bluuebunny/crossref_metadata_2025 huggingface dataset:
Specifications for Automated License Plate Reading Equipment for Transportation Planning
Authors: French L. James , Martinelli David R. , Eck Ronald W. , Pascoli Jack
Published: April 2007

Recent technological advances in computer hardware, software, and image processing have led to the development of an automated license plate reader (ALPR). This equipment was developed primarily for enforcement and security applications, such as monitoring parking garages or border crossings. Because license plate data are used in several transportation planning studies, ALPRs have the potential to increase the quality and efficiency of many typical activities of transportation planning agencies. The key performance attributes of an ALPR with respect to the specific needs of transportation planning are determined. The following general needs are investigated: ( a) the specific license plate data requirements of transportation planning studies; ( b) the effect of the equipment on traffic operations and safety; and ( c) special equipment characteristics required because of the temporary nature of transportation planning and the constraints of transportation planning agencies. In addition, an existing ALPR was tested in situations likely to be encountered in transportation planning applications. Technical specifications for an ALPR for transportation planning are developed. These specifications can be used to provide motivation and direction for the future development of an ALPR for transportation planning. Finally, the technical challenges to developing the ALPR are discussed.
Metaanalysis of Travel Survey Methods
Authors: Korimilli Madhuri S. , Pendyala Ram M. , Murakami Elaine
Published: April 2007

Travel surveys often serve as the primary sources of information on travel demand characteristics. They provide critical data for transportation planning and decision making. In recent times, several factors motivate a comparative examination of travel survey methods. First, new travel demand modeling tools, such as those based on activity-based methods, are placing greater demands on travel behavior data gathered from household travel surveys. Second, response rates from household travel surveys have been showing a steady decline, possibly because of an increasingly survey-fatigued population. Third, declining resource availability at metropolitan planning agencies places emphasis on the need to maximize response rates to lower data collection costs per completed respondent. Ideally, a comparative examination of travel survey methods is best done through a carefully constructed experimental design that permits the isolation of the impact of various survey design parameters on response rates. However, the conduct of such a controlled experiment virtually is impractical. A metaanalysis of a sample of travel surveys conducted in the past 10 years is presented. A predictive model of response rates is developed by using linear regression techniques and the practical application of the model is demonstrated through several numerical examples.
Highway Freight Flow Assignment in Massachusetts Using Geographic Information Systems
Authors: Krishnan Venkatesh , Hancock Kathleen L.
Published: April 2007

Goods movement is an important aspect of the transportation system. Freight flow, complemented with the much-researched passenger movement, provides a way for understanding the complete vehicle flow scenario on the highways. Commodity movement prediction has not received much attention because of the lack of sufficient and easily accessible data sources. Most data sources give aggregated commodity movements and, because of the heterogeneity of freight, accurate predictions of truck flows have not been possible. A methodology for calculating the truck flows on the various highways in Massachusetts from interstate commodity flow data is presented. Freight tons originating and ending in Massachusetts have been converted to truck numbers by using a quantitative procedure and distributed to different areas in the state by using employment as an economic indicator variable. The truck flow is assigned to the important highways and validated against existing survey counts. On comparison, a large percentage of the roads show the estimated truck counts are within a tolerable error margin. The research also shows that statewide analyses need to be refined near urban areas because of a variety of complexities involved.
Application of Geographic Information Systems Technology in Freight Data Analysis: Case Study of I-90/I-94 Corridor Analysis
Authors: Alam Mohammed , Fekpe Edward
Published: April 2007

Availability of adequate and relevant information in certain formats is important in the analysis of possible impact of policy relating to freight transportation. The application of geographic information system (GIS) technology is a valuable tool in integrating spatial data with other forms of data. Such integration in a visual format facilitates understanding of the interrelationships between variables and provides a better feel for the potential implications of any policy initiatives. The application of GIS techniques to freight movement in a corridor analysis is presented. The nature of trucking activities along the I-90/I-94 corridor from Seattle to Chicago and how these activities are influenced by truck size and weight (TS&W) regulations are investigated. The GIS approach allows the analyst or policy maker to address a range of what-if public policy questions. The policy questions for TS&W are complex and are beyond simply understanding the overall freight and transportation characteristics of the corridor. The database allows the analyst to visually understand freight movement on a given highway and forecast the probable outcome of changing certain rules and regulations that control such movement.
Analysis of Strategies To Control Traffic Noise at the Source: Implications for Policy Makers
Authors: Herman Lloyd A.
Published: April 2007

