bluuebunny/crossref_metadata_2025 huggingface dataset:
Reinduction of Albatross Decision Rules with Pooled Activity-Travel Diary Data and an Extended Set of Land Use and Cost-Related Condition States
Authors: Arentze Theo , Hofman Frank , Timmermans Harry
Published: April 2007

Operationalization of the Albatross model—a rule-based model of activity-travel scheduling—is described for applications on a national scale. For this purpose, the original model was extended to include the generation of schedule skeletons and travel cost variables. Furthermore, to account for the increase of scale of the study area, the location decision component of the model was completely restructured. The complete set of 27 decision trees involved in the decision process model were newly induced from several pooled existing activity diary data sets in the Netherlands. The results indicate that the goodness of fit of the model is satisfactory at the level of individual decisions as well as aggregate distributions.
Effect of Mineral Fillers on Fatigue Resistance and Fundamental Material Characteristics: Mechanistic Evaluation
Authors: Kim Yong-Rak , Little Dallas N. , Song Injun
Published: April 2007

Complex characteristics of fatigue behavior were evaluated on the basis of test results and their mechanical analyses. The dynamic shear rheometer was used to characterize fundamental linear viscoelastic properties of asphalt binders and mastics. Various dynamic mechanical tests using cylindrical sand–asphalt samples mixed with pure binders, mastics, or both were also performed to estimate viscoelastic characteristics and fatigue behavior. To assess the filler effect, two distinctly compositionally different asphalt binders, AAD-1 and AAM-1, and two fillers, limestone and hydrated lime, were selected. Test results were analyzed using viscoelastic theory, a fatigue prediction model based on continuum damage mechanics, and a rheological composite model. The role of fillers in fatigue resistance was quantified, and induced mechanisms due to filler addition were investigated. The effect of hydrated lime, which is highly binder specific, as a filler was further discussed by comparing test results from hydrated lime filler and test results from limestone filler.
Evaluation of Moisture Susceptibility of Asphalt Mixtures Containing Bottom Ash
Authors: Zeng Menglan , Ksaibati Khaled
Published: April 2007

Bottom ash, as a by-product of coal-fired electric power plants, has recently been used in constructing transportation facilities. However, the use of bottom ash in asphalt mixtures is still in an early stage. The moisture resistance of asphalt mixtures containing bottom ash, which has not been adequately researched, is investigated in this study. Eight asphalt mixtures produced with one type of asphalt cement, two types of aggregate, three sources of bottom ash, and lime additive were evaluated using the principles in AASHTO T283. Analysis of test data indicated that granite mixtures had higher tensile strength values than did limestone mixtures in dry conditions. Addition of lime or bottom ash did not substantially change these values. All mixtures tested met the Superpave volumetric mix design requirement of tensile strength ratio ( TSR) after one freeze–thaw cycle. The addition of lime significantly improved the moisture resistance of the asphalt mixtures as measured by the TSR. With lime addition, aggregate type, bottom ash addition, and bottom ash source were all insignificant with respect to TSR. On the basis of TSR rate ( TSRR), the addition of lime significantly improved the moisture resistance of the asphalt mixtures subjected to multiple freeze–thaw cycles. Without lime addition, bottom ash played a role similar to that of lime in improving the TSRR for the materials tested.
Effectiveness of Lime in Hot-Mix Asphalt Pavements
Authors: Sebaaly Peter E. , Hitti Edgard , Weitzel Dean
Published: April 2007

The pavement community has recognized that moisture damage of hot-mix asphalt (HMA) has been a serious problem since the early 1960s. Numerous additives have been evaluated with the objective of reducing the potential of moisture damage in HMA mixtures; lime has been one of the most common ones. The Nevada Department of Transportation has been using lime in HMA mixtures since the mid-1980s. The objective of this research was to quantify the improvements in pavement performance that have been realized through the addition of lime to HMA mixtures. The program evaluated field samples and pavement performance data from untreated and lime-treated pavements. The properties of untreated and lime-treated mixtures from field projects in the southern and northwestern parts of Nevada indicate that lime treatment of Nevada's aggregates significantly improves the moisture resistance of HMA mixtures. The study showed that lime-treated HMA mixtures become significantly more resistant to multiple freeze–thaw cycles than do the untreated mixtures. Long-term pavement performance data indicate that under similar environmental and traffic conditions, the lime-treated mixtures provide better-performing pavements with fewer requirements for maintenance and rehabilitation activities. The analysis of the impact of lime on pavement life indicates that lime treatment extends the performance life of HMA pavements by an average of 3 years. This extension represents an average increase of 38% in the expected pavement life.
Aggregate Imaging System for Characterizing the Shape of Fine and Coarse Aggregates
Authors: Fletcher Thomas , Chandan Chandan , Masad Eyad , Sivakumar Krishna
Published: April 2007

