bluuebunny/crossref_metadata_2025 huggingface dataset:
The Executive Support System of Ontario, Canada
Authors: Guerre Joseph A. , Robert William E. , Bradbury Alison , Goodale Michael
Published: May 2018

The Ministry of Transportation of Ontario (MTO), Canada, is currently implementing an asset management business framework (AMBF). The AMBF provides the ministry with an ambitious blueprint for incorporating asset management concepts into its existing business processes. A key component in the AMBF is the ability to integrate results from the ministry's existing management systems. In support of the AMBF, MTO has developed a prototype executive support system (ESS). The ESS is a what-if analysis tool that predicts network performance over time using data from the ministry's pavement and bridge management systems. It enables decision makers to evaluate the relationship between performance and budget and to view results by region, corridor, or functional class. This paper presents the analytical approach used to develop the ESS and describes how it was implemented by MTO. The ESS uses a candidate-based approach to system integration, which enables the integration of any management system capable of generating work candidates and estimating their impact on a defined set of performance measures. The ESS brings together data from these systems and performs an additional level of cross-asset economic optimizations, taking into account user-defined operating assumptions. Although much work has recently been done on the integration of pavement and bridge systems, the objective of this paper is to present a practical example implemented by MTO.
Chip Seal Program Excellence in the United States
Authors: Gransberg Douglas D.
Published: May 2018

A survey of U.S. public highway and road agencies that use chip seals as a part of their roadway maintenance program was developed and conducted to identify best practices in chip seal design and construction. A total of 72 individual responses from 42 U.S. states and 12 U.S. cities and counties were received; of those, nine respondents reported that they were getting excellent results from their chip seal programs. Those responses were grouped together and analyzed by the case study method to identify trends that lead to consistently excellent chip seal results. The study found that the successful chip seal programs had much in common. They use chip seals as a preventive maintenance tool, applying them to roads before distress levels were classified as moderate. They require their contractors to use the latest technology, and they exploit advances in material science such as the use of modified binders. And most of them use chip seals on both high- and low-volume roads.
Cost–Benefit Analysis of Continuous Pavement Preservation Design Strategies versus Reconstruction
Authors: Smith Kelly L. , Titus-Glover Leslie , Darter Michael I. , Von Quintus Harold , Stubstad Richard , Scofield Larry
Published: May 2018

The Arizona Department of Transportation (ADOT) has traditionally employed continuous pavement preservation as part of an overall design strategy to maintain the highest levels of service for highway users. Concerned about the effects of continual weakening of substructure material layers on preservation treatment cost and performance (i.e., more extensive and more frequent preservation activities), ADOT sponsored a study to determine the cost-effectiveness of the continuous preservation approach as compared with a reconstruction strategy. One goal of the study was to determine the break-even point for the two strategies (i.e., after how many rehabilitation treatments reconstruction becomes as cost-effective as continuous preservation). With inputs such as ( a) service life estimates, ( b) best estimates of unit costs, ( c) work zone-related user costs, and ( d) the typical analysis period and discount rate used by ADOT, the total life-cycle costs for four alternative strategies were determined and compared for the 15 commonly occurring pavement scenarios in Arizona. The results of the analysis showed a consistent reduction in total life-cycle costs as the number of rehabilitation treatments performed between original construction and reconstruction increased from none to two. Results also showed that for nine of the 15 scenarios, total life-cycle costs associated with the third reconstruction alternative (two rehabilitations occurring prior to the first reconstruction event) were within 3% of the total life-cycle costs of the continuous preservation strategy. Hence, the break-even point occurs when two to three rehabilitation treatments are performed prior to reconstruction.
Field and Laboratory Evaluations of Hot-Poured Thermoelastic Bituminous Crack Sealing of Asphalt Pavements
Authors: Carter Steve , Ksaibati Khaled , Huntington George
Published: May 2018

This paper describes the results of field and laboratory tests evaluating four configurations and three materials used for crack surfacing. Crack surfacing, as defined in this paper, is the sealing of cracks over 1 in. (25 mm) wide in asphalt pavements. Laboratory testing using the thermal stress restrained specimen test (TSRST; AASHTO TP 10-93) determines the temperature at which a specimen with its ends restrained fails due to thermal contraction. Field studies evaluate the performance of two materials with the uniform overband configuration on three roads in Wyoming. All crack surfacing materials are commercially available hot-poured thermoelastic bituminous products. Overband configurations are found to be the preferred method for applying crack surfacing, based on the TSRST. Failure modes are evaluated and generally found to propagate from the interface between the surfacing material and the pavement to which it is bonded. Field studies indicate that traffic and snowplowing have a significant influence on the performance of crack surfacing. Cracks sealed with the same configuration and the same material performed substantially better on US-26 than on I-25 over the same time periods. The only obvious difference between the two is that I-25 has three to four times as much traffic and correspondingly greater snow control efforts. This study concludes that materials, configurations, and traffic or snowplowing frequency influence the performance of crack surfacing.
Deterioration of Asphalt Pavement at Long-Term Pavement Performance Program Site 49-1001 in Utah
Authors: Blankenagel Brandon J. , Guthrie W. Spencer
Published: May 2018

Highway 191 near Bluff, Utah, features a well-monitored section of the long-term pavement performance (LTPP) program. Constructed in 1980, this section of flexible pavement performed well for nearly 13 years. Through this time, cracking of the asphalt layer was minimal. In the fourteenth year, however, the extent of longitudinal cracking in the wheel path increased and necessitated placement of a chip seal on the pavement surface. The purpose of this research was to determine the cause of pavement deterioration using LTPP data. Deflection basins obtained from falling-weight deflectometer testing were analyzed to investigate the extent to which structural degradation influenced deterioration of the pavement. Pavement layer modulus values were plotted against time and clearly show that weakening of the pavement base layer immediately preceded the occurrence of cracking. The geography of the site, as documented in photographs, supports the conclusion that inadequate water drainage at the site permitted saturation of the aggregate base layer during a period of midsummer flooding. This finding emphasizes the importance of specifying non-moisture-susceptible base materials and providing necessary drainage works in pavement design.
Experimental Analysis of Car-Following Dynamics and Traffic Stability
Authors: Ranjitkar Prakash , Nakatsuji Takashi , Kawamura Akira
Published: May 2018

The study of car-following dynamics is useful for capacity analysis, safety research, and traffic simulation. There is also growing interest in its applications in intelligent transportation systems, such as advanced vehicle control and safety systems and autonomous cruise control systems. A large number of car-following models have been developed in the past five decades. Some of them were investigated and validated against experimental data; nevertheless, the results were not that consistent for some models, e.g., those for the General Motors (GM) model. As a part of the problem, the data acquisition and calibration techniques were not advanced then. The past few decades have seen remarkable advancements in these techniques, e.g., the use of the differential Global Positioning System (GPS) for position measurement, the use of Doppler's principle for speed measurements, and the use of genetic algorithms for optimization. It might be useful to reassess some outstanding issues in car-following dynamics in light of the latest technological advancements. This paper attempts to investigate car-following dynamics on the basis of the real-time kinematic GPS data collected from test track experiments. The GM model was evaluated along with some well-known simulation models, including the Gipps model and the Leutzbach and Wiedemann model. A genetic algorithm-based optimization technique was adapted for calibration. The sensitivities of drivers to their speeds and spacings from the vehicle ahead were found to vary among drivers. The interpersonal variations in model performance were significant. The GM model parameters were identified with improved reliability. The stability of traffic flow was analyzed experimentally.
Car-Following Model for Motorway Traffic
Authors: Wang Jiao , Liu Ronghui , Montgomery Frank
Published: May 2018

This paper presents a new car-following model that aims to capture some of the key motorway flow characteristics, namely, traffic breakdown, hysteresis, and shock wave propagation, as well as close-following behavior. The model proposes three different driving states: nonalert, alert, and close following. Under the different driving states, drivers apply different reaction times and accelerations. This paper presents the formulation and algorithmic implementation of the model. The theoretical analysis of the macroscopic flow–density relationships of the model is discussed. Simulation experiments were conducted, and the results are examined at both the macroscopic level (speed breakdown and traffic hysteresis) and the microscopic level (gap distribution and shock wave propagation). The results show that the model is able to capture realistically the speed drop, traffic hysteresis, and shock wave propagation as well as close-following behavior. Further studies of the sensitivities of key model parameters suggest that the drivers’ reaction times have a significant effect on the modeled capacity and occupancy, while the effect of the speed threshold that distinguishes congested from noncongested traffic flow is less significant.
First-Order Pedestrian Traffic Flow Theory
Authors: Daamen Winnie , Hoogendoorn Serge P. , Bovy Piet H. L.
Published: May 2018