Traffic noise control strategies that reduce traffic noise at the source were identified. The strategies were grouped according to the vehicle noise sub-sources: engine, intake air, exhaust, cooling fan, transmission/driveline, and tire/pavement. Examples of the strategies and recent advancements in vehicle noise control are given. The analysis yielded a number of implications for policy makers. In the United States, market forces are currently fostering technological advancements to reduce most of the vehicle noise subsources. However, the reduction of tire/pavement noise, the dominant subsource at freeway speeds, is currently benefiting little from market forces and may be hindered in the future by trends in passenger car tires. Policies and regulations, where warranted, should be aimed at reducing tire/pavement noise through a concerted effort on the part of both tire and pavement industries as well as transportation agencies.
Aircraft Community Noise Impact Model
Authors: Stusnick Eric , Thompson Richard L. , Thompson Terence R. , Evans Bryan A. , DiFelici John
Published: April 2007

The Aircraft Community Noise Impact Model (ACNIM) is a computer software system being developed by Wyle Laboratories and Metron, Inc., for the National Aeronautics and Space Administration–Langley Research Center. It is intended to provide a user-friendly tool for analysis of the impact of the noise from aircraft operations on communities near airports. The history of the development of ACNIM and some of its unique features are outlined and the optimization algorithms that are used by ACNIM to produce minimally impacting flight trajectories are discussed in some detail.
Comparative Field Measurements of Tire Pavement Noise of Selected Texas Pavements
Authors: Mcnerney Michael T. , Landsberger B.J. , Turen Tracy , Pandelides Albert
Published: April 2007

The effects of traffic noise are a serious concern in the United States and in the rest of the world. One significant component of traffic noise is tire-pavement interaction. If tire-pavement noise can be reduced at the source instead of through the use of traffic noise barriers set up to protect individual receivers, then potential savings can accrue. This research effort conducted field testing on 15 different pavement types found in Texas, and on six pavement types found in South Africa. A test procedure was developed with roadside microphones and microphones mounted on a test trailer to record and analyze the differences in tire-pavement noise. The test procedure was designed to develop comparisons of pavements while other variables were kept constant. The results, measured on the standard A-weighted scale, indicated for the 15 test pavements in Texas a difference of roadside noise levels of up to 7 dBA. Additionally, a roadside noise level of one pavement measured in South Africa was more than 2 dBA quieter than any Texas pavement.
Sound Barrier Applications of Recycled Plastics
Authors: Saadeghvaziri M. Ala , Macbain Keith
Published: April 2007

An innovative noise wall design that uses recycled plastic and takes advantage of multilayering to increase stiffness and sound effectiveness is proposed and analyzed. Prototypes of the proposed design were constructed and tested for sound transmission to determine their effectiveness and show the desirability of a multilayered approach. The results show that, acoustically, the transmission loss of the proposed design is as effective as traditional designs. Furthermore, finite element analyses as well as an analytical model developed specifically for recycled plastics indicate that, structurally, the proposed design can increase spans between posts resulting in a design that is potentially more economical than current designs. Results of material tests conducted in support of the analytical model and noise wall development are also discussed.
Transportation Planning Process for Linking Welfare Recipients to Jobs
Authors: Metaxatos Paul , Sööt Siim , Thakuriah Vonu , Sen Ashish , DiJohn Joseph , Jarzab James
Published: April 2007

The recent welfare reform act requires most current welfare recipients to be employed within 5 years. For any program to find jobs for those previously on welfare, transportation services need to be in place before the job search process begins. Therefore, it is essential that the latent demand for commuting among welfare recipients be assessed when any public transportation service is developed. Such a planning effort is described by ( a) providing an overview of the relevant issues relating to welfare to work, ( b) proposing a regionwide planning process, and ( c) demonstrating the process by implementing the first three steps, which rely on creative data preparation and analysis. Because the most recent data sets are not currently available, the implementation phase is considered to be preliminary, but it is crucial in testing the proposed regionwide planning procedure. A full-scale study is currently under way.
Evaluation Results of Three Prototype Automatic Truck Rollover Warning Systems
Authors: Strickland Rodney R. , McGee Hugh W.
Published: April 2007

Three prototype Automatic Truck Rollover Warning Systems (ATRWS), located in Virginia and Maryland, were evaluated over three years to assess how the ATRWS performed and to determine the cost-effectiveness. More specifically, the requirements of this evaluation were to (1) evaluate performance and maintenance requirements, (2) evaluate the effectiveness of the ATRWS on speed reduction of detected trucks traveling at or near their rollover speed or maximum safe speed, and (3) evaluate any improvements in safety resulting from the systems. Based on truck classification and speeds as measured by the ATRWS, it was concluded that these systems do affect truck speed reduction. The results showed that for all three ATRWS sites (five lanes total), a speed reduction was observed when the fiber optic sign was activated. The results also showed that this speed reduction was usually higher than the speed reductions of trucks that did not activate the sign. In fact, for the first and second evaluation periods, an overall 29.0 and 21.7 percent speed reduction from Stations 2 to 3 and Stations 5 to 6 was observed. These percentage speed reductions equate to approximate speed reductions at the Springfield, McLean, and Beltsville ATRWS sites of 4.6 km/h (2.9 mph), 3.9 km/h (2.4 mph), and 2.3 km/h (1.4 mph) for the first evaluation period. The second evaluation period had similar speed reductions.
Cracking Characteristics of Model Continuously Reinforced Concrete Pavements
Authors: Emtazul Haque MD. , Zaman Musharraf , Soltani Alan A.
Published: April 2007