A unified computer-automated system was designed and developed for characterizing the shape of fine and coarse aggregates. The unique features of the system and the experimental design considerations are described. These considerations are related to the required image resolution, field of view, and lighting scheme. The unique features of the system include the ability to analyze fine and coarse aggregates and to quantify texture, angularity, and the three dimensions of form. The developed system is used to measure aggregate shape properties for a wide range of fine and coarse aggregates, and the results are compared with hot-mix asphalt laboratory performance. The analysis shows that the developed procedure yields detailed information on shape properties of aggregates in a short time. The measurements have very good correlation with the resistance of asphalt mixes to permanent deformation measured in the laboratory using different wheel-tracking devices.
Development and Finite Element Implementation of Stress-Dependent Elastoviscoplastic Constitutive Model with Damage for Asphalt
Authors: Collop Andrew C. , (Tom) Scarpas A. , Kasbergen Cor , de Bondt Arian
Published: April 2007

The development and finite element (FE) implementation of a stress-dependent elastoviscoplastic constitutive model with damage for asphalt is described. The model includes elastic, delayed elastic, and viscoplastic components. The strains (and strain rates) for each component are additive, whereas they share the same stress (i.e., a series model). This formulation was used so that a stress-based nonlinearity and sensitivity to confinement could be introduced into the viscoplastic component without affecting the behavior of the elastic and delayed elastic components. A simple continuum damage mechanics formulation is introduced into the viscoplastic component to account for the effects of cumulative damage on the viscoplastic response of the material. The model is implemented in an incremental formulation into the CAPA-3D FE program developed at Delft University of Technology in the Netherlands. A local strain compatibility condition is utilized such that the incremental stresses are determined explicitly from the incremental strains at each integration point. The model is demonstrated by investigating the response of a semirigid industrial pavement structure subjected to container loading. Results show that the permanent vertical strains in the non-stress-dependent case are significantly lower than the permanent vertical strains in the stress-dependent case. Results also show that in the stress-dependent case, there is a more localized area of high permanent vertical compressive strain directly under the load at approximately halfdepth in the asphalt compared with the non-stress-dependent case, in which the distribution is more even.
Considering Material Heterogeneity in Crack Modeling of Asphaltic Mixtures
Authors: Soares Jorge Barbosa , de Freitas Felipe Araújo Colares , Allen David H.
Published: April 2007

Cracking in the asphaltic layer of pavement has been shown to be a major source of distress in roadways. Previous studies in asphaltic mixture cracking have typically not considered the material heterogeneity. A numerical method of analysis is presented that is based on the theory of fracture mechanics, in which the binder and the aggregates are treated as distinct materials. The simulations performed are verified and calibrated from simple and conventional laboratory tests. The study investigates crack evolution under monotonic loading, even though the method outlined can be further developed for the investigation of asphalt mixture fatigue. The approach discussed is part of a multiscale framework for pavement analysis, in which the damage due to cracking at the local scale can be considered in a global analysis at the actual pavement scale.
Fatigue Endurance Limit for Highway and Airport Pavements
Authors: Carpenter Samuel H. , Ghuzlan Khalid A. , Shen Shihui
Published: April 2007

The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.
Examination of Gamma-Ray Method for Measuring Bulk Specific Gravity of Hot-Mix Asphalt Concrete
Authors: Hall Kevin D. , Williams Stacy G. , Griffith Frances T.
Published: April 2007

Much attention has been given to the determination of bulk specific gravity (Gmb) of compacted hot-mix asphalt (HMA) specimens. For relatively open-graded HMA mixtures, such as those produced by Superpave® and stone matrix asphalt design methods, perceived potential shortcomings in traditional test methods may be pronounced. Recently, a new device was introduced for measuring Gmb that features the use of gamma-ray technology. To evaluate the efficacy of the device, 221 compacted HMA specimens were tested with three test methods: saturated surface dry (SSD) (AASHTO T-166), vacuum-sealing (Corelok), and gamma-ray technology (CoreReader). Each specimen was tested three times in each of the three methods. The specimens represented field-sampled and laboratory-prepared mixtures, 12.5-mm and 25-mm nominal maximum aggregate sizes, and a variety of aggregates typically used in Arkansas. Test results indicated that statistically significant differences exist between mean Gmb-values generated by each of the three testing methods. In general, the vacuum-sealing method yielded the lowest Gmb-values, followed (in order of low to high) by the gamma-ray and SSD methods. Significant differences in the variability of test results were not observed between test methods. In ease of testing and testing variability, the CoreReader gamma-ray device does not appear to offer significant advantages for determining the bulk specific gravity of compacted HMA cores. Further, departments of transportation wishing to replace or allow alternatives to traditional SSD-based tests should consider the impact of test results on existing volumetric property specifications.
Preliminary Field Validation of Simple Performance Tests for Permanent Deformation: Case Study
Authors: Zhou Fujie , Scullion Tom
Published: April 2007

