bluuebunny/crossref_metadata_2025 huggingface dataset:
Transit-Oriented Urban Design Impacts on Suburban Land Use and Transportation Planning
Authors: Dock Frederick C. , Swenson Carol J.
Published: April 2007

The relationship between urban form, as shaped through transit-oriented urban design, and transportation demand, as represented by regional travel demand forecasting model techniques, is investigated. The research from two studies is synthesized and, through development of travel demand forecasting model enhancements in the form of a subarea model and off-line estimation techniques, a link is sought between data analysis at the regional scale and urban design and land use strategies applied at the local and subregional scales. A methodology for aggregating individual transit-oriented development sites into a subregional growth scenario is described. Findings are reported from use of the subarea model to compare impacts of a transit-oriented growth scenario with a conventional growth scenario for a subregion of suburban communities.
UPlan: A Versatile Urban Growth Model for Transportation Planning
Authors: Johnston Robert A. , Shabazian David R. , Gao Shengyi
Published: April 2007

Urban models useful in transportation planning are reviewed, focusing especially on ones that are based on geographic information system (GIS) software. Then UPlan, a simple model written by the authors in the ArcView GIS, is described. Several different applications of UPlan are outlined, involving transportation planning and analysis of the growthinducing effects of new facilities, to demonstrate its use. Such models are coming into use for National Environmental Policy Act of 1969 assessments and for joint land use and transportation planning.
Moisture Damage Evaluation of Asphalt Mixtures by Considering Both Moisture Diffusion and Repeated-Load Conditions
Authors: Cheng DingXin , Little Dallas N. , Lytton Robert L. , Holste James C.
Published: April 2007

Two moisture damage models based on major moisture failure mechanisms are proposed. The adhesion failure model was developed to analyze the adhesive fracture between asphalt and aggregate in the presence of water. Cohesive and adhesive fractures in an asphalt-aggregate system are directly related to the surface energy characteristics of asphalt and aggregate. The surface energy of adhesion with or without the presence of water can be calculated from the surface energies of asphalt and aggregate. A moisture diffusion model was developed based on the one-dimensional consolidation of soil and a gas adsorption model. The moisture diffusion model was used to obtain the moisture diffusion characteristics of asphalt binders, including the amount of moisture that can permeate a binder and the diffusivity of the binder. The amount of moisture that permeates a binder is identified as a key factor in the moisture damage. Finally, mechanics-based experiments conducted on asphalt mixtures validated the results from the adhesion failure and diffusion models.
Evaluation of Permeability of Superpav® Asphalt Mixtures
Authors: Mohammad Louay N. , Herath Ananda , Huang Baoshan
Published: April 2007

The presence of water in a pavement system is detrimental to its life. Permeable asphalt concrete pavement structures are vulnerable to stripping, which causes premature damage under heavy traffic. To assess the permeability of asphalt mixtures, a research study was conducted at the Louisiana Transportation Research Center (LTRC). Laboratory permeability tests were performed on field cores taken from 17 Superpave® projects in Louisiana. An LTRC-modified version of Karol-Warner's falling-head permeameter was used to conduct the permeability test. A sensitivity analysis was performed to relate the permeability test results to mixture volumetric properties such as air void content, compaction effort, mixture gradation, and lift thickness. A statistical regression model was developed to predict the permeability of Superpave mixtures from the mixture volumetric properties. The model successfully predicted the coefficient of permeability of asphalt mixtures from a separate data set that was not included in the model development.
Simulation of Asphalt Materials Using Finite Element Micromechanical Model with Damage Mechanics
Authors: Sadd Martin H. , Dai Qingli , Parameswaran Venkit , Shukla Arun
Published: April 2007

A theoretical and numerical study of the micromechanical behavior of asphalt concrete was undertaken. Asphalt is a heterogeneous material composed of aggregates, binder cement, and air voids. The load-carrying behavior of such a material is strongly related to the local load transfer between aggregate particles, and this is taken as the microstructural response. Numerical simulation of this material behavior was accomplished by developing a special finite element model that incorporated the mechanical load-carrying response between the aggregates. The finite element scheme incorporated a network of special frame elements, each with a stiffness matrix developed from an approximate elasticity solution of the stress and displacement field in a cementation layer between particle pairs. A damage mechanics approach was then incorporated within this solution, and this approach led to the construction of a softening model capable of predicting typical global inelastic behavior found in asphalt materials. This theory was then implemented within the ABAQUS finite element code to conduct simulations of particular laboratory specimens. A series of model simulations of indirect tension (IDT) tests were conducted to investigate the effect of variation of specimen microstructure on the sample response. Simulation results of the overall sample behavior compared favorably with experimental results. Additional comparisons were made of the evolving damage behavior within the IDT test samples, and numerical results gave reasonable predictions.
Time–Temperature Superposition for Asphalt Mixtures with Growing Damage and Permanent Deformation in Compression
Authors: Zhao Yanqing , Richard Kim Y.
Published: April 2007

