bluuebunny/crossref_metadata_2025 huggingface dataset:
Los Angeles I-10 Field Experiment: Incident Patterns
Authors: Skabardonis Alexander , Petty Karl F. , Varaiya Pravin P.
Published: April 2007

The Los Angeles I-10 field experiment has produced a large, comprehensive database on incidents and freeway traffic flow characteristics. Field data on incidents were collected through observations of probe vehicle drivers over a 12.5-km (7.8-mi) freeway section. Supplementary information was collected from the California Highway Patrol computeraided dispatch (CHP/CAD) system and freeway service patrol logs. The incident patterns at the study area are described, and the major factors affecting incident frequency and duration are identified. Comparisons of the findings with other databases are discussed. The effects of incidents on traffic flow are also investigated using the empirical data to determine the proportion and characteristics of delay-causing incidents.
Evaluation of Anaheim Adaptive Control Field Operational Test: Institutional Issues
Authors: McNally Michael G. , Mattingly Stephen P. , Moore James E. , Hu Hsi-Hwa , MacCarley C. Arthur , Jayakrishnan R.
Published: April 2007

An overview is provided of the institutional and technical issues associated with the evaluation of the federally sponsored Anaheim Advanced Traffic Control System Field Operations Test. The primary test objectives were the implementation and performance evaluation of adaptive traffic signal control technologies, including an existing second-generation approach, the Split, Cycle, and Offset Optimization Technique (SCOOT), and a 1.5 generation control (1.5GC) approach under development. Also selected for implementation was a video traffic detection system (VTDS). The SCOOT evaluation was defined relative to existing control based on first-generation Urban Traffic Control System (UTCS) but using standard field detectorization rather than that normally associated with SCOOT. Furthermore, SCOOT was installed to operate in parallel to UTCS. The 1.5GC system was planned to be efficiently used to update baseline timing plans. The VTDS was planned for use as a low-cost system detector for deployment in critical areas. Both SCOOT and the VTDS were implemented with some degree of success, with technical and institutional issues limiting expected performance. Technical issues that limited SCOOT performance included less-than-anticipated quality of existing communication and controller systems; corresponding institutional factors included inconsistent project management due to staff changes and delays due to contractual issues. Both SCOOT and a modified version of the VTDS are in use in selected areas, with plans for system expansion.
Rule-Based Approach to Real-Time Distributed Adaptive Signal Control
Authors: Owen Larry E. , Stallard Charlie M.
Published: April 2007

Most solutions for the problem of adaptive signal control involve optimization of an objective function. This paper presents a departure from this approach and describes a rule-based algorithm for effective distributed adaptive signal control of traffic networks. The control strategy, which has been termed GASCAP (Generalized Adaptive Signal Control Algorithm Project), uses queue estimates and a set of rules to determine the signal state at each intersection in the network. The GASCAP queue estimation algorithm uses upstream detector information to estimate the number of vehicles approaching an intersection and the vehicles in queue. The queue estimation algorithm is relatively insensitive to the extreme variations that may exist for cycle-to-cycle turning percentages because it uses the concept of a “partial” vehicle. The queue estimation logic and the control logic used to determine the signal state reside locally at each intersection and can be implemented as a distributed system. The signal control logic consists of a set of rules for uncongested control and an algorithm that creates a fixed time plan for congested control. The occupancy of the upstream detectors on opposing approaches are used to determine if a node is experiencing congestion. This control strategy has been tested with the TSIS/CORSIM simulation tool for three arterial traffic networks. The traffic conditions and network geometries for these arterials provide a wide range of challenges for any adaptive control strategy. Results from simulation indicate that GASCAP significantly reduced the delay and increased the throughput for each of these networks.
Load-Equivalency Factors Based on Extended California Bearing Ratio Method
Authors: Divinsky Michael , Livneh Moshe , Nesichi Shimon
Published: April 2007

The use of load-equivalency factors (LEFs) in pavement design is well established and represents a major factor in various design procedures. The use of the most commonly known AASHTO LEFs in the Israeli design method, however, leads to an underdesign of approximately 10 percent in pavement thickness or to a reduction of 70 percent in design life. New LEF values were developed to be compatible with this design method. This was achieved, first, by attaining straightforward regression equations that are fully compatible with the original total thickness equations given in the Israeli design method (through the MOD software). The built-in LEF values then were calculated by using these regression equations. A comparison was made with LEF values obtained by other established values, and the effect of these values on several overloading issues was evaluated. The conclusion is that the LEFs obtained are the most critical values leading to a substantial reduction in service life or to a substantial increase in the required thickness from overloading.
Evaluation of Rigid Pavement Joint Seal Movement
Authors: Morian Dennis A. , Suthahar Nadarajah , Stoffels Shelley
Published: April 2007