This paper discusses the validity of first-order traffic flow theory for the description of two-dimensional pedestrian flow operations in the case of an oversaturated bottleneck in front of which a large high-density region has formed. The paper shows how observations of density, speed, and flow that have been collected from laboratory walking experiments can be interpreted from the viewpoint of first-order theory. It is observed that pedestrians present at the same cross section inside of the congested region may encounter different flow conditions. This mainly depends on the lateral position of the pedestrian with respect to the center of the congested region. In the lateral center, high densities and low speeds are observed. However, on the boundary of the congested region, pedestrians may walk in nearly free-flow conditions and literally walk around this congested region. Visualization of these data in the flow– density plane results in a large scatter of points that have similar flows (bottleneck capacity) but different densities. This can be explained by noticing that observations of congestion of pedestrian traffic over the total width of the cross section do not belong to a single fundamental diagram but belong to a set of different fundamental diagrams. This observation has consequences for estimation of the fundamental diagram describing pedestrian traffic.
Analysis and Comparison of Microscopic Traffic Flow Models with Real Traffic Microscopic Data
Authors: Punzo Vincenzo , Simonelli Fulvio
Published: May 2018

The evermore widespread use of microscopic traffic simulation in the analysis of road systems has refocused attention on submodels, including car-following models. The difficulties of microscopic-level simulation models in the accurate reproduction of real traffic phenomena stem not only from the complexity of calibration and validation operations but also from the structural inadequacies of the submodels themselves. Both of these drawbacks originate from the scant information available on real phenomena because of the difficulty with the gathering of accurate field data. In this study, the use of kinematic differential Global Positioning System instruments allowed the trajectories of four vehicles in a platoon to be accurately monitored under real traffic conditions on both urban and extraurban roads. Some of these data were used to analyze the behaviors of four microscopic traffic flow models that differed greatly in both approach and complexity. The effect of the choice of performance measures on the model calibration results was first investigated, and intervehicle spacing was shown to be the most reliable measure. Model calibrations showed results similar to those obtained in other studies that used test track data. Instead, validations resulted in higher deviations compared with those from previous studies (with peaks in cross validations between urban and extraurban experiments). This confirms the need for real traffic data. On comparison of the models, all models showed similar performances (i.e., similar deviations in validation). Surprisingly, however, the simplest model performed on average better than the others, but the most complex one was the most robust, never reaching particularly high deviations.
Transformation between Uninterrupted and Interrupted Speeds for Urban Road Applications
Authors: Pueboobpaphan Rattaphol , Nakatsuji Takashi , Suzuki Hironori , Kawamura Akira
Published: May 2018

Unlike the freeway traffic stream, the urban traffic stream is generally interrupted by signals, and the traffic data observed may differ from the true (uninterrupted) flow characteristics. This paper deals with the transformation between interrupted and uninterrupted speeds on an urban road with signalized intersections. The conventional shock wave model and two modified versions of the shock wave boundary that address unrealistic characteristics of the conventional shock wave model are developed. A method of integrating probe and detector data for speed transformation is also discussed. The proposed methods are tested with a virtual isolated signalized intersection by varying the approach demand. The numerical results suggest that all models can significantly reduce the difference between the actual and the estimated uninterrupted (or interrupted) speeds compared with the case of doing nothing. The applications of the proposed methods, including the development of a flow–speed model and link travel time estimation, are also given.
Driver Turn-Taking Behavior in Congested Freeway Merges
Authors: Cassidy Michael J. , Ahn Soyoung
Published: May 2018

Data from four merge locations in northern California and Toronto, Ontario, Canada, unveil a notable feature of driver turn taking. It was observed that queued vehicles from the on-ramp and freeway traffic streams entered a congested merge in some (nearly) fixed ratio that was independent of the merge outflow. Drivers in competing traffic streams thus entered the merge by adopting some definite turn-taking behavior, and this behavior was not influenced by the severity of the exogenous flow restriction from downstream. The findings validate part of an existing theory of merging traffic and should be considered when any new such theories are developed.
Vehicle-Type and Lane–Specific Free Speed Distributions on Motorways
Authors: Hoogendoorn Serge P.
Published: May 2018

A new approach to estimation of vehicle type–specific free speed distributions on multilane facilities is presented on the basis of the concept of censored observations. The original distribution-free method of Kaplan and Meier is generalized to include partially censored data, i.e., observations that are censored with a certain probability or to a certain degree. The method is applied with cross-section data collected at a busy two-lane motorway in the Netherlands. The results provide robust estimates of the speed distributions for different vehicle classes, while they remove the structural error made when more common approaches are applied.
Paramics Simulation of Periodic Oscillations Caused by Network Geometry
Authors: Jin Wen-Long , Zhang Yu
Published: May 2018

