bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Implementation of Parallel Dynamic Shortest Path Algorithms for Intelligent Transportation Systems Applications
Authors: Chabini Ismail , Ganugapati Sridevi
Published: April 2007

The problem of computing shortest paths in time-dependent networks is considered. This computational problem is at the heart of solution methods to a variety of dynamic network models that arise in the context of intelligent transportation systems applications. The design, implementation, and computational testing are reported for parallel algorithms that exploit possibilities offered by low-cost, commonly available, parallel, and distributed computing platforms to solve many-to-many shortest path problems in time-dependent networks. Five shared-memory implementations and five message-passing implementations are developed. The parallel implementations adopt three decomposition strategies based on the sets of destination nodes, origin nodes, and departure times at origin nodes. The algorithms are coded with two types of parallel computing environments: a message-passing environment based on the parallel virtual machine library and a multithreading environment based on the Sun Microsystems Multi-Threads library. Numerical results are obtained with large-sized dynamic networks and two types of parallel computing platforms: a distributed network of Unix workstations and a Sun shared-memory machine containing eight processors. Satisfactory speedups of sequential algorithms are achieved. Numerical results obtained indicate that, overall, shared-memory platforms appear to be the most appropriate type of parallel computing platforms to solve dynamic shortest path problems that arise in the context of intelligent transportation systems applications.
Estimating Highway Earthwork Cross Sections by Using Vector and Parametric Representation
Authors: Kim Eungcheol , Schonfeld Paul
Published: April 2007

Two methods are introduced for using vector and parametric representation for precisely estimating cross-sectional areas for highway earthwork. Accurate estimation of cross-sectional areas can minimize errors in the total earthwork cost calculation. The vectors and the parametric representation are used to describe mathematically any referencing point along a cross section. Two methods by which to calculate cross-section earthwork areas—proportionally weighted interpolation and planar interpolation—are developed and are based on the cases most likely to be encountered. These methods can supply precise earthwork cost estimates to highly automated alignment optimization processes. An example study shows that the proposed methods give more-precise results than do the existing methods. The proposed methods not only are simple but also have important advantages in automation, ease of handling, and good adaptability to highway alignment optimization algorithms.
Study of Scalp-and-Replace Equation in: Compaction Specification for Soil with: High Gravel Content
Authors: Lin Deng-Fong , Chang Meng-Kung , Luo Huan-Lin
Published: April 2007

Under AASHTO T224, AASHTO-1 and AASHTO-2 are adapted to AASHTO T180 Method A or B to obtain the adjusted maximum dry density of soil and soil aggregates. If AASHTO T180 Method C or D is followed, the adjusted density is obtained from the graphical method. However, if the amount of field test data is very large, the graphical method is not pragmatic. Within a study, compaction tests followed AASHTO T180-D and an equation, called the scalp-and-replace equation, was derived. This equation method is proposed to replace the graphical method, especially for the cases of large amounts of field-test data. In addition, the applicability of AASHTO-1, AASHTO-2, and ASTM-1 to AASHTO T180-D is examined. The study result reveals a positive effect because the difference between the graphical method and the scalp and- replace equation method is about ±0.3 percent. Results of the study also indicate that AASHTO-1 is more applicable than AASHTO-2 and ASTM-1 to obtaining the adjusted densities for coarse particles retained on the 19-mm sieve. Percentage differences among AASHTO-1, AASHTO-2, ASTM-1, and the scalp-and-replace equation method are high for coarse particles retained on the 4.75-mm sieve. This shows that AASHTO-1, AASHTO-2, and ASTM-1 are not applicable to AASHTO T180-D for calculating the adjusted densities. Finally, changing coefficient and correction factors propose two revised equations of AASHTO-1 and AASHTO-2. The study results show that smaller percentage differences are obtained. The proposed revised AASHTO equations are applicable to AASHTO T180-D for computing the adjusted densities for particles retained on the 4.75-mm sieve.
Engineering Analysis of Dynamic Behavior of Micropile Systems
Authors: Juran Ilan , Benslimane Aomar , Hanna Sherif
Published: April 2007

A series of centrifugal tests was conducted on micropile groups and network systems to investigate the system response to earthquake loading and the superstructure soil-micropile interaction behavior. Model tests on vertical and batter micropile systems embedded in loose to medium-dry sand under different levels of shaking are described. Group and network effects were investigated for different configurations and at different levels of loading. The experimental test results were analyzed parametrically to study the effect of the main controlling parameters. For the model testing conditions, the experimental and parametric results indicated a positive group effect increasing with the number of piles and the batter angle. Dynamic p-y curves were found to be nonlinear with low damping and to be much softer than the published data. For inclinations of 10° and 30°, a substantial improvement is observed in the superstructure response with acceleration reduction to 40 percent of the values obtained in the case of vertical piles. The computer programs LPILE and GROUP were used in a pseudostatic analysis approach to simulate the representative centrifugal model tests. Comparisons between the method predictions and the experimental results illustrate that these methods could be used as engineering tools to assess the seismic behavior of micropile groups and network systems.
Limit States and Factor of Safety in Design of an Anchored Sheet Pile Wall
Authors: Schriver A. B. , Valsangkar A. J.
Published: April 2007

