bluuebunny/crossref_metadata_2025 huggingface dataset:
Network Traffic Signal Optimization Formulation with Embedded Platoon Dispersion Simulation
Authors: Wey Wann-Ming , Jayakrishnan R.
Published: April 2007

The existing network traffic signal optimization formulations usually do not include traffic flow models, except for control schemes such as SCOOT that use simulation for heuristic optimization. Other conventional models normally use isolated intersection optimization with traffic arrival prediction using detector information, or optimization schemes based on green bandwidth. A complete formulation of the problem is presented, including explicit constraints to model the movement of traffic along the streets between the intersections in a time-expanded network, as well as constraints to capture the permitted movements from modern signal controllers. The platoon dispersion model used is the well-known Robertson’s model, which forms linear constraints. Thus, it is a rare example of a traffic simulation being analytically embedded in an optimization formulation. The formulation is an integer-linear program and does not assume fixed cycle lengths or phase sequences. It assumes full information on external inputs but can be incorporated in a sensor-based environment as well as in a feedback control framework. The formulation is an integer-linear program that may not be efficiently solved with standard simplex and branch and bound techniques. Network programming formulations to handle the linear platoon dispersion equations and the integer constraints at the intersections are discussed. A special-purpose network simplex algorithm for fast solutions is also mentioned.
Fatigue and Static Testing of Concrete Slabs
Authors: Roesler Jeffery R. , Barenberg Ernest J.
Published: April 2007

Fully supported concrete slabs (FSS) were constructed and tested under static and cyclic loading in the laboratory. Deflection, strain, and load data were acquired for each slab test. The results of the FSS fatigue tests were plotted as the stress ratio (bending stress in the slab divided by the concrete modulus of rupture) versus the number of cycles to failure. FSS had a resistance to fatigue 30 percent higher than simply supported beams (SSB). For the same number of cycles to failure, concrete slabs could sustain a stress level 30 percent higher relative to beams. The concrete modulus of rupture from an SSB was found not representative of the true strength of an FSS. FSS tests under static load had a flexural strength 30 percent higher than the concrete modulus of rupture from a SSB test configuration. When the actual slab strength under static loading was accounted for in the stress ratio, the fatigue curves for concrete beams and slabs were essentially identical. Strain gauges indicated that plastic deformation in the slab occurred almost immediately with cyclic loading. Strain gauges also showed that partially cracked slabs resisted the load through cantilever action. Deflection measurements showed that crack initiation and propagation occurred in the slab before fatigue failure. Crack propagation through the slab thickness was found to consume most of the slab’s fatigue life.
Mechanistic Reappraisal of the Current Design Methodology for Rigid Airfield Pavements
Authors: Lee Ying-Haur
Published: April 2007

The current design methodology for rigid airfield pavements, based on the plate theory approach, was reevaluated in an attempt to accommodate the new Boeing B-777 airplanes. The differences between the conventional FAA design method and the newly developed Layered Elastic Design–FAA design methodology are investigated. The original concept of pass-to-coverage ratio is reevaluated. The prediction models developed are used for the estimation of critical edge stresses for design. The problems and difficulties of the conventional method, especially in the conversion of different aircraft types, are identified. The concept of cumulative damage factor should be used to account for the combined damages of different aircraft types and departures. Structural deterioration relationships are compared and tentative modification alternatives are explored. Consequently, the concept of an equivalent stress factor is introduced and an alternative structural deterioration model is proposed for trial design applications. Further investigations and verifications should be conducted as well.
Rehabilitation Performance Prediction Models for Concrete Pavements
Authors: De Solminihac Hernán , Salsilli Ricardo , Covarrubias Juan Pablo , Vidal Mariana
Published: April 2007

Successful implementation of a pavement management system requires the necessary simulation tools, among which deterioration prediction models form an important part. These models can be either aggregate or incremental. Aggregate models calculate total accumulated deterioration and require knowledge of the past history of the pavement to predict future behavior. Incremental models, however, require only knowledge of the current pavement conditions. For this reason, incremental models generally are more advantageous when historical pavement condition data are not available. One of the most well-known and widely used methods for pavement evaluation is the World Bank program Highway Design and Maintenance Standards Model (HDM), whose latest version, HDM 4, attempts to accommodate the analysis of both asphalt and concrete pavements. In the case of concrete pavements, the models used are of the aggregate type. Incremental prediction models are used for asphalt pavements. As part of research into the application of incremental models for the prediction of distresses in concrete pavements, rehabilitation performance prediction models in incremental form have been developed and are presented. Rehabilitation performance refers to pavements that already have received repair or rehabilitation to enhance their structural or functional capabilities. The rehabilitation models presented here have been developed by using mathematical combinations of models for new concrete pavements, derived as function of time. The results of validation analyses of the models are presented, along with a discussion of the advantages and disadvantages of the proposed models with respect to existing methods.
Full-Depth Reclamation Process
Authors: Kearney Edward J. , Huffman John E.
Published: April 2007