An experimental program was conducted in the laboratory to predict the behavior of model continuously reinforced concrete (CRC) slabs in tension. A tensile loading arrangement was devised using a Universal Testing Machine for this purpose. Model concrete slabs were cast for two types of reinforcement arrangements: a regular grid pattern, and an inclined grid pattern. Tests were conducted for different rebar spacings and orientations. In the numerical study, a two-dimensional model of the CRC slabs was developed using FLAC, a commercially available software package based on the finite difference method. Experimental and numerical results were compared and were found to be in close agreement. Finally, the average crack spacings for different rebar spacings and orientations from both experimental and numerical studies were compared with the results obtained from the Concrete Reinforcing Steel Institute design method.
Thermal Cracking Models for AC and Modified AC Mixes in Alaska
Authors: Raad Lutfi , Saboundjian Stephan , Sebaaly Peter , Epps Jon
Published: April 2007

Low-temperature cracking is a major distress mode in Alaskan pavements because of the extreme temperature conditions—which range, in some instances, from about −50°C in winter to more than 40°C in summer. The use of asphalt modifiers in Alaskan pavements occurred over the past 15 years. These modifiers include Styrene-Butadiene-Styrene polymers, Styrene-Butadiene-Rubber polymers, ULTRAPAVE, and CRM [both the dry process (PlusRide) and the wet process]. Field observations and laboratory studies in Alaska and elsewhere indicate that the use of these modifiers would improve the low-temperature cracking resistance of pavements. The degree to which these modifiers provide beneficial effects for Alaskan pavements needs to be evaluated. The objectives of this research were (1) To characterize asphalt and polymer modified asphalt from a number of selected sites using Superpave PG grading system and to conduct thermal stress restrained specimen tests (TSRST) and Superpave IDT laboratory tests on field specimens; (2) To compare low-temperature cracking performance using field surveys; (3) To verify the applicability of the Superpave thermal cracking model (TCMODEL) and other available models for predicting low temperature cracking; and (4) To recommend guidelines for predicting minimum pavement temperatures in Alaska. Results of this study indicate, in general, significant improvement in low-temperature cracking resistance when polymer modifiers are used. Comparisons between predicted and observed low-temperature cracking using available crack propagation models, including Superpave TCMODEL, were poor. An improved regression model was developed using minimum air temperature, TSRST fracture temperature and strength, and pavement age to fit the observed field data for both conventional and polymer modified sections.
Concept for Mechanistic-Based Performance Model for Flexible Pavements
Authors: Mamlouk Michael S. , Mikhail Magdy Y.
Published: April 2007

A concept for a mechanistic-based performance model for flexible pavement was developed that considers the interaction between vehicles and pavement. A dynamic vehicle model was used to estimate the dynamic wheel force, and a three-dimensional finite element nonlinear dynamic pavement model was used to determine the dynamic pavement response. The effect of pavement roughness on vehicle bouncing and the effect of vehicle bouncing on the progression of pavement roughness were investigated under different roughness levels, suspension types, and layer thicknesses. The increase in roughness after each load repetition can be calculated using basic material properties from which the pavement service life can be estimated. The number of equivalent 80-kN single axle load repetitions to failure was estimated under different conditions without the need for empirical observations. It was found that the number of load repetitions to go from one level of present serviceability index (PSI) to the next largely decreases as the PSI level decreases. The air bag suspension results in the longest pavement life, while the walking beam suspension results in the shortest pavement life. The total number of load repetitions to reach failure for thick pavement sections is 14 percent higher than that for medium-thick sections, and 63 percent greater than that for thin sections. The reverse of this analysis can be used to design the pavement section so that it would sustain a certain number of load repetitions before failure using a mechanistic procedure. The proposed concept for a mechanistic-based performance model developed in this study can be refined to increase the mechanistic portion of the model, reduce empirical involvement, and improve computational procedure.
Characterization of Clayey Subgrade Materials for Mechanistic Design of Flexible Pavements
Authors: Uzan Jacob
Published: April 2007