Factors of safety in the traditional design of anchored sheet pile walls have been introduced in a variety of ways. Furthermore, empirical and semiempirical factors are used to modify the calculated depth of embedment, anchor rod force, and maximum bending moment in sheet piling. This leads to a range of designs within the traditional allowable stress design (ASD) approach. Even in the new ultimate limit states design (LSD) method, two approaches are available. One approach is to use load and resistance factor design (LRFD), and the other is to use partial safety factors on the material properties in combination with load factors. In view of the number of design alternatives available, a calibration study of LSD with ASD for an anchored bulkhead was performed. The practical problem of a steel sheet pile wall in a layered cohesionless soil and cohesionless soil overlying cohesive soil was analyzed. The depth of embedment, the anchor rod force, and the maximum bending moment in sheet piling were determined for a range of soil parameters by using LSD and ASD methods. The factors recommended in various codes, manuals, and handbooks were used to perform calibration studies. The results of the parametric study indicate that the load and resistance factors recommended in the LRFD approach must be reevaluated.
Geocomposite Capillary Barrier Drain System with Fiberglass Transport Layer
Authors: Stormont J. C. , Ramos R. , Henry K. S.
Published: April 2007

A geocomposite capillary barrier drain (GCBD) removes water from soil while pore pressures remain negative, that is, the soil to be drained does not need to be saturated. GCBDs are being evaluated for inclusion in pavement systems, particularly between the base course and subgrade layer. The GCBD system comprises a capillary barrier layer (a geonet) sandwiched between transport layers (certain geotextiles). Improved GCBD performance is expected with a transport layer that has a greater affinity for water compared with conventional geotextiles. After many materials were evaluated, a woven fiberglass product was selected for further evaluation as a transport layer. A GCBD with a fiberglass transport layer was placed between a subgrade and a base course in a 3-m-long sloped test device used to measure lateral drainage. Water was infiltrated on the top of the base course, and drainage from the GCBD and the soil layers was collected. Measurements of soil suction were made within the soil layers. The GCBD performance was evaluated during three test phases: constant rate infiltration, subsequent drainage with no infiltration, and transient infiltration corresponding to a design storm. The GCBD was successful in draining sufficient water under suction to prevent positive pore water pressures from developing in the base course and to limit water movement into the underlying subgrade soil.
Modeling Pavement Subdrainage Systems
Authors: Hassan Hossam F. , White Thomas D.
Published: April 2007

A comprehensive study of pavement subdrainage systems was conducted. In the study, three test sections were constructed as part of a new bypass, I-469, at Fort Wayne, Indiana. Location of the drainage layer and materials for the bituminous base course and filter materials were varied from section to section. Instrumentation was installed in the three sections during construction and included sensors to measure temperature, frost, and moisture. Tipping bucket flowmeters were attached to the subdrainage system outlet pipes. A rain gauge was located at each section. A comprehensive laboratory testing program was conducted in the study. Hydraulic conductivity tests were conducted on subgrade, filter, pavement, and trench materials. In addition to conventional saturated permeability, moisture-suction tests were conducted on all materials to determine their partially saturated permeability. Movement of water through the three pavement sections was modeled by using the finite element method analysis. Laboratory-determined hydraulic properties of each material were input directly to the analysis. Several rainfall events were analyzed. Two events were used to verify the analysis model. Subsequent analyses were conducted on new events. Data were recorded for the three sections for 3 years. Measurements indicated that one of the three subdrainage sections drained in one-third the time of the other two sections. This was in agreement with the finite element method analysis. Also, a theoretical subdrainage section was analyzed by using optimal materials from all three sections. This optimized section was shown to further reduce the time of drainage. Conclusions and recommendations address drainage layer location, filter materials, material permeability, and collector pipe capacity.
In Situ Measurement and Empirical Modeling of Base Infiltration in Highway Pavement Systems
Authors: Randy Rainwater N. , Zuo Gang , Drumm Eric C. , Wright Wesley C. , Yoder Ronald E.
Published: April 2007