Simple performance tests (SPTs) to be used with the Superpave® volumetric mixture design procedure were recently recommended by NCHRP Project 9-19 (Simple Performance Test for Superpave Mix Design). Field validation of the SPTs is critical to their final acceptance and implementation in Superpave mixture design practice. Special Pavement Studies-1 (SPS-1) prematurely rutted sections on US-281 in Texas were used to validate the SPTs for permanent deformation, including the dynamic modulus test and repeated-load test and associated rutting indicators E*/sin δ and flow number ( F n), respectively. The results of this case study clearly show that both the dynamic modulus test and E*/sin δ and the repeated-load test and F n can effectively distinguish the good mixtures from the bad. Compared with E*/sin δ, F n can better differentiate the performance of asphalt mixtures. These results preliminarily validated both SPTs for permanent deformation. In addition, the location of the tertiary point in the plot of permanent strain versus number of load repetitions is clarified; a simple linear model needs to be added in order to determine the F n. Furthermore, the possibility of using the number of load repetitions ( Nps) corresponding to the initial point of the secondary stage to characterize the rutting resistance of asphalt mixtures is discussed. The new indicator proposed is supported by the limited data presented in this paper and can be easily determined and can reduce test duration significantly.
Updated Review of Stone Matrix Asphalt and Superpave® Projects
Authors: Watson Donald E.
Published: April 2007

Stone matrix asphalt (SMA) and Superpave® represent relatively new mix design technologies in the United States. Therefore, a condition survey was conducted of mixes that had been in service for several years to evaluate the long-term performance of SMA and Superpave projects. This study is a follow-up to a 1995 review of SMA projects and a 1998 review of Superpave projects. Both SMA and Superpave are acknowledged to be rut-resistant mixes, and this resistance was shown to be the case during this project review. However, a significant amount of cracking occurred early in the life of some of these mixtures. Overall, the SMA mixtures appeared to be more durable than the Superpave mixtures evaluated. The SMA mixtures have been in place about 2½ years longer than the Superpave mixtures, but the overall condition is about the same. Some of the primary conclusions from the survey are as follows: both SMA and Superpave mixtures were shown to be rut-resistant even when placed on facilities with high traffic volume; much of the observed cracking, especially load cracking, appeared to be more related to problems other than mix design or material properties; and SMA mixtures can be expected to last longer than Superpave mixtures before reaching the same condition level.
Economic Benefits of Freight Policy Relating to Trucking Industry: Evaluation of Regional Transportation Plan Freight Policy for a Six-County Region, Chicago, Illinois
Authors: Seetharaman Anusha , Kawamura Kazuya , Dev Bhatta Saurav
Published: April 2007

The economic impact of freight transportation has been the focus of policy debate for many years. Attempts have been made to measure the benefits of freight policy. However, the overall economic impact, as reflected in increased output from efficiency improvements or generated employment, has not been evaluated effectively in long-range planning. This study attempts to quantify the economic benefits of freight policy relative to recommendations in the 2020 Regional Transportation Plan (RTP) for a six-county region of Chicago, Illinois. RTP projections for fuel consumption savings and shorter delays (and thus lower labor costs) were translated into output changes for the motor freight industry and, subsequently, demand changes. Using rather conservative assumptions, annual savings of $270 million were calculated as the total direct economic impact of RTP policy and project implementation on the regional motor freight and warehousing industry. Increases in output and demand for the motor freight industry were fed into an input–output model. The model found that direct, indirect, and induced impacts on the regional economy exceeded $675 million and generated nearly 7,000 jobs annually. In particular, both wholesale and retail markets were expected to increase output by almost $30 million because of freight movement efficiency improvements.
Operation of Long Semitrailers in the United States
Authors: Clayton Alan , Montufar Jeannette , Middleton Dan
Published: April 2007