The design of flexible pavements is based on the empirical approach and in some cases on the empirical-rational approach. Funds are being invested in developing new design methods that will principally be based on the mechanistic-rational approach. A procedure for characterizing clayey subgrade materials to provide the properties needed by the new methods is presented. The procedure addresses the following elements: first, the material should be brought to the condition that prevails under pavements. Sample preparation and a soaking procedure to simulate field condition are described. Second, after about 10 days of sample conditioning, the material is tested under repetitive loading to provide both resilient and permanent properties. In clayey soils, two samples are tested under different deviatoric stresses and for 10,000 to 100,000 load repetitions. The stress level should correspond to the stress induced by overburden and traffic load. Tests are conducted on a swelling clay, and the results are analyzed. It is seen that (a) the proposed procedure for sample conditioning is appropriate for Israeli climatic conditions, but it can be changed to fit other climatic conditions; (b) the stress level in subgrades is relatively low, so the behavior of the clayey materials can be fairly well described by linear elastic theory; and (c) the total deformation increases either linearly or exponentially with number of load repetitions (in a log-log scale).
Correlation of Superpave G*/Sin δ with Rutting Test Results from Accelerated Loading Facility
Authors: Sherwood James A. , Thomas Nathaniel L. , Qi Xicheng
Published: April 2007

In 1992, FHWA initiated a Superpave validation study by utilizing the Accelerated Loading Facility (ALF) at the Turner-Fairbank Highway Research Center in McLean, Virginia. The study focused on the validation of the concepts, tests, and predictive models underlying the Superpave binder specifications and mixture analysis system. Twelve full-scale pavement lanes with 48 test sites were constructed at the FHWA Pavement Testing Facility in 1993. Pavement testing with the ALF started in late spring of 1994. The results of accelerated full-scale pavement tests in conjunction with extensive laboratory tests will be used to validate the Superpave binder parameters for rutting and fatigue cracking. Presented in this paper are the results of rutting tests and some of the data analysis completed through June 1997.
Identification of Moisture-Susceptible Asphalt Concrete Mixes Using Modified Environmental Conditioning System
Authors: Murshed Alam Muhammad , Tandon Vivek , Nazarian Soheil , Tahmoressi Maghsoud
Published: April 2007

Moisture damage is a common problem faced by highway agencies. Researchers have developed laboratory test methods over the years to identify moisture-susceptible asphalt concrete mixtures, but none of them has been consistently successful. A new laboratory test method, the Environmental Conditioning System, was developed under the Strategic Highway Research Program. This new test method has a distinct advantage over the existing methods because it can simulate field conditions. However, a comprehensive evaluation of the method showed that although it is a promising concept, it needs further modification and evaluation. In this paper, several modifications to the original Environmental Conditioning System are proposed. The results from a preliminary evaluation of the system are also included. The new system has been able to identify poor and marginally performing mixtures.
Summary of Current Quality Control/ Quality Assurance Practices for Hot-Mix Asphalt Construction
Authors: Schmitt Robert L. , Russell Jeffrey S. , Hanna Awad S. , Bahia Hussain U. , Jung Galadriel A.
Published: April 2007

State highway agencies and contractors have been implementing quality control/quality assurance (QC/QA) specifications in recent years to advance the quality of hot-mix asphalt (HMA) construction. During their continued development, attributes of these QC/QA specifications have varied among states. The objective of this paper is to provide a compilation of state-of-the-practice in QC/QA for HMA construction and provide recommendations for state highway agencies and contractors when modifying or developing a QC/QA specification. Survey data from 42 state highway agencies and 61 contractors working within 14 states found that a majority of states are using contractor data for acceptance. A review of QC/QA specifications from 40 states found that most states are using plant-produced mix properties, density, and smoothness tests to determine overall quality and acceptance of HMA construction work. A larger number of states are using quality level analysis for specification compliance by estimating percent within limits or percent defective for mix properties and density. Consideration is given to key attributes of a QC/QA specification, including ( a) whether to use contractor or agency data for acceptance, ( b) use of quantity or time for lots, and ( c) testing frequency. State highway agencies and contractors may find this report useful for understanding the components of different QC/QA specifications and furnishing essential information as both parties collaborate during specification development.
Numerical Modeling of Spread Footings at Bridge–Embankment Interfaces
Authors: Arduino Pedro , Macari Emir J.
Published: April 2007

The use of spread footings on slopes is a common practice in the design of bridge foundations. Footings generally are constructed in the slope or at its crest to minimize the bridge length, thereby minimizing costs. However, the analytical methods that frequently are used to predict the ultimate bearing capacity of shallow spread footings on slopes yield a wide range of solutions. There has been an increased effort in recent years to evaluate and improve techniques for predicting the deformation and ultimate bearing capacity of shallow spread footings located on or near slopes. Research in the development of numerical techniques used in conjunction with sophisticated elastoplastic constitutive models continues to be an area in which additional effort is needed. Physical model tests were used to obtain maximum bearing pressures of shallow spread footings located near sand slopes. These results were compared with classical bearing capacity solutions and numerical predictions obtained with finite element discretizations. Deformed meshes and incremental nodal displacements are presented.
Performance Measurement for Traffic Management Systems
Authors: Banks James H.
Published: April 2007