Many roads and streets fail structurally after having performed well for several years. The standby treatment of a hot-mix overlay does not address the real problem with most of these roads—inadequate roadbase strength. Public agencies throughout the United States are making fulldepth reclamation (FDR) one of the most popular pavement rehabilitation methods. The FDR process allows complete reconstruction using 100 percent of the existing pavement materials, while correcting grade, cross slope, and underlying pavement problems. In FDR a new base is produced by pulverizing the existing asphalt pavement and mixing it with some of the underlying granular materials. Additional structural strength can be achieved by incorporating new crushed aggregates, asphalt emulsion, foamed asphalt, and chemical stabilizers. Laboratory testing of the reclaimed asphalt pavement (RAP), the subgrade soils, and a mixture of the two will determine whether an additive is needed. The RAP testing should include an extraction for asphalt content and an aggregate sieve analysis. For soils, the minimum testing would include a sieve analysis, sand equivalent, liquid limit, plastic limit, and plasticity index. Guidelines for selecting stabilizers on the basis of these test results are included. Additional strength tests on the stabilized materials can be used in structural design of the pavement. A thorough project evaluation is essential to ensure success. This includes a pavement condition survey, a traffic study, and structural design, in addition to the testing. Proper construction procedures and quality control plus an experienced contractor are necessary.
Churchmans Crossing Infrastructure Investment Project: A Comprehensive Approach to Transportation and Land Use Solutions
Authors: Athey Lorene J. , Abbott Eugene E. , Hellmann William K.
Published: April 2007

Details are provided about a process that successfully achieved multimodal transportation solutions through integrated land use and transportation planning in New Castle County, Delaware. The process included identification and participation of stakeholders; active involvement of the land use agency; development of a vision for the study area; and identification of problems and options, analyses, and recommendations. The effort was guided by three working groups: a policy committee of top agency officials, a steering committee of community and business leaders along with local elected officials, and a technical committee of agency professional staff and a consultant team. Four types of solutions were recommended as a package: land use, transit, travel demand management, and roadway connections/intersections. The resulting multimodal solutions are interdependent, provide options to single-occupant vehicles, and maximize the potential use of nonhighway alternatives before roadway and intersection improvements are made. The final package of solutions had a high degree of public and agency buy-in; as a result, implementation is well under way.
People’s Opinions and Road Policies: Effects of Public Involvement Activities by the Road Council in Japan
Authors: Ishida Haruo , Matsuda Waka , Montalbo Cresencio
Published: April 2007

The Road Council is the adviser to the Japanese Ministry of Construction (MOC) on matters of road policy at the national level. To be more responsive to society’s needs, the council implemented public involvement (PI) activities to solicit people’s opinions about the New 5-Year Road Improvement and Management Program. The council issued a series of reports that provided information to the people and solicited their opinions before it made its final recommendations to MOC. The focus was on the effects that people’s opinions have on the road policies contained in the reports. The relationship between road policies set by the Road Council and MOC and people’s opinions was analyzed. A document-analysis methodology for extracting key words representing policy measures and identifying policy fields was developed. The study assumed that the number of key words indicates the degree of emphasis in the report. Frequency of opinions for each policy field also was determined. Relationships between the number of key words and the frequency of opinions were analyzed using Kendall’s correlation coefficient. Causal relations within each policy field were analyzed. The results clearly established the influence of people’s opinions on the resulting road policies. The findings also showed two kinds of changes in the documents: ( a) changes initiated by people’s opinions and ( b) changes initiated by the Road Council. So far, PI activities have been applied only at the national planning level. These activities also can be applied to other levels and aspects of planning.
In the Possibilities Are the Solutions: Assessment and Implications of the Public-Involvement Process During the Environmental Impact Study of the Woodrow Wilson Bridge
Authors: Keever David , Frankoski Geraldine , Lynott Jana
Published: April 2007

The Woodrow Wilson Bridge is an essential part of the Washington, D.C., and Interstate transportation systems. The bridge provides the only Potomac River crossing for the southern half of the greater Washington region. Because of substantial local and regional growth, travel demand across the drawbridge has grown to more than twice the design capacity of the structure. To address these mobility challenges, FHWA initiated the Woodrow Wilson Bridge Improvement Study in 1988 as a cooperative effort among affected jurisdictions, agencies, and the public. Given the complexities of the project and time-critical nature to reach a decision on a preferred alternative, public involvement was a key feature of the environmental study process. The essential elements of the publicparticipation and outreach process are highlighted. An assessment of the outreach process was conducted once the environmental study was completed. A randomized, statistically based telephone survey was conducted to measure the effectiveness of the public-involvement program, to guide public-involvement programs for the next phase of this project and for future projects, and to help gauge attitudes toward public involvement of those with a vested interest in the project. Results of the survey and implications for the design of public-participation programs are presented.
Evaluation of Truck Crashes Using a GIS-Based Crash Referencing and Analysis System
Authors: Harkey David L.
Published: April 2007