Traffic oscillations such as stop-and-go waves in a traffic system can occur for a variety of reasons, such as instabilities. This paper describes a study of a type of periodic oscillations caused by network geometry with a microscopic simulation model, Paramics. With careful tuning in Paramics, periodic oscillations in which traffic states change periodically between a diverging junction and a merging junction are successfully simulated. The formation process is discussed in detail. The study suggests that, given an appropriate network structure and traffic conditions, the local oscillations caused by randomness in car-following and lane-changing models in Paramics can be maintained and can become periodic and global. Finally, the consistencies between a macroscopic kinematic wave model and Paramics are discussed, and future research topics and the implications of the findings of the study are presented.
Hybrid Mesoscopic–Microscopic Traffic Simulation
Authors: Burghout Wilco , Koutsopoulos Haris N. , Andréasson Ingmar
Published: May 2018

Traffic simulation is an important tool for modeling the operations of dynamic traffic systems. Although microscopic simulation models provide a detailed representation of the traffic process, macroscopic and mesoscopic models capture the traffic dynamics of large networks in less detail but without the problems of application and calibration of microscopic models. This paper presents a hybrid mesoscopic–microscopic model that applies microscopic simulation to areas of specific interest while simulating a large surrounding network in less detail with a mesoscopic model. The requirements that are important for a hybrid model to be consistent across the models at different levels of detail are identified. These requirements vary from the network and route choice consistency to the consistency of the traffic dynamics at the boundaries of the microscopic and mesoscopic submodels. An integration framework that satisfies these requirements is proposed. A prototype hybrid model is used to demonstrate the application of the integration framework and the solution of the various integration issues. The hybrid model integrates MITSIMLab, a microscopic traffic simulation model, and Mezzo, a newly developed mesoscopic model. The hybrid model is applied in two case studies. The results are promising and support both the proposed architecture and the importance of integrating microscopic and mesoscopic models.
Calibration of Flow–Density Relationships on Urban Streets
Authors: Leclercq Ludovic
Published: May 2018

The aim of this paper is to gather some observations resulting from the study of traffic data in an urban environment (Toulouse, France) rather than on freeways, as is often the case in papers that deal with flow–density relationship calibration. Methods developed for freeway data are studied and new ones are presented to address the specificity of traffic behavior in urban areas. A two-step approach is proposed. First, the data are processed to obtain consistent observations for simulation use. This processing includes the calculation of density from occupancy and space mean speed and the aggregation and the selection of data to make them suitable for equilibrium traffic state representation. Then, a best-fit curve is applied to the selected data to obtain flow–density relationships. Finally, the resulting relationships are studied to highlight the peculiarities of traffic behavior in urban streets.
Online Calibration of Traffic Prediction Models
Authors: Antoniou Constantinos , Ben-Akiva Moshe , Koutsopoulos Haris N.
Published: May 2018

A methodology for the online calibration of the speed–density relationship is formulated as a flexible state–space model. Applicable solution approaches are discussed and three of them–-the extended Kalman filter (EKF), the iterated EKF, and the unscented Kalman filter (UKF)–-are selected and presented in detail. An application of the methodology with freeway sensor data from two networks in Europe and the United States is presented. The improvement in the estimation and prediction of speeds due to online calibration (compared with the speeds obtained from the relationship calibrated offline) is demonstrated. EKF provided the most straightforward solution to this problem and, indeed, achieved considerable improvements in estimation and prediction accuracy. The benefits obtained from the use of the more computationally expensive iterated EKF algorithm are shown. An innovative solution technique (UKF) is also presented.
Stationary Models of Unqueued Traffic and Number of Freeway Travel Lanes
Authors: Anani Shadi B. , Cassidy Michael J.
Published: May 2018

Occupancies and flows were jointly sampled from freeway segments in nearly stationary, unqueued traffic. When plots of occupancy per lane versus flow per lane were normalized by n (the number of travel lanes in the freeway segment from which a data set came), the plots took shapes that were piecewise linear in form (except for conditions that were near capacity) and were clearly influenced by n. Drivers adopted a higher speed (for a given occupancy) while traveling on segments of greater n. Yet, the speeds on these wider segments exhibited greater sensitivity: drivers began decelerating at relatively low occupancies. These findings came from a comparison of a data plot from each of five different freeway segments with the plot from its neighboring segment. Because each segment appeared to differ from its neighbor only in its n, the comparisons (approximately) controlled for other influential factors, including geometric design standards, speed limit, and driver population. The five pairwise comparisons, which verify the reproducibility of the effects of n on the data, were performed for freeways in and near Toronto, Ontario, Canada, and California. The findings are compared with the information currently provided in traffic handbooks.
Robust Route Guidance Model Based on Advanced Traveler Information Systems
Authors: Lu Jiangang , Ban Xuegang , Qiu Zhijun , Yang Fan , Ran Bin
Published: May 2018