Performance measurement refers to attempts to quantify some aspect of the performance of an organization. A study was conducted to analyze needs, opportunities, and techniques for measuring performance of transportation management centers (TMCs). Opportunities and needs were identified by analyzing the interrelationships among performance measurement objectives, objects, and study designs. This analysis suggests that before-and-after evaluation studies of traffic management actions and monitoring of traffic data to detect system changes are the most appropriate forms of performance measurement for TMCs. Important potential measures of effectiveness for traffic management systems include travel time and related measures, ramp delay, traffic volumes, accident rates, traffic information accuracy, incident duration, and equipment status. Techniques are available for quantifying these measures, although there are a number of concerns with data accuracy, especially where travel times are estimated from loop-detector data. Case studies of two California TMCs suggest that, although sophisticated data collection systems are available or planned, the institutional infrastructure to carry out performance measurement may be lacking.
Fuzzy ART Neural Network Model for Automated Detection of Freeway Incidents
Authors: Ishak Sherif S. , Al-Deek Haitham M.
Published: April 2007

Pattern recognition techniques such as artificial neural networks continue to offer potential solutions to many of the existing problems associated with freeway incident-detection algorithms. This study focuses on the application of Fuzzy ART neural networks to incident detection on freeways. Unlike back-propagation models, Fuzzy ART is capable of fast, stable learning of recognition categories. It is an incremental approach that has the potential for on-line implementation. Fuzzy ART is trained with traffic patterns that are represented by 30-s loop-detector data of occupancy, speed, or a combination of both. Traffic patterns observed at the incident time and location are mapped to a group of categories. Each incident category maps incidents with similar traffic pattern characteristics, which are affected by the type and severity of the incident and the prevailing traffic conditions. Detection rate and false alarm rate are used to measure the performance of the Fuzzy ART algorithm. To reduce the false alarm rate that results from occasional misclassification of traffic patterns, a persistence time period of 3 min was arbitrarily selected. The algorithm performance improves when the temporal size of traffic patterns increases from one to two 30-s periods for all traffic parameters. An interesting finding is that the speed patterns produced better results than did the occupancy patterns. However, when combined, occupancy–speed patterns produced the best results. When compared with California algorithms 7 and 8, the Fuzzy ART model produced better performance.
Traffic Monitoring and Congestion Management in the SCOOT Urban Traffic Control System
Authors: Bretherton David , Wood Keith , Raha Neil
Published: April 2007

The SCOOT Urban Traffic Control system is now operating in over 170 cities worldwide, including 7 systems in North America. Since the first system was installed, there has been a continuous program of research and development to provide new facilities to meet the requirement of the traffic manager. The latest version of SCOOT (Version 3.1) incorporates a traffic information database, ASTRID, and an incident-detection system, INGRID, and provides a number of facilities for congestion control. The traffic monitoring facilities of SCOOT, including a new facility to estimate emissions from vehicles, and the current program of work to enhance the incident-detection system and to provide additional facilities to manage incidents and congestion are reported in this paper. The work is being carried out as part of the European Union, DGXIII 4th Framework project, COSMOS, with additional funding from the UK Department of Transport. The enhanced system is to be installed in the Kingston Borough of London, where it will be tested in combination with congestion warning information provided by variable message signs.
Disaggregate Safety Performance Models for Signalized Intersections on Ontario Provincial Roads
Authors: Persaud Bhagwant , Nguyen Thu
Published: April 2007

The more advanced methods for identifying unsafe intersections and evaluating the safety effect of treatment are based on an Empirical Bayesian framework that requires the use of safety performance functions relating the expected safety of an intersection to characteristics such as traffic flow. Aggregate and disaggregate models were developed to estimate the safety performance of three-legged and four-legged signalized intersections on Ontario provincial roads. Models were disaggregated by time period, accident severity, and environment class. Two levels of models were calibrated for different levels of data availability and model requirements. For Level 1, the safety of an intersection was estimated as a function of the sum of all entering flows; separate estimates were obtained for rear-end, right angle, and turning movement accidents, the three most prominent impact types. In Level 2, specific patterns were defined by the movements of involved vehicles prior to collision, and accidents for the main patterns at four-legged intersections were estimated as a function of flows relevant to each pattern. Aside from the theoretical aspects, the models provide a basis for comparison with available models for other jurisdictions. There are some novel aspects in that, unlike most models available for roads outside municipalities, the ones presented here do allow for safety estimates to be disaggregated by time period, accident severity, impact type, and accident pattern. Moreover, the calibrated models can be used in an Empirical Bayesian framework to estimate the safety of an individual intersection. This is an important feature generally lacking in available models.
Let the People Be Heard: San Diego County Bicycle Use and Attitude Survey
Authors: Jackson Michael E. , Ruehr Erik O.
Published: April 2007