The subject of sealing concrete pavement joints has been studied for many years, and a wealth of technology exists for successfully installing pavement joint seals. However, in practice, a great deal of inadequate performance has been observed by highway agencies in the United States in recent years. A primary reason for the observed problems is inadequate control of construction processes. Another very significant factor affecting the performance of joint seals is climatic conditions. Examined are the effects of climate on the movement of rigid pavement joints. Temperature, joint movement, and other data collected as a part of the Long-Term Pavement Performance (LTPP) program data collection for seasonal sites have been used to assess actual joint movements in various climatic conditions throughout the United States and Canada. These measured data are compared with theoretically calculated joint movements. In most cases the actual movements appear to be greater than those theoretically predicted. On the basis of measured joint openings from LTPP seasonal sections, the conclusion is made that the measured joint opening values are greater than joint opening values calculated using the AASHTO equation described below. The data also provide evidence that irregular joint openings are present at all the sites evaluated.
Controlling Early-Age Cracking in Continuously Reinforced Concrete Pavement: Observations from 12 Years of Monitoring Experimental Test Sections in Houston, Texas
Authors: McCullough B. Frank , Dossey Terry
Published: April 2007

Presented are findings drawn from 12 years of monitoring and analyzing thermal cracking in experimental continuously reinforced concrete (CRC) pavements placed in and around Houston, Texas. Between 1986 and 1995, 85 CRC test sections were built at eight locations (projects) in the greater Houston area. Each project consists of between 8 and 22 experimental sections of slightly different design. These sections were closely controlled and monitored during construction, and periodic condition surveys continue to be conducted. Adjacent placement of the experimental sections in each project minimized the effect of uncontrolled variables such as traffic and climate. The purpose of the study was to evaluate new design elements and construction considerations intended to control earlyage thermal cracking and cracking-related distress caused by coarse aggregate with a high thermal coefficient of expansion. Experimental factors considered include coarse aggregate type, percentage of steel reinforcement, bar size, double or single mat steel, paving time, and paving season. Findings from the study show significant differences in performance between low and high thermal coefficient aggregates, along with some effective methods to minimize them as well as some attempts that were not as successful. Aggregate type and placement season were found to be the most significant factors affecting PCC performance, whereas day or night placement, steel percentage, bar size, and skewed placement proved less significant.
Field Performance of Continuously Reinforced Concrete Pavement in Illinois
Authors: Gharaibeh Nasir G. , Darter Michael I. , Heckel Laura B.
Published: April 2007

Reviewed are the design and performance of continuously reinforced concrete pavement (CRCP) in Illinois. Illinois has built more than 4267 two-lane km (2,650 mi) of CRCP on the Interstate system since the mid-1950s. CRCP has been constructed on nearly all urban freeways in the Chicago area and has shown excellent performance under severe weather and heavy traffic conditions. The effect of key design and construction parameters on long-term CRCP performance is investigated by using a database based on field surveys conducted from 1977 to 1994 compiled by the Illinois Department of Transportation. Analysis of the data shows the following variables have significant effects on performance: longitudinal reinforcement content (greatest effect of all variables), slab thickness (also very significant), traffic load applications, depth of reinforcement, base type, and D-cracking of concrete. CRCP built with tubes or chairs exhibited overall about the same performance. Experimental field studies in Illinois showed that depth of reinforcement has a large effect on crack width and, eventually, on punchouts. Specifically, the investigation indicated that CRCP sections with a slab 178 mm (7 in.) thick and steel content less than 0.6 percent developed the most structural failures. CRCP sections with a slab 254 mm (10 in.) thick and steel content from 0.7 to 0.8 percent developed the fewest failures. However, all the CRCP sections in this study, regardless of thickness designs and steel content, typically have carried more traffic than they were designed for and have lasted longer than their design traffic life.
Longevity of Diamond-Ground Concrete Pavements
Authors: Rao Shreenath , Yu H. Thomas , Khazanovich Lev , Darter Michael I. , Mack James W.
Published: April 2007

Diamond grinding restores a smooth riding surface with the desirable friction characteristics on concrete pavements. This technique was first used in 1965 on a 19-year-old section of I-10 in California to eliminate excessive faulting. Since then, diamond grinding has become a major element of concrete pavement restoration projects. Despite this long history, little valid documentation of the performance of diamond-ground pavements exists. In recognition of the critical need for such information, the Portland Cement Association, in association with the American Concrete Pavement Association and the International Grooving and Grinding Association, sponsored a study of the performance of diamond-ground pavements. The study involved conducting a comprehensive review of existing information on diamond grinding, data collection, data analysis, and documentation of the study findings. Extensive field surveys were conducted to obtain the performance data needed for the analysis. In all, 60 pavement sections in 18 states were surveyed. In addition, performance data for 133 sections were obtained from an earlier study of the performance of diamond-ground pavements. The Long-Term Pavement Performance database also was used because the SPS-6 sections (concrete pavement rehabilitation) provide opportunity for the direct, side-by-side comparison of the performance of diamond-ground pavement sections and other rehabilitation alternatives. Various analyses were conducted to document the performance of diamond-ground pavements, including an evaluation of faulting performance, longevity of diamond-ground texture, and the effects of diamond grinding on service life. Presented are a brief description of the work conducted and a summary of the findings.
Cost-Effective Rehabilitation of Portland Cement Concrete Pavement in Nevada
Authors: Bemanian Sohila , Sebaaly Peter
Published: April 2007

The feasibility of several rehabilitation strategies for portland cement concrete pavement was evaluated. Recommendations were made for future rubblization, crack and seat, and reconstruction projects based on a review of specifications from several other states, the data gathered during the I-80 project, the experience gained during the construction phase of the project, and review of several overlay design procedures. The results of the study, based on 4 years of field performance, indicate rubblization, crack and seat, and reconstruction techniques all are viable options. The economic analysis indicates crack and seat has the lowest initial cost. However, on the basis of projected future performance, both rubblization and crack and seat have approximately the same lifecycle cost over a 35-year analysis period. Pavement performance monitoring is continuing in order to evaluate long-term performance and cost-effectiveness of each strategy.
Structural Adequacy of Rubblized Portland Cement Concrete Pavement
Authors: Galal Khaled A. , Coree Brian J. , Haddock John E. , White Thomas D.
Published: April 2007

The objective of rubblization is to eliminate reflection cracking in hot-mix asphalt (HMA) overlay by the total destruction of the existing slab action. Rubblization is applicable when there is little potential for retaining slab integrity and structural capacity of the original jointed reinforced concrete pavement. Rubblization has been used successfully for rehabilitation of other portland cement concrete (PCC) pavement types. Typically, the slab is reduced to pieces less than 300 mm in size. Subsequently, the slab is converted to a high-strength granular base. Restoration of the structural capacity is accomplished with an overlay of HMA. In 1991, the Indiana Department of Transportation (INDOT) awarded a contract to apply the rubblization technique to a portion of US-41 in Benton County. The pavement sections were evaluated before and after rubblizing and overlay to estimate the AASHTO layer coefficient of rubblized concrete pavements. The layer coefficient determined in this study ( a2 = 0.25) represents a value of two standard deviations less than that reported by PCS/Law. Currently, INDOT uses a layer coefficient of 0.20 for rubblized PCC pavements. On the basis of the results of this study, the layer coefficient can be set within two standard deviations of the mean (i.e., 0.22). This layer coefficient of 0.22 represents a conservative value that is recommended for rubblized PCC pavements with similar conditions. If INDOT continues to use the rubblization technique in pavement rehabilitation, a study encompassing slabs of different thicknesses on different subgrades should be undertaken for confirmation of the values that are reported herein.
Overview of Hot In-Place Recycling of Bituminous Pavements
Authors: Button Joe W. , Estakhri Cindy K. , Little Dallas N.
Published: April 2007

A general definition of hot in-place recycling (HIPR) is provided. The three basic types of HIPR, including multiple-pass and single-pass operations, are described briefly, and their benefits and shortcomings are discussed. Reasons for using HIPR as a tool for rehabilitation of asphalt pavements, along with its limitations, are summarized. The types of pavements that are suitable candidates for HIPR are addressed. Significant results from a telephone survey, conducted in 1992 to determine the extent of HIPR use by state departments of transportation, are discussed. Current HIPR asphalt mixture design philosophy and procedures are summarized. The need for uniform mixture design procedures, construction specifications, and construction guidelines is indicated. Performance of HIPR pavements relative to conventional new overlays is discussed in terms of correcting pavement surface distress, serviceability, structural value, comparative cost, and energy savings. It is pointed out that considerable research is needed to furnish the paving industry with appropriate mixture design procedures (particularly with regard to sample curing), materials and construction specifications, and general construction guidelines.
(Un)predictability in Traffic and Transport Decision Making
Authors: van Zuylen Henk J. , van Geenhuizen Marina S. , Nijkamp Peter
Published: April 2007

Ill predictability is often a problem in decision making in the domain of traffic and transport. Especially posing problems are the uncertainty of short-term processes in the traffic process, such as congestion, and of long-term forecasts. Results are reported from a study of the limits to predictability. The sources of uncertainty are described: on the one hand, uncertainty and incompleteness of data and models, and, on the other hand, intrinsic uncertainties due to the complexity of the processes, such as chaos and nonlinearity, human behavior, and changing values and goals. The role of uncertainties in decision making is highlighted, and suggestions are given for improving the decision-making process. The role of forecasts in different kinds of decision making, with different kinds of information requirements, is described.
Optimizing Transportation Infrastructure Planning with a Multiobjective Genetic Algorithm Model
Authors: Taber John T. , Balling Richard , Brown Michael R. , Day Kirsten , Meyer Gregory A.
Published: April 2007