The regulation and use of long semitrailers (57 to 60 ft) in the United States are discussed. Industrial information was obtained from interviewing 42 state and federal regulatory and compliance officials, vehicle manufacturers, motor carriers, and shippers. Field data from a June 2002 investigation of long semitrailer use on an Interstate highway section in Texas are presented. No known significant literature exists on the topic under discussion. The research found that long semitrailers operate, either regularly or under permit, in 19 states. They are principally used by a few large private and for-hire carriers, transporting mainly tissue paper, empty cans, hay, cotton, empty storage container drums, household goods, snack foods, and general freight. The extent of their operation is largely unknown or unclear to many of those involved with truck size and weight research and development activities, highway planners and designers, and industry participants. The following are addressed: ( a) issues about long semitrailer operation in the United States and the growth potential of these vehicles relative to the TRB Special Report 267 proposal to allow wide-scale use of six-axle tractor-semitrailers at a gross vehicle weight of 90,000 Ib; ( b) background on using long semitrailers; ( c) operational issues associated with long semitrailers; ( d) typical dimensional characteristics and cubic payloads of long semitrailers compared with standard semitrailers; ( e) field data on the use of long semitrailers in Texas; and ( f) regulations, permit requirements, and allowable geographic scope of operation for long semitrailers.
Practical Implications of Modeling Commercial Vehicle Empty Trips
Authors: Holguin-Veras José , Thorson Ellen
Published: April 2007

Implications of modeling commercial vehicle empty trips are discussed, a theoretical derivation for parameter estimation is provided, and insight is given into the order of magnitude of estimation errors because of the improper modeling of commercial vehicle empty trips. A set of relatively simple cases was designed to illustrate the most important implications. Also addressed are estimation errors from using naïve approaches to compensate for the lack of explicit modeling of empty trips and the errors associated with more advanced empty trip models. In the simplest simulation, directional errors for a basic complementary model were from three to six times fewer than those for the naïve models. In the more complex case, a more sophisticated complementary model performed slightly better than the basic model and both complementary models were considerably better than the naïve approaches. The directional errors for the naïve models were four to seven times greater than those for the complementary models. Moreover, an analysis of the statistical distributions of the errors indicated that the complementary models had higher probabilities of producing accurate results, whereas the naïve approaches had higher probabilities of producing very large errors. These analyses indicate that the naïve approaches translate into significant errors in directional-traffic estimates. For that reason, their use should be discontinued in favor of the more advanced models presented.
Deterioration in Concrete Pavements Constructed with Slag Coarse Aggregate
Authors: Van Dam Thomas John , Peterson Karl R. , Sutter Larry L. , Housewright Meghan E.
Published: April 2007

In Michigan, sections of an Interstate-type pavement are suffering extensive cracking and joint deterioration after 10 years of service, having been constructed in 1992. An adjacent section constructed in 1993 with comparable design features and materials remains in good condition, with little visual sign of distress. A study was conducted to determine, if possible, the cause of the observed distress in the highway built in 1992. In all, cores from nine different projects were evaluated, all of which were made with iron blast-furnace-slag coarse aggregate and natural fine aggregate containing chert constituents. The analyses conducted included stereo and petrographic microscopy and chemical extractions to determine levels of exchangeable and soluble potassium and sodium, as well as sulfates. The findings indicate that, in distressed pavement sections, the chert constituents in the fine aggregate are deleteriously alkali–silica reactive (ASR), whereas these same constituents are not deleterious in the sections rated as fair. Further, the distressed sections all had sulfate levels significantly higher than predicted by the mixture design. It is hypothesized that, in addition to the ASR in the fine aggregate, dissolution of the calcium sulfide dendrites in the slag coarse aggregate is providing excess internal sulfates, resulting in in-filling of the air-void system with ettringite and potentially sulfate attack. The exact nature of the deterioration mechanisms is not fully understood, but it seems clear that some type of interaction exists between the ASR and excess sulfates.
Using Gyratory Compaction to Investigate Density and Mechanical Properties of Roller-Compacted Concrete
Authors: Amer Nader , Delatte Norbert , Storey Chris
Published: April 2007

Roller-compacted concrete (RCC) is a durable, economical, low-maintenance material for low-speed, heavy-duty paving applications, including industrial and multimodal pavements. However, it is difficult to prepare laboratory specimens to represent field performance, because RCC is very dry and requires considerable compactive effort to achieve field densities. The gyratory compactor, commonly used to prepare hot-mix asphalt specimens, may be used in preparing specimens for laboratory testing. Materials and mix designs from two industrial paving projects were used to prepare specimens for comparison. Field results indicated that the gyratory compactor produced specimens with mechanical properties consistent with those achieved in the field. Specimens had high strength and consistent density, with low variability. The gyratory compactor may be used to replace other methods presently used for preparing RCC specimens such as the modified Vebe apparatus, the vibrating table, and the vibrating hammer. These methods have limitations that may be overcome with the gyratory compactor because of its consistency and its compatibility with field results. The effects of density and specimen aspect ratio on compressive and splitting tensile strength were investigated. The number of gyrations applied to the specimen may be used to duplicate the desired field density. For the industrial pavements investigated, approximately 60 gyrations accurately replicated field conditions.
Air Change in Hydraulic Concrete Due to Pumping
Authors: Ksaibati Khaled , Zeng Menglan , Sellers Fane R. , Dolan Charles W.
Published: April 2007