What is the best way to promote bicycle transportation? Are people afraid to ride bicycles because motorists will run them over? Are there enough bicycle facilities available? Is promoting bicycle transportation a wise use of tax dollars? What percentage of the population currently rides bicycles? The San Diego Association of Governments allocates approximately $2 million annually on bicycling projects throughout San Diego County, California. Both the county of San Diego and the city of San Diego employ full-time bicycle coordinators. Periodically, questions and comments will arise regarding bicycling policies. “Why are they spending so much money on bicycle lanes? No one ever bicycles down this street.” “If they would build more bicycle paths, I would ride my bicycle to work instead of drive.” “How do they expect people to ride bicycles if they don’t maintain the pavement?” The San Diego County Bicycle Use and Attitude Survey was commissioned at the behest of the San Diego County Public Works Department to determine existing levels of bicycle usage and bicycling attitudes among San Diego County residents. A total of 3,800 interviews, conducted during February and March 1994 by telephone throughout the county, provided valuable insight into a large range of bicycling issues. The survey found that a majority (58 percent) of those residents polled reported that they were bicycle owners, and that a majority (68 percent) of those households in which bicycles were present reported that the adults bicycled. Respondents who bicycle chose bicycle paths, which are separated from motor vehicles, as their preferred bikeway facility. Almost three-fourths of the respondents (73 percent) stated that they did not bicycle at night. Only 15 percent of respondents who rode a bicycle at least once within the past year reported riding for transportation purposes. Over 99 percent of all respondents stated that they did not belong to a bicycling organization. A majority of respondents (over 70 percent) had not heard of various government programs that provided bicycle maps and bicycle information, and less than 10 percent of respondents have used these services. The majority of bicycling households (86 percent) reported being at least somewhat satisfied with the level of bikeway maintenance provided. Overall, survey respondents expressed support for government efforts to promote bicycle transportation.
Research Design Insights from a Survey of Urban Bicycle Commuters
Authors: Aultman-Hall Lisa , Hall Fred L.
Published: April 2007

A bicycle route and safety survey was distributed to 6,000 bicycle commuters in Ontario in 1995. The objective of the survey was to collect both collision/fall histories and detailed travel behavior information. A description is provided of the questionnaire development, which included a map for route tracing, as well as the sampling procedures that involved attaching the mail-back survey to the crossbars of parked bicycles. The resulting analyses, which address methodological issues, are presented. No differential response rates between men and women were found. No evidence was found to suggest that cyclists who had experienced accidents were more likely to respond. A slight decrease in incidents was found as one moves backward in the time, suggesting slight recall bias, but, overall, the time period over which information was collected (3 years for collisions and 1 year for falls) was deemed appropriate. The measure of travel exposure combined information from the map with estimates of commute trips per month. The aggregate overall estimate was deemed satisfactory but the ability of cyclists to recall commute trips on exact days even in the near past was inadequate. Overall, the survey was successful, and the insights should provide helpful guidance to others who seek to gather bicycle travel information.
Flow Characteristics on Shared Hiking/Biking/Jogging Trails
Authors: Virkler Mark R. , Balasubramanian Rajesh
Published: April 2007

Trails shared by hikers, bicyclists, and joggers present the unusual traffic flow situation of a facility serving three classes of users with distinctly different flow characteristics. Data on typical trail volumes are summarized. A procedure developed by Botma to describe quality of flow on shared pedestrian/bicycle paths is then discussed. Data from two sites, the MKT Trail in Columbia, Missouri, and a riverside trail in Brisbane, Australia, were collected to describe speed and passing time characteristics on shared trails. The frequency of desired overtakings (passes) and potential conflicts on trails are estimated based on measured speeds and passing times using basic relationships of traffic flow theory. These estimates are then compared with measured values of overtaking frequency and delayed overtakings. The estimates for passing demand and potential conflicts were higher than the measured values for hikers passing hikers and joggers passing hikers. However, estimates for bike passing bike, bike passing jogger, bike passing hiker, and jogger passing jogger were found to be similar to the measured values. The results support the Botma framework for describing quality of flow on shared pedestrian/bicycle paths.
Who, What, Why, and How of Technology Transfer: Survey Findings from a Cross-Section of Experienced Practitioners
Authors: Coleman Fred , Benekohal Rahim F. , Shim Eunjae
Published: April 2007