Most transportation infrastructure planning studies are conducted with only a few alternative networks and land use scenarios. Generally, these studies analyze only a few transportation-related measures of effectiveness, such as vehicle-miles traveled, congestion, and air-quality emissions. When such a small subset of possible alternatives and variables is analyzed, it is probable that optimal alternative designs are not included. Ideally, all combinations of land use, infrastructure, and social variables would be examined; however, even a small city of 200 traffic zones with an average of 10 land uses will have more than 10200 possible zoning alternatives. A more efficient way to examine an extremely large search set of feasible designs is to employ artificial intelligence techniques to quickly narrow the number of alternatives to be considered. The use of a multiobjective genetic algorithm model to optimize land use, infrastructure, social, and fiscal variables is demonstrated. The model considers three primary objective functions: minimizing travel time, minimizing per capita cost (as related to property taxes), and minimizing land use change. A large number of constraints are used. A Pareto fitness function is used to develop a small set of optimal solutions. The model was applied to Provo, Utah, which is a fast-growing community. More than 1.9 million alternative designs were evaluated, and 195 optimal Pareto plans were found. The Pareto set of optimal solutions indicated that solutions clustering higher-density development along existing arterials were most likely to meet the objectives.
Through-Trip Tables for Small Urban Areas: A Method for Quick-Response Travel Forecasting
Authors: Horowitz Alan J. , Patel Minnie H.
Published: April 2007

Regionwide travel forecasts in small urban areas require good knowledge of through-trip tables for each of several vehicle classes. Survey data are often unavailable or incomplete, so planners would benefit from a means of estimating through-trips from readily available information. A model for a through-trip table from trip-distribution theory and elementary geographical principles is postulated and tested. The model considers the level of through-traffic at external stations, the shape of urban areas, and the necessity that trips between any two external points pass through the region because of barriers that impede travel. Separate model variations are developed for a region of arbitrary shape and for a region of circular shape. To ascertain the validity of the approximations, the model is applied to two cities: Oshkosh, Wisconsin, and Tallahassee, Florida. The model for circular-shaped urban areas has produced excellent results for both cities, each of which previously had prepared external-to-external trip tables by sampling actual traffic. Oshkosh’s geography is particularly interesting because of two large neighboring lakes that constitute barriers to travel. The model explains almost 96 percent of the variation in the trip table in Oshkosh and almost 100 percent of the variation in Tallahassee. These values exceed goodness-of-fit measures that are reported for other models that are described in the literature. Errors in through-trip flows on individual links that potentially serve through-trips are estimated at only about 10 percent in Oshkosh and 14 percent in Tallahassee.
Issues Relating to Use of Travel Models in Benefit-Cost Analysis
Authors: DeCorla-Souza Patrick
Published: April 2007

Benefit-cost (B/C) analysis is a useful tool to compare the economic worth of transportation alternatives across modes. However, the application of tools such as MicroBENCOST, IDAS, and STEAM for B/C analysis in metropolitan areas raises several important technical issues that can significantly affect the results of the analysis. Several issues relate to use of four-step travel model outputs in estimation of benefits. Use of an inappropriate “No Build” base for comparison can exaggerate benefit estimates, as can a lack of consideration of the impact of induced travel. Link-level analysis can overestimate benefits from travel time savings, and at the system level, only trip-based analysis can adequately address issues relating to the “constant travel time budget” theory. Finally, use of congested speeds output by traffic assignment models can exaggerate travel time savings. These issues and their implications in metropolitan transportation decision making are discussed.
Analysis of Demand for Road-Based Transport Facilities: A Bi-Level Programming Approach
Authors: Tam Mei-Lam , Lam William H. K.
Published: April 2007

A bi-level programming model is presented for determining the number of parking spaces and road-capacity expansions that are required to satisfy road traffic and parking demand. The lower-level problem is an equilibrium trip-distribution/assignment problem, and the upper-level problem is to maximize the net user benefit (or consumer surplus) by considering travelers’ route and destination choice behavior and by satisfying the network capacity and attraction-end parking supply constraints. The use of consumer surplus in the objective function reflects an economic tradition that public investment in transport facilities (parking spaces and road capacities) should be operated in a way that maximizes the facilities’ social benefits. A sensitivity-analysis-based heuristic algorithm is developed to solve the proposed bi-level problem and is illustrated with numerical examples.
Scenarios and Regional Strategic Transportation Planning
Authors: Muñoz-Loustaunau Abel , Sussman Joseph M.
Published: April 2007

The use of scenarios for regional strategic transportation planning is studied. Scenario methodology is related to central issues identified in three contexts that define the environment in which the development of scenarios for transportation systems is likely to take place: strategic planning, regional transportation, and public–private partnerships. Limitations and concerns that are common to many regional transportation plans and strategic-planning activities are presented. The concept of scenarios is introduced. Several functions that scenario planning can perform in the context of regional transportation are discussed. The way in which scenarios address the identified shortcomings in transportation and general planning are highlighted. The province of Mendoza, Argentina, is introduced, and a scenario exercise for its transportation system is outlined. The primary conclusion is that the scenario methodology is an approach that is responsive to the needs and characteristics of modern regional strategic planning.
Using a Transportation Improvement Program Database and a Partnership Approach To Improve Project Delivery
Authors: Murray David G. , Birner Cécilie R.
Published: April 2007