The air content of concrete plays an important role in the durability of concrete. Excess air may reduce the strength of the concrete, while inadequate air will result in premature deterioration of the concrete due to scaling caused by freeze–thaw cycles and deicing chemicals. Pumping of hydraulic concrete has been a common practice for placing concrete. Although the air content before pumping is relatively easy to control, the air change during pumping has not been well understood. The purpose of this study was to investigate the change in air content of hydraulic concrete caused by pumping. Air content and other properties of concrete before and after pumping were measured at 36 construction projects in two phases. Analysis on data from 31 projects in Phase I indicated that most concrete experiences air loss because of pumping. Many factors could be behind this air loss. Analysis on data from five control projects in Phase II indicated that sampling methods had a moderate effect on the air change. Errors in measurement were minimal for certified testers and calibrated pots. The air change of concrete was significantly affected by the configuration of the boom, in addition to the air content before pumping. Attachments to the boom played key roles in reducing the air loss. Two mathematical models were developed for the prediction of air loss.
Accessibility, Connectivity, and Captivity: Impacts on Transit Choice
Authors: Beimborn Edward A. , Greenwald Michael J. , Jin Xia
Published: April 2007

Travelers can be classified into two groups: choice users and captive users. Choice users select transit or automobile service when they view one option as superior, whereas captive users have only one travel option. Surprisingly, little is known about captivity effects on mode split models. This research examines the way transit service factors such as accessibility and connectivity relate to mode captivity and mode choice. Data for this investigation come from the Portland, Oregon, 1994 Household Activity and Travel Diary Survey, the Regional Land Information System for the Portland area, the U.S. Environmental Protection Agency fuel economy database, and the U.S. Department of Energy. Individual trip data were segmented into transit captive, automobile captive, and choice users based on information about private vehicle availability, transit connectivity, and distance from a transit stop. Traditional transit mode split models are compared with models that segment users into choice and captive groups. It was found that traditional models underestimate the variation in mode choice for captive users, while overestimating the attractiveness of transit for choice users. These results indicate that better transit forecasts can result if accessibility and connectivity are used to help identify captive users. Additionally, among choice transit users, differences in travel times between automobile and transit modes do little to influence mode selection, while walk access to transit has more effect than previously thought.
Forecasting Transit Walk Accessibility: Regression Model Alternative to Buffer Method
Authors: Zhao Fang , Chow Lee-Fang , Li Min-Tang , Ubaka Ike , Gan Albert
Published: April 2007

A description is given of a methodology for estimating transit walk accessibility at the home end of transit trips and for forecasting transit walk accessibility at the home end for a future year, given forecast population and employment data, transit route information, and type of street configuration. The methodology for estimating transit walk accessibility overcomes the problems associated with natural and man-made barriers such as water bodies and community walls and the problem of uneven distribution of population. A comparison of the results with those from the traditional buffer method, as well as with network ratio methods that consider actual walk distance along streets, showed that both the buffer method and network ratio methods tended to overestimate transit walk accessibility. Regression analysis also showed that the new transit walk accessibility measure was a stronger predictor of transit use than that produced using the buffer method. The methodologies may be applied to transit planning, urban design for sustainable development, and long-range transit demand modeling.
University Transportation Survey: Transportation in University Communities
Authors: Daggett John , Gutkowski Richard
Published: April 2007

Universities and transit agencies across the United States have been finding innovative ways of providing and financing mobility services on and around university campuses. Many transit agencies are providing substantially more service and moving substantially more riders than their counterparts in nonuniversity environments. Determining what types of relationships exist between transit performance and university policies or practices is the research premise. To that end, the purpose is to document the types of transportation policies, demographics, and land use characteristics that exist on university campuses, and to examine the relationship between transit performance, land use on university campuses, types of university communities, university transportation and parking policies, and student demographics. These characteristics of university transportation systems were examined through demographic data and a mailed questionnaire. The questionnaire was sent to 48 universities and transit agencies across the United States, with 23 responding with enough valid data and information to be included in the study. It has been demonstrated in a significant number of university communities across the country that transit performance is enhanced dramatically by certain fare policies. However, that enhancement differs from one community to the next. It is believed that the answer to maximizing transit performance can be found in a combination of factors and that the optimum mix can be identified empirically.
Regulation of Road-Based Public Transportation and Strategies for the Developing World
Authors: Darido Georges B.
Published: April 2007