Development and adoption of new airport pavement design methods and procedures will depend in large measure on understanding how to transfer design procedures to the airport pavement design and construction industry. Technology transfer activities and programs have been implemented successfully in a variety of fields to move ideas and technology from the research lab to end users for direct application or further refinement. The Federal Aviation Administration (FAA) Center of Excellence (COE) for Airport Pavement Research recognizes that technology transfer will be crucial to fulfilling its mission of developing and promulgating new airport pavement design methods and procedures. To this end, a survey of a cross-section of experienced technology transfer agencies from the public and private sectors has been conducted. The overall purpose for conducting the survey was to learn the most effective characteristics and attributes of technology transfer programs in order to develop a program for the FAA COE for Airport Pavement Research.
Engineering Properties of Polymer-Modified Asphalt Mixtures
Authors: Khattak Mohammad Jamal , Baladi Gilbert Y.
Published: April 2007

A large research program sponsored by the Michigan Department of Transportation was designed and completed to evaluate the effect of polymer modification on the various properties of asphalt mixtures. These include the micro- and macrostructural, morphological, chemical, and engineering properties. Some of the engineering properties of the styrene-butadiene-styrene and styrene-etylene-butylene-styrene polymer-modified asphalt mixtures are presented and discussed. The elastic, fatigue, tensile, and permanent deformation properties were investigated at 60, 25, and –5°C. It was found that, for some polymer systems, the fatigue life and the indirect tensile strength increased considerably at 25°C while the elastic properties at -5°C were not affected by the addition of polymer. The implication of this is that the use of some polymer systems in asphalt mixtures enhances their fatigue cracking and rutting resistance without affecting the low temperature cracking potential.
Low Temperature Studies of Amorphous, Interfacial, and Crystalline Phases in Asphalts Using Solid-State 13C Nuclear Magnetic Resonance
Authors: Netzel Daniel A.
Published: April 2007

The road performance behavior of an asphalt depends upon its susceptibility to changes in its rheological properties with time and temperature. One important fundamental molecular property of an asphalt, which dictates its temperature-dependent performance, is the nature of the molecular motions associated with the asphalt molecular components. Changes in the rotational motions of the methyl carbons and the segmental motions of the methylene carbons in the 1- to 10-kHz frequency range were studied (via changes in spin-spin dipolar-dephasing relaxation times) as a function of temperature for three Strategic Highway Research Program asphalts using carbon-13 dipolar-dephasing cross polarization with magic angle spinning nuclear magnetic resonance. The data indicate that the rotational motion of the terminal methyl carbons of n-alkanes in the amorphous phase is nearly independent of decreasing temperature until the glass-transition region is reached. Below the Tg, the rotational motion of the methyl carbons decreases slowly with decrease in temperature for asphalts AAA-1 and AAB-1. However, the methyl rotation in asphalt AAM-1 decreases more rapidly. The segmental motions of the methylene carbons in the mobile-amorphous phase for the different asphalts decrease rapidly with decreasing temperature from 20 to – 20°C. At temperatures below — 20°C, the segmental motions have essentially ceased. The slow, low-frequency motions of the methylene carbons in the inter-facial (rigid-amorphous) and crystalline phases were found to be independent of temperature above and below Tg. It is suggested that the methyl rotation and segmental motions of the methylene carbons in the amorphous phase extensively influence the low-temperature rheological properties of asphalts.
Changes in Corbett Fraction Composition During Oxidation of Asphalt Fractions
Authors: Liu Milton , Chaffin Jay M. , Davison Richard R. , Glover Charles J. , Bullin Jerry A.
Published: April 2007

The naphthene aromatic (NA) fractions and polar aromatic (PA) fractions of five Strategic Highway Research Program asphalts (AAA-1, AAD-1, AAF-1, AAG-1, and AAM-1) along with six supercritical fractions of AAF-1 were subjected to oxidative aging. Asphaltenes and residual polar aromatics were recovered from the aged PA material. Produced asphaltenes and PAs and residual NAs were recovered from the aged NA samples. It was determined that NAs convert to PAs and subsequently become asphaltenes during oxidative aging of asphalt binders. However, within the extent of aging encountered in roadways, it is concluded that negligible asphaltenes are produced from NAs. Depending on the relative rates of oxidation of PAs and NAs, the content of PAs may either increase or decrease. Newly produced asphaltenes and PAs are smaller in molecular size than those present in the original whole asphalts. Also, the residual PAs in the aged PA fractions and the residual NAs in the aged NA fractions have smaller molecular size than those of the parent asphalts. The smaller molecular-sized material, whether PA or NA, is more slowly converted to asphaltenes or PAs, respectively. These data indicate that materials high in NAs and perhaps smaller PAs will harden very slowly in service.
Factors Affecting the Stiffening Potential of Mineral Fillers
Authors: Shashidhar Naga , Romero Pedro
Published: April 2007