Metropolitan planning organizations (MPOs) historically have not been involved in project delivery. That involvement is crucial, however, if MPOs want to retain the funding authority granted them in the Intermodal Surface Transportation and Efficiency Act and the continued Transportation Equity Act for the 21st Century. MPOs must help deliver projects in the Transportation Improvement Program (TIP) in a timely manner so that policy makers and the public can see the benefits of MPO involvement. In the San Francisco Bay Area, the Metropolitan Transportation Commission (MTC), which is the MPO for the region, delivered 473 projects, worth $460 million, in a partnership process that relied partly on MTC’s TIP database. For the past 6 years, MTC has made full use of the obligation authority that was available to the region, delivering projects on time and within budget. They experienced success because they ( a) established common TIP project delivery goals among all regional transportation agencies, ( b) streamlined the review and amendment processes, ( c) built appropriate TIP database tools (and web access) for tracking projects, ( d) developed a unique project identifier “set” for each TIP project and carried it throughout the statewide database systems, and ( e) established an oversight committee to resolve delivery problems. The MTC experience is described. One focus is on the use of the TIP database, and another is the cooperative approach to project delivery. A new California state law [Senate Bill 45 (Kopp), 1997] has issued further delivery challenges. Steps in meeting this challenge are outlined.
It’s Not Just for Projects Anymore: Kansas Department of Transportation’s Innovative, Agencywide Public-Involvement Program
Authors: Lorenz Julie L. , Ingram Rosemary
Published: April 2007

To advance the level of public-involvement (PI) practices throughout the agency, meet the public’s demand for an expanded role in decision making, and develop better relationships with customers, the Kansas Department of Transportation (KDOT) is implementing one of the first agencywide PI Programs in the nation. Qualitative surveys were conducted with employees, the public, and 22 DOTs, and input from more than 200 agency personnel was used to develop the KDOT PI Plan. The three “landmarks” of KDOT’s innovative PI Program include ( a) an agencywide PI Program instead of a project-specific program, ( b) training programs and additional resources that help enable every KDOT employee to better serve as an ambassador for the agency, and ( c) recommendations to change business practices that seek public input and use input in decision-making processes. One major area of focus is decentralizing communication and increasing district involvement to develop closer local ties. Revisions to business practices include ( a) screening projects early in the development phase so that the scope, budget, and schedule can be revised, if necessary, in response to public concerns; ( b) convening a Project Delivery Group made up of representatives from various bureaus and the district to improve internal and external communication on complex projects; ( c) using a 10-part step-by-step process to create project-specific PI Plans; ( d) hiring PI professionals at headquarters and in each district; and ( e) encouraging employees to address questions and issues at the local level.
Drafting Japan’s New 5-Year Road Improvement and Management Program A New Approach
Authors: Kikukawa Shigeru , Yoshioka Mikio , Mori Masafumi , Ishida Haruo
Published: April 2007

In Japan, a public-involvement approach (PI Approach) was adopted for the new 5-year road improvement and management program that was approved by the Prime Minister’s cabinet in May 1998, with a view to reflecting increasingly diverse public opinion in the program. The program was based on a proposal by the Road Council and reflected the opinions of approximately 130,000 people, in addition to the vision and recommendations submitted by local business communities and regional requests concerning the program. The proposal of the Road Council was produced by means of dialogues with the general public. People’s opinions were collected via The Kick-Off Report, The Voice Report, and The Interim Report. The PI Approach was adopted in a policy-making process at the national level for the first time. The process is described, along with results of communication with the general public leading up to the formation of the new 5-year road improvement and management program. Also discussed are the end products of each phase: The KickOff Report, The Voice Report, The Interim Report, the Road Council proposal, and The New 5-Year Road Improvement and Management Program.
Transportation Concurrency: Florida’s Example
Authors: Steiner Ruth L.
Published: April 2007

The Florida Local Government Comprehensive Planning and Land Development Act of 1985 called for local communities to develop concurrency-management systems that ensure that public facilities and services, including transportation, whose purpose is to support development, shall be available “concurrent with the impacts of such development.” Although most local communities have been implementing concurrency requirements since their comprehensive plans were approved in the early 1990s, little empirical research has been completed to document how the concurrency requirements have been implemented. Florida and Washington are the only states to require local governments to implement transportation concurrency as a form of adequate public-facilities requirements. The effectiveness of such policies for planners in other states and local municipalities throughout the United States is documented. The results of interviews with policymakers and planners in 25 metropolitan planning organizations in Florida are presented. The interviews were conducted on the subject of implementation of concurrency-management areas and transportation concurrency-exception areas. The concurrency-management process is outlined, and benefits and criticisms of the concurrency-management system are discussed in light of interviews, a review of the statutes, and observations of the Transportation and Land Use Study Committee.
Traffic Calming in New Developments: Avoiding the Need for Future Fixes
Authors: Ewing Reid
Published: April 2007