In most cities of the developing world road-based public transport (i.e., buses, paratransit, jitneys, etc.) is the primary mode of motorized travel. Varying degrees of regulation control its provision; regulation is sometimes the role of government, private organizations, or the operators themselves. Many characteristics of developing world cities and travel markets influence the implementation and performance of regulatory schemes for public transportation. By exploring these factors and the spectrum of regulatory options, it is possible to suggest a methodology framework to make regulation and competition of public transportation services more effective and sustainable. This methodology attempts to capture local conditions, priorities, implementation issues, and sustainability strategies for developing regulatory schemes. Research concludes with suggested practices and strategies to increase the acceptance and sustainability of regulations by maximizing the potential benefits and minimizing the negative impacts.
Fuzzy-Neural Network Traffic Prediction Framework with Wavelet Decomposition
Authors: Xiao Heng , Sun Hongyu , Ran Bin , Oh Youngtae
Published: April 2007

The framework of a traffic prediction model that could eliminate noise caused by random travel conditions is investigated. This model also can quantitatively calculate the influence of special factors. The framework combined several artificial intelligence technologies, such as wavelet transform, neural network, and fuzzy logic. The wavelet denoising method is emphasized and analyzed.
Developed Incident Detection Algorithm Compared with Neural Network Algorithms
Authors: Teng Hualiang(Harry) , Qi Yi(Grace) , Martinelli David R.
Published: April 2007

The CUSUM (cumulative sum of log-likelihood ratio) algorithm is an optimization-based algorithm that is attractive for many applications because it can minimize detection delay and can explicitly incorporate the characteristics of processes before and after changes. One such application is freeway incident detection, where field-measurable traffic-flow parameters are used to flag incidents in real time in an expedient and reliable manner. In the presented study, the special characteristics of traffic processes associated with incidents are incorporated into the CUSUM algorithm for freeway incident detection. In the algorithm evaluation, the most recently developed neural networks are compared with an enhanced CUSUM algorithm. The neural network algorithms are systematically evaluated first among themselves, and then the best of them is compared with the CUSUM algorithm. The results demonstrate that the CUSUM incident detection algorithm can perform better than the neural network algorithms. The neural network algorithm may show inferior performance because it cannot adjust its decision threshold in real time.
Use of Local Linear Regression Model for Short-Term Traffic Forecasting
Authors: Sun Hongyu , Liu Henry X. , Xiao Heng , He Rachel R. , Ran Bin
Published: April 2007

The traffic-forecasting model, when considered as a system with inputs of historical and current data and outputs of future data, behaves in a nonlinear fashion and varies with time of day. Traffic data are found to change abruptly during the transition times of entering and leaving peak periods. Accurate and real-time models are needed to approximate the nonlinear time-variant functions between system inputs and outputs from a continuous stream of training data. A proposed local linear regression model was applied to short-term traffic prediction. The performance of the model was compared with previous results of nonparametric approaches that are based on local constant regression, such as the k-nearest neighbor and kernel methods, by using 32-day traffic-speed data collected on US-290, in Houston, Texas, at 5-min intervals. It was found that the local linear methods consistently showed better performance than the k-nearest neighbor and kernel smoothing methods.
Design of Granular Pavement Layers Considering Climatic Conditions
Authors: Werkmeister Sabine , Numrich Ralf , Dawson Andrew R. , Wellner Frohmut
Published: April 2007

A new simple design approach that uses test results from the repeated load triaxial apparatus to establish the risk level of permanent deformations in the unbound granular layers (UGL) in pavement constructions under consideration of the seasonal effects was developed. From these data, a serviceability limit line (plastic shakedown limit) stress boundary for the unbound granular materials (UGM) was defined for different moisture contents. Below this line, the material has stable behavior. The serviceability limit line was applied in a finite-element (FE) program, FENLAP, to predict whether stable behavior occurs in the UGM. To calculate the stress in the UGL, a nonlinear elastic model (Dresden Model) was implemented into the FE program. The effects of changing moisture content during spring thaw period and asphalt temperature on pavement structural response were investigated. Additionally, permanent deformation calculations for the UGL were performed taking the stress history into consideration. The results clearly demonstrate that, for pavement constructions with thick asphalt layers, there is no risk of rutting in the granular base, even at a high number of load repetitions. The proposed design approach is a very satisfactory simple method of assessing the risk of rutting in the UGL, even without the calculation of the exact permanent deformation of the pavement construction.
Commuter Rail Reelectrification: Is It Still Justified?
Authors: Allen John G. , Aurelius John P.
Published: April 2007