In this paper a new robust optimization (RO) model is proposed for route guidance based on the advanced traveler information system. The arc travel time is treated as a random variable, and its distribution is estimated from historical data. Traditional stochastic routing models just minimize the expected travel time between the origin and the destination. Such approaches do not account for the fact that travelers often incorporate travel time variability in their decision making. Recently some RO models were proposed to incorporate more statistical information into the models, but these models still ignore much information available from historical travel time data. The probability measurement, time at risk (TaR), is introduced in this paper, and a multiobjective model is built up that allows a trade-off between the expected travel time and the TaR. Thus, the skewness and kurtosis of the arc travel time distribution are taken into consideration; that is important because the travel time distributions of typical arcs show high asymmetry and long tails on the right side as a result of the impact of random incidents and events. This approach is applied in two examples, one of which is a real traffic network.
Evaluation of AASHTO SiteManager Performance on High-Latency Satellite Communication Links
Authors: Chen Tien-Chien , Krogmeier James V. , Bullock Darcy M.
Published: May 2018

Most transportation agencies and departments have deployed transmission control protocol–Internet protocol (TCP-IP) applications in their offices and are beginning to deploy TCP-IP applications in remote or satellite field offices. Deployment of TCP-IP applications where broadband access is not available can be quite challenging. Satellite-based communication offers an opportunity to provide high-bandwidth connections quickly. However, satellite communications incur significant travel time delay that may result in poor performance of applications designed for a low-latency environment. This paper presents an evaluation of the AASHTO SiteManager software suite with two different satellite broadband providers. SiteManager clients performed poorly in the high-latency environment, in some cases up to 50 times slower than with SiteManager running on a low-latency terrestrial network with equivalent bandwidth. In general, the performance of SiteManager was relatively insensitive to the bandwidth provided by the satellite provider. In most tasks, SiteManager performed better over a 50-kbps dial-up connection than over a 384-kbps satellite connection. In an alternative architecture in which SiteManager was operated remotely via a terminal emulation service over a satellite connection, the performance was observed to be robust. This architecture requires considerably more equipment, software, and technical support. Furthermore, the delay in seeing some key-strokes and cursor movements appear can be somewhat awkward for the user. However, given the extensive bursts of short messages between SiteManager clients and the server, the high-latency constraints of a satellite network make a terminal emulation procedure the only viable method of deploying SiteManager via a commercial satellite IP service.
Exploring the Relationship between Data Aggregation and Predictability to Provide Better Predictive Traffic Information
Authors: Oh Cheol , Ritchie Stephen G. , Oh Jun-Seok
Published: May 2018

Providing reliable predictive traffic information is a crucial element for successful operation of intelligent transportation systems. However, there are difficulties in providing accurate predictions mainly because of limitations in processing data associated with existing traffic surveillance systems and the lack of suitable prediction techniques. This study examines different aggregation intervals to characterize various levels of traffic dynamic representations and to investigate their effects on prediction accuracy. The relationship between data aggregation and predictability is explored by predicting travel times obtained from the inductive signature–based vehicle reidentification system on the I-405 freeway detector test bed in Irvine, California. For travel time prediction, this study employs three techniques: adaptive exponential smoothing, adaptive autoregressive model using Kalman filtering, and recurrent neural network with genetically optimized parameters. Finally, findings are discussed on suggestions for applying prediction techniques effectively.
ISO 19133 Tracking and Navigation Standard
Authors: Scarponcini Paul
Published: May 2018

Most information maintained by a department of transportation (DOT) includes a physical location to specify where the data apply. Most often, this location is described with a linear referencing method (LRM). Because no single method is best for all applications, multiple methods are often used in each DOT. Engineers use stationing to locate construction items. Transportation data administrators may use mile point to locate roadway characteristics. Safety officers often use reference markers to locate crashes. TRB has stated that location can serve as an integrating concept for assimilating data from multiple sources. Until now, there were no standards for linear referencing methods; they vary between databases and between DOTs. Consequently, it has been difficult to integrate data from numerous sources by using locations with disparate formats. A new ISO standard should help remedy this situation. The ISO 19133 tracking and navigation standard includes a package for linear reference systems. It generalizes how linear locations are specified to enable translation between locations from different methods. It is based on the generalized model for linear reference, an abstraction of the NCHRP 20-27 conceptual model. According to the standard, locations are formalized as position expressions composed of a method of measurement (LRM), a linear element along which the measure is made, and the measurement itself. Locations can be on the linear element or offset laterally to either side. This paper explains the standard, how it was derived, and its implementation at the Minnesota DOT in its location data manager project.
Geographically Stratified Importance Sampling for the Calibration of Aggregated Destination Choice Models for Trip Distribution
Authors: Li Min-Tang , Chow Lee-Fang , Zhao Fang , Li Shi-Chiang
Published: May 2018