Computerized crash analysis systems in which crash data, roadway inventory data, and traffic operations data can be merged are used in many states and municipalities to identify problem locations and assess the effectiveness of implemented countermeasures. By integrating this traditional system with a geographic information system (GIS), which offers spatial referencing capabilities and graphical displays, a more effective crash analysis program can be realized. In a recent FHWA-sponsored study, a crash referencing and analysis system within a GIS was developed within the Highway Safety Information System (HSIS) of the state of North Carolina for the area of Wake County. The system provides the functions needed to edit both tabular and spatial crash and roadway data as well as to perform crash analyses related to intersections, roadway segments, and special highway features, such as bridges. The second phase of the project was undertaken to illustrate the advantages of a GIS-based crash analysis system. The problem selected was identifying and analyzing locations of high numbers of truck-crashes, both along designated truck corridors and on other roadways within the county. The goal of the study was to determine if there are benefits to using a GIS-based crash referencing system over the traditional databases that contain crash, roadway feature, and operations data files and can be linked by location. Specific objectives for the truck-corridor analysis project included ( a) identifying locations of high numbers of truck crashes using the GIS-based system, and ( b) exploring the applicability of nontraditional databases to this type of analysis.
Estimating Truck-Rollover Crashes on Ramps by Using a Multistate Database
Authors: Wang Jun , Council Forrest M.
Published: April 2007

Currently, among other intelligent transportation system applications, there is an increased interest in using an “in-vehicle warning system” to mitigate truck-rollover crashes on interchange ramps. Because the cost of installing the system in an entire truck fleet would be significant, a basic question is how large a safety problem is addressed. This study was an attempt to estimate the annual national frequency and cost of large-truck accidents on interchange ramps that result in rollovers. Using tabular analysis of a five-state database, the estimate was that approximately 11 percent of total truck involvements are on interchange ramps and that between 44 and 52 percent of the incidents result in rollovers. Both urban and rural locations present significant problems that could be addressed by an in-vehicle warning system. Combining this information with General Estimates System figures for total national truck crashes, it is estimated that there are between 4,400 and 5,000 truck rollovers on ramps each year nationwide. The annual economic cost of these rollovers is between $405 million and $460 million. These data provide both information to safety engineers on the size of a significant truck safety problem and a base for a meaningful cost-benefit analysis of installing the in-vehicle warning system. Although available data do not allow a detailed cost-benefit analysis, a simplified analysis of “breakeven costs” indicates that such a device is highly dependent on the level of effectiveness, ranging from approximately $300 per truck to $3,200 per truck.
Effects of Cargo Loading and Unloading on Truck Driver Alertness
Authors: O’Neill Timothy R. , Krueger Gerald P. , Van Hemel Susan B. , McGowan Adam L. , Rogers William C.
Published: April 2007

The relationship between physical and mental fatigue is not well understood or well documented, a lapse that affects understanding of the interaction between loading and unloading activities and safe operation in the trucking industry. This experiment addresses the effects of loading and unloading on driving performance by measuring driving impairment in volunteer truck drivers operating a truck-driving simulator. Ten drivers participated, each for 17 days, including 2 driving weeks of 5 days with 14-h duty cycles separated by two 58-h rest periods. During one of the driving weeks, participants were given a significant hand-loading task, 3 hours of hand-loading pallets of boxes on 3 of 5 days; during the remaining week, only driving tasks were scheduled. Performance measurement focused on driver responses to planned and unplanned crash-likely challenges and vigilance tasks, supported by simulator-mediated driving indicators, such as lane-keeping performance. Measures of subjective drowsiness also were maintained. The effects of the loading and unloading task were mixed. There was an initial improvement in alertness, apparently because of the break in activity and a period of exercise; however, this effect wore off as the day progressed and may have contributed to a decrease in overall performance after 12 to 14 h of duty.
Resilient Modulus of Soft Soil Beneath High-Speed Rail Lines
Authors: Heelis Mchael , Dawson Andrew , Collop Andrew , Chapman David , Krylov Victor
Published: April 2007