From the late 1960s through the mid-1990s, North American commuter railroads electrified with overhead wire moved toward high-voltage alternating current (AC) at commercial frequency so as to adopt state-of-the art technology. The extent and complexity of reelectrification have varied greatly, as projects in New Jersey, Connecticut, and Montreal, Canada, (and one planned for the Netherlands) show. Changes in the justification threshold for reelectrification are reviewed, along with a decision to retain a direct current (DC) system in Chicago. The recent development of onboard inverters, changing DC into AC for traction motors, has made it easier for electric rail operations to enjoy the benefits of AC propulsion without reelectrification costs.
Customer Perspectives on Multilevel Coaches for Increasing Rail System Capacity
Authors: Pepper Janice , Spitz Gregory , Adler Thomas
Published: April 2007

The numbers and lengths of New Jersey Transit (NJT) commuter trains accessing New York’s Penn Station are currently at the limits of available capacity during peak periods, as evidenced by the significant number of standees at these times. NJT is planning to purchase multilevel coaches to address this critical passenger capacity issue. A study was conducted to determine the design of these multilevel coaches so that they will provide the extra capacity needed and also reflect customers’ preferences. The study focused on interior issues, including the seating configuration and seat design, that relate directly to the amount of seated (and standee) capacity on the new coaches. A two-part research approach was used to obtain customer input. First, focus groups and product clinics were conducted to get qualitative feedback on the multilevel coach concepts and on specific seat designs. A detailed, computer-based survey was administered to customers to quantify their preferences among key elements of the multilevel concepts, and to estimate their willingness to pay for those elements. The study found that additional seating capacity in the configuration preferred by customers provides a substantial net benefit to NJT passengers, equivalent to about $2.20 fare value per trip. The benefits are higher for this application because of the crowded conditions on existing trains. The study also suggests that multilevel coaches and improved interior design have benefits well beyond increased capacity.
MagneMotion Maglev System
Authors: Thornton Richard , Clark Tracy , Stevens Ken
Published: April 2007

The MagneMotion Maglev system, called M3, is an alternative to all conventional guided transportation systems. Advantages include major reductions in capital cost, travel time, operating cost, noise, and energy consumption. Vans or small-bus size vehicles operating automatically with headways of only a few seconds can be moved in platoons to achieve capacities of at least 12,000 passengers per hour per direction. Small vehicles lead to lighter guideways, shorter waiting time for passengers, lower power requirements for wayside inverters, more effective regenerative braking, and reduced station size. The design objectives were achieved by taking advantage of high-energy permanent magnets, improved microprocessor-based power electronics, precise position sensing, lightweight vehicles, a guideway matched to the vehicles, and the ability to use sophisticated computer-aided design tools for analysis, simulation, and optimization. Arrays of permanent magnets on both sides of a vehicle provide suspension, guidance, and a field for linear synchronous motor propulsion. Feedback-controlled current in control coils wound around the magnets stabilizes the suspension. The motor windings are integrated into suspension rails and excited by inverters along the guide-way. M3 is designed to provide speeds up to 45 m/s (101 mph) and acceleration and braking up to 2 m/s2 (4.5 mph/s) without onboard propulsion equipment. Operating speeds and accelerations can be modified by changing only the power system and wayside inverters. Capital cost, travel time, and operating cost are predicted to be less than half that of any competing transit system.
Method of Calculating Spare Ratios
Authors: Klein Jonathan H.
Published: April 2007

An industrial engineering approach was used to determine what proportion of a rail vehicle fleet would need to be unavailable for revenue use. This proportion is often called the spare ratio (SR). The number of rail vehicles required as spares remains in dispute. This SR question is important because each spare rail car and locomotive represents an investment of millions of dollars. The prevalent approach for determining the number of spares is to use a fixed ratio, for example, 15%. This fixed percentage is not a function of several variables, or even property-specific parameters. The industrial engineering approach shows that an SR is a variable that can change annually. The significant variables driving the SR are annual use, reliability, inventory support, train length, and repair scheduling aggressiveness. Equations were developed to enable calculations specific to a transit or commuter rail operation. Further, the duration of the peak vehicle requirement (PVR)—peak hours—was shown to be as important as the PVR size.
Dynamic Value Pricing as Instrument for Better Utilization of High-Occupancy Toll Lanes: San Diego I-15 Case
Authors: Supernak Janusz , Steffey Duane , Kaschade Christine
Published: April 2007

Selected results are presented of the Traffic Study, one of 12 studies conducted by San Diego State University for the I-15 Congestion (Value) Pricing Project in San Diego, California, a 3-year federal demonstration that converted underutilized high-occupancy-vehicle (HOV) lanes into a high-occupancy toll (HOT) facility. The studies addressed traffic and traveler-related aspects, as well as economic, equity, and public relations issues. The Traffic Study constituted the core of the evaluation effort. One of the project's main objectives was better utilization of the express lanes to carry more traffic during peak commuting periods. This study examines the possibility that dynamic, traffic-sensitive value pricing, represented by the FasTrak phase of the project, is uniquely suited to improve both utilization and volume distribution during peak periods while effectively controlling level of service on the facility. Measures of utilization and volume distribution were defined and studied in spring and fall waves of the study. The study confirms statistically significant improvements in both peak-period utilization and volume distribution across the study waves. The results strongly suggest that the FasTrak program's dynamic fee structure was able to create desirable redistribution of a portion of express lane traffic from the middle of the peak to the shoulders. The fixed-fee structure of ExpressPass, the preceding program, was not able to create such redistribution. Despite the steady increase of express lane volume during the entire 3-year demonstration, the comfortable level of service C required by law was maintained at virtually all times.
Measuring Economic Costs of Urban Traffic Congestion to Business
Authors: Weisbrod Glen , Vary Don , Treyz George
Published: April 2007

Key findings are provided from NCHRP Study 2-21, which examined how urban traffic congestion imposes economic costs within metropolitan areas. Specifically, the study applied data from Chicago and Philadelphia to examine how various producers of economic goods and services are sensitive to congestion, through its impact on business costs, productivity, and output levels. The data analysis showed that sensitivity to traffic congestion varies by industry sector and is attributable to differences in each industry sector's mix of required inputs and hence its reliance on access to skilled labor, access to specialized inputs, and access to a large, transportation-based market area. Statistical analysis models were applied with the local data to demonstrate how congestion effectively shrinks business market areas and reduces the "agglomeration economies" of businesses operating in large urban areas, thus raising production costs. Overall, this research illustrates how it is possible to estimate the economic implications of congestion, an approach that may be applied in the future for benefit-cost analysis of urban congestion-reduction strategies or for development of congestion pricing strategies. The analysis also shows how congestion-reduction strategies can induce additional traffic as a result of economic benefits.
Improving Assessment of Transport Policies by Dynamic Cost-Benefit Analysis
Authors: Schade Wolfgang , Rothengatter Werner
Published: April 2007

In the history of cost-benefit analysis (CBA), macroeconomic and micro-economic foundations have been developed. The latter has dominated in transport CBA during the last decades. The most widely used CBA approach can be characterized as comparative static and based on separate partial modeling. However, when it comes to significant indirect effects in the economic, social, and environmental systems connected with the transport system, alternative approaches to the microeconomic approach become inevitable. A system dynamics platform was developed that allows for a dynamic CBA integrating the most important indirect effect of transport policies. The approach was tested with large infrastructure programs and transport policy packages. Results of the dynamic approach reveal that the choice of the most favorable policy can change over time and depend on the time horizon defined for the analysis. In particular the dynamic approach allows for a clear allocation of costs and benefits to periods of time, which might be valuable information for policy acceptance and implementation. This research is integrated within a stream of European Commission projects on integrated and dynamic assessment, starting with the Assessment of Transport Strategies project (ASTRA) and extended by the projects Transport Infrastructure and Policy: A Macroeconomic Analysis for the European Union (TIPMAC) and Integrated Appraisal of Spatial Economic and Network Effects of Transport Investments and Policies (IASON). IASON focuses on analysis of indirect, second-round, or induced benefits and costs that occur through feedback effects between the transport sector and other economic sectors.
Impact of Highways on Property Values: Case Study of Superstition Freeway Corridor
Authors: Carey Jason , Semmens John
Published: April 2007

The effects of freeway development on land use and property values were examined. A case study was prepared for the Superstition Freeway (US-60) corridor in Mesa and Gilbert, Arizona. Among the findings were the following observations. First, access benefits are transferred from highway users to nonusers through changes in property values. Freeway construction may have an adverse impact on some properties, but in the aggregate, property values tend to increase with freeway development. Second, freeways do not affect all properties' values in the same way. Proximity to the freeway was observed to have a negative effect on the value of detached single-family homes in the US-60 corridor but a positive effect on multifamily residential developments (e.g., condominiums) and most commercial properties. Finally, the most important factor in determining negative impact on property values appears to be the level of traffic on any major roads in the proximate area, which implies that regional traffic growth is more significant than the presence of a freeway per se.