Free-drainage lysimeters, commonly used in agriculture to monitor evapotranspiration and solute transport, were installed at three highway test sites in Tennessee. The lysimeters were installed below flexible pavement systems just beneath the coarse-graded asphalt stabilized base. The lysimeters collect water infiltrating the unbound aggregate (stone base) and monitor the quantity of infiltration by diverting the flow into tipping bucket rain gauges. One test site indicated infiltration beneath the longitudinal joint in the first several months of monitoring. A second test site, where the dense surface layer was not in place, indicated infiltration correlating with rainfall. Data from this site were used to develop a model to predict the measured infiltration based on the recorded rainfall. The monitoring method and modeling approach may be applicable in the investigation of pavement permeability, drainage system efficiency, and the role of infiltration in the seasonal variation of water content of unbound pavement layers.
Quality Assurance Procedure to Assess Maintenance Adequacy of Drainage Assets
Authors: Mallela Jagannath , White Patricia A. , Titus-Glover Leslie , Smith Kelly L.
Published: April 2007

The engineering community has long recognized the need for adequate maintenance of drainage structures. However, despite several regional and national studies that highlight the damaging effects of poor maintenance, few agencies have improved their inspection and maintenance schedules. Although inadequate funding is the most plausible reason for this scenario, the lack of formal procedures to survey drainage assets, determine their conditions vis-à-vis their functional objectives, and objectively quantify their condition also adds to the problem. Described is a practical prototype maintenance quality assurance (QA) procedure for evaluating the adequacy of drainage asset maintenance in a consistent manner. Key components of the QA procedure are discussed in detail. A software program developed to implement the various components of the QA procedure is described. The program is a simple tool with which to check the condition and functionality of drainage assets at any time. Designed to handle both surface and subsurface drainage assets, the program can be implemented at any level of maintenance jurisdiction. A complete description of the program’s functionality, from the selection of inspection units to the generation of maintenance quality ratings, is provided. Implementing the presented concepts could result in a substantial economic benefit for the implementing agency.
Installation Survivability of Flexible Geogrids in Various Pavement Subgrade Materials
Authors: Wayne Hsieh Chiwan , Han Wu Jeng
Published: April 2007

An on-site installation survivability study of polyvinyl chloride-coated polyester flexible geogrids from a single manufacturer, placed in three types of commonly used pavement subgrade material, was performed to evaluate the amount and degree of installation damage. A series of singlerib strength tests, in-isolation junction strength tests, and wide-width tensile tests was performed to evaluate the strength of reduction due to the installation procedure. The results of the study indicated that installation damage to a flexible geogrid is a function of grain size distribution and angularity of backfill materials, and lift thickness. The test results showed that the tensile strength retained for flexible geogrids placed within clayey gravel, poorly graded silty gravel, and well-graded crushed stone gravel is 84 percent to 95 percent, 66 percent to 88 percent, and 57 percent to 88 percent. The reduction factor for tensile strength due to installation damage is related significantly to soil type and varies from 1.05 to 1.74. The retained strength of junction for flexible geogrid ranges from 71 percent to 100 percent for various types of subgrade material. The reduction factor for junction strength due to installation damage varies from 1.00 to 1.40 for different types of soil. Additionally, 2 percent of the maximum load is recommended as the preload for single-rib tensile strength test. Comparison of the test results shows that wide-width tensile strength of the test geogrids is about 10 percent to 20 percent lower than that obtained from single-rib tensile strength tests.
Building Communities with Transportation
Authors: Burden Dan
Published: April 2007

Important change is sweeping across villages, towns, and cities worldwide. It is taking place in rural hamlets, middle burgs, and huge metropolises. While some people are just going from foot to mechanical transport for the first time in their civilization’s history, others are learning to return to their feet and to build with proper scale and proportion. We will focus on the early steps of returning towns and people to sensible, smart growth and sustainable people-focused transportation and land use practices. I will reflect on what is occurring in both urban and suburban places.
Development of Rumble Strip Configurations That Are More Bicycle Friendly
Authors: Torbic Darren , Elefteriadou Lily , El-Gindy Moustafa
Published: April 2007

This research was initiated to develop new rumble strip configurations for the Pennsylvania Department of Transportation that would alert inattentive or drowsy motorists and could be safely and comfortably traversed by bicyclists. Three primary steps were involved in the development of the new configurations. First, simulation was used to evaluate different configurations for their potential to be bicycle friendly. Second, several configurations that had the greatest potential to be bicycle friendly were installed and field experiments were conducted to further evaluate their effectiveness. Finally, the field data were analyzed and the configurations that were installed were ranked based on their ability to provide a comfortable and controllable ride for bicyclists and to alert inattentive or drowsy motorists. On the basis of results of bicycle and motor vehicle tests, two new rumble strip configurations were recommended for implementation along nonfreeway facilities. One configuration was recommended for use along nonfreeway facilities with higher operating speeds, and a second was recommended for nonfreeway facilities with lower operating speeds.
Accuracy of Numerical Rectification of Video Images to Analyze Bicycle Traffic Scenes
Authors: Khan Sarosh I. , Raksuntorn Winai
Published: April 2007