A key feature in estimating and applying destination choice models with aggregate alternatives is to sample a set of nonchosen traffic analysis zones (TAZs), plus the one a trip maker chose, to construct a destination choice set. Computational complexity is reduced because the choice set would be too large if all study area TAZs were included in the calibration. Commonly, two types of sampling strategies are applied to draw subsets of alternatives from the universal choice set. The first, and simplest, approach is to select randomly a subset of nonchosen alternatives with uniform selection probabilities and then add the chosen alternative if it is not otherwise included. The approach, however, is not an efficient sampling scheme because most alternatives for a given trip maker may have small choice probabilities. The second approach, stratified importance sampling, draws samples with unequal selection probabilities determined on the basis of preliminary estimates of choice probabilities for every alternative in the universal choice set. The stratified sampling method assigns different selection probabilities to alternatives in different strata. Simple random sampling is applied to draw alternatives in each stratum. However, it is unclear how to divide the study area so that destination TAZs may be sampled effectively. The process of and findings from implementing a stratified sampling strategy in selecting alternative TAZs for calibrating aggregate destination choice models in a geographic information system (GIS) environment are described. In this stratified sampling analysis, stratum regions varied by spatial location and employment size in the adjacent area were defined for each study area TAZ. The sampling strategy is more effective than simple random sampling in regard to maximum log likelihood and goodness-of-fit values.
Calibration of Microsimulation Models Using Nonparametric Statistical Techniques
Authors: Kim Seung-Jun , Kim Wonho , Rilett L. R.
Published: May 2018

The calibration of traffic microsimulation models has received widespread attention in transportation modeling. A recent concern is whether these models can simulate traffic conditions realistically. The recent widespread deployment of intelligent transportation systems in North America has provided an opportunity to obtain traffic-related data. In some cases the distribution of the traffic data rather than simple measures of central tendency such as the mean, is available. This paper examines a method for calibrating traffic microsimulation models so that simulation results, such as travel time, represent observed distributions obtained from the field. The approach is based on developing a statistically based objective function for use in an automated calibration procedure. The Wilcoxon rank–sum test, the Moses test and the Kolmogorov–Smirnov test are used to test the hypothesis that the travel time distribution of the simulated and the observed travel times are statistically identical. The approach is tested on a signalized arterial roadway in Houston, Texas. It is shown that potentially many different parameter sets result in statistically valid simulation results. More important, it is shown that using simple metrics, such as the mean absolute error, may lead to erroneous calibration results.
Modeling Location Choice of Secondary Activities with a Social Network of Cooperative Agents
Authors: Marchal F. , Nagel K.
Published: May 2018

Activity-based models in transportation science focus on the description of human trips and activities. Modeling the spatial decision for so-called secondary activities is addressed in this paper. Given both home and work locations, where do individuals perform activities such as shopping and leisure? Simulation of these decisions using random utility models requires a full enumeration of possible outcomes. For large data sets, it becomes computationally unfeasible because of the combinatorial complexity. To overcome that limitation, a model is proposed in which agents have limited, accurate information about a small subset of the overall spatial environment. Agents are interconnected by a social network through which they can exchange information. This approach has several advantages compared with the explicit simulation of a standard random utility model: ( a) it computes plausible choice sets in reasonable computing times, ( b) it can be extended easily to integrate further empirical evidence about travel behavior, and ( c) it provides a useful framework to study the propagation of any newly available information. This paper emphasizes the computational efficiency of the approach for real-world examples.
Travel Time Prediction Algorithm Scalable to Freeway Networks with Many Nodes with Arbitrary Travel Routes
Authors: Kwon Jaimyoung , Petty Karl
Published: May 2018

A travel time prediction algorithm scalable to large freeway networks with many nodes with arbitrary travel routes is proposed. Instead of constructing separate predictors for individual routes, it first predicts the whole future space–time field of travel times and then traverses the required subsection of the predicted travel time field to compute the travel time estimate for the requested route. Compared with the traditional approach that offers the same flexibility, the proposed method substantially reduces storage and computation time requirements at the relatively small computational cost at the time of actual prediction. It is first established that travel times computed by traversing travel time fields are compatible with more direct measurements of travel times from a vehicle reidentification technique based on electronic toll collection tags. This provides a conceptual justification of the proposed approach. When applied to the loop data from an 8.7-mi section of the I-80 freeway, the proposed approach with a time-varying coefficient (TVC) linear regression model as the component predictor not only improves the baseline historical travel time predictor substantially, with a 40% to 60% reduction in the prediction error, but also improves the traditional whole-route predictor based on the same TVC regression model by 6% to 9%. The result suggests that the proposed algorithm not only achieves the scalability but also improves prediction accuracy, both of which are critical for successful deployment of the advanced traveler information system for large freeway networks.
Vehicle Detection and Classification Using Model-Based and Fuzzy Logic Approaches
Authors: Cheng Heng-Da , Du Haining , Hu Liming , Glazier Chris
Published: May 2018