Modern high-speed rail lines are being built increasingly on marginal land, to reach city centers while avoiding housing areas. Often this land is composed of soft alluvial soils, which exhibit a low resilient modulus. The measurement, prediction, modeling, and implications of resilient modulus values for such subgrades are discussed. Measurement considers the use of repeated-load triaxial testing, resonant column, and in situ methods, illustrating these with sample data. Prediction draws on both analytical and finite-element techniques to illustrate the critical speed (the bow-wave effect) and how it is influenced by resilient modulus. Modeling reveals the available relationships—and their limitations—for deriving subgrade stiffness in this dynamic situation. Implication then uses these to define the relevant effects of resilient modulus values on design problems.
Noninvasive Measurement of Permanent Strain Field Resulting from Rutting in Asphalt Concrete
Authors: Wang L. B. , Frost J. D. , Lai J. S.
Published: April 2007

Asphalt concrete is a bonded granular material composed of aggregates and asphalt binder. The chemical, physical, and mechanical properties of these constituents are different. Under typical repeated tire loads, the aggregates do not deform but instead rigidly translate and rotate within the binder. Rutting is the surface manifestation of the internal-structure evolution in asphalt concrete under repeated wheel loading. A procedure to quantify the permanent strain field of asphalt concrete underlying the rutted zone produced by an accelerated wheel testing device is described. This new, noninvasive procedure has been automatically implemented in a computer program named MATCH, which was developed to compare the locations of particles before and after testing and therefore to permit the displacement of individual particles to be tracked. Pattern recognition based on each particle’s cross-sectional area, perimeter, and aspect ratio was used to match the particles. Application of the new procedure to measure the permanent strain field of an asphalt concrete specimen in a Georgia loaded wheel tester is described. The reliability of the procedure for automatically matching the particles in successive images was confirmed by manual procedures. It was found that the permanent strain and the mastic/solid area ratio evolution measured in this application demonstrated strong localism. Dilatancy and contraction were quite significant locally but insignificant globally. The strains in the mastic were much larger than the global or macrostrain. The proposed procedure has significance in the future study of micro-macro properties of bonded granular materials and how factors such as aggregate size, shape, and distribution affect the global response.
Evaluation of Geosynthetics Used as Separators
Authors: Loulizi Amara , Al-Qadi Imad L. , Bhutta Salman A. , Flintsch Gerardo W.
Published: April 2007

Geosynthetics have been used in pavement systems for several purposes, including reinforcement, layer separation, drainage, and moisture barriers. For the layer-separation application, the geosynthetic material is used to prevent soil fines from migrating into the base-course layer as well as stones from this layer from penetrating into the subgrade. This material migration would affect the drainage capability as well as the structural capacity of the pavement. However, such an effect is very hard to detect since soil pumping will occur under the pavement surface, and therefore a comparison of the performance of different types of geosynthetic separators is almost impossible. A 3-year project to study the in situ behavior of geosynthetically stabilized flexible pavements in Bedford County, Virginia, ended recently. Results from ground-penetrating radar surveys and materials excavation are presented. Ground-penetrating radar surveys, falling-weight deflectometer results, rutting measurements, and ground-truth excavation indicated that the separation provided by geotextiles was important in reducing base-course contamination by subgrade soil. Such a reduction will significantly reduce the resilient modulus of the base-course layer. In addition, service-life predictions of evaluated sections were conducted based on the traffic applied and rutting distress. Geosynthetics improved secondary-road pavement performance; geotextiles increased service life more than geogrids, due to their separation function.
Simplified Method for Shear Design of Prestressed Concrete Girders
Authors: Myint Lwin M. , Khaleghi Bijan
Published: April 2007

The new AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications incorporate the modified compression field theory for shear design of prestressed and non-prestressed concrete members. This method is based on the variable-angle truss analogy model and takes into account the inclination of diagonal shear cracks, the strain in longitudinal steel, and the applied shear stress on a section. This is a realistic approach to predict the shear resistance of any section of a concrete member. However, for prestressed concrete sections, an iterative process is required in conjunction with charts and tables to determine the shear resistance of the sections. The process is cumbersome and time consuming. In an effort to simplify the process, Washington State Department of Transportation has completed a parametric study that results in a simplified method of using fixed shear design parameters. The simplified method saves significant time in shear design of prestressed girders, especially when it is used to standardize the shear reinforcement in a series of standard prestressed concrete girders.
Transverse Cracking in Concrete Bridge Decks
Authors: French Catherine , Eppers Laurice , Le Quoc , Hajjar Jerome F.
Published: April 2007

