bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Road Profilers
Authors: Perera Rohan W. , Kohn Starr D. , Bemanian Sohila
Published: August 2018

Devices available to measure road profiles vary from the hand-held Dipstick to high-speed, vehicle-based profilers. High-speed, vehicle-based profilers generally use an ultrasonic, laser, or optical measuring system. A profiler calibration study was conducted by the road profiler user group in 1994 by establishing regional calibration centers in Mississippi, Nevada, Pennsylvania, and South Dakota. The study compared the data collected by the profilers with the Dipstick data, and analyzed the effect of surface texture on data collection. At each regional calibration center, asphalt concrete and portland cement concrete test sections were established. Thirty-eight road profilers belonging to state agencies, equipment manufacturers, and FHWA participated in the calibration study. Dipstick measurements and sand-patch tests were conducted at all test sites. The International Roughness Index (IRI) was used as the parameter for performing the analyses. The results of the analyses for the sites in Pennsylvania and South Dakota are presented. The agreement between Dipstick IRI and profiler IRI for a specific profiler varied from site to site. For a specific profiler at some sites, the agreement with the Dipstick IRI was good, while at other sites the agreement was poor. The profilers with ultrasonic measuring systems generally had poor agreement with Dipstick IRI values for asphalt-surfaced sites that had aggregate seal coats.
Development of Automated Road Inspection Vehicle for Nondestructive Evaluation of Road Surface Condition
Authors: Guralnick Sidney A. , Suen Eric S. , Zoruba Sergio
Published: August 2018

An ever-growing need exists for a fast, objective, and relatively inexpensive automated road inspection system. Unlike traditional methods of road inspection, the proposed automated road inspection system relies on video images and distance tracking systems housed within a survey vehicle. The road inspection vehicle is capable of acquiring full field road surface distress information at speeds in excess of 85 km/hr. Only two individuals are needed to drive the towing vehicle and trailer along the appropriate roadways where a surface analysis is required and to operate the acquisition equipment. This type of road inspection process eliminates the need to class a road for inspection and greatly increases safety levels when compared with the traditional road inspection methods. Acquisition of roadway surface distress information is accomplished using the shadow moiré method. The shadow moiré method has been proven to be a fast and accurate means of measuring out-of-plane surface deformation. This method is relatively inexpensive and requires minimal maintenance while providing accurate results. The objective of this research is to refine or improve, or both, the various subsystems that form the integrated prototype system.
Experimenting with Recognition Accelerator for Pavement Distress Identification
Authors: Nallamothu Sudhakar , Wang Kelvin C. P.
Published: August 2018

A study was conducted using a computer board embedded with an artificial neural network (ANN) microchip for pattern recognition of pavement distress classification. The basic principles behind ANNs and pattern recognition are discussed. The hardware architecture of the Ni1000 recognition accelerator chip, which is the core of the ANN computer board, is presented, and the principle of operation of the restricted coulomb energy algorithm used in the chip is discussed. It is demonstrated that the Ni1000 Recognition Accelerator chip can be used for pattern recognition of pavement distress. Distresses in pavement images have been successfully classified using the Ni1000 recognition accelerator. The Ni1000 has the potential to be used as the core processing unit for distress classification at highway speeds.
Fiber Optics for Evaluation of Pavement Reinforcement Materials in Resisting Reflection Cracking
Authors: Abdel-Mooty Mohamed , Mohamed El-Hussein H. , Haddad Joseph
Published: August 2018

A major maintenance problem of pavement is the reflection cracking of pavement overlays at the location of joints and cracks in the underlayers. Pavement reinforcement materials (PRM) are used to reinforce the asphalt concrete (AC) overlay to delay reflection cracking. Assessing the effectiveness of PRM in limiting reflection cracking can be achieved by direct measurement of strain distribution within the PRM and AC overlay. A fiber-optic sensor is the only alternative that is compatible with the fiberglass structure of the PRM used in this study and, therefore, is used to measure strain within the PRM. A program of investigation, developed at the Institute for Research in Construction of the National Research Council Canada, aims at studying the state of stress leading to joint opening in pavement layers and assessing the effectiveness of PRM in reducing such cracks through monitoring the performance of PRM using embedded fiber-optic strain sensors. The investigation involves both laboratory testing and long-term field monitoring of instrumented road section. The instrumentation aspect of the laboratory evaluation of PRM effectiveness using embedded fiber-optic sensors is described. An instrumentation procedure is developed that includes sensor mounting and embedding, mechanical protection, calibration, and data acquisition system. The performance of the developed monitoring system in asphalt concrete pavement specimens is assessed in controlled laboratory conditions.
Application of Computer-Integrated Transportation to Commercial Vehicle Operations
Authors: Hall Randolph W. , Chatterjee Indrajit
Published: August 2018