Recent efforts in the United States to include traffic-calming design in new developments are described. These efforts prevent the need to fix speeding and cut-through traffic problems later. It is clearly more costeffective to design residential streets for speed and volume control than to go back and retrofit, as hundreds of communities are now forced to do. Traffic-calming initiatives of communities that are featured in the upcoming Institute of Transportation Engineers’ book Traffic Calming State-of-the-Art are summarized. The emphasis is on regulatory mechanisms that can be used to implement traffic-calming standards in new developments. Then the standards themselves are presented, and street-network-design principles from the state of Florida’s Best Development Practices are summarized. Standards are established for network connectivity and route density. Next, street-subdivision standards prepared for the Wilmington Area Planning Council, and currently under review for statewide adoption, are outlined. A rationale is provided for each proposed standard that differs from AASHTO’s generally accepted standard.
Identifying Intermodal Connector Needs: Oregon’s Approach
Authors: Kale Steven R. , Kuehn Rick , Wade John E.
Published: April 2007

Interest continues in intermodal transportation planning, including the identification of needs for intermodal connectors on the National Highway System (NHS). FHWA, in response to a requirement in the Transportation Equity Act for the 21st Century, is conducting an Intermodal Connectors Condition and Investment Study on recent improvements and impediments to transportation on NHS intermodal connectors. Similarly, the Oregon Department of Transportation (ODOT) is collecting information about intermodal connector needs as part of its 1999 update of the Oregon Highway Plan, as well as its ongoing development of an Intermodal Management System (IMS). ODOT’s efforts to develop intermodal connector cost estimates for the Highway Plan update are described, and the ways in which ODOT uses IMS performance measures to help identify intermodal needs and impediments are discussed. A comparison is provided of results using ODOT’s procedures versus FHWA’s conditions and investment checklist. Overall, ODOT’s and FHWA’s procedures are complementary, and differences are minor. Together, their results will help increase understanding of the location, condition, and extent of impediments and improvements needed for intermodal freight transportation movements nationally and also at the state and local levels.
Effectiveness Analysis of SafeStat: Motor Carrier Safety Status Measurement System
Authors: Madsen David G. , Wright Donald G.
Published: April 2007

SafeStat (Safety Status Measurement System) is an automated analysis system developed for FHWA’s Office of Motor Carriers (OMC) that combines current and historical safety data to measure the relative safety fitness of interstate motor carriers. SafeStat enables OMC to quantify and monitor the safety status of motor carriers and guides the deployment of resources to focus on carriers posing the greatest safety risk. SafeStat resulted from research performed by the U.S. Department of Transportation’s Volpe Center for OMC to improve motor carrier safety fitness assessment and prescribe actions for correcting safety deficiencies. SafeStat initially was developed and implemented as part of a federalstate pilot program. It has been implemented nationally by OMC to identify and rank individual motor carriers for on-site safety compliance reviews. An effectiveness study was devised to confirm that SafeStat-identified carriers were high-safety-risk carriers. Postidentification carrier crash experience was examined and SafeStat’s effectiveness was tested by comparing the crash rates of identified and nonidentified carriers. The effectiveness study shows that SafeStat identifies carriers likely to have significantly higher crash rates than carriers not identified. Specifically, the carriers designated in the highest “at risk” category by SafeStat had a much higher crash rate (169% percent higher) following their identification than carriers not identified as safety risks. In addition to confirming SafeStat’s effectiveness, the results of the study enable SafeStat developers and OMC to assess the relative strengths of SafeStat’s components and to continue enhancing its efficiency.
Evaluation of the On-Road Behavior of 16-ft-Wide Mobile Homes in North Carolina
Authors: Hall William L. , Harkey David L.
Published: April 2007

The overall objective of this effort was to evaluate the operational behavior and effect on surrounding traffic of 16-ft (4.9-m) wide mobile homes on various types of roadways and compare the results with similar measures for 14-ft (4.3-m) wide units. The evaluation was accomplished by following a sample of 16-ft and 14-ft units on Interstates, other multilane highways, and two-lane roads and videotaping the positions of the vehicles in relation to the roadway and to oncoming and overtaking vehicles. In addition, standardized measures were made for a sample of individual images from the videotapes, and the resulting data were analyzed to determine differences in operations between 14-ft- and 16-ft-wide units as well as differences in the effects on other traffic. Measures examined included lane positioning of the mobile homes and surrounding traffic and shoulder encroachments by both the mobile homes and other traffic. Encroachments of oncoming or overtaking vehicles on the shoulder show significant differences between the two sizes of mobile homes. Where lane or shoulder widths are narrow, the oncoming or overtaking vehicles used the shoulder to get by or around the 16-ft units more often than when they encountered the 14-ft units. The results produced recommended pavement widths for the two sizes of mobile homes. For 14-ft units, the amount of paved surface required is 4.9 m (16 ft). For 16-ft-wide units, the required amount of paved surface is 5.2 m (17 ft).
Effect of an Afternoon Nap on Nighttime Performance in a Driving Simulator
Authors: Ranney Thomas A. , Simmons Lucinda A. , Boulos Ziad , Macchi M. Mila
Published: April 2007