Vehicle detection and classification information is invaluable in many transportation issues. Vehicle feature extraction and detection are the preprocesses required for vehicle classification. Current automatic vehicle classification systems have deficiencies: low accuracy, special requirements, fixed orientation of the camera, or additional hardware and devices. This paper discusses a vehicle detection and classification system using model-based and fuzzy logic approaches. The system was tested with the use of a variety of images captured by the highway traffic control center of the Utah Department of Transportation. In comparison with existing systems, major advantages of the proposed system are ( a) no special orientation of the camera is required, ( b) no additional devices are needed, and ( c) high classification accuracy is provided. Experimental results show that the performance of the proposed system exceeds that of the existing video-based vehicle classification systems.
Ettringite Formation in Lime-Treated Soils
Authors: Little Dallas N. , Herbert Bruce , Kunagalli Sachin N.
Published: May 2018

The use of calcium-based stabilizers such as calcium oxide (lime) in sulfate-bearing clay soils has historically led to structural distress because of the formation of a mineral called ettringite and possibly thaumasite. In trying to control the damage associated with such formations, engineers have attempted to determine a threshold level of soluble sulfates–-a quantity that is relatively easy and quick to measure at which significant ettringite growth and, therefore, structural distress occurs. This is indeed a complex problem related to not only soil composition but also construction methods, availability of water, ion migration, and the ability of the void structure to accommodate the expansive mineral growth. Unfortunately, experience alone and rules-of-thumb based on experience are not sufficient to deal with this complex issue. Thermodynamic geochemical models of the lime-treated soil can be used as a first step toward establishing thresholds for problematic levels of soluble sulfates for a specific soil. A foundation for the model development is presented, and two soils are compared to illustrate their sensitivities to ettringite growth on the addition of lime. Because the model predicts ettringite growth on the basis of site-specific properties, the model can be used to assess the potential amelioration effects of soluble silica.
Development of Methodology to Include Structural Contribution of Alternative Working Platforms in Pavement Structure
Authors: Tanyu Burak F. , Kim Woon-Hyung , Edil Tuncer B. , Benson Craig H.
Published: May 2018

A methodology was developed to incorporate the structural contribution of working platforms, including those constructed with industrial byproducts, into the design of flexible pavements. Structural contribution of the working platform was quantified with the 1993 AASHTO flexible pavement design guide in terms of a structural number or an effective roadbed modulus. Two methods are proposed. One method treats the working platform as a subbase layer and assigns a structural number to the working platform for use in computing the overall structural number of the pavement. The other method adjusts the effective roadbed modulus to account for the improvement in the roadbed provided by the working platform. Resilient modulus obtained from large-scale model experiments conducted on several working platform materials (e.g., breaker run stone, Grade 2 gravel, foundry slag, foundry sand, and bottom ash) was used in the analysis. Design charts show the structural number or the roadbed modulus as a function of type of material and thickness of the working platform.
Development of U.S. Army Corps of Engineers Engineering Guidance for the Barge Impact Design of Navigation Structures
Authors: Patev Robert C.
Published: May 2018

U.S. Army Corps of Engineers (USACE) guidance, Engineering Technical Letter 1110-2-563, was developed for the design of navigation structures subject to barge impact loading. The new guidance was developed with the use of the results from full-scale experiments conducted under the Innovations for Navigation Projects Research and Development Program. An empirical impact force model was derived from the experimental data, and probabilistic procedures were developed to assist with the design and analysis of navigation structures for impact loads from transiting vessels. Uncertainties in loadings due to a wide range of events from both natural and human sources are crucial in the design of these critical structures. These uncertainties are defined in terms of the distributions for impact angles, velocities, and tow masses, as well as the need to account for loss of power and control events. The methods developed in the guidance for the design and analysis of these structures are focused on defining the return periods for the usual, unusual, and extreme loads for the navigation structures. An example of the probabilistic procedures developed in the guidance is highlighted for the design of an upper guide wall at a navigation project.
Improvement of the Geotechnical Axial Design Methodology for Colorado's Drilled Shafts Socketed in Weak Rocks
Authors: Abu-Hejleh Naser M. , O'Neill Michael W. , Hanneman Dennis , Attwooll William J.
Published: May 2018