Computer-integrated transportation (CIT) is envisioned as an integrated network of public and private transportation organizations, each of which has unique responsibilities but is working toward a common mission of facilitating travel across all modes of transportation. The research on CIT is extended to commercial vehicle operations, specifically to examine how government can work with trucking companies (i.e., motor carriers) within a CIT framework. The research entailed a review of how government currently interacts with trucking companies, interviews with trucking terminal managers, and case studies of terminal operations at five of the nation's largest motor carriers. Opportunities are identified in the area of unifying the interaction between government and industry (along four lines: licensing, roadway information, incident clearance, and enforcement) and in the area of in-vehicle devices for automated record keeping.
E-ZPass: Case Study of Institutional and Organizational Issues in Technology Standards Development
Authors: Gifford Jonathan L. , Yermack Larry , Owens Cheryl A.
Published: August 2018

During the past 5 years seven toll agencies operating in the greater New York metropolitan area have combined to develop a regionally compatible electronic toll collection system, called E-ZPass. The members of the E-ZPass Interagency Group (IAG) collectively process more than 1 billion toll transactions per year, two-thirds of all toll revenue collected in the United States. E-ZPass illustrates the degree of interagency cooperation necessary for interoperability, as well as some of the challenges to achieving consensus on technical and institutional issues. The IAG faced numerous institutional and organizational issues during the development of the E-ZPass specification. These included separate procurement procedures and requirements of the participating agencies, differences in agency missions, the pace of technological change, and parallel standard-setting efforts at the national level. In the large-scale procurement of cutting-edge technology, the IAG's regionally cooperative effort is unprecedented and provides valuable insights into the conflicts that occur and how they can be resolved.
Determination of Number of Probe Vehicles Required for Reliable Travel Time Measurement in Urban Network
Authors: Srinivasan Karthik K. , Jovanis Paul P.
Published: August 2018

Several intelligent vehicle–highway system demonstration projects are currently assessing the feasibility of using probe vehicles to collect realtime traffic data for advanced traffic management and information systems. They have used a variety of criteria to determine the number of probes necessary, but few generalizable algorithms have been developed and tested. The described algorithm explicitly considers the time period for travel time estimation (e.g., 5, 10, or 15 min), the number of replications of travel time desired for each link during each measurement period (reliability criterion), the proportion of links to be covered, and the length of the peak period. This algorithm is implemented by using a simulation of the Sacramento Network (170 mi2) for the morning peak period. The results indicate that the number of probe vehicles required increases non-linearly as the reliability criterion is made more stringent. More probes are required for shorter measurement periods. As the desired proportion of link coverage in the network increases, the number of probes required increases. With a given number of probes a greater proportion of freeway links than of major arterials can reliably be covered. Probe vehicles appear to be an attractive source of real-time traffic information in heavily traveled, high-speed corridors such as freeways and major arterials during peak periods, but they are not recommended for coverage of minor arterials or local and collector streets or during off-peak hours.
Modeling Revealed and Stated En-Route Travel Response to Advanced Traveler Information Systems
Authors: Polydoropoulou Amalia , Ben-Akiva Moshe , Khattak Asad , Lauprete Geoffrey
Published: August 2018

Advanced traveler information systems (ATISs) are being developed to provide travelers with real-time information about traffic conditions. To evaluate the benefits of ATIS products and services, questions concerning the potential market, use, and travel response must be addressed. The present focus is on the en-route travel response to ATISs. The main objective is to explore how travelers deal with unexpected congestion and how they might respond to qualitative, quantitative, prescriptive, and predictive information. Data on travelers' route-switching decisions were obtained through a survey of California Bay Area automobile commuters. The effects of various factors, such as sources of congestion information (radio traffic reports versus observation), trip characteristics, and route attributes on traveler response to unexpected congestion, were investigated. Future response to ATIS technologies was explored by using stated preferences, that is, hypothetical ATIS scenarios. A combined reported and stated preference model of traveler response was developed. The results indicate that expected delays on the usual route, travel time on alternative routes, perceived congestion level on alternative routes, and information sources are important determinants of travel decision changes in response to unexpected delays. The modeling methodology identifies the effects of experience and behavioral inertia on choices and captures inherent biases in the stated preference responses. Overall, travelers are more likely to respond to specific quantitative delay information.
Modeling Revealed and Stated Pretrip Travel Response to Advanced Traveler Information Systems
Authors: Khattak Asad , Polydoropoulou Amalia , Ben-Akiva Moshe
Published: August 2018

Advanced traveler information systems (ATISs) offer benefits to travelers and may improve transportation system performance in congested areas. An understanding of how information affects travelers' decisions can help in evaluating benefits and designing demand management strategies. The objective of the present study was to explore how people deal with unexpected congestion during the pretrip stage and how they might respond to ATISs. Travelers' routes, departure times, and mode selection decisions were investigated through a survey of Bay Area automobile commuters. The effects of various factors such as sources of congestion information (radio traffic reports versus observation), trip characteristics, and route attributes on travelers' responses to unexpected congestion were examined. The pretrip response to future ATIS technologies was explored through stated preferences (hypothetical scenarios). A combined reported preference and stated preference model of traveler response was developed by using the multinomial logit formulation. The estimations indicate that travel time and information are important determinants of changes in travel decisions in response to unexpected delays. The model indicates a strong relationship between reported and stated preferences. The results indicate that ATISs overcome behavioral inertia and that individuals are more likely to change their travel patterns in response to prescriptive information. More specific findings and their implications for ATIS design are also discussed.
Advanced Traveler Information System Users' Needs in I-95 Northeast Corridor
Authors: Hobeika Antoine , Sivanandan R. , Jehanian Karen M. , Ameen Mary D.
Published: August 2018

The I-95 Corridor Coalition, comprising 28 transportation agencies and state and local departments of transportation and supported by a number of federal and quasipublic organizations, has embarked on an aggressive program to study and implement intelligent transportation system services along this priority corridor from Maine to Virginia. A key element to the success of this effort is that the travel information needs and desires of the I-95 travelers be satisfied. A comprehensive multimodal study was initiated by the I-95 Corridor Coalition to assess the advanced traveler information system needs of I-95 corridor users and to determine the market potential for such information. The stakeholders include user groups, providers, and producers. The target groups include local and long-distance (business and recreation) automobile travelers, transit users, intercity air travelers, and intercity rail travelers. The provider groups include state, regional, and local transportation agencies, whereas the producer groups include telecommunications companies, automobile manufacturers, and traveler information service providers. Several survey mechanisms were used to assess the user and provider information needs and will be used to assess the market potential. These include focus groups, telephone surveys, on-site surveys, and individual interviews. Thus far in the study users have ranked roadway safety, personal security, and traffic information high in importance. Users have also indicated a willingness to pay for multimodal traveler information services both for their pretrip planning and while en route.
Pedestrian Facilities in South Africa: Research and Practice
Authors: Ribbens Hubrecht
Published: August 2018

An overview of the pedestrian accident problem in South Africa is given, and the engineering solutions implemented to improve pedestrian safety are discussed. The pedestrian problem accounts for part of the road safety problem in South Africa. In recent years there has been a reduction in the number of pedestrian fatalities and injuries. Research findings in the early 1980s showed that inadequate provision was being made for pedestrians in a country where about 80 percent of all trips were made by public transport and by foot. A comprehensive research program has been conducted since 1980 to upgrade all the facilities through the development of warrants for the provisions and guidelines for the correct layout and siting of the various types of pedestrian facilities. The various operational problems encountered at the different types of pedestrian facilities are discussed to provide a safer environment. These problems and solutions are dealt with according to the various traffic engineering approaches adopted to improve pedestrian safety. First, the methods used to integrate pedestrians with vehicular traffic are highlighted, namely through temporal separation (pedestrian crossings, school patrol crossings, traffic lights) and soft separation (traffic calming measures). Second, the technologies developed to segregate pedestrians from vehicular traffic through horizontal separation (pedestrian malls, township layout, sidewalks) and vertical separation (foot bridges and subways) are discussed. Other aspects are pedestrian facilities on rural roads, pedestrian signs and markings, and facilities for disabled pedestrians. Apart from the dissemination to practitioners of individual research reports on pedestrian facilities produced since 1980, the warrants and guidelines developed since 1980 were incorporated into a pedestrian facility manual published in 1993. Technology transfer workshops were conducted throughout South Africa to train road authorities and consulting engineers on use of the manual. It is concluded that the implementation of these warrants and guidelines since the mid-1980s together with a holistic traffic safety management plan have contributed to the reduction in pedestrian fatalities and injuries since 1989.
Field Evaluation of Fluorescent Strong Yellow-Green Pedestrian Warning Signs
Authors: Clark Kenneth L. , Hummer Joseph E. , Dutt Navaneet
Published: August 2018

Recent improvements in manufacturing processes have allowed the development of a fluorescent, microprismatic sign material with a unique strong yellow-green color. Although this color is listed in the Manual on Uniform Traffic Control Devices, it is currently unassigned. Pedestrian accidents continue to be a major safety problem in the United States, and the Federal Highway Administration has requested research on the application of fluorescent strong yellow-green warning signs for pedestrian, bicycle, and school crossing applications. The research effort sought to evaluate the effectiveness of fluorescent strong yellow-green pedestrian warning signs in improving safety at midblock pedestrian crossing areas, using sound experimental methodology and encompassing multiple users and varied crossing conditions in several North Carolina cities. An experimental plan with a single treatment was used (replacement of existing signs with fluorescent strong yellow-green) and followed a model of before and after with a comparison site. The measures of effectiveness used were vehicle-pedestrian conflicts and motorist slowing and stopping. Results indicate that the fluorescent strong yellow-green treatment produced only marginal improvements in perceived safety at the crossing sites. Although the occurrence of motorists slowing and stopping increased significantly at three of the seven test sites, the proportion of vehicle pedestrian conflicts did not change significantly. Based on the results it is recommended that FHWA tentatively designate fluorescent strong yellow-green for nonmotorized applications until such time that long-term accident-based and cost-effectiveness research is available to justify permanent designation or alternative uses.
Evaluation of Detectable Warning Surfaces for Sidewalk Curb Ramps
Authors: O'Leary Amy A. , Lockwood Philomena B. , Taylor Richard V.
Published: August 2018

The 1991 Americans with Disabilities Act Accessibility Guidelines required installation of a detectable warning surface (raised truncated domes) on sidewalk curb ramps to alert visually impaired persons to potential hazards at pedestrian crossings. In 1994 the requirement was temporarily suspended for 2 years. Whether visually impaired persons need (or want) detectable warnings on ramps and whether domes are the best option continue to be debated. The Virginia Department of Transportation's current standard requires an exposed aggregate (gravel mixed into concrete) surface on curb ramps. Seven warning surfaces (five domed, two exposed aggregate) were evaluated for their detectability by the visually impaired and the maneuverability they afford the mobility impaired. The performance characteristics of different ramp surfaces were also obtained through a telephone survey of transportation officials in Virginia and 21 other states. Field-test results for 47 visually impaired participants indicated that the five domed surfaces were far more detectable than the aggregate surfaces. A majority of the totally blind participants failed to detect the two exposed aggregate surfaces. Some visually impaired test participants disliked the feel of the domed surfaces underfoot; however, many were unfamiliar with any type of warning surface on ramps. Six mobility-impaired individuals clearly preferred the exposed aggregate surfaces. There is a fundamental tradeoff between surface detectability and easy maneuverability. The telephone survey indicated that other states use a variety of ramp surfaces, not all of which provide detectable warnings. Some areas using domed surfaces reported substantial freeze-thaw and winter-maintenance damage. No maintenance damage to aggregate was reported, but Virginia respondents reported other kinds of problems with its installation and use. Virginia's experience illustrates the kinds of dilemmas state departments of transportation face in their efforts to select an optimum surface for all curb ramp users.
Using Medical Records in Non-Motor-Vehicle Pedestrian Accident Identification and Countermeasure Development
Authors: Eck Ronald W. , Simpson E. Darin
Published: August 2018

A study was conducted to determine the feasibility of using emergency room and emergency medical service records in quantifying rural non-motor-vehicle pedestrian accidents and in developing countermeasures to reduce injuries resulting from such accidents. A literature review indicated that although non-motor-vehicle pedestrian accidents are a significant injury problem in the United States, there does not appear to be an effective process for collecting data about those accidents that corresponds to the data collection methods used at present for motor-vehicle accidents. A multistep process for obtaining detailed pedestrian accident data using a combination of medical records and telephone surveys is described. Data collection was time consuming and labor intensive. Therefore, it was concluded that it is not practical for traffic engineers to use medical records on a routine basis for pedestrian accident analysis. The method outlined yields a data base rich in details about pedestrian fall accidents, making it valuable in research. Whereas the results of the telephone survey did not produce a large enough sample size to extrapolate to pedestrian accidents in general, they did point out the importance of surface condition to pedestrian safety. Two general types of surface-condition problems were identified: slippery surfaces caused by accumulation of snow and ice and surface holes or openings.
Modeling Fault among Bicyclists and Drivers Involved in Collisions in Hawaii, 1986–1991
Authors: Kim Karl , Li Lei
Published: August 2018

Subsequent to a review of trends in collisions between bicyclists and motorists in Hawaii during the period 1986 to 1991, characteristics of bicyclists and drivers involved in crashes are compared. On the basis of police-reported crash data it can be concluded that bicyclists tend to be young, male, and, not surprisingly, more likely to be seriously injured than motorists in bicycle–motor-vehicle collisions. Bicyclists are much less likely to be attributed with inattention than motorists, and slightly less likely to be attributed with misjudgment or alcohol or drug use than motorists. Bicyclists, however, are much more likely than motorists to disregard traffic controls or go the wrong way on a street just before becoming involved in a collision. Motorists are more likely than bicyclists to fail to yield, to engage in improper overtaking, or to follow too closely before becoming involved in a collision. The largest proportion of bicycle collisions occurs during the period 3:30 to 6:30 p.m. Other temporal and locational features of bicycle collisions are described. Among the most significant findings presented is that motorists in Hawaii are much more likely to be classified at fault than bicyclists. Whereas motorists are at fault in approximately 83.5 percent of incidents, bicyclists are at fault in only 16.5 percent of incidents. A logistic model is developed and used to explain the likelihood of motorists being at fault in collisions with bicyclists. Covariates that increase the likelihood of motorist fault include motorist age (squared), bicyclist age, bicyclist helmet use, and motorist turning actions. Variables that decrease the likelihood of motorist fault include motorist age, bicyclist age (squared), bicyclist alcohol use, bicyclists making turning actions, and rural locations.
Bicycle Collisions in Washington State: A Six-Year Perspective, 1988–1993
Authors: Wessels Ralph L.
Published: August 2018

A categorical data analysis of collisions between bicycles and motor vehicles was performed in Washington State using 8,540 collision records from 1988 through 1993. The collisions were categorized by action and location of bicyclists and motorists, age groups, road ownership, and county, using a modified version of the Cross/Fisher methodology. Various statistics on demographics, contributing circumstances, and environmental conditions were developed. The results of the analysis indicate that the type and severity of accidents vary by classification of roadway and age group and among similar areas within the state. One-half of the bicycle collisions involved those aged 15 or less. Male bicyclists were involved in 80 percent of the collisions, which was likely due to greater exposure instead of a behavioral difference by gender. Intersections accounted for one-half of the collision locations. The merit of developing a statewide bicycle-collision report that stratifies information at the local level is presented, along with practical applications of the data. An inherent bias against safety improvements for bicycles that is due to collision-reporting thresholds is also discussed.
Bicycle-Helmet Use Evaluation Using Comparison-Site Observation
Authors: Womack Katie N.
Published: August 2018

The Texas Transportation Institute (TTI) conducted observational surveys of bicycle-helmet use in six cities. Three of the cities (Austin, Houston, and San Antonio) were targeted by a Texas Office of Disabilities and Prevention program to increase bicycle-helmet use among 5 to 14 year-olds. Three control cities (Fort Worth, Dallas, and El Paso) were selected. Target-city and control-city observation zones were designated using census data for school attendance zones merged with county geographic files. School attendance zones in target and control cities were matched for ethnicity and socioeconomic characteristics. Observations were conducted in succession from July through September 1994. Helmet use data was collected through mobile surveillance. Observations in school areas were made in at least two socioeconomi-cally diverse neighborhoods whenever such neighborhoods existed in an attendance zone. Observers canvassed each observation zone, traveling by car on as many public roads as possible during each observation period. Overall, 1,485 bicyclists were observed in the six study areas. In each study area the number of bicyclists observed was between 200 and 350. Helmet use ranged from 3 percent overall in San Antonio to 22 percent overall in Austin; however, a great deal of variation was observed within each city. TTI plans to monitor program effects at the observation zones with two additional survey waves. Legislation mandating helmet use in Texas was introduced in 1994, but failed. Program efforts to be undertaken by the Texas Injury Control and Prevention office are planned for 1995 and 1996.
Evaluation of Planning and Design Issues for Multiuse Trail and Highway Crossings
Authors: Gittings Gary L. , Torbic Darren J. , Zangwill Leonard A.
Published: August 2018

Across the country a network of multiuse trails is evolving from abandoned rail corridors. This phenomenon creates a new set of demands on public highway and transportation agencies. These demands are most evident at public highway crossings of rail-trail projects. These demands raise new policy, planning, and engineering issues. The most difficult and controversial of the engineering issues is whether to retain or remove grade-separating rail structures. The issue often pits trail advocates against public highway and transportation engineers in a debate over whether safety is enhanced or degraded by the removal of the structure. Decisions on structures rely on a variety of factors, including the physical condition of the structure; the alignment, clearance, and sightlines at the crossing; the quality of trail plans; and the magnitude and division of responsibility for current and future costs. To effectively resolve trail and highway crossing issues, it is important to recognize that, in matters related to the crossings, the highway or transportation agency's customer base includes trail users as well as motor vehicle drivers and passengers. Decisions on crossing issues should evolve from a balanced appraisal of the sometimes differing safety and operating needs of trail as well as highway users. The process of reaching balanced, multimodal design decisions begins with better public planning before rail line abandonment. The state highway or transportation agency can enhance its decision making through better communication, coordination, and encouragement of trail planning with sister state agencies, local government(s), regional planning agencies, and trail development organizations.
Efforts by North Carolina Department of Transportation to Develop Mechanistic Pavement Design System
Authors: Corley-Lay Judith B.
Published: August 2018

A first generation mechanistic empirical pavement design procedure was developed using falling weight deflectometer deflections taken over a 3-year period at 16 test sections in Siler City, North Carolina. Information available for use in developing the procedure included deflection data, surface and air temperature, coring thicknesses at each test location, pavement performance records regarding rate of cracking, and traffic records. Jung's method, based on the curvature of the deflection bowl, was used to calculate strain at the bottom of the asphalt layer as a measure of fatigue. This calculated strain was used to obtain a calculated number of load repetitions to failure. Comparision of actual loads to failure with calculated loads to failure resulted in a table of shift factors by pavement type.
Using Time Series to Incorporate Seasonal Variations in Pavement Design
Authors: Ali Hesham A. , Parker Neville A.
Published: August 2018

Analysis of the seasonal monitoring program data of the long term pavement performance program indicated that some pavement structural properties often follow predictable seasonal patterns. Time series is a statistical technique that may be used to develop periodic functions to predict the values of such properties as a function of time. The application of time series technique in characterizing the seasonal variations of pavement structural properties as simulated functions is presented. In addition, the incorporation of such variations in both empirical and mechanistic-empirical methods of flexible pavement design is demonstrated. To this end, a computer program, seasonal variation in pavement design, was written to carry out the required calculations and to facilitate the comparison between empirical and mechanistic-empirical design methods.
Simplified Generalized California Bearing Ratio Pavement Design Equation
Authors: Divinsky Michael , Ishai Ilan , Livneh Moshe
Published: August 2018

The probabilistic approach to pavement design and evaluation requires estimation of the diversity associated with each design parameter. Results and conclusions should be based on statistical analysis with wide application of mathematical statistics and theory of reliability methods. Consequently, statistical analysis of the California bearing ratio design equation was performed, and a new generalized design equation suggested. This equation provides a simplified and rapid pavement design prediction using the common basic design parameters. The suggested model and equation provide at least the same and, possibly, greater accuracy than the current deterministic pavement design method provides. At the same time, they eliminate the need to determine the equivalent single-wheel load curve for each loading and wheel configuration, depending instead on the number of wheels in the assembly only. It is believed that the suggested model and equation also provide an appropriate step toward the application of stochastic pavement design methods.
Effect of Overloaded Heavy Vehicles on Pavement and Bridge Design
Authors: Chou Chia-pei J.
Published: August 2018

A large number of infrastructure projects have been undertaken in Taiwan in recent years because it is a developing country. These large-scale constructions have caused rapid growth in the number of heavy vehicles in service, as well as a dramatic increase in the size and weight of heavy vehicles. A very serious truck overloading problem has resulted, which significantly affects pavement performance and bridge safety. In the described study, weigh-in-motion (WIM) equipment was introduced to Taiwan's freeway systems. After data collection and analysis it was found that the average truck load factor for combined heavy vehicles computed from the WIM data collection was 2.7 times higher than the original design value, which already took into account 30 percent truck overloading. It was also found that computed axle load ratios for various types of heavy vehicles were dramatically different from the ratios given in the bridge design standard specification. Bridge deck designs for a simply supported bridge were studied. It was concluded that the current bridge design standard specification will result in a 28 percent underestimation of steel volume in bridge deck design.
Field Investigation into Effects of Vehicle Speed and Tire Pressure on Asphalt Concrete Pavement Strains
Authors: Chatti Karim , Kim Hyung B. , Yun Kyong K. , Mahoney Joe P. , Monismith Carl L.
Published: August 2018

An asphalt concrete section on a test track in the PACCAR Technical Center in Mount Vernon, Washington, was fitted with strain gauges at the surface and in pavement cores and tested using an instrumented truck operated at different speeds and with different tire pressures. The field test results are presented. The results indicate that the effects of both vehicle speed and tire pressure–contact area on pavement strains are significant: increasing vehicle speed from 2.7 km/hr (1.7 mi/hr) to 64 km/hr (40 mi/hr) caused a decrease of approximately 30 to 40 percent in longitudinal strains at the bottom of the asphalt concrete layer, which was 137 mm (5.4 in.) thick. The speed effect on transverse strains is lower, causing only a 15 to 30 percent decrease. Reducing tire pressure from 620 kPa (90 psi) to 214 kPa (30 psi) caused a decrease of approximately 20 to 45 percent in the horizontal strains at the bottom of the asphalt concrete layer. The pressure effect on surface strains was significantly lower, causing only a 5 to 20 percent decrease. The speed effect was somewhat reduced at lower pressures, and the pressure effect was reduced at higher speeds.
Considerations on Finite-Element Method Application in Pavement Structural Analysis
Authors: Cho Yoon-Ho , McCullough B. Frank , Weissmann José
Published: August 2018

Finite-element models have been applied extensively to the design and analysis of pavement structures. Three types of models have been used to study multilayered pavement structures: plane strain, axisymmetric, and three-dimensional (3-D). The applicability of each these three models and their disadvantages and advantages are discussed. Within the research community, an issue frequently raised about the application of the finite-element method (FEM) to pavement structures is the dependence of the solution on the simplifications that are introduced to reduce computational time and mesh configurations and element size, type, and aspect ratio. This issue is discussed extensively with the primary objective of comparing the solutions derived from FEM models with those from classic mechanistic models. The FEM solutions were derived with a commercial software package, ABAQUS, which is designed as a flexible tool for the implementation of FEM. The solution from the BISAR layered theory model for the traffic loading results was chosen for comparisons with the FEM solution. The 3-D and axisymmetric FEM models yielded results suitable for the traffic loading analysis.
Effect of Poor Workmanship and Lack of Smoothness Testing on Pavement Life-Cycle Costs
Authors: Zaghloul Sameh M.
Published: August 2018

Pavement performance is commonly evaluated using the concept of pavement serviceability, in which pavement failure is defined by terminal serviceability instead of strict structural failure. The present serviceability index (PSI), the measure of pavement serviceability, is a function of pavement roughness, cracking, patching, and rutting. Pavement roughness is the major component of PSI and represents more than 95 percent of its value. Because roughness is such an important consideration, changes in roughness control pavement life cycles, and, therefore, construction quality, which influences roughness, influences performance and life cycle as well. A case study of a $120,000,000 project is presented. In this project, poor workmanship and lack of smoothness testing led to a considerably high initial roughness. A study was conducted to quantify the long-term effects of the high initial roughness. Results of this study indicate that the pavement service life of the project will be reduced significantly. In addition, a huge increase in the project life-cycle costs is expected. In another study, consideration was given to some of the available smoothness evaluation criteria in which roughness indices, such as the international roughness index and PSI, are used. Results of the study showed that most of these criteria are not capable of adequately addressing the high roughness associated with repeated transverse pumps. Recommendations for overcoming this inadequacy are presented.
A Pavement Design and Rehabilitation System
Authors: Uzan Jacob
Published: August 2018

Because the Superpave system is not readily available for use, an interim pavement design and rehabilitation method was developed that can be used for Israeli traffic and environmental conditions. The existing method was upgraded to include most of the relevant available information and to produce reliable pavement design for the specific conditions in Israel. The upgrading concentrated on multiple topics. An axle-load distribution specific to Israeli conditions was included because analysis indicates that axle loads in Israel are typically above the standard 80-kN single axle load. The extended California bearing ratio (CBR) method was adapted to a variety of axle-load combinations by using Miner's law for damage accumulation. Converting the axle-load distribution to the standard 80-kN equivalent single axle load leads to underdesign of approximately 10 percent in pavement thickness (or to a reduction of about 70 percent of the design life). A fatigue consideration to determine the asphalt-layer thickness was added. Local temperatures were analyzed to determine an equivalent temperature for fatigue calculation. For Israeli conditions, an equivalent temperature of 14°C can be used countrywide for asphalt-layer thicknesses up to 250 mm. An overlay design method consistent with the upgraded design procedure was assembled. It includes backcalculation of layer moduli to determine the subgrade CBR and the quality of the pavement layers; pavement condition surveys to evaluate a representative effective thickness of the asphalt layer; and component-layer analysis to determine the overlay thickness.
Design of Pavement Structures: The French Technical Guide
Authors: Corté Jean-François , Goux Marie-Thérese
Published: August 2018

Until recently in France the design of pavement structures was specified in catalogs of standard structures in which course thicknesses are fixed according to the traffic category and subgrade load-bearing capacity. This type of document is appropriate when the constituent materials of the pavements and their mechanical performance are predefined and investment strategies are firmly established. During the past 10 years the technical and economic context in France has changed considerably. The standardization of road products and materials has introduced material classes characterized by their mechanical performance, and road management has been transferred from state to local authorities and has been accompanied by a differentiation in the various owners' investment and maintenance strategies. Catalogs of existing pavement structures have had to be supplemented through an approach that made it possible to set the parameters for the mechanical properties of materials and pavement investment strategies. The publication of the French technical guide for the design of pavement structures serves as such a supplement. This manual makes explicit the mechanistic approach in use for many years in France. The basic concepts, design criteria, and application of this method are described, and examples for asphalt and cement-concrete pavements are provided.
Development of Bayesian Regression Model to Predict Hot-Mix Asphalt Concrete Overlay Roughness
Authors: Kajner Lyle , Kurlanda Marian , Sparks Gordon A.
Published: August 2018

Predictive equations are central to the many tools highway professionals use to design, maintain, and manage our highway infrastructure. However, adequate data bases to support the development and updating of these models are often lacking. These data bases are often inadequate in sample size, noisy, or incomplete. Conventional statistical modeling tools, such as classical regression analysis, meet with limited success in these applications. A promising solution lies in the use of Bayesian regression, which explicitly allows expert judgment, collected from in-house or external experts, to be used to supplement poor-quality data. An overview is presented of the development of a Bayesian predictive model to forecast the progression of roughness in hot-mix asphalt concrete overlays using data and expert judgment provided by Alberta Transportation and Utilities.
Revised Predictive Model for Dynamic (Complex) Modulus of Asphalt Mixtures
Authors: Witczak M. W. , Fonseca O. A.
Published: August 2018

Many predictive techniques for determining the dynamic modulus of asphalt concrete mixes have evolved over the past 25 years. One such model, developed at the University of Maryland, has been widely incorporated in design manuals and methods used throughout the world. However, the current predictive model only allows the determination of the dynamic modulus from the original bitumen properties among other variables. This model has been developed from dynamic (complex) modulus tests on laboratory-prepared specimens and does not take into account the hardening effects that take place during short- and long-term aging. By incorporating recent field studies on the aged viscosity of conventional asphalt cements, a revised model for the dynamic modulus of asphalt mixtures has been developed using the actual bitumen viscosity as the most important predictor variable in place of temperature. This modification now allows the model to be used to predict dynamic modulus for mixtures exhibiting any degree of binder aging. Also, by using a sigmoidal function model form, significant improvement in prediction rationality was achieved for using the model at extreme temperature conditions.
Probabilistic Finite-Element Analysis of Airfield Pavements
Authors: Lua Yuan Jie , Sues Robert H.
Published: August 2018

Mechanistic pavement analysis and design based on either layered elastic analysis (LEA) or the finite element method (FEM) is increasingly being used to replace the empirical design process. The simplifying assumptions of a uniform, homogeneous layer of linear material used in LEA can render its analysis inaccurate for real pavement structures. The FEM is more attractive for structural analysis of pavements; the generality of the FEM also allows both the use of comprehensive material models and modeling of the spatial variability that exists in pavement systems. To date, spatial variability and uncertainty are ignored in pavement system finite element analyses. Ignoring spatial variability and uncertainty implies a false sense of accuracy in the results and can lead to inaccurate assessment of the pavement. The first application of the probabilistic finite element method to pavement response analysis and life prediction and the first investigation of the effects of spatial variability on pavement life prediction are presented. It is concluded that the probabilistic FEA, with spatial variability, is a more accurate representation of the true physical condition and leads to results that are less conservative than those obtained with probabilistic LEA.
Rational Selection of Factors of Safety in Reliability-Based Design of Flexible Pavements in Saudi Arabia
Authors: Noureldin A. Samy , Sharaf Essam , Arafah Abdulrahim , Al-Sugair Faisal
Published: August 2018

Explicit applications of reliability in pavement engineering have been of interest to pavement engineers for the last 10 years. Variabilities in parameters affecting pavement design performance result in variability in pavement performance prediction and thus affect the reliability of how long the pavement will last. Rational quantification of those variabilities is essential for incorporating reliability and selecting the proper factors of safety in the pavement design performance process. The prevailing methodology in Saudi Arabia of quantifying the variability in pavement performance due to the variabilities of the parameters affecting that performance is demonstrated. Factors of safety for flexible pavement design at various reliability levels and based on those prevailing variabilities are presented. These factors of safety are recommended for flexible pavement design in Saudi Arabia.
Establishing the California Department of Transportation Accelerated Pavement Testing Program
Authors: Nokes W. A. , Stolarski P. J. , Monismith C. L. , Harvey J. T. , Coetzee N. , Rust F. C.
Published: August 2018

How the California Department of Transportation Accelerated Pavement Testing (CAL/APT) Program was established is described. Discussion includes history of the program, search for full-scale pavement testing technology suitable to California, results of a pilot project conducted on test pavements built in South Africa, laboratory tests included in the CAL/APT program, and development of an organization to manage CAL/APT and implement its products. A status report on testing and planning is included.