The dominant parameters that lead to premature transverse cracking in bridge decks are determined, and recommendations to reduce cracking tendency in bridge decks are developed. The project is divided into two parts: a field study and a parametric study. The objective of the field study is to determine the correlation between the observed cracking and available design-, material-, and construction-related data. Seventy-two bridges in the Minneapolis/St. Paul metropolitan area are included in the field study. According to the results of the study and correlation with other research, restrained concrete deck shrinkage is the leading cause of cracking. The dominant factors affecting transverse cracking are the longitudinal end restraint, girder stiffness, cross-frame location, splice location, deck thickness, cutoff length of the deck supplemental reinforcing bar, size of the top transverse bar, concrete shrinkage, deck concrete modulus of elasticity, cement content, aggregate type and quantity, air content, and ambient air temperature at deck placement. Recommended practical improvements to bridge deck construction include reducing the shrinkage of the deck concrete through mix design or better curing practices and minimizing deck restraint.
Comparison of Experimental and Analytical Load-Rating Methodologies for a Pony-Truss Bridge
Authors: Schenck Timothy S. , Laman Jeffrey A. , Boothby Thomas E.
Published: April 2007

Vehicle and environmental loading, combined with the effects of deicing salts and inadequate maintenance, have resulted in a large number of structurally deficient bridges in the United States. Because of the limited resources of county and district bridge owners, aging structures must be evaluated and rated to facilitate suitable bridge repair, replacement, and posting strategies. A 1937 riveted pony-truss bridge in Pennsylvania was studied to evaluate the effect of increasingly refining rating parameter inputs to the analysis of the bridge. The study considered results from experimental field testing of the bridge, a detailed sectionloss inspection, and a refined analytical modeling using STAAD III, a commercially available software package, to increase the accuracy of the rating analysis. The research team evaluated the relative effect of using ( a) allowable stress versus load-factor design methodologies; ( b) experimentally derived versus code-specified impact and distribution factors; ( c) experimental stress measurements versus manual- and computer-stress calculations; and ( d) member fixity and composite action for both inventory and operating rating with an AASHTO HS20-44 and ML-80 rating vehicle. Results for selected truss members, floor beams, and stringers are presented. The investigators found that the rating increased with increasingly refined parameter input, with the rating factor increasing as much as 60 percent over a standard manual rating analysis when an experimentally based rating analysis was used. The best agreement with experimental results was obtained by using reduced deck stiffness to model deck deterioration, fully composite action between stringers and the deck, pinned stringer-floor beam connections, and fixed floor beam-to-truss connections. The study procedures can be applied to other similar bridge structures.
Issues in Superload Crossing of Three Steel Stringer Bridges in Toledo, Ohio
Authors: Turer Ahmet , Emin Aktan A.
Published: April 2007

A 371-ton (816.7-kip) cooling unit crossed over three steel stringer bridges in Toledo, Ohio. Any bridge damage was compensated if scientifically documented. Researchers predicted the superload responses by using finite element analysis and experimental test results, and then measured the superload responses to establish whether the event caused any damage. Although the conservative results of the finite element model predicted an overbound of critical stresses, experimental results gave closer predictions of the measured response under superload. During the superload crossing, the maximum stress levels at the girders remained at about 34.5 MPa (5 ksi). The cross braces were stressed up to 68.9 MPa (10 ksi), exceeding the girder stresses. The study included questions about the real behavior versus design assumptions regarding cross braces in steel stringer bridges. (Cross braces are the weak links that fail first, causing lateral instability and failure.) Research revealed the possibility of predicting superload responses and behavior quite reliably by using a combination of diagnostic tests and finite element analysis. These tools permit the best design for superload axle configuration, crossing paths and positions on bridges, and possible options for effective bridge strengthening when needed.
Jointless Bridges and Bridge Deck Joints in Washington State
Authors: Van Lund John A. , Brecto Barry B.
Published: April 2007

Highlights of a 1997 Quality Improvement Review (QIR) of jointless bridges and bridge deck joints in Washington State are summarized. The purpose of the QIR is to determine, assess, and disseminate the current state of the practice and to share this information with the other FHWA Region 10 states and other FHWA regions. The inspection team included personnel from FHWA, the Oregon Department of Transportation, and the Washington State Department of Transportation (WSDOT). Interviews were conducted with design, construction, inspection, and maintenance personnel. During the QIR, 18 WSDOT bridges were inspected in the field to gauge the performance of jointless bridges and bridge deck joints. Background information on jointless bridges is given, and current practices involving bridge deck joints are presented. The use of jointless bridges eliminates the need for expansion joints and joint maintenance. The QIR found that WSDOT’s semi-integral jointless bridges, with overall lengths of 122 m and skews less than 30 degrees, performed well. Approach slabs are recommended for jointless bridges to minimize the effects of approach settlement. Quality improvement recommendations are presented in the review. WSDOT has developed a new saw-cutting procedure for compression seals, as well as a specification for a second-generation, fatigue-based, modular bridge-expansion joint to improve long-term durability.
Seismic Retrofit of the North Approach Viaduct of the Golden Gate Bridge
Authors: Imbsen Roy A. , Schamber Robert A.
Published: April 2007

