bluuebunny/crossref_metadata_2025 huggingface dataset:
Construction Issues in Steel Curved-Girder Bridges
Authors: Grubb Michael A. , Yadlosky John M. , Duwadi Sheila Rimal
Published: August 2018

The construction of horizontally curved steel bridges is generally more complex than the construction of comparable straight-girder bridges of similar span. Curved-girder bridges, once completed, have generally performed as intended. Most problems that have occurred with curved-girder bridges have been related to fabrication and assembly procedures or unanticipated and unaccounted for deformations that occur during construction. As a result, these construction issues take on primary importance in the successful completion of the structure. Successful completion requires that each phase of construction proceeds as anticipated to ensure that the final structure is at the correct elevation to provide proper deck drainage and good riding quality. In some cases, construction issues for curved bridges have been given little or no special consideration by designers, or, at the very least, no more consideration than has been given to these issues for straight bridges. Thus, there is a need to better identify these issues, assemble and provide more in depth information on each of these issues to the design community, and emphasize their importance to designers. The significance of construction issues to complex horizontally curved steel bridges is in many ways analogous to their prominence in the design of segmental concrete bridges; construction issues often drive the design decisions. The objective is to promote awareness in the design of horizontally curved steel bridges to some of these construction issues.
Use of Fatigue Fuses for Prediction of Fatigue Life of Steel Bridges
Authors: McEwen Everett , Tsiatas George
Published: August 2018

The fatigue fuse is a device for predicting the fatigue life of steel highway bridge members when the bridge is subject to variable loads. The fuse is calibrated so that the cracking of each of its four legs can be related to damage in the structure. In a preliminary laboratory study, fatigue fuses are attached to eight steel girders, selected to represent three types of structural details found in existing highway bridges. The fuses are cemented to the girders and the girders subjected to a constant-amplitude fatigue loading. Cracking of the fatigue fuses is monitored by checking electrical continuity across each fuse leg. Tests are continued until girder failure or until all fuse legs are broken and the mean fatigue life of the girder as predicted by AASHTO is reached. The breaking of the fuse legs is used to predict the fatigue life of each girder, which is then compared with the actual cycles to failure of the girder and the AASHTO mean life. The prediction gives satisfactory agreement with the AASHTO mean life in four of the tests. In two tests, the predictions vary significantly from the AASHTