrument. However, because of the difference in signal strength along the probe, all segments do not provide the same level of accuracy. Several factors that must be considered when using these probes are discussed, including the sources of measurement error and the temperature dependence of the measurements in some segments. A method is described by which the results from lower accuracy segments can be used when higher accuracy segments fail during service, taking advantage of the redundancy provided by multisegment probes. The method is demonstrated on data from a site from which over 4 years of continuous water content measurements have been obtained.
Performance of Lime Cement-Stabilized Soils for the I-15 Reconstruction Project: Salt Lake City, Utah
Authors: Bartlett Steven , Farnsworth Clifton
Published: April 2007

The application and performance monitoring of lime cement stabilization were studied for the Interstate-15 Reconstruction Project at 300 West Street in Salt Lake City, Utah. Lime cement columns (LCCs) were used to support a large mechanically stabilized earth (MSE) wall constructed over soft foundation soils and in close proximity to a commercial building. The Utah Department of Transportation has installed instrumentation at this site to measure the construction and postconstruction deformation within the treated zone and around the adjacent building. Also, total pressure cells have been installed atop the treated zone and in an adjacent untreated area to measure differences in load transfer. The use of LCC-stabilized soil has reduced the amount of primary settlement from about 1 m without treatment to about 0.2 m in the treated zone. Ground settlement at the nearest wall of the adjacent building has been about 5 cm total during a 2.5-year monitoring period with 3 of the 5 cm occurring during MSE wall construction and surcharge placement. Also, measurements indicate that the global stability of the MSE wall foundation has been notably improved. It is hoped that the data gathered from this array will provide a valuable case history of LCC performance for evaluation and modeling.
Durability of Recycled Fiber-Reinforced Polymer Piling in Aggressive Environments
Authors: Iskander Magued , Mohamed Ahmed , Hassan Moataz
Published: April 2007

Fiber-reinforced polymer (FRP) composites represent an alternative construction material without many of the performance disadvantages of traditional materials. The use of FRP as a pile material can eliminate deterioration problems of conventional piling materials in waterfront environments and aggressive soils. A 1-year experimental study was conducted to assess the durability of piling made of recycled plastics in aggressive soils for long-term usage in civil infrastructure applications. An accelerated testing protocol permitting prediction of the behavior of plastic piles was developed. Specimens were exposed to solutions with fixed acidic, basic, and neutral pH at elevated temperatures. Compressive strength was used as an index to quantify the degradation of the specimens. An Arrhenius model was used to predict the service life of the product. An estimated 25% loss in strength at 10% strain is projected to take 21 years for coupon specimens incubated at a pH of 2 and 25 years for coupon specimens incubated at a pH of 12.
Deflection-Based Analysis Techniques for Jointed Concrete Pavement Systems
Authors: Crovetti James A.
Published: April 2007

Techniques are presented that are based on the dense-liquid foundation model for analyzing deflection data obtained at center slab, slab edge, and slab corner positions to provide indications of the quality and uniformity of support beneath jointed concrete slabs. Deflections obtained at central slab positions are used to quantify a baseline foundation k-value for each slab tested. Edge and corner deflection data are used to establish the foundation edge and corner k-values of each slab. Adjustments for slab size and temperature curling during testing are discussed. Slab support ratios are determined on a slab-by-slab basis using the ratio of edge and corner k-values to center-of-slab k-values, ke/ki, and ke/ki. When nonuniform support exists, the foundation support ratio will typically be less than 0.75. Example and field results are provided to illustrate the analysis techniques and the interpretations necessary to distinguish between poor support due to slab curling or foundation voids.
Transverse Joint Analysis for Mechanistic-Empirical Design of Rigid Pavements
Authors: Hiller Jacob E. , Roesler Jeffery R.
Published: April 2007

With the further adoption of mechanistic-empirical design methods in the pavement industry, the calculation of critical responses and cumulative damage for a variety of parameters will be imperative. Traditionally, the critical tensile stress developed by loads at the midslab edge has been used as a mechanistic parameter to determine the required thickness in jointed concrete pavements. However, the inclusion of both temperature and shrinkage gradients in concrete pavement analysis can drastically alter the critical stress location and subsequent distress type that predicts pavement performance. Longitudinal and corner cracking have been found in California to be distresses as significant as transverse cracking. Most of the longitudinal and corner cracking can be explained by excessive differential drying shrinkage. Using finite-element analysis, this study compared the critical tensile stress near the transverse joint with the critical tensile stress at the midslab edge (relative reference stress) for California-type jointed plain concrete pavements. The analysis of the data showed that transverse joint loads were more significant in critical stress calculations for a considerable number of input parameters. These loads at the transverse joint can manifest themselves as top-down or bottom-up longitudinal, transverse, or corner fatigue cracks unlike the bottom-up transverse cracks traditionally predicted by midslab edge loads. The likelihood of critical slab stresses near the transverse joint was considerably increased with the use of negative temperature gradients and extended lane widths.
Crack Resistance of Jointed Plain Concrete Pavements
Authors: Jensen Elin A. , Hansen Will
Published: April 2007

The crack sensitivity of jointed plain concrete pavement is investigated experimentally in the laboratory for a limited number (seven) of large-scale slabs and numerically as well using nonlinear fracture mechanics. The basis for modeling is the concrete crack-width relation and the elastic modulus. The stress-crack width relations for the concrete were obtained on the concretes tested in the laboratory. The slab dimensions in the experimental and numerical analysis were 1.8 m wide and 3.0 m long, and a full-depth cross section (250 mm) containing a full-width surface crack extending 20% to 25% of the slab thickness was used. The major findings are that the numerical analysis verifies that the results from laboratory testing resemble field fracture behavior. Further, irrespective of the aggregates used, a concrete pavement is highly crack sensitive, although the coarse aggregate can affect the sensitivity by approximately 30%. The experimental and numerical results showed that a crack-to-slab-thickness ratio of 20% to 25% reduced the in-plane tensile capacity of the cracked section by 60% to 75% depending on the concrete used.
Determining Amount of Built-in Curling in Jointed Plain Concrete Pavement: Case Study of Pennsylvania 1-80
Authors: Beckemeyer Curt , Khazanovich Lev , Thomas Yu H.
Published: April 2007

During the late 1980s and 1990s, the Pennsylvania Department of Transportation constructed numerous miles of its new drained jointed plain concrete pavement (JPCP) design. Portions of the JPCP were built in reconstruction efforts, and some of the JPCP was placed as an overlay on rubblized sections of old jointed reinforced concrete pavement. The performance of the new JPCP has been quite variable; in some instances, it has performed very well, and in others some slab cracking and joint-related concerns have occurred. Two different base types were used beneath the JPCP: an untreated open-graded granular material (OGS) and an asphalt-treated permeable base. In general, the cracking has occurred only in the sections with the untreated OGS base layer. The cracking was top-down, transverse cracking that is generally located near midslab. A comprehensive study of the cracking was performed to identify its probable cause and to develop a repair (or preventive repair) technique. The results of this study showed that the top-down cracking was caused by a combination of excessive upward slab curling, loss of slab support (slab lift-off), and repeated heavy-truck loadings. The built-in slab curling was also found to be a major contributor to the observed top-down cracking. One of the keys to the analysis effort was quantifying the amount of built-in curling in the slabs; the techniques are described that the research team used to determine the amount of built-in curling in the in-place JPCP slabs.
WesTrack Fatigue Performance Prediction Using Miner’s Law
Authors: Tsai Bor-Wen , Harvey John T. , Monismith Carl L.
Published: April 2007

The objectives of this paper are to present an approach using statistical analysis and Miner’s law to predict the fatigue performance (crack initiation) of the WesTrack test sections. A strain function, calculated by a layered-elastic program, was statistically determined in terms of temperature at the bottom of the asphalt layer, temperature gradient, subgrade modulus, air-void content, and asphalt content. With integration of laboratory fatigue test results, strain calculation, and Miner’s law, the methodology produces the output in terms of cumulative fatigue damage versus cumulative repetitions for both wander and no-wander cases. Lack of consideration of nonlinear stiffness deterioration of asphalt concrete, crack propagation, and an appropriate correction factor makes long-term fatigue performance prediction conservative and not fully compliant with the condition survey data from WesTrack. The simulation indicated that the WesTrack coarse mixes took longer to initiate fatigue cracks than the fine and fine-plus mixes did but may propagate cracks faster in cold weather.
Testing and Performance Evaluation of Ultrathin Whitetopping Pavements at Spirit of St. Louis Airport
Authors: Wu Chung-Lung , Sheehan Matthew J.
Published: April 2007

To obtain a better understanding of ultrathin whitetopping (UTW) pavement behavior under traffic loading and environmental effects and to collect data for calibration and development of a mechanistic design procedure, a UTW test pavement was constructed, instrumented, and load tested. The UTW pavement test section is located at the Spirit of St. Louis Airport, a general aviation airport in Chesterfield, Missouri, and is designed to carry a light aircraft load of 56 kN. The results of analyses conducted on this test pavement and its performance to date are described. The UTW test section was constructed in February 1995 and consisted of six slabs with dimensions of 1.3 × 1.3 m and a design slab thickness of 89 mm. The load testing was conducted in May and September 1995. Load-induced strains, temperature distribution, and surface profiles were measured at different locations and at different times. Pavement core samples were also taken and subjected to laboratory testing. It was observed from the evaluation that ( a) there was very little vertical slab movement in spite of the temperature differential in the slabs, ( b) there was no apparent change in load-induced strains (stresses) with temperature changes, ( c) pavement exhibited high load transfer efficiencies across contraction joints, and ( d) an interface shear strength of 689 kPa was achieved by the commonly used technique for asphalt surface preparation, milling and cleaning. A recent performance review of this pavement also showed that it has performed extremely well after over 6 years in service. Of the 11620 m2 of UTW pavements (about 72,000 UTW panels), only 18 panels have cracked.
Measuring and Defining Fatigue Behavior of Asphalt Binders
Authors: Bonnetti Karen S. , Nam Kitae , Bahia Hussain U.
Published: April 2007

Fatigue damage is a distress mechanism observed in asphalt, particularly at moderate to low temperatures. Preliminary studies have shown that unmodified asphalts are sensitive to fatigue and that the use of modifiers in asphalt binders can dramatically improve the binder’s response to fatigue. One of the major challenges encountered has been the lack of a definition of fatigue failure consistent with the actual performance of the material regardless of testing conditions. Superpave® asphalt binder specification has improved the evaluation of modified and neat asphalts, but the definition of failure for fatigue damage is still unclear. A selected set of unmodified and modified binders was chosen and tested under a range of loading modes, stress or strain amplitudes, temperatures, and frequencies. The fatigue data were analyzed using the dissipated energy ratio concept. Np, the number of cycles to crack propagation, was used as the fatigue criterion for the analysis. Using the initial dissipated energy per cycle ( Wi) as the main independent variable for modeling fatigue of binders appears to be a promising technique to normalize some of the testing conditions. The parameter Np20, defined as the number of cycles at which the dissipated energy ratio shows 20% deviation from the no-damage ratio, appears to be a promising parameter to define failure. Using Np20 values, all modification methods used showed improvement in the fatigue behavior of unmodified asphalts. The level of improvement, however, was highly dependent on the modifier type and the testing conditions. Initial dissipated energy, testing frequency, and temperature were found to be important factors. If damage parameters are used in future specifications of binders, testing frequency and testing stress or strain levels should be carefully selected to represent pavement structural conditions and traffic speed.
Dynamic Signal Coordination for Networks with Oversaturated Intersections
Authors: Girianna Montty , Benekohal Rahim F.
Published: April 2007

An algorithm to design signal coordination for networks with oversaturated intersections is presented. The basic concept of signal coordination applied to oversaturated single arterials is extended for a grid network of arterials, which involves greater analytical and computing complexity. In this algorithm, signal coordination is formulated as a dynamic optimization problem. The problem is developed to coordinate oversaturated signals along an arterial that crosses multiple, parallel coordinated arterials. Signals along crossing arterials are also oversaturated. During an oversaturated period, the algorithm manages local queues by spatially distributing them over a number of signalized intersections and by temporarily spreading them over signal cycles. Depending on the traffic demand’s variation and the position of critical signals, the algorithm intelligently generates optimal signal timing (green times and offsets) along individual arterials. If critical signals are located at the exit points, the algorithm sets the optimal signal timing that protects them from becoming excessively loaded. If critical signals are located at the entry points, the algorithm ensures that queues are reduced or cleared before released platoons arrive at a downstream signal system. In addition, the algorithm eventually finds a set of common cycles propagated from upstream signals, thus promoting traffic progression. The micro-genetic algorithm was used to solve the signal optimization problem. The algorithm was tested on a one-way arterial system with 20 signals. The results indicate that the algorithm successfully managed queues along coordinated arterials, made the signals share the burden of traffic, and created the opportunity for traffic progression in specified directions.
Program for Optimizing Diamond Interchanges in Oversaturated Conditions
Authors: Kovvali Vijay G. , Messer Carroll J. , Chaudhary Nadeem A. , Chu Chi-Leung
Published: April 2007

Traditionally, optimization of diamond interchange timings has been done with PASSER III for standard and special diamond phasing sequences. PASSER III is limited because it is designed for undersaturated conditions. It applies vertical stacking of queues and is not capable of modeling queue spillback conditions in its current form. This deficiency is addressed by the arterial signal coordination software (ASCS), whose capabilities in timing diamond interchanges in under-saturated and oversaturated conditions are presented here. ASCS consists of three modules: ( a) input module, a user interface through which volume and geometry inputs can be provided to the program; ( b) optimization module, a genetic algorithm-based optimization routine that can optimize signal timings; and ( c) analysis module, which consists of a bandwidth analysis routine and a delay analysis routine (DAR). The DAR is a mesoscopic simulator that applies a second-by-second analysis of flows for modeling flows accurately. DAR applies horizontal stacking of queues and shock wave analysis to estimate the performance of traffic operations. Validation of ASCS for oversaturated arterial links against PASSER III and CORSIM was conducted. The results indicate that delay and throughput estimation in ASCS are realistic. The genetic algorithm-based optimization routine in ASCS was applied to estimate diamond interchange timings for three scenarios. Where queue spillback occurred, ASCS clearly outperformed PASSER III. ASCS produced near-optimal results for all scenarios studied.
Toll Rates and Related Factors on China’s Highways
Authors: Jia Yuan-Hua , Tian Zong Z.
Published: April 2007

Toll rates and traffic volumes (or demand) are the two major factors affecting revenue as well as investment strategies on toll roads. Although China has been experiencing dramatic growth in its highway systems during the past 10 years, there has been a lack of understanding in maintaining and operating its toll roads. Since most of the freeways in China are toll roads, it is necessary to establish a methodology for the toll road system based on the characteristics of China’s transportation systems and social economy. A methodology to determine the toll rates for China’s toll road systems is introduced. Factors affecting the toll rate are analyzed, including gross domestic product, total number of vehicles, growth rates of passenger and freight transport, and roadway conditions. The theory of elasticity is applied in a case study to investigate the effect of toll rate on traffic volumes. A critical-volume model is established on the basis of the analyses of various factors such as construction costs, operating costs, expected time of return, and internal rate of return.
Multipurpose Asset Valuation for Civil Infrastructure: Aligning Valuation Approaches with Asset Management Objectives and Stakeholder Interests
Authors: Amekudzi Adjo , Herabat Pannapa , Wang Shuchun , Lancaster Creighton
Published: April 2007

Valuation is a critical component of asset management for civil infrastructure because it provides a means for evaluating facilities whose value is to be preserved or enhanced. Although the basic concept of valuation is generic, there are various quantitative approaches for valuing assets. These approaches can be classified to provide guidance for selecting the right valuation approach to accomplish different asset management objectives. Various approaches are examined for valuing assets in transportation corridor, financial, and corporate real estate asset management from the viewpoint of the purpose of valuation. How different valuation approaches support different purposes is shown, and the importance of selecting appropriate valuation methods to achieve different objectives is discussed. On this basis, some of the critical issues are identified for developing useful valuation classification frameworks to relate valuation approaches with an agency’s asset management objectives and the scope and emphases of stakeholder interests. Building on the purposes of valuation associated with the Governmental Accounting Standards Board Statement 34 requirements, a prototype framework is developed for classifying valuation approaches, and emerging opportunities to expand the scope of valuation tools for multipurpose infrastructure valuation are discussed. The results should be useful to agency staff interested in understanding how various valuation tools can help them to accomplish different asset management objectives as they upgrade their infrastructure management systems to asset management systems.
Determining Air Void Content of Compacted Hot-Mix Asphalt Mixtures
Authors: Crouch L. K. , Copeland Audrey R. , Todd Walker C. , Maxwell Richard A. , Duncan Gregory M. , Goodwin William A. , Badoe Daniel A. , Wayne Leimer H.
Published: April 2007

A project to develop a new method or adapt a current method with wide applicability for determining bulk specific gravity of compacted hot-mix asphalt (HMA) mixtures ( Gmb) is described. A more reliable Gmb would result in more reliable HMA volumetric properties, specifically, percent air voids. Consequently, pavement distress types such as rutting, bleeding, stripping, and age hardening (whose occurrence is related to percent air voids, among other factors) could be avoided more often. The project goal was accomplished in three steps. In Step 1, a literature review and survey of state departments of transportation revealed 13 existing Gmb determination techniques. In Step 2, a feasibility study of the seven methods selected was conducted to evaluate cost, logistical factors, and preliminary repeatability. In the final step, 50 compacted HMA samples and four aluminum cylinders were used to evaluate the precision and accuracy of the four methods selected. The dimensional analysis (AASHTO T269) and the parafilm (ASTM D1188) methods were found to form upper bounds for true sample air voids, whereas the saturated surface-dry method (AASHTO T166) was found to form a lower bound for true air voids. Although the true air voids can never be determined, for 90% of Tennessee Department of Transportation sample groups tested, the InstroTek Corelok method yielded results in this range between the upper and lower bounds for accurate air void results. In the precision and accuracy evaluation, all four methods were found to be capable of producing high-precision results.
Evaluation of High-Speed Profilers for Measurement of Asphalt Pavement Smoothness in Florida
Authors: Choubane Bouzid , McNamara Ronald L. , Page Gale C.
Published: April 2007

The Florida Department of Transportation initiated a field study to assess the feasibility and appropriateness of implementing the use of laser-based high-speed profilers to automate its process of determination of ride acceptance. If a high-speed profiler is to be considered for determination of ride acceptance, it is essential that its level of accuracy and precision be assessed. For such a purpose, profile measurements were acquired by using five profilers concurrently on a large number of asphalt pavement sections. Also, to evaluate the effects of surface texture on these measurements, the test sections were randomly selected to include both open-and dense-graded surface mixtures. The profile data collected were first analyzed to determine the profile indices in terms of the ride number and the international roughness index at each test site. The results were then used as a basis for an evaluation of the repeatability and reproducibility of the profiling units. In addition, the effects of a profiler operating speed gradient as well as those of the pavement surface texture on roughness measurements were assessed.
Detecting Segregation in Bituminous Pavements
Authors: Chang Chieh-Min , Baladi Gilbert Y. , Wolff Thomas F.
Published: April 2007

Field and laboratory studies were conducted to determine the feasibility of detecting and quantifying segregation in hot-mix asphalt pavements. The study involved extensive testing at 19 field sites in Michigan. Areas of apparent segregation were classified as light, medium, and heavy. At the selected sampling areas, 1-min nuclear density measurements were made, cores were taken and incinerated, asphalt contents and air voids were determined, and gradation tests were performed. Statistical comparisons were made by using t-tests to characterize the differences between the measured nuclear density and percent passing various sieves. More than 80% of the nuclear density measurements supported the visual observations of a heavy degree of segregation when the significance of the differences (the p-value) between the areas compared was less than 10-3. Moreover, for areas with medium or heavy segregation, the probability that significant differences in nuclear density between segregated and nonsegregated areas with p-values less than 10-3 corresponded to significant differences ( p-values less than 10-2) in aggregate gradation was .88. On the basis of the results, a spreadsheet, mbitseg2, was developed to perform statistical tests with the nuclear density measurements obtained during the paving operation. After 6 months of trial testing, the program has been accepted and implemented by the Michigan Department of Transportation, the Michigan Asphalt Paving Association, and the asphalt industry. The program is available on a web page (http://www.egr.msu.edu/prce) in Excel (mbitseg2.xls) and QuattroPro (mbitseg2.wb3) formats.
Precision Statements for Ignition Oven for Use with Plant-Produced Mixtures
Authors: Sholar Gregory A. , Page Gale C. , Musselman James A.
Published: April 2007