The north viaduct seismic retrofit construction project is the first of several projects to upgrade the Golden Gate Bridge crossing. The upgrade design strategy for this portion of the crossing includes changing the five-span simply-supported truss bridge to a partially continuous bridge, replacing the substructure towers and foundations, constructing new expansion joints at the ends of the bridge, and installing new isolation bearings. Construction is being carried out under traffic and will include erecting temporary supports during the building of the new substructure. The construction techniques anticipated for use in transforming a bridge designed with yesterday’s engineering to one that reflects today’s technology are described. The north approach viaduct of the Golden Gate Bridge extends from the north end of the north anchorage housing to the north abutment. In 1982, the viaduct was retrofitted to the California Department of Transportation’s seismic retrofit guidelines. In 1996, a subsequent retrofit design was completed to upgrade the viaduct so it could remain open after a major earthquake. Using the results of a nonlinear earthquake analysis of the structure, seismic deficiencies were identified in the superstructure, bearings, towers, foundations, and abutments. The overall strategy used on the north viaduct includes changing the simple spans of the steel truss superstructure to a system that is continuous in the lateral direction by making the bottom chord continuous. This strategy ties the overall system together and distributes the seismic forces to all the towers. In addition, the overall system is tuned by replacing steel bearings with isolation bearings.
Micro DAS: In-Vehicle Portable Data Acquisition System
Authors: Barickman Frank S. , Goodman Michael J.
Published: April 2007

The evolution of the National Highway Traffic Safety Administration’s Data Acquisition System (DAS) for Crash Avoidance Research into a relatively inexpensive portable system (Micro DAS) that can be implemented in virtually any vehicle has opened up a wide range of research possibilities never before possible. Micro DAS is very small and can be installed directly into a test participant’s own vehicle in a short time period. Its video recording system is capable of collecting over 22 h of full-motion video. Data collection can be triggered manually or based on events defined by the researcher. Micro DAS is also designed to collect antecedent data, allowing the information leading up to an event to be studied. These features allow the system to collect real-world information on driver behavior, driver and vehicle performance, and roadway environments in situ without concerns associated with vehicle familiarity or researcher presence. The Micro DAS philosophy, architecture, sensor array, and versatility are discussed in detail.
Dynamic Behavioral Data Collection Using an Instrumented Vehicle
Authors: Brackstone M. , McDonald M. , Sultan B.
Published: April 2007

A significant problem that has become increasingly apparent in the development of models of driver behavior over the last few years is the absence of reliable data with which simulated processes, such as car following, may be compared. Obtaining such data, and the associated increase in model validity that this would allow, is clearly becoming of greater importance since a reliable baseline is required against which improvements in traffic flow and safety produced by many advanced transport telematics systems can be judged. One source of such data is an instrumented vehicle; a vehicle equipped with relative distance- and speed-measuring sensors that may be deployed in the traffic stream to collect data that are realistic, accurate, and dynamic. The opportunities for data collection afforded by instrumented vehicles are examined, in particular, the construction and testing of a new facility fitted with an optical speedometer, a radar rangefinder (capable of measuring the distance to, and relative speed of, the next vehicle in the traffic stream), and forward- and rear-looking video camera. Examples are given of the use of the vehicle in several current research projects, the operational strategies for which will be presented and discussed along with output. These include experiments on close-following, lane-changing, and the perception of relative speed. In conclusion, future areas of research and development are examined.
Driver Understanding of Abbreviations on Changeable Message Signs in New Jersey
Authors: Hustad Marc W. , Dudek Conrad L.
Published: April 2007

The objectives of this research were to evaluate abbreviations currently used on changeable message signs (CMSs) in New Jersey and develop new abbreviations specific to the needs of New Jersey transportation agencies. A special emphasis was on developing abbreviated phrases that could be displayed on portable CMSs that have only eight characters per line. Human factors laboratory studies were conducted in both New Jersey and Texas in which a list of abbreviations was given to drivers, who were asked to write down the meanings. The results revealed that a group of 18 abbreviations was quite well understood by New Jersey drivers and met the acceptability criterion of 85 percent of the drivers surveyed. Other abbreviations were understood by 75 to 84 percent of New Jersey drivers, and it will require an extensive educational effort before they can be used on CMSs. Some of the abbreviations were considered unacceptable. There were regional differences with respect to driver understanding of some of the abbreviations. Proper noun abbreviations were found that were understood by 85 percent or more of the drivers tested in New Jersey. As expected, there were regional differences in New Jersey. Generally, the proper noun abbreviations were understood better by drivers who live in the part of the state where the facility or structure is located whose name was abbreviated.
Crashworthiness of Roadside Features Across Vehicle Platforms
Authors: Bligh Roger P. , Mak King K.
Published: April 2007