A method is presented to process full motion video of traffic scenes to estimate bicycle location, speed, and acceleration at a given rate of image processing. The technique presented to estimate bicycle location data from video frames is based on transforming screen coordinates of video frames to ground or roadway coordinates and is known as rectification. The numerical technique and the error analysis are presented. This technique will allow researchers to video record traffic scenes and analyze them to estimate various microscopic and macroscopic traffic flow measures. These measures may be used to develop and validate traffic flow models. Very few studies have been conducted to study bicycle flow characteristics. The data collection technique presented here should allow researchers to collect bicycle flow data at very low cost.
Operational Characteristics of Inline Skaters
Authors: Birriel Elizabeth , Pernia Juan C. , John Lu Jian , Petritsch Theodore A.
Published: April 2007

Inline skating has been considered the fastest growing sport in the United States for the past 10 years. More than 30 million people in the United States are participating, and more than a million are Floridians. Many people view the sport as a new mode of transportation. Some inline skaters believe they should be allowed access to roadways with the same rights as bicyclists. The Florida Department of Transportation (FDOT) cannot make an informed decision on this matter without knowledge of the operational characteristics of the skaters. This project’s main purpose was to measure those characteristics so that FDOT can use the information when trails are designed. During the past year the University of South Florida has been working on a research project sponsored by FDOT focused on determining inline skaters’ operating speeds, sweep width, stopping techniques, stopping distances, and stopping widths on both road facilities and trails. During the project inline skaters were videotaped on roads and trails located in west and south Florida. Operational characteristics of the skaters were obtained from the videotapes using reference dimensions placed at each site. The skaters were analyzed and placed in categories: male, female, learner, advanced, and composite group. Logit models were developed to determine the 50th and 85th percentile values for the operational characteristics. These characteristics affect the desirability of allowing inline skaters on the street system. In addition to helping FDOT make an informed decision on this issue, the project will supply data useful in developing multiuse trail geometrics and operational design criteria.
Advance Yield Markings: Reducing Motor Vehicle—Pedestrian Conflicts at Multilane Crosswalks with Uncontrolled Approach
Authors: Van Houten Ron , Louis Malenfant J. E. , McCusker Dave
Published: April 2007

Motorists yielding to a pedestrian at the crosswalk line can screen the view of the pedestrian crossing in front of them. This places the pedestrian at risk from vehicles approaching in adjacent travel lanes. An experiment was conducted in which advance yield markings and a symbol sign prompting motorists to yield to pedestrians at the markings were placed at several intersections. Their effects on pedestrian safety at multilane crosswalks with pedestrian-activated yellow flashing beacons were evaluated. Motorist and pedestrian behaviors measured throughout the experiment included the following: occurrence of motor vehicle—pedestrian conflicts that involved evasive action, distance before the crosswalk that motorists stopped when yielding to pedestrians, and percentage of motorists yielding to pedestrians. The introduction of the markings and the sign 10 m before the crosswalk increased the distance in front of the crosswalk that motorists yielded to pedestrians and it markedly reduced the percentage of motor vehicle-pedestrian conflicts. Placing markings 15 m and 25 m in advance of the crosswalk produced similar benefits, demonstrating that treatment effects can be produced over a wide range of values.
Scanning “Eyes” Symbol as Part of the Walk Signal: Examination Across Several Intersection Geometries and Timing Parameters
Authors: Van Houten Ron , Louis Malenfant J. E. , Steiner Ruth
Published: April 2007

The use of animated scanning “eyes” in conjunction with Walk interval was examined by a series of studies. In the first experiment, conflicts that involved either the pedestrian or the motorist taking evasive action were examined before and after the scanning eyes were introduced at the following locations: two intersections with one-way traffic on both streets, four intersections with two-way traffic on both streets, and two intersections with one-way traffic on one street and two-way traffic on the other. Conflicts were reduced at crosswalks on all eight streets; reductions on seven of the eight streets were significant. The second experiment examined whether it was better to have the eyes look in both directions (eyes scanning back and forth with equal dwell times in each direction) or only in the direction of the threat (unequal dwell times with the eyes looking longer in the direction of the threat at crosswalks on one-way streets). Results showed that looking one way was no more effective than looking both ways. The effectiveness of steady versus intermittently applied scanning eyes was examined in the second experiment and in the third. The results of this study show that a steady scanning eyes display applied in conjunction with the Walk interval was no more effective than an intermittently applied scanning eyes display, with the eyes alternately on for 3.5 s and off for 3.5 s, but was more effective than an intermittent scanning eyes display that was alternately on for 3.5 s and off for 7 s.
Modeling the Roadside Walking Environment: Pedestrian Level of Service
Authors: Landis Bruce W. , Vattikuti Venkat R. , Ottenberg Russell M. , McLeod Douglas S. , Guttenplan Martin
Published: April 2007