The workability and performance of bituminous mixes is known to be affected by the filler-asphalt mixture (or mastic) properties. The addition of fillers is known to stiffen asphalt. The degree of stiffening is a function of several filler and asphalt properties, which are not well understood. A fundamental approach to understanding the influence of such factors on the stiffening potential of filler in asphalt is discussed. This complex problem is simplified by introducing two intermediate measurable parameters, the maximum packing fraction, ϕ m, and the generalized Einstein coefficient, KE. This enables a better understanding of the influence of various factors such as average particle size, gradation, particle shape, presence of agglomerates, degree of dispersion, and the asphalt-filler interface on the stiffening potential of asphalt. First, the relationship between these two parameters and stiffening is thoroughly examined. The physical meaning of these parameters is discussed. Second, the influence of each factor on stiffening potential is addressed individually, supported by experimental data and relevent literature to derive a quantitative relationship. Finally, the relative advantages of the approach over the traditional treatment are discussed. It is further shown that, since the parameters φm and KE take into account the properties of an asphalt-filler system as a whole, they are likely to predict stiffening more accurately than Rigden’s fractional voids approach which is based on the properties of fillers alone.
Field Study of In Situ Subgrade Soil Response Under Flexible Pavements
Authors: Dai Shongtao , Van Deusen Dave
Published: April 2007

Falling weight deflectometer (FWD) and truck tests were performed on three instrumented flexible pavement sections at the Minnesota Road Research project. The purposes of the study were (1) to investigate sub-grade soil response under FWD and moving truck loads and (2) to estimate in situ resilient modulus of the subgrade soil. The truck tests were performed at various speeds ranging from 16 to 78 km/h. The subgrade deformations and the vertical pressures on the top of the subgrade soils were measured from in situ displacement and soil pressure gauges. The experimental results showed that the deformations and the vertical pressures, in general, did not show significant dependency of truck speed within the above speed range. However, a slight decrease of the vertical pressure with increase of speed was observed for a thin conventional pavement section, while the vertical pressure in a relatively thick pavement section appeared to be less sensitive to speed. The results from FWD tests indicated that the subgrade deformation was linearly related to the FWD loads up to approximately 40 kN. Furthermore, a method is presented to estimate in situ subgrade modulus using the linear elastic theory and the measurements from the in situ sensors. The estimated modulus is comparable with the laboratory results at a low deviator stress level and is lower than modulus obtained from the backcalculation using FWD deflection basins.
Analysis of Concrete Pavement Responses to Temperature and Wheel Loads Measured from Intrumented Slabs
Authors: Yu H. Thomas , Khazanovich Lev , Darter Michael I. , Ardani Ahmad
Published: April 2007

The structural response of jointed plain concrete pavement slabs was evaluated using data obtained from instrumented slabs. The instrumented slabs were a part of newly constructed jointed plain concrete overlay that was constructed on existing asphalt concrete pavement on I–70 in Colorado, near the Kansas–Colorado border. The instrumentation consisted of dial gauges for measuring curling deflections at the slab corner and longitudinal edge and surface-mounted strain gauges for measuring load strains at the longitudinal edge at midslab. The through-thickness temperature profiles in the pavement slabs were also measured at 30-min intervals during the field test. Analysis of the field data showed that the instrumented slabs had a considerable amount of built-in upward curling and that concrete slabs on a stiff base can act completely independent of the base or monolithically with the base, depending on the loading condition. The built-in upward curling of the slabs has the same effect as negative temperature gradients. These findings suggest that the effects of temperature gradients on the critical edge stresses may not be as great as previously thought and that the corner loading, in some cases, may produce more critical conditions for slab cracking. Another important finding of this study is that a physical bond between pavement layers is not required to obtain a bonded response from concrete pavements.
Continuous Profiling of Runway and Taxiway Pavements with Rolling Dynamic Deflectometer at Dallas–Fort Worth International Airport
Authors: Bay J. A. , Stokoe K. H. , McNerney M. T. , McCullough B. F.
Published: April 2007

The rolling dynamic deflectometer (RDD) is powerful tool for use in managing airport pavements. With the RDD, continuous deflection profiles of runways and taxiways can be efficiently and effectively measured. These continuous profiles, both in the longitudinal and transverse directions, provide valuable information about the condition of the pavement system. The profiles are especially valuable because the entire pavement is tested and characterized rather than approximating the system with a limited number of discrete measurements to represent the entire pavement. The capabilities of the RDD were demonstrated by testing pavements at Dallas–Fort Worth International Airport. One existing runway, one existing taxiway, and a newly constructed (but not yet opened) runway were tested. The conditions of the different intact pavement sections and the various pavement joints are readily shown in the measured deflection profiles. In most cases, heavily trafficked pavement sections showed higher deflections than comparable sections with lower traffic, with the lowest deflections measured on the newly constructed runway. However, one recently constructed runway extension showed unusually high deflections, especially at the joints. The taxiway that was tested generally exhibited lower deflections than the operating runway. In the cases of the in-service pavements, transverse profiles clearly showed the softening of the highly trafficked central portion of the pavement.