Each year more than 14,000 persons are killed and 1 million persons are injured as a result of roadside crashes. Recent estimates of the annual societal costs associated with these roadside crashes amounted to $80 billion. Clearly, there is a need for further understanding of the roadside safety problem. The impact performances of roadside safety features are typically evaluated through full-scale crash testing with two vehicles selected from the extremes of the passenger vehicle fleet in terms of weight and size. The implicit assumption is that if a roadside safety feature successfully passes the test requirements for vehicles at the extremes for the fleet, the feature will perform satisfactorily for all other vehicles in between. Many vehicle parameters could influence performance during impacts, and this assumption may or may not be valid. The safety performances of roadside features for various passenger car platforms and light-truck subclasses were evaluated. The study approach consists of evaluations of the frequency and severity of roadside crashes for these generic platforms and subclasses by using recent crash data from the Fatal Accident Reporting System, the General Estimates System, and the Highway Safety Information System.
Choosing an Inventory Data Collection System
Authors: Hummer Joseph E. , Scheffler Craig R. , Khattak Aemal J. , Karimi Hassan A.
Published: April 2007

As part of NCHRP Project 15-15, Collection and Presentation of Roadway Inventory Data, the authors conducted a nationwide survey of the state departments of transportation (DOTs), visited several DOTs and vendors, and reviewed the literature regarding roadway inventory data collection. On the basis of that work, a process to help state DOTs match inventory needs to data collection technologies is presented. The process that is described may help state DOTs narrow their focuses to the most relevant inventory data collection technologies. The authors present a four-step process that can be used to select inventory data collection technologies. First, the authors help agencies view their inventory data collection in context. The authors show how successful inventory data collection in the past has focused on the provision of timely information that is used to solve problems. Second, inventory units must select the proper mode of transport for the data collection technologies. Units should consider vans, the popular choice, versus satellites at one extreme and backpacks at the other extreme. Next, inventory units need to select the georeferencing technology. The relative merits of global positioning systems, inertial navigation systems, distance-measuring instruments, and range finders are discussed. Finally, inventory units must select sensors to provide descriptive information. For each common inventory element, the authors estimate the accuracy of collection with six common technologies and other special techniques. The authors also describe the initial costs and labor needed for the different collection technologies.
Surveyor: Mobile Highway Inventory and Measurement System
Authors: Maerz Norbert H. , McKenna Steve
Published: April 2007

Surveyor is a mobile highway data collection system designed to collect measurement data about objects, features, structures, and landmarks located along highways and roadways for highway planning, management, and maintenance. It creates classified inventories annotated with object dimensions, object position relative to the road, and global position reference. The mobile data collection part of the system consists of a high-speed multifunction vehicle with minimum complement of a right-of-way video system with a precisely calibrated high-resolution video camera, a distance-measuring instrument for spatial positioning, a gyroscopic geometries system, and an ultrasonic grade system for precise measurement of vehicle attitude. Data acquisition is facilitated by multiple on-board computers, and the right-of-way video uses a time code for synchronization to the geometric and position databases. The interactive (postprocessing) part of the system uses a workstation to retrieve and buffer the video for the user to identify targets by using point and click with a mouse, to classify them, and to request position or size measurements. The software can make measurements on multiple images by using triangulation or on single images by using the idealized plane of the highway as a reference.
Factors Related to Probability of Joint Flooding on Paired Streams in Ohio
Authors: Koltun G.F. , Sherwood J.M.
Published: April 2007

Factors related to the probability of joint flooding on paired streams were investigated. Stream pairs were considered to have flooded jointly at the design-year flood threshold (corresponding to the 2-, 10-, 25-, or 50-year instantaneous peak stream flow) if peak stream flows at both streams in the pair were observed or predicted to have equaled or exceeded the threshold on a given calendar day. Daily mean stream-flow data were used as a surrogate for instantaneous peak stream-flow data to determine which flood thresholds were equaled or exceeded on any given day. Instantaneous peak stream-flow data, when available, were used preferentially to assess when the flood threshold was exceeded. Observed probabilities of joint flooding were computed as the ratios of the number of days when stream flows at both streams concurrently equaled or exceeded their flood thresholds (events) to the number of days when stream flows at either stream equaled or exceeded its flood threshold (trials). Logistic regression equations for estimating the probability of joint flooding at the 2-year flood threshold were developed on the basis of event-trial ratio and basin characteristic data. Distance between drainage area centroids, the ratio of the smaller drainage area to the larger drainage area, mean drainage area, and the centroid angle adjusted 30 degrees were the characteristics most closely associated with the probability of joint flooding on paired streams in Ohio. In general, the probability of joint flooding decreased with an increase in centroid distance and increased with increases in drainage area ratio, mean drainage area, and centroid angle adjusted 30 degrees.
Hydrodynamic Countermeasures for Local Pier Scour
Authors: Richardson Jerry R. , York Kevin
Published: April 2007