A method is needed to objectively quantify pedestrians’ perception of safety and comfort in the roadside environment. This quantification, or mathematical relationship, would provide a measure of how well roadways accommodate pedestrian travel. Essentially, it would provide a measure of pedestrian level of service (LOS) within a roadway environment. Such a measure of walking conditions would greatly aid in roadway cross-sectional design and would help evaluate and prioritize the needs of existing roadways for sidewalk retrofit construction. Furthermore, the measure can be used to evaluate traffic-calming strategies and streetscape designs for their effectiveness in improving the pedestrian environment. Such a measure would make it possible to merge pedestrian facility programming into the mainstream of transportation planning, design, and construction. To meet the need for such a method, as well as to fulfill a state mandate to establish levels of service standards for all transportation modes, the Florida Department of Transportation sponsored the development of the Pedestrian LOS Model. The model was developed through a stepwise multivariable regression analysis of 1,250 observations from an event that placed 75 people on a roadway walking course in the Pensacola, Florida, metropolitan area. The Pedestrian LOS Model incorporates the statistically significant roadway and traffic variables that describe pedestrians’ perception of safety or comfort in the roadway environment between intersections. It is similar in approach to methods used to assess automobile operators’ level of service established in the Highway Capacity Manual.
Estimating Pedestrian Exposure Prediction Model in Rural Areas
Authors: Qin Xiao , Ivan John N.
Published: April 2007

"Pedestrian exposure" is defined as the exposure risk of pedestrians to collisions with motor vehicles. It is one of the important factors influencing pedestrian crashes. Because pedestrian exposure or even pedestrian volume counts are not readily available, population density is usually used as a substitute in pedestrian crash prediction models. Unfortunately, population density is not a good replacement for pedestrian exposure because it does not account for the amount of walking people do. This study investigates the relationship between the weekly pedestrian exposure in rural areas of Connecticut and factors such as population density, presence of sidewalks, number of lanes, area type, traffic control type, and median household income. General linear modeling and Tukey and Duncan multiple comparison of means methods are used to identify the significant factors. Only the number of lanes, area type, and sidewalk system significantly explain the variation in the resulting pedestrian exposure prediction model. This study suggests extra improvement in pedestrian facilities for the areas with high pedestrian exposure. Ongoing research will take advantage of the model to estimate pedestrian crash models in rural areas of New England.
Autonomous Agents for Traffic Simulation and Control
Authors: Manikonda Vikram , Levy Renato , Satapathy Goutam , Lovell David J. , Chang Peter C. , Teittinen Anna
Published: April 2007

The development of an infrastructure for multiple autonomous agents, with an application to urban traffic signal control, is described. The agent-based infrastructure, Cybele, allows for distributed computing, interagent communication, agent migration, and computational resource allocation. The agents that are used to solve the traffic signal control problem are known collectively as DAARTS (Decentralized Adaptive Agents for contRol of Traffic Signals). DAARTS adopts a hierarchical multiagent-based architecture in which the lowest level (intersection agents) involves individual intersection-traffic dynamics and phase selection based on “local” information, while higher levels take into account the supervisory (network-level) dynamics. The controller design is based on a receding-horizon model predictive control approach. Coordination between intersections is achieved in a decentralized manner at the lowest level. The agents are integrated into a simulation test bed with the microsimulator CORSIM, using the DAARTS simulation tool kit. This kit enables communications between the CORSIM real-time extension, the communications management functions of Cybele, and the traffic control agents. The control process is truly distributed, and each of these components can reside on a different computer. Descriptions of all of the software components are given, and the control algorithm is discussed in detail. Some encouraging results from the simulation of a small network are included. Ongoing and future research activities are discussed.
PEDFLOW: Development of an Autonomous Agent Model of Pedestrian Flow
Authors: Kukla Robert , Kerridge Jon , Willis Alex , Hine Julian
Published: April 2007