Eight professional drivers completed two replications of a 2-day (43- to 47-h) protocol, each including 8 h of overnight driving following a truncated (5-h) sleep period on the previous night. One replication included a 3-h nap on the afternoon before the overnight driving. The overnight driving consisted of four 2-h runs separated by half-hour breaks. The driving task, conducted in a fixed-base heavy-truck simulator, included vehicle control on straight and curved roads, detection of pedestrians appearing alongside the roadway and of targets in the mirrors, and avoidance of obstacles and oncoming vehicles. The results indicated that extended overnight driving following a night of partial sleep restriction induced significant driving impairment. Specifically, crash frequencies increased over time, and the proportion of driving completed before the first crash decreased. Drivers detected fewer mirror targets and became slower in detecting pedestrian targets over time. The afternoon nap improved overall driving performance, as reflected by reductions in crash frequencies. On average, drivers completed 72 percent of each 2-h run without crashes in the nap condition, compared with 51 percent in the no-nap condition. Implications of napping as a fatigue countermeasure are discussed.
Regression Model for Resilient Modulus of Subgrade Soils
Authors: Mohammad Louay N. , Huang Baoshan , Puppala Anand J. , Allen Aaron
Published: April 2007

Subgrade soil is an important part in both flexible and rigid pavement structures. AASHTO recommends the use of bulk stress and deviatoric stress models to characterize granular and cohesive soils, respectively. However, these models oversimplify the fundamental behavior of subgrade soils. Being proposed is the use of an octahedral stress-state model to characterize the resilient modulus of different soils. Eight different soils representing major soil types in Louisiana were selected to validate the model and to calibrate the model parameters. Additional analysis was then performed to develop correlations between the model parameters and other soil properties. Three types of correlation were produced: ( a) model parameter with soil properties, ( b) model parameters with California bearing ratio, and ( c) model parameters with unconfined compressive strength. Statistical analysis indicated that the correlation between model parameter and soil properties yielded the best results.
Micromechanical Model for Temperature Effects of Hot-Mix Asphalt Concrete
Authors: Chang George K. , Meegoda Jay N.
Published: April 2007

The stress-strain behavior and internal structure of hot-mix asphalt (HMA) concrete due to the change in temperature was investigated. A micromechanical model, ASBAL, was used to simulate the stress-stain behavior and variation of the internal structure of HMA. The ASBAL program is a modification of a computer program based on the discrete element method. The Burgers’ element was added to ASBAL to describe the viscoelastic behavior of asphalt cement. The master curves of asphalt binder, which describe the stress-strain behavior of asphalt cement, from Strategic Highway Research Program research at different temperatures, were used. The Burgers’ element parameters of springs and dashpots were backcalculated at different temperatures from master curves. The resulting Burgers’ parameters and other properties of asphalt and aggregate were used to simulate the mechanical behavior of HMA. Behavior of HMA at four different temperatures subjected to constant-P (average stress) compression and triaxial compression tests were simulated. Both simulations showed effects of temperature on the stress-strain behavior, with higher strength and stiffness at low temperatures. Beyond 25°C, the specimen temperature did not seem to be a major contributor to the shear strength. At higher temperature during shear, there was a smaller number of dry and asphalt contacts.
Laboratory and Case Study for Geogrid-Reinforced Flexible Pavement Overlay
Authors: Chang Dave Ta-Teh , Ho Nuan-Hsuan , Chang Horng-Yi , Yeh Harn-Sheng
Published: April 2007