The results of laboratory studies investigating the energy dissipation caused by the placement of roughness elements to impede the downward thrust of water near pier faces are summarized. The purpose of the investigation was to evaluate the effectiveness of the method as a viable countermeasure for local pier scour. The results indicate that the roughness element size and spacing had various effects on the energy dissipated from the downward thrust of water and, therefore, the potential to reduce local pier scour. On the basis of the results that are presented, it should be feasible to develop countermeasures that can be retrofitted to existing piers, which will measurably reduce local pier scour. However, additional laboratory and prototype scale testing will be required.
Simplified Track Evaluation for Low-Speed, Low-Traffic Railroad Lines
Authors: Plotkin Donald , Sandhaas Larry
Published: April 2007

The development of a railroad track–evaluation computer program called TRACK is described, and its application is summarized. TRACK was created to provide a simple tool to help determine the need for track rehabilitation. The program assesses the track’s vertical load–carrying capability and shows some relative effects of track improvements or deterioration. The evaluation is based on five equations that provide values for rail bending stress, tie bending stress, tie reaction, ballast surface stress, and subgrade surface stress. This information is important for initial design, rehabilitation planning, and basic track evaluation, but has not always been readily available in an easy-to-use format. Although the evaluation method in TRACK is simplified, it illustrates the complex interaction among the main track components—namely, that a change in one component affects the others. TRACK automatically selects values for equation variables from information about track characteristics and types of cars handled; the program then solves the equation. Calculated stresses are displayed beside suggested limiting values for the track. The basic approach is that if none of the four main track components (i.e., rail, ties, ballast, and subgrade) are overstressed, the track structure is considered suitable for the given traffic loading. TRACK is intended for low-speed, low-traffic railroad lines—those with conventional wood-tie track, with either jointed or welded rail, on which traffic is less than approximately 5 to 8 million gross tons per year, with maximum speeds of 25 to 30 mph.
Shear Strength of Douglas Fir Timber Bridge Ties
Authors: Madsen Borg , Sweeney Robert A.P.
Published: April 2007

Tests on 480 240- × 290-mm (nominal 10- × 12-in.) bridge ties, both old and new, indicate that the characteristic strengths for shear given in most North American codes of practice seem to be unduly conservative. As a result of this test program, it is suggested that design requirements for shear in timber codes of practice be revised to reflect more correctly the structural behavior of the material, using concepts such as the weakest link principle and fracture mechanics considerations. The test program also clearly demonstrates that in many cases the allowable shear capacity can be doubled by using an overhang equal to the beam depth. The research indicates a savings on paper of over Can$200 million for the Canadian National Railway Company if the recommendations presented in this research are followed instead of those in the current Canadian Standards Association design code (086.1, 1994), the American Railway Engineering and Maintenance of Way Association’s manual of recommended practice, or other typical North American codes of practice.
Advance Warning Flashers: Do They Improve Safety?
Authors: Sayed Tarek , Vahidi Homayoun , Rodriguez Felipe
Published: April 2007

The main findings of a study to evaluate the safety of advance warning flashers (AWFs) are presented. A portion of the traffic accidents that occur at signalized intersections relate to poor driver decisions during the change interval time. Providing drivers with advance information about the status of a downstream traffic signal can help the driver make safer decisions. An AWF is a traffic warning device that can be used to provide such information to drivers. The study methodology is based on comparing the expected accident frequency at intersections with and without AWFs through the development of accident prediction models. The study used sample traffic volume, accident, and AWF data pertaining to 106 signalized intersections operated by the British Columbia Ministry of Transportation and Highways. The results from this study indicate that intersections equipped with AWFs have a lower frequency of accidents than similar locations without AWFs. However, the results indicate that this observed reduction in accident frequency, as correlated with AWF-equipped intersections, is not statistically significant at the 95 percent confidence level. Furthermore, a correlation has been found between the magnitude of the minor approach traffic volumes and the accident reduction capacity of AWFs. In this regard, it is observed that AWF benefits exist only for moderate to high minor approach traffic volumes.
Driver’s Speed Reduction Behavior at Highway–Rail Intersections
Authors: Moon Young J. , Coleman Fred
Published: April 2007

Speed data as a component of driver behavior were measured at two sites where four-quadrant gates are under consideration. Previous research work assumed a constant speed approach for vehicles approaching and crossing a highway–rail intersection with four-quadrant gates. Video data collection techniques were used to statistically test whether vehicle speeds were constant or reduced on approach. The findings were that drivers do reduce their speed on approach to highway–rail intersections, which requires adjusting four-quadrant-gate timing to avoid vehicle entrapment.