The need for an autonomous agent approach for the modeling of pedestrians in urban environments is discussed, and PEDFLOW is placed in the context of existing models. PEDFLOW is a microscopic model of pedestrians’ movement; each pedestrian is represented as an agent capable of making its own decisions on the basis of a part of the observable scene local to that pedestrian. The model, implemented in Java, provides a framework in which agents are visualized as squares in a grid and movement is modeled as a change of grid position with a delay that characterizes the speed of the agent. A single rule set that is made specific to each agent by the incorporation of parameters characterizing types of pedestrians is used. The rules originate from computer-aided analysis of video footage and are transformed into a form that can be efficiently processed by the agent. By adding tools to extract measures of pedestrian flow, the PEDFLOW model will be made useful to urban planners to evaluate infrastructural changes intended to promote walking in the urban environment.
Use of Fuzzy Inference for Modeling Prediction of Transit Ridership at Individual Stops
Authors: Kikuchi Shinya , Miljkovic Dragana
Published: April 2007

Fuzzy inference has become a popular approach to modeling systems in which uncertainties associated with human perception and decision are present. Its use for the modeling framework of travel demand prediction is promising. The possibility of applying fuzzy inference to the problem of predicting bus ridership at individual stops is examined. The required properties for such a model are identified, and the mathematics of fuzzy inference is examined. The factors that may cause transit use at individual stops are identified, and their relationships to ridership are modeled using the hierarchically structured fuzzy rule basis. This fuzzy rule–based model is similar to that of the cross-classification approach, with the boundaries of the classes being fuzzy. The artificial neural network and regression methods are used to model the same problem, and the results are compared with those of the fuzzy inference method. The data used for calibration are obtained from a study of actual bus stops in Delaware. Although no conclusion is drawn as to which approach is superior, fuzzy inference provides an alternative to the traditional regression approach in which the phenomenon’s causality is complicated yet the behavior of the output must be consistent with commonsense knowledge. In particular, it is suited for problems in which the actual volume to be predicted fluctuates widely. Such problems require strength of logical explanatory power and understanding of the pattern rather than accuracy in fitting the data.
Measuring Aggregate Productivity Benefits from Intelligent Transportation System Applications: The California Experience
Authors: Gillen David , Haynes Matt
Published: April 2007

A stated purpose of intelligent transportation system (ITS) applications has been to increase the productivity of the existing transportation system. Such productivity increases, should they occur, would be an important input into any benefit-cost analysis for the evaluation of ITS applications. The impact of different ITS applications on highway productivity in California is investigated. Using time series data for California counties, two forms of analysis are undertaken. The first examines ITS applications using a production function model, and the second uses total factor productivity (TFP) techniques to find the regional aggregate benefit of ITS strategies. The results of these two analyses are particularly interesting, in part because ITS impacts have not been evaluated in this way before. The production function model indicates that there is a slight advantage to the economy in a particular region due to ITS services. Findings also indicate that this advantage is a result of aggregate growth and not merely redistributive effects. The TFP analysis indicates that ITS applications contribute to regional economies and county product as well, though these results are only significant at the 10 percent level. Whereas the findings indicate an apparent need to include economic benefits in any study of ITS projects, further study in this area is needed to draw more concrete conclusions. In particular, the notion of synergies between multiple projects of the same type or different types is one of the next steps to be taken.
Evaluation of the Environmental Effects of Intelligent Cruise Control Vehicles
Authors: Bose Arnab , Ioannou Petros
Published: April 2007

Intelligent cruise control (ICC) vehicles are already commercially available in Japan and should be ready for the North American market by next year. Although the controllers are local and string stable, it is not clear how the vehicles perform environmentally. It is shown that ICC vehicles can accurately track a lead vehicle and attenuate position errors generated by the lead vehicle during smooth transients. Furthermore, the smooth response of ICC vehicles designed for human factor considerations filters out traffic disturbances caused by rapid acceleration transients. Such ICC vehicle properties have beneficial air pollution and fuel consumption effects that are significant when the manual vehicles perform aggressive rapid acceleration maneuvers. These results are obtained using the Pipes human driver vehicle following model, which models the slinky-type effects observed in today’s manual driving. The response of the Pipes model is compared with that of human drivers. The Pipes model is observed to give a smooth approximation of human driver response during transients. Simulations have demonstrated that the fuel consumption and pollution levels present in manual traffic can be reduced during rapid acceleration transients by 28.5 percent and 1.5 to 60.6 percent, respectively, by the presence of 10 percent ICC vehicles. Experiments with actual vehicles are used to validate the theoretical and simulation results.
Backscattered Electron Imaging to Determine Water-to-Cement Ratio of Hardened Concrete
Authors: Badger Steve R. , Clark B. A. , Sahu Sadananda , Thaulow Neils , Lee Richard J.
Published: April 2007