Drilled shaft foundations embedded in weak rock formations support a large percentage of bridges in Colorado. Since the 1960s, empirical methods that entirely deviate from the AASHTO design methods have been used for the axial geotechnical design of these shafts. The margin of safety and expected shaft settlement are unknown in these empirical methods. Load tests on drilled shafts provide the most accurate design and research data for improvement of the design methods. Four Osterberg axial load tests were performed in Denver on drilled shafts embedded in soil-like claystone, very hard sandy claystone, and extremely hard clayey sandstone. An extensive program of simple geotechnical tests was performed at the load test sites, including standard penetration tests (SPT), unconfined compressive strength tests (UCT), and pressuremeter tests (PMT). Information on the construction and materials of the test shafts was documented, followed by thorough analysis of all test results. Conservative equations were suggested to predict the unconfined compressive strength and mass stiffness of weak rocks from SPT and PMT data. Colorado Department of Transportation (CDOT) and AASHTO–FHWA design methods for drilled shafts were thoroughly assessed. Design equations to predict the shaft ultimate unit base resistance ( qmax), side resistance ( fmax), and an approximate load–settlement curve as a function of the results of simple geotechnical tests were developed. The qualifications and limitations for using these design methods are presented (e.g., construction procedure, field conditions). Finally, a detailed strategic plan to identify the most appropriate design methods per LRFD for Colorado's drilled shafts was developed.
Comparison of the Bidirectional Load Test with the Top-Down Load Test
Authors: Kwon Oh Sung , Choi Yongkyu , Kwon Ohkyun , Kim Myoung Mo
Published: May 2018

For the past decade, the Osterberg testing method (O-cell test) has been proved advantageous over the conventional pile load testing method in many aspects. However, because the O-cell test uses a loading mechanism entirely different from that of the conventional pile loading testing method, many investigators and practicing engineers have been concerned that the O-cell test would give inaccurate results, especially about the pile head settlement behavior. Therefore, a bidirectional load test using the Osterberg method and the conventional top-down load test were executed on 1.5-m diameter cast-in-place concrete piles at the same time and site. Strain gauges were placed on the piles. The two tests gave similar load transfer curves at various depth of piles. However, the top-down equivalent curve constructed from the bidirectional load test results predicted the pile head settlement under the pile design load to be approximately one half of that predicted by the conventional top-down load test. To improve the prediction accuracy of the top-down equivalent curve, a simple method that accounts for the pile compression was proposed. It was also shown that the strain gauge measurement data from the bidirectional load test could reproduce almost the same top-down curve.
Approach to Evaluating Damage from Thermal Bridge Displacements
Authors: Arsoy Sami , Duncan J. M. , Barker R. M.
Published: May 2018

Bridges are subject to daily and seasonal thermal displacement cycles. In conventional bridges, expansion joints are used to accommodate these displacements. However, in integral bridges, the expansion joints are eliminated, and the superstructure, along with the bridge abutments, undergoes displacements during each temperature cycle. A practical approach to model both daily and seasonal temperature cycles was proposed. The effectiveness of the proposed approach was verified by conducting large-scale laboratory tests on segments of a bridge abutment supported by two different pile types: an H-pile and a prestressed reinforced concrete pile. The results of the tests have shown that the proposed method is practical and capable of detecting damage mechanisms induced by daily thermal displacement cycles. Test results also have shown that damage from daily thermal displacements is more pronounced in materials with nonlinear stress–strain properties.
Modeling Water Flow Patterns in Flexible Pavements
Authors: Hansson Klas , Lundin Lars-Christer , Šimůnek Jirka
Published: May 2018

Most road design models do not explicitly account for moisture transport mechanisms in roads, even though it is well known that water content plays an important part in the deterioration of roads. The Swedish National Road Administration aims to improve the current situation by supporting the development of models that eventually can provide a better and more complete description of the road and environment system. The applicability of hydrological theories and methods to the road and environment system was investigated. Particular attention was paid to flow patterns inside the road as affected by capillary barriers and generated by mechanisms of surface runoff, followed by infiltration into cracks, and the embankment. Particle tracking was used to investigate the effect of rain intensity, precipitated amount, or fracture conductivity on the flow patterns. Changes in rain intensity had a small effect on flow patterns, but velocities were higher for larger rain intensities. Both changes in precipitated amount and fracture conductivity controlled the appearance of the flow patterns, but capillary barrier effects were limited. The numerical code used proved to be mostly appropriate in describing the relevant processes.