The formation and development of fatigue cracks in asphalt concrete beams have been extensively studied. Among these studies, however, very few have focused on the effects of geogrids in enhancing the resistance of asphalt concrete to fatigue failure. In addition, findings and conclusions of those studies cannot be effectively applied to most situations in Taiwan. It is therefore necessary to study the formation and development of fatigue cracks in overlaid dense-graded asphalt concrete. Among geogrids used in this laboratory study, two were made of glass fiber with strength of 100 kN/m and 200 kN/m, respectively, and one was made of high-density polyethylene (HDPE) with a strength of 25 kN/m. A series of tests for a beam reinforced with glass geogrids of 100-kN/m strength showed a fatigue life 3 to 5 times that of an unreinforced beam; and for a beam reinforced with 200-kN/m glass geogrids, the fatigue life was 5 to 9 times as long. Beams reinforced with the HDPE geogrids showed a fatigue life equivalent to those reinforced with 100-kN/m glass geogrids. Based on the findings of the laboratory study, an on-site performance study was carried out at a section of the Taiwan Second Freeway (already open for operation) from 80 km 837.5 m to 81 km 262. 5 m. A 10-month rutting-depth measurement was obtained, which confirmed that the improvement from these geogrids over the fatigue life of the pavement overlay so far was obvious and significant.
Steel Orthotropic Decks: Developments in the 1990s
Authors: Wolchuk Roman
Published: April 2007

Recent developments in the field of steel orthotropic decks, which made possible the design of several recently completed highway bridges with record-breaking spans, are summarized. The more efficient, but fatigue sensitive, decks with closed ribs were prevalently used. Extensive research on the fatigue of closed-rib orthotropic decks was conducted, and the results were used in new deck design provisions in the United States and in Europe. Empirical design of details subject to distortion-induced fatigue has been adopted in the AASHTO Specifications. Recent fatigue cracks and failures in the deck plates of closed-rib orthotropic decks in the Netherlands brought to light the stress concentrations in the deck plate at rib intersections with the floor beams that were not previously recognized in the design. This observation is discussed, and a solution is proposed for future designs. Orthotropic decks with open ribs are free from second-order, local stress concentrations, and their fatigue performance has been generally satisfactory. Such decks have been extensively used on railway bridges in Europe. Also, several long-span highway bridges with open-rib decks have been built recently. Because of their good performance record, a more frequent use of the decks with open ribs on future bridges may be indicated. Surfacing research has shown that deck cracking is directly related to a composite action with the orthotropic deck, which must have adequate rigidity for good surfacing performance. Elastic properties of surfacings need more research. The possibilities for further development are included in the discussion.
Cyclic Testing of Steel-Latticed Members for the San Francisco–Oakland Bay Bridge
Authors: Uang Chia-Ming , Kleiser Michael
Published: April 2007

To evaluate the cyclic behavior of a type of as-built steel-latticed member for the seismic retrofit of the San Francisco–Oakland Bay Bridge, cyclic testing of three half-scale specimens was conducted at the University of California-San Diego. For eccentrically loaded specimens, local buckling in the end panel caused significant degradation in compressive strength. Net-section fracture of flange angles near rivet holes in which laces were connected also was observed. Bifurcation-type global buckling was observed for the concentrically loaded specimen, causing a drastic drop in compressive strength. The buckling strength could be reliably predicted when the shearing effect and the appropriate effective length were considered. The ductility capacity of these specimens ranged from 2.0 to 2.4. All three specimens were able to reach and exceed the strength predicted by the load and resistance factor design (LRFD) interaction curve by about 6 percent, but this “overstrength” was slightly lower than that typically found in wide flange-beam columns. On the basis of the test results, a modified axial force-moment interaction relationship was proposed.
Large Studs for Composite Action in Steel Bridge Girders
Authors: Kakish Hussam F. , Splittgerber Darin L. , Baishya Mantu C. , Tadros Maher K.
Published: April 2007

Improved connection systems for composite action between steel girders and concrete decks to allow for rapid replacement of bridge decks are developed. The most common diameters of steel shear studs used in composite bridge construction are 19.1 mm (¾ in.) and 22.2 mm (7/8 in.), with a general height of 127 mm (5 in.). The strength of the proposed 31.8-mm (1¼-in.) studs is about twice that of the 22.2-mm(7/8-in.) studs. This increased strength would allow for fewer studs along the length of the steel girder, which would decrease the effort of deck removal from around these studs as well as decrease the probability of damage to these large studs and to the girder top flange. Research involves the feasibility of using studs with a diameter of 31.8 mm (1¼ in.) and a height of 127 mm (5 in.).
Verification of Girder-Distribution Factors for Short-Span Steel Girder Bridges by Field Testing
Authors: Nowak Andrzej S. , Eom Junsik , Sanli Ahmet , Till Roger
Published: April 2007

The procedure and results of field tests performed on five simplysupported, short-span steel girder bridges to verify girder-distribution factors (GDFs) are presented. Prior analytical studies have shown that, in most cases, currently used GDFs are too conservative. However, these studies also showed that, for short spans and short girder spacing, the GDFs can be too permissive. Therefore, this paper focuses on the experimental evaluation of girder-distribution factors for short-span steel girder bridges. The research work involved formulating the testing procedure, selecting the structures, installing the equipment, determining the measurements, and processing the results. Strains and deflections were measured and filtered to calculate GDFs. The results were compared with the distribution factors specified by the AASHTO Standard Specifications (1996) and the AASHTO LRFD Code (1998). The measured GDFs were found to be lower than the AASHTO values in all cases.