A methodology has been developed for the determination of the water-to-cement (w/c) ratio in hardened concrete using backscattered electron imaging (BEI) within a scanning electron microscope. Reproducible quantitative data are obtained by using standards from polished sections as well as by controlling brightness and contrast on the instrumentation. The method is based on concrete sections that have been vacuum impregnated with epoxy and polished to a flat surface. During impregnation, epoxy fills capillary porosity as well as cracks, voids, and other defects. The w/c ratio is directly related to the capillary porosity and degree of hydration and therefore can be measured. The epoxy-impregnated porosity appears black in BEI, whereas other phases such as calcium silicate hydrate, ferrite phases, and aggregate appear as brighter phases. Signal production, brightness, contrast, sample preparation, general methodology, and resolution are discussed.
Petrographic Analysis of Concrete Deterioration by Feature Relocation
Authors: Sahu Sadananda , Badger Steve R. , Osgood Barbara , Thaulow Niels
Published: April 2007

Petrographic analysis of concrete specimens that uses both optical microscopy and scanning electron microscopy (SEM) with backscatter electron detector and energy-dispersive X-ray spectrometer (EDS) provides a unique opportunity to obtain information on mineralogical, chemical, and microstructural features. Combining optical microscopy and SEM-EDS provides complementary information of concrete suffering from alkali silica reaction or sulfate attack. Feature relocation software enables the petrographer to identify an object of interest with one technique and confirm its identity with another, thereby using the strength of both techniques.
Hardened Concrete Air Void Analysis with a Flatbed Scanner
Authors: Peterson Karl W. , Swartz Raymond A. , Sutter Lawrence L. , Van Dam Thomas J.
Published: April 2007

Digital images collected from a polished concrete surface with a flatbed scanner are used to quantify air void characteristics. The surface is scanned a total of three times. Between the first and second scans, the surface is stained with phenolphthalein to color the cement paste pink. Between the second and third scans, the surface is painted black, and white powder is pressed into depressions left by air voids. The images collected from the three scans are aligned and input into a classification scheme to yield an output image. Each pixel in the output image is categorized as air void, cement paste, or aggregate. By digitally applying a grid of points and a series of lines to the output image, a modified point count is automatically performed according to ASTM C457, Standard Test Method for Microscopical Determination of Parameters of the Air-Void System in Hardened Concrete. A comparison is made between results obtained by an automatic analysis of the digital output image and results obtained by a manual analysis of the surface with an optical microscope.
Examination of Effect of Driver Population at Freeway Reconstruction Zones
Authors: Al-Kaisy Ahmed , Hall Fred
Published: April 2007

An investigation into the effect of the driver population factor on the capacities of long-term freeway reconstruction zones is presented. A major reconstruction project in Ontario, Canada, provided an opportunity to conduct the investigation. Comprehensive data on traffic, weather, and work activity were used. Three different analyses were conducted. These analyses compared mean capacity flows during different times of the day and days of the week to estimate the effect of the noncommuter driver population during weekdays and weekends. The study found that the effect of the driver population factor on the capacity of the reconstruction site was highly significant. On the basis of a factor of 1.0 for commuter traffic, a driver population factor of 0.93 was estimated for the afternoon peak period and a driver population factor of 0.84 was estimated for weekends. Also, the driver population factor is likely responsible for a capacity reduction on weekends compared with the capacity on weekdays. This capacity reduction was 12 percent in one direction of travel and 17 percent in the other direction. Both the driver population factors and the capacity reductions on weekends found in the study are considered conservative, given that these data were collected in April and early May and that there is a higher proportion of tourist drivers during the summer season at this site. Nonetheless, numbers are consistent with empirical observations from other studies and provide further guidance for use of the driver population factor in the 2000 Highway Capacity Manual procedures.
Delay Model for Planning Analysis of Main-Line Toll Plazas
Authors: Lin Feng-Bor
Published: April 2007

Main-line toll plazas are major bottlenecks on toll roads. The capacity and level-of-service analysis of these facilities, however, have not been addressed by the various versions of the Highway Capacity Manual. Traffic operations at toll plazas can be realistically analyzed through computer simulation, but there is a need for a simple analytical delay model that can provide quick and reasonably accurate estimates to help with the planning of toll plazas. Such a delay model is formulated and calibrated on the basis of simulation results. For volume to capacity ratios below 1.4, discrepancies between the estimates obtained from this delay model and from computer simulation are mostly less than 10 percent.
Use of Image Analysis to Estimate Average Stopped Delays per Vehicle at Signalized Intersections
Authors: Saito Mitsuru , Walker Jaylen , Zundel Alan
Published: April 2007