The current precision values given in Florida Method FM 5-563 for the determination of asphalt binder content by use of the ignition oven are based on laboratory-fabricated specimens with known binder contents and gradations. A study was conducted to determine precision values for both asphalt binder content and gradation for use with plant-produced mixtures. This approach would encompass the variability associated with ( a) differences in an asphalt mixture within the truck bed, ( b) collection of samples from the truck, ( c) splitting of the mixture into samples for testing, ( d) differences in ignition oven equipment, and ( e) the operator. The current precision values include only the variability associated with the last two items and the variability associated with batching and mixing of laboratory-prepared specimens. Twelve laboratories tested nine different mixtures containing a wide variety of gradations and aggregate types. The results of the study indicate that the allowable difference between two test results for asphalt binder content should be no greater than 0.32% within a laboratory and 0.44% between laboratories. New graphs were developed for the within-laboratory and between-laboratory precision values for aggregate gradation. Separate graphs were developed for dense-graded Superpave® mixtures and open-graded friction course mixtures, as it was determined that allowable tolerances differ significantly for each type of mixture.
Mathematical Modeling of Pavement Smoothness
Authors: Weed Richard M.
Published: April 2007

The vast majority of states, as well as many local agencies, now use statistical end-result specifications to encourage high-quality construction by awarding payment in proportion to the level of quality received. Because many of the specification procedures were developed by intuition and guesswork, more recent efforts have been directed at converting the specifications to true performance-related specifications, thus providing a rational and defensible basis for price-adjustment decisions. To develop practical and effective specifications of this type, it is necessary to have at least approximate quantitative (mathematical) models of the manner in which construction quality affects performance. By using pavement smoothness as an example, a method is presented by which empirical performance data can be combined with logical assumptions about mathematical form and boundary conditions to develop quantitative models sufficiently accurate for use with statistical construction specifications.
Construction of Fiber-Reinforced Plastic Modular Decks for Highway Bridges
Authors: Shekar Vimala , Petro Samer H. , GangaRao Hota V. S.
Published: April 2007

Fiber-reinforced polymer (FRP) composite materials have shown great potential as alternative bridge construction materials to conventional materials such as steel and concrete. This is especially valid in the field of repair and rehabilitation of existing bridges as well as in new bridge construction. The acceptance of composites in the highway bridge industry is mainly due to their superior properties such as high strength, durability, corrosion resistance, and fatigue resistance. Moreover, FRPs are well suited for mass production of structural shapes because of their high strength-to-weight ratios, which has resulted in the rapid installation of FRP modular decks on highway bridges. Details related to the construction of FRP modular decks as replacements on existing highway bridge superstructures are provided. In addition, details on shipping, handling, erection, assembly, deck-to-deck connections, deck-to-stringer connections, joints, and wearing surfaces are discussed.
Static Measurement of Beam Deformations via Close-Range Photogrammetry
Authors: Jáuregui David V. , White Kenneth R. , Woodward Clinton B. , Leitch Kenneth R.
Published: April 2007

Preliminary results from a pilot study of beam deformation measurement using digital close-range terrestrial photogrammetry (DCRTP) are reported. The study consisted of both a laboratory and a field exercise. In the laboratory exercise, photogrammetric deflection measurements of a steel beam under single-point loading were made and compared with dial gauge readings and elastic beam theory. Laboratory results showed an accuracy ranging from 0.51 to 1.3 mm (0.02 to 0.05 in.). It was shown that DCRTP provides a feasible way of evaluating the global deflected shape of a structure, which is otherwise not practical using traditional instruments. In the field exercise, the initial camber and dead-load deflection of prestressed concrete bridge girders were measured photogrammetrically and compared with level rod and total station readings. Field results fit well to the rod-measured girder camber, and an average difference of approximately 3.2 mm (0.13 in.) was achieved compared with elevation measurements made with the total station. A comparison of the photogrammetric measurements with the dead-load deflection diagram was also made. Work is in progress to improve the accuracy of photogrammetric measurements for field applications. It is anticipated that DCRTP will provide highway agencies with a cost-effective alternative to high-cost systems using metric cameras or laser technology with the potential for several types of measurements in bridge applications.