The objective in this study was to check the validity of the time–temperature superposition principle for hot-mix asphalt (HMA) with growing damage and viscoplastic strain in the compression state, which is essential for the permanent deformation characterization of HMA. Constant crosshead rate compression tests were conducted at temperatures between 25°C and 55°C, and data were analyzed to construct the stresslog reduced-time master curves for various strain levels. Research results indicate that HMA with growing damage remains thermorheologically simple in the temperature range used in this study and that the time–temperature shift factor is only a function of temperature and is independent of the strain level. Two types of tests, the repeated creep and recovery test and the cyclic sinusoidal loading test, were performed in this study to validate the time–temperature superposition in loading histories commonly used in asphalt mixture testing. The results further confirm that the time–temperature superposition is valid for HMA with growing damage and permanent deformation and that the response of HMA depends only on the reduced loading history.
Ultrasonic Pulse Wave Velocity Test for Monitoring Changes in Hot-Mix Asphalt Mixture Integrity from Exposure to Moisture
Authors: Birgisson Bjorn , Roque Reynaldo , Page Gale C.
Published: April 2007

The ultrasonic pulse wave velocity test is evaluated as a possible tool for monitoring changes in the integrity of mixtures due to moisture conditioning. Two sets of mixtures were prepared. The first group involved fine-grained (above the restricted zone) and coarse-grained (below the restricted zone) limestone mixtures commonly used by the Florida Department of Transportation (FDOT) that were produced with multiple void structure and permeability configurations by varying the gradations and proportions for a common set of aggregates and asphalt cement. The second set of mixtures consisted of three granite-based mixtures commonly used by FDOT. The results presented show that the small strain modulus obtained with the ultrasonic pulse wave velocity test appears to be sensitive to changes in mixture integrity due to moisture, and therefore it may be a possible tool for the characterization of damage in both laboratory and field specimens. Additional work remains to be performed to better define the meaning of the values obtained. However, the current results indicate that the ultrasonic pulse wave velocity test may be used as an indicator of damage in specimens as well as a quick monitoring device for detecting changes in the integrity of mixtures due to exposure to moisture.
Evaluation of Rapid Triaxial Test in Quality Control of Hot-Mix Asphalt
Authors: Gould Jonathan S. , Nanagiri Yamini V. , Mallick Rajib B. , Petruccelli Joseph D. , Crockford William C.
Published: April 2007

The objectives of this research were to evaluate the rapid triaxial test method for use in quality control of hot-mix asphalt production and, if possible, determine test conditions for reliable results. The scope of this study consisted of testing different mixes at two different temperatures and frequencies and evaluating the results. The equipment was rugged and portable, and the hardware and software were easy to handle and did not require extensive technician training. The results from this study show that modulus and phase angle values obtained from testing are sensitive to key mixture components and properties. The coefficients of variation of results obtained from tests conducted at 60°C and 1 Hz are low. Tests with fine-graded mixes showed good correlation of dynamic stiffness parameters with rutting, and the stiffness parameters were found to be sensitive to the ratio of dust to effective binder. One significant advantage of using this test procedure as a regular quality control tool is that decisions can be made on the basis of performance-related parameters rather than on the basis of volumetric properties only. In view of its desirable qualities, this test method seems to be usable on a regular basis for quality control testing. However, before it is used, agencies must adopt a test protocol and establish target values and allowable variations.
Road Transportation and Trade Facilitation Strategy for Central Asia
Authors: Seneviratne Prianka N.
Published: April 2007

Changes in trade patterns and consequent demand for transportation are continuing to change in the Central Asian Republics (CAR). Since independence, these nations have formulated and implemented basic strategies to improve transportation and meet changing demand characteristics. International financial institutions have supported these efforts through various lending and nonlending programs. However, the next level of changes in policies, legislation, and management practices to achieve greater efficiency are costlier and will take more time to institute. These changes would have to be backed by a coherent development program with a definite agenda and commitment to create a seamless, international transportation system. The challenges and a systematic approach to developing transport strategies for the CARs are discussed. An overview is provided of the existing demand, emerging trade patterns, and current supply that are the basis for a road transportation strategy to foster travel and trade, with a specific reference to Kazakhstan. The ideal composition of a strategy is discussed along with the issues, constraints, and implementation timing.
Assessing Pipeline Adequacy to Meet Natural Gas Demand for Electricity Generation: New York State Case Study
Authors: Hasan Masroor , Neill Charles
Published: April 2007

A conceptual framework and modeling approach are presented for assessing pipeline adequacy to meet existing and future demands for natural gas in electricity generation after gas demands for traditional end users have been met. Transportation logistics and economics issues are identified that natural gas (and electric) suppliers face in trying to meet traditional and electricity generation gas demands. An integrated electric and gas modeling approach is used for this purpose. The approach uses separate models for electric and gas systems. Consistent equilibrium solutions are obtained by iterating between the two models. The economic decisions and logistical issues facing the gas and electric industries are quite stark. The incentives of the two industries need to be realigned to achieve greater electric efficiency, reliable generation, and better air quality at a reasonable cost. As a detailed case study of the modeling approach, results are presented from an analysis of the ability of the natural gas delivery system to meet future electricity generation requirements in New York State. The analysis integrates the modeling of the gas demands of New York State electric generators with the modeling of available gas supply and delivery capacity to the state. Although the analysis indicates that the gas and electric systems in New York can reliably meet their future loads under a range of electricity generation and gas pipeline expansion scenarios, oil use by electric generators remains a key substitute for gas during times of peak gas demands (e.g., cold winter days).
Perceived Benefits of Congestion Pricing for Trucks
Authors: Kawamura Kazuya
Published: April 2007

Empirically derived value-of-time distributions are used to calculate the perceived benefits from the time saved by trucks in using toll lanes. The conditions on the SR-91 congestion pricing facility in California are used in a case study. Assuming that the value of time for trucks is lognormally distributed, the probabilistic truck mode share for the toll lanes was estimated separately for in-house and for-hire trucks. The mean values of time for toll-lane users and nonusers were estimated using Monte Carlo simulations. The benefits were calculated as the value of travel time savings that accrue for both toll-lane users and nonusers. The analyses found that the opening of the congestion pricing facility in 1995 has resulted in more than $2 million in annual savings for trucks. Trucks would realize an added $660,000 annually if the toll lanes were open to trucks. The disproportional share of the benefit goes to a few trucks with very high values of time, especially when the toll is expensive. Also, forhire trucks receive, on average, greater benefit than in-house carriers because of higher values of time.
Effects of Truck Driver Wages and Working Conditions on Highway Safety: Case Study
Authors: Rodríguez Daniel A. , Rocha Marta , Khattak Asad J. , Belzer Michael H.
Published: April 2007

The role of human capital and occupational factors in influencing driver safety has gained increased attention from trucking firms and policy makers. The influence of these factors, along with demographic factors, on the crash frequency of truck drivers is examined. A unique driver-level data set from a large truckload company collected over 26 months was used for estimating regression models of crash counts. On the basis of estimates from a zero-inflation Poisson regression model, results suggest that human capital and occupational factors, such as pay, job tenure, and percentage of miles driven during winter months, have a significantly better explanatory power of crash frequency than demographic factors. Relative to the zero-inflation and count models, results suggest that higher pay rates and pay increases are related to lower expected crash counts and to a higher probability of no crashes, all else held equal. Although the data come from one company, the evidence provided is a first step in examining the structural causes of unsafe driving behavior, such as driver compensation. These results may motivate other companies to modify operations and driver hiring practices. Also, the need for a comprehensive study of the relationship between driver compensation and driver safety is demonstrated.
Shrinkage of Latex-Modified and Microsilica Concrete Overlays
Authors: Buchanan Patricia M. , Mokarem David W. , Weyers Richard E. , Sprinkel Michael M.
Published: April 2007

Shrinkage performance was examined of Virginia Department of Transportation-approved latex-modified and microsilica concrete overlay mixtures. Research was conducted on both field-sampled and laboratory-fabricated restrained and unrestrained specimens. From crack and delamination surveys of sampled bridge decks and laboratory test results, a shrinkage performance-based specification for the Virginia Department of Transportation was developed. There was no significant difference between the unrestrained shrinkage values of latex-modified and microsilica concrete overlay mixtures for the specified time periods. Restrained microsilica concrete specimens generally cracked earlier and more frequently than restrained latex-modified concrete specimens. However, the bridge deck crack and delamination surveys show that conditions and quality of construction and type and frequency of traffic may have a greater effect on cracking than the overlay material.
Effect of Curing Methods on Early-Age and Drying Shrinkage of High-Performance Concrete
Authors: Nassif Hani , Suksawang Nakin , Mohammed Maqbool
Published: April 2007

Many engineers and agencies have observed that the field implementation of high-performance concrete (HPC) is highly dependent on curing and placing conditions. The effect of curing conditions on the early-age properties and long-term durability of HPC is not fully understood. There is a need to expand the knowledge of early-age properties and of the effect of pozzolanic material (like silica fume and fly ash) on drying shrinkage. Results are presented of a study performed to identify the effect of various curing methods on the early-age (autogenous) as well as drying shrinkage of normal and lightweight HPC. The study included a comparison of available analytical models for predicting early-age and drying shrinkage with results from tests performed on different mixes. HPC mixes were developed and evaluated as part of an overall study for the New Jersey Department of Transportation to develop and implement mix designs and technical specifications for HPC transportation structures, such as pavements and bridges. The effect of using three different curing methods on the early-age performance of HPC is presented. The curing conditions consisted of air-dry curing, burlap or moist curing, and use of a curing compound. Results show that moist (burlap) curing should be applied within 1 h after the placement of concrete to improve early-age performance. For very low water-to-cement plus pozzolan ratios, fly ash and lightweight aggregate improved the autogenous shrinkage performance. Moreover, current shrinkage models need to be revised to address HPC mixes.
Effectiveness of Portland Cement Concrete Curing Compounds
Authors: Whiting Nancy M. , Snyder Mark B.
Published: April 2007

Many different spray-on compounds are available for curing concrete, including newer products that are intended to address the environmental concerns associated with high volatile organic compound (VOC) contents. A laboratory study was conducted to examine the effectiveness of different types of curing compounds in retaining water for hydration, promoting concrete strength, and reducing permeability, relative to classic curing techniques such as plastic sheeting and ponding and relative to the use of no curing treatment. Comparisons of moisture loss, compressive strength, permeability, and capillary porosity were made for samples representing three high-VOC curing compounds, three low-VOC curing compounds, water curing, and plastic-sheet curing, and for samples with no curing treatment after 3 days and 28 days of curing. The performance of the six compounds tested varied greatly, but none of the compounds performed as well as the samples cured with water or plastic sheeting. All compounds performed better than samples with no curing treatment.
Application of Modified ASTM C1260 Test for Fly Ash-Cement Mixtures
Authors: Shon Chang-Seon , Sarkar Shondeep L. , Zollinger Dan G.
Published: April 2007

The ASTM C1260 accelerated mortar-bar test is a commonly used method for rapid identification of potential alkali-aggregate reactivity and may also be used for assessing the effectiveness of supplementary cementitious materials in suppressing alkali–silica reactivity (ASR). A general criticism of this test method is the severity of test conditions. It is not uncommon for aggregates with a good field-performance track record and no history of ASR to test reactive by this method. The purpose of this study was to evaluate the effectiveness of fly ash in controlling expansion due to ASR, using a modified ASTM C1260 test. Three different strengths of NaOH solution were used to test reactive, potentially reactive, and nonreactive aggregates in the presence of Class F and Class C fly ash at 20% and 35% replacement by mass of cement. The other variables included high- and low-alkali cement, extended curing time, and a longer testing period of 28 days. A correlation was drawn between additional evaporable water and expansion due to ASR.
Value of the Facilities and Attributes of New Heavy Rail and Bus Rapid Transit Projects in a Developing City: The Case of Lima, Peru
Authors: Martínez Manuel J. , Cornejo Javier
Published: April 2007

Preferences of heavy rail (HR) system users are studied in relation to the system’s alignment and bus connections in the context of a developing city. Stated preferences techniques are applied to estimate the monetary value of a long set of attributes of a new mass transit service: HR connected to bus rapid transit (BRT). Attributes include time, fare, bicycle storage at stations, stairways, feeder bus integration, integration with BRT, type of bus service, bus itinerary, and quality of buses. The long set of attributes deserved three stated preference experiments grouped by time and fare, characteristics of HR, and characteristics of BRT. They were linked by the common attribute of the fare. Results of the values of the attributes are presented. The value of the preference for HR is reduced to 8% when a feeder bus is not offered and the HR route does not reach downtown. The value of a feeder bus using small vehicles is higher than the value of BRT even if BRT operates with new buses and express service to downtown. Bicycle storage or escalators have no value for the prospective passenger. After the response of users to the new services is analyzed, conclusions for the operational design of the system are presented.
Asset Management Framework for State Departments of Transportation to Meet Transit Fleet Requirements
Authors: Khasnabis Snehamay , Bartus Joseph , Ellis Richard Darin
Published: April 2007

State departments of transportation that provide the bulk of matching funds to local transit agencies for the purchase of new buses are duly concerned about the escalating costs of new buses and the lack of sufficient funds to keep up with their replacement costs. An asset management framework is presented that can be used by state departments of transportation to ( a) allocate capital dollars for the dual purpose of purchasing new buses and rebuilding existing buses within the constraints of a fixed budget when the needs of all constituent agencies in a peer group are considered and ( b) distribute funds among the agencies equitably. The proposed framework includes two optimization models. Model 1 attempts to maximize the weighted fleet life of all the buses being purchased and rebuilt for a given peer group within the constraints of a fixed budget. Model 2 is designed to maximize the remaining life of the entire peer group, including the existing buses and those being replaced or rebuilt. Case studies presented to demonstrate the application of the models show that the framework is viable and can be used for the designated purpose with fleet data currently available from transit agencies. Further research on testing the framework is recommended to ensure its applicability under different sets of circumstances.
Critical Measures of Transit Service Quality in the Eyes of Older Travelers
Authors: Burkhardt Jon E.
Published: April 2007

Older travelers use public transportation services for relatively few of their trips. Attracting additional older riders will require that transit operators pay more attention to the specific mobility preferences of older travelers. Focus group research generated measures of transit service quality. These measures rate factors that affect the relative levels of consumer satisfaction for older persons, who rate certain factors differently from other travelers. The travel attributes that were most highly valued by seniors in the focus groups are used to assess current travel modes and to suggest near-term and long-term improvement strategies for public transit operators. Public transit systems most likely to succeed in attracting older persons (and other riders as well) are expected to be those systems that offer the following: more choices in travel modes and their corresponding attributes, especially price; greater focus on higher-quality services; and greater degree of service articulation, in which travel services are more closely tailored to the specific travel needs of the individual traveler and a specific trip.
Analysis of Effects of Fare-Free Transit Program on Student Commuting Mode Shares: BruinGo at University of California at Los Angeles
Authors: Boyd Brent , Chow Melissa , Johnson Robert , Smith Alexander
Published: April 2007

Spring 2002 concluded the second year of the BruinGo pilot demonstration program of the University of California at Los Angeles (UCLA). BruinGo allows students and employees of UCLA to board buses of the Santa Monica Municipal Bus Lines (Big Blue Bus) free of charge. At a time when the future of BruinGo is at stake (both its existence and the possible expansion of the program to other transit agencies), a brief analys is of what has been accomplished by the program at this stage is provided. The program is analyzed using two methods: ( a) the analysis of the changes in the commuting mode share for all off-campus student commuters and ( b) an intricate process of geocoding survey data in which the relationship of the proximity of a student’s residence to the Big Blue Bus lines and the corresponding choice of mode to campus is analyzed. The conclusion is that providing fare-free transit to students did, in fact, increase transit ridership and decrease students’ reliance on the automobile to reach campus. Transit ridership for 2001 (the first year of BruinGo) increased by more than 50% over ridership in 2000 (the year before BruinGo), while more than 1,000 fewer automobile trips were taken to the UCLA campus each day. Even more striking is the rate at which students are leaving their cars at home in the areas best served by the Big Blue Bus. After BruinGo, fully 50% of all students in walking distance of a direct line to campus took transit (compared with 35% before BruinGo). That is much higher than in other areas. The mode share of walking and bicycling also decreased dramatically, however.
Cognition and Relative Importance Underlying Consumer Valuation of Park-and-Ride Facilities
Authors: Bos llona , Molin Eric , Timmermans Harry , van der Heijden Rob
Published: April 2007

Results are reported of a study designed to identify the cognitive constructs underlying the valuation of park-and-ride (P&R) facilities and to measure the relative importance attached to the attributes of such facilities. Results show that the reliability of public transport is quite important. Furthermore, time and, to a lesser degree, costs considerably influence a traveler’s decision to use P&R or not. Parking aspects are less important, except for information about parking. Finally, respondents evaluated the attributes about staying at P&R facilities to be least important. These results do, however, seem to vary between user groups.
Integration of Light Detection and Ranging Technology with Photogrammetry in Highway Location and Design
Authors: Veneziano David , Souleyrette Reginald , Hallmark Shauna
Published: April 2007

Surface terrain information is needed to economically site new or relocate existing infrastructure facilities and make final design plans. Field surveying and photogrammetric mapping are the methods most widely used to acquire these data. However, these methods are time- and resource-intensive, as significant data collection and reduction are needed to provide the level of detail necessary for facility location and design. Light detection and ranging (LIDAR) is a relatively new alternative technology for obtaining terrain information more efficiently. With LIDAR, data can be collected under a variety of environmental conditions, including low sun angle, cloudy skies, and even darkness, resulting in expanded windows for data collection. Although less accurate than photogrammetric mapping, LIDAR can help expedite the highway location and design process by providing designers with preliminary terrain information earlier in the process. Presented is a proposed methodology for using LIDAR in conjunction with photogrammetric mapping to speed up highway location and design activities, including estimates of time and cost savings.
Toward More Effective Transportation Applications of Computational Intelligence Paradigms
Authors: Sadek Adel W. , Spring Gary , Smith Brian L.
Published: April 2007

While information technology has facilitated the collection of neverbefore-seen quantities of data, these data have not always provided the information needed by transportation professionals to support sound decision making. Computational intelligence (CI) has great potential to support the needs of transportation professionals. CI is a result of synergy among information processing technologies such as artificial neural networks (ANNs), fuzzy sets, and genetic algorithms. As the number of CI applications to transportation problems grows, so does the need to evaluate these systems. The issue of validating and evaluating transportation CI applications is addressed. A case study that evaluates the effectiveness of two CI paradigms, case-based reasoning and ANNs, for estimating the benefits of real-time traffic diversion is presented. The case study illustrates the need for regarding validation and evaluation as a part of the development effort and the need for tuning the design parameters of CI paradigms.
Real-Time Coordinated Signal Control Through Use of Agents with Online Reinforcement Learning
Authors: Choy Min Chee , Cheu Ruey Long , Srinivasan Dipti , Logi Filippo
Published: April 2007

A multiagent architecture for real-time coordinated signal control in an urban traffic network is introduced. The multiagent architecture consists of three hierarchical layers of controller agents: intersection, zone, and regional controllers. Each controller agent is implemented by applying artificial intelligence concepts, namely, fuzzy logic, neural network, and evolutionary algorithm. From the fuzzy rule base, each individual controller agent recommends an appropriate signal policy at the end of each signal phase. These policies are later processed in a policy repository before being selected and implemented into the traffic network. To handle the changing dynamics of the complex traffic processes within the network, an online reinforcement learning module is used to update the knowledge base and inference rules of the agents. This concept of a multiagent system with online reinforcement learning was implemented in a network consisting of 25 signalized intersections in a microscopic traffic simulator. Initial test results showed that the multiagent system improved average delay and total vehicle stoppage time, compared with the effects of fixed-time traffic signal control.
Integration of Spatial Point Features with Linear Referencing Methods
Authors: Hallmark Shauna L. , Schuman William G. , Kadolph Steven W. , Souleyrette Reginald
Published: April 2007

The Global Positioning System (GPS) offers a cost-effective and accurate method for inputting, updating, and analyzing spatial data. However, many data-storage and reporting methods at state departments of transportation and other transportation agencies rely on linear referencing methods (LRMs) for managing transportation data. Consequently, GPS data must be able to coexist with linear referencing systems (LRSs). Unfortunately, the two systems are fundamentally different in the way they collect, integrate, and manipulate data. For spatial data collected with GPS to be integrated into an LRS or shared among LRMs, several issues must be addressed. Various issues are discussed for integrating point features from a typical inventory system with an LRM or between LRMs, including two- or three-dimensional GPS to one-dimensional LRM, linear offset error, lateral offset error, matching to the wrong segment, and locating points between LRMs.
Common Data Format Archiving of Large-Scale Intelligent Transportation Systems Data for Efficient Storage, Retrieval, and Portability
Authors: Kwon Taek M. , Dhruv Nirish , Patwardhan Siddharth A. , Kwon Eil
Published: April 2007

Intelligent transportation system (ITS) sensor networks, such as road weather information and traffic sensor networks, typically generate enormous amounts of data. As a result, archiving, retrieval, and exchange of ITS sensor data for planning and performance analysis are becoming increasingly difficult. An efficient ITS archiving system that is compact and exchangeable and allows efficient and fast retrieval of large amounts of data is essential. A proposal is made for a system that can meet the present and future archiving needs of large-scale ITS data. This system is referred to as common data format (CDF) and was developed by the National Space Science Data Center for archiving, exchange, and management of large-scale scientific array data. CDF is an open system that is free and portable and includes self-describing data abstraction. Archiving traffic data by using CDF is demonstrated, and its archival and retrieval performance is presented for the Minnesota Department of Transportation–s 30-s traffic data collected from about 4,000 loop detectors around Twin Cities freeways. For comparison of the archiving performance, the same data were archived by using a commercially available relational database, which was evaluated for its archival and retrieval performance. This result is presented, along with reasons that CDF is a good fit for large-scale ITS data archiving, retrieval, and exchange of data.
Spatiotemporal Object Database Approach to Dynamic Segmentation
Authors: Huang Bo , Yao Li
Published: April 2007

Dynamic segmentation is viewed as one of the most important functions of geographic information systems for transportation applications. Although the road network and associated events (e.g., pavement material, traffic volume, incidents) can be referenced to both space and time, the spatial and temporal dimensions have not been well integrated. Modeling space-varying, time-varying, and space-time-varying events in dynamic segmentation by using an object database approach that is in line with the Object Database Management Group standard is explored. A mechanism called parametric polymorphism is used to lift conventional data types to spatial, temporal, and spatiotemporal types for maintaining knowledge about events that could change spatially, temporally, and spatiotemporally along linear features. An associated object query language, DS-OQL, was designed to support the formulation of spatial, temporal, and spatiotemporal queries on the road and event information.
Design of Archival Traffic Databases: Quantitative Investigation into Application of Advanced Data Modeling Concepts
Authors: Smith Brian L. , Lewis David C. , Hammond Ryan
Published: April 2007

Given the enormous quantities of data collected by intelligent transportation systems (ITS), transportation professionals recently have focused on developing archived data user services (ADUS) to facilitate efficient use of these data in myriad transportation analyses. Most ITS systems were designed by using a transactional database design, which is not well suited to support the ad hoc queries required by ADUS. Research investigated the application of data-warehousing concepts to better support the requirements of ADUS. A case study is presented in which an ADUS for the Hampton Roads Smart Traffic Center, the regional freeway management system, was redesigned from a transactional approach to one based on data warehousing. Test queries run by using both approaches demonstrated that dramatic increases in efficiency are achievable through the use of data-warehousing concepts in ADUS.
Measuring Sulfate in Subgrade Soil: Difficulties and Triumphs
Authors: Harris Pat , Scullion Tom , Sebesta Stephen , Claros German
Published: April 2007

The accurate analysis of sulfate sulfur in subgrade soil is essential for road construction that involves calcium-based stabilizers (lime or cement). The objective was to determine if other tests give more reproducible results in a more timely fashion than Texas’s current sulfate test method (Tex-620-J), a gravimetric method. Literature review and interviews with commercial soil testing laboratories revealed three techniques to compare with Tex-620-J: ion chromatography, conductivity, and colorimetry/spectrophotometry. Soils were manufactured with known sulfate (gypsum and anhydrite) concentrations and sent to laboratories that performed gravimetric analysis and ion chromatography. Conductivity and colorimetric testing were performed in-house. Testing showed that Tex-620-J is not very precise, which creates the need for an unrealistic number of samples to obtain an accurate estimate of the sulfate concentration. To define the 95% confidence interval for true sulfate content to within ±10% of the true known value for a concentration of 5,000 ppm, Tex-620-J requires 43 tests; ion chromatography requires 14 tests. The colorimeter achieved the desired results in only one test, based on sulfate standard solutions. Results of this study revealed the difficulty with obtaining accurate sulfate measurements in the laboratory and indicated a few inexpensive pieces of equipment that can be used in both the field and laboratory settings that may yield better results.
Stabilization of Sulfate-Containing Soil by Cementitious Mixtures Mechanical Properties
Authors: Wang Lan , Roy Amitava , Seals Roger K. , Metcalf John B.
Published: April 2007

Winn Rock (CaSO4) gravel from a quarry in Winn Parish in north Louisiana was used extensively as a surface course for local parish roads. Stabilization of these roads with Type I portland cement followed by an overlay of asphaltic concrete resulted in heaving. A study was undertaken to investigate the cause or causes of the expansion as well as to identify an alternate means of stabilization. Specimens of representative soil from the affected area were stabilized in the laboratory using various cementitious materials and were cured using a variety of methods. The mix contained 5% to 20% cementitious material. The cementitious materials were Type I portland cement, lime, and supplementary cementing materials such as granulated blast furnace slag (BFS), Class C fly ash (CFA), silica fume, and an amorphous silica (AS). The unconfined compressive strength of the stabilized soil was determined. The effect of size fractions other than the gravel on the expansion was assessed, and the expansion of the specimens over time was monitored. The cement and BFS mixtures almost doubled the compressive strength of the specimens compared with portland cement alone. The finer size fractions were responsible for expansion. The magnitude of expansion was directly proportional to the amount of Type I portland cement, the amount of available moisture, and the curing temperature. Replacement of a part of the portland cement by BFS significantly reduced the amount of expansion even at the highest moisture content. No expansion was detected when CFA and AS partially replaced the cement.
Field Evaluation of the Stiffness of Unbound Aggregate Base Layers in Inverted Flexible Pavements
Authors: Terrell Ronald G. , Cox Brady R. , Stokoe Kenneth H. , Allen John J. , Lewis Dwayne
Published: April 2007

Unbound aggregate base layers in a quarry haul road in Georgia were characterized using embedded sensors and in situ seismic testing. Two sections of the road were constructed as inverted pavements, one using a South African Roads Board method and the other using a conventional Georgia Department of Transportation method. A third was constructed using a traditional method. Miniaturized versions of traditional cross-hole and downhole seismic tests were conducted to determine the stiffnesses of each base layer. Horizontally propagating compression and shear waves were measured under four different loading conditions to determine Young’s moduli and Poisson’s ratios of the base. An increase in stiffness with an increase in load was measured. Additionally, it was found that the Georgia and South Africa sections had similar stiffnesses. Surprisingly, the traditional section was found to be somewhat stiffer than the other sections. This higher stiffness is thought to be caused by a prolonged period of compaction before construction of the unbound aggregate base layer, which essentially transforms the traditional section into an inverted pavement. Using the vertical total normal stresses computed from ILLI-PAVE, a value of 0.3 for the earth pressure coefficient was found to be reasonable for this material in determining the radial total normal stresses. The radial effective normal stresses were calculated from the radial total normal stresses and experimentally determined pore water pressures. Additionally, the negative pore water pressures in the partially saturated granular base had a significant impact on the stiffness of the unbound aggregate base layer, especially under small load levels.
Refinement and Validation of the Hydraulic Fracture Test
Authors: Embacher Rebecca A. , Snyder Mark B.
Published: April 2007

The hydraulic fracture test was developed under the Strategic Highway Research Program to address the need for a more rapid, less expensive test for concrete aggregate freeze–thaw durability. Although the test concept appeared sound, the original test and analysis procedures were not sufficiently reliable and accurate to merit widespread adoption and implementation. Several follow-up research efforts have been performed, and each has resulted in improvements to the test. The results of the most recent study, which evaluated changes in both the test procedure (to include additional test sieves for better characterization of particle fractures) and the analysis procedures, are described. The “hydraulic fracture index” has been replaced by a model that predicts freeze–thaw test dilation as a function of the distribution of particle mass retained on the test sieves. This model was developed using data obtained from freeze–thaw and hydraulic fracture testing of 18 quarried carbonate and gravel aggregate sources; the resulting correlation is exceptional ( r2 = 0.98). An additional improvement is the development of a large test chamber capable of handling aggregate samples five times larger than the original small chamber, which thereby allows aggregate durability characterization with a single test run. It is believed that the hydraulic fracture test is now ready for more broad-based validation testing and eventual widespread acceptance and implementation as an accurate screening tool for concrete aggregate freeze–thaw durability.
Delineation of Dynamic Envelope of Light Rail Transit Cars and Trains
Authors: Boorse Jack W.
Published: April 2007

Visual delineation of the outline of the dynamic envelope occupied by light rail transit cars or trains as they travel along or across roadways and walkways was examined. An argument was formulated against the routine installation of delineation features, except in situations deemed beneficial. Conditions when such delineation on paving surfaces is useful were identified, as well as conditions when it is unnecessary and sometimes detrimental. Various methods to accomplish delineation were also addressed.
Reallocation of Empty Personal Rapid Transit Vehicles en Route
Authors: Andréasson Ingmar
Published: April 2007

Personal rapid transit (PRT) accommodates groups of passengers that request transport to a desired destination. Empty vehicles need to be moved to stations with waiting passengers or with expected demand. Efficient redistribution of empty vehicles is critical in larger PRT networks, which have running times longer than acceptable waiting times. Previous studies have developed methods for allocating destinations to empty PRT vehicles sequentially as they become available. This study refines the allocation of empty vehicles into three stages. The first stage is essentially the previous sequential allocation. In the second and third stages, empty vehicles en route are reallocated by switching destinations. In the second stage, waiting passengers are allocated the nearest vehicle on the basis of waiting time. In the third stage, the remaining empty vehicles en route are reallocated on the basis of minimum running distance. The optimization problem in the third stage corresponds to the transportation problem, and it is solved approximately by a heuristic method suggested by Russel. Applied to a network with 25 stations, 16 km of guideway, and 200 vehicles, the combined reallocation methods reduced average waiting and the longest wait to about half compared with sequential decisions alone.
New Approach to Effective and Sustainable Urban Transport
Authors: Lowson Martin
Published: April 2007

An effective and sustainable transport system has been devised to meet public transport demand. Urban light transport (ULTra) is an innovative form of personal rapid transit. In contrast to other forms of public transport, there is no waiting, stopping, or transferring. In many situations, the new system can offer better transport than available by other means. ULTra has been designed to demanding sustainability requirements. Typically, ULTra reduces energy use and emissions by a factor of three compared with existing transport systems and also complements those systems. By providing a network link to major rail and bus stations, ULTra can make current transport services more attractive to passengers. The new system is also well suited for other major activity centers such as airports. In essence, ULTra replaces the old mass transit paradigm for transport with a new paradigm based on just-in-time transit. ULTra is now undergoing engineering development funded by the U.K. Department for Transport on a 1-km test track in Cardiff, Wales. The Cardiff County Council has received funding commitments by the National Assembly of Wales that could lead to system implementation by 2005. The system offers a new approach to public transport, with a real prospect of significant gains in effectiveness and sustainability.