Average stopped delay has been used to determine the level of service (LOS) of signalized intersections. This work has mostly been done offline by using manual field observation methods, analytical models, and simulation software. Dynamic evaluation of the LOS of signalized intersections has been difficult because the use of conventional methods requires a large amount of labor and cost if such analyses were conducted periodically. However, many traffic operations centers wish to be able to coordinate surface street and freeway management when congestion occurs. It is demonstrated that image analysis can be used to dynamically determine average stopped delay. Two methods—the gap method and the motion method—were developed and compared with ITE’s field delay observation method. Traffic Software Integrated System software was used to create images of queued vehicles. To eliminate parallax problems, two simple assumptions were made: the queued vehicles were viewed from the direction normal to the pavement, and all lines of sight were parallel to the camera’s view direction. At present, the algorithms are simple, but they produced promising results. Various analysis time intervals from 1 to 20 s were used to estimate stopped delay. The gap method gave a good result when the time interval was about 15 s; the motion method produced a good result when the time interval was 1 or 2 s. The manual observation method resulted in a good estimate similar to that which the simulation software produced, especially when the time interval was about 10 s or less.
Saturation Flow Estimation by Traffic Subgroups
Authors: Rouphail Nagui M. , Nevers Brandon L.
Published: April 2007

A framework for the estimation of saturation flow rates at signal-controlled intersections is presented. The proposed framework is grounded in existing highway capacity theories found in U.S. and international highway capacity guides. It is intended to provide a high level of flexibility to the end user for analyzing complex approach configurations and signal control schemes. This flexibility is achieved through the decomposition of the traffic stream on an approach into a subset of homogeneous traffic subgroups, each of which has a unique average saturation flow headway. The proposed approach enables the analyst to produce saturation flow rates at multiple levels, ranging from turning-movement saturation flows on individual lanes (exclusive or shared) to overall approach estimates that can encompass multiple lane groups. The proposed framework can accommodate cases with uneven distribution of traffic across lanes because of lane impedance differentials or prepositioning. When assumptions similar to those found in the Highway Capacity Manual (HCM) were used, the model’s saturation flows were found to be virtually identical to those estimated by the 1997 HCM.
Predicting Right Turns on Red
Authors: Tarko Andrzej P.
Published: April 2007

The Highway Capacity Manual (1997) does not provide a method for the prediction of right turns on a red signal (RTOR). A model for prediction of the RTOR volumes at isolated and coordinated signals is presented. The model has been derived by using clear assumptions and equations consistent with these assumptions. The method was implemented in the form of a spreadsheet and was evaluated without any previous calibration. CORSIM was used to generate benchmark data. The evaluation results show that the model produces unbiased results if the impedance from the queue on the approach with the right turns is the prevailing factor in the RTOR volume. A limited bias appears if the impedance from the flows on the cross street is critical for the RTOR volume. Adequate setting of the model parameters (critical gap and follow-up time) should reduce this bias. A way of estimating delays of right-turning vehicles is briefly addressed.
Delay Model for Right-Turn Lanes at Signalized Intersections with Uniform Arrivals and Right Turns on Red
Authors: Qureshi Mohammad A. , Han Lee
Published: April 2007

A framework for the future incorporation of proper right-turn-on-red (RTOR) delay estimation procedures into the Highway Capacity Manual signalized intersection chapters is provided. Models of uniform delay that are based on queuing theory and that incorporate RTORs are developed. Queuing accumulation polygons (QAPs) were used to analyze the effects of RTOR operations. A classification system for placement of any signal phasing scheme into one of four classes based on a sequence of three red regimes and one green regime is showcased. The three red regimes are characterized by the traffic stream that is given priority over the RTOR traffic during the red regime. One red regime gives priority to the intersecting and conflicting traffic. The second red regime gives priority to the intersecting but nonconflicting traffic. The third red regime prioritizes the opposing and conflicting traffic. It is further demonstrated that the four classes of signal phasing schemes result in one of two general QAP patterns. The first pattern consists of two conflicting regimes, followed by two nonconflicting regimes. The second consists of alternating conflicting and nonconflicting regimes. Models used to calculate delay for each basic pattern are presented. The parameters needed to calculate delays based on the models that were developed are discussed. Furthermore, models from related research that may be used to develop any necessary parameter estimates are also presented.
Model of Free-Flow Speed for Indiana Arterial Roads
Authors: Ye Q. , Tarko A. , Sinha K. C.
Published: April 2007

As a basic characteristic of traffic flow, vehicular travel speed is indispensable in many research and management tasks. In travel speed estimation, vehicular free-flow speed is a crucial determining factor, particularly when the traffic is light or moderate. The current state-of-the-art modeling of free-flow speeds is explored. The development of models of free-flow speed for Indiana arterial roads that may also be suitable for other states in the Midwest is described. Separate free-flowspeed models are presented for cars and trucks during daytime and nighttime hours. Aggregate models could easily be available if the methods provided are followed. The presentation includes the research background, the data-collection and data-processing procedures, a description of model development, and an analysis and a description of a means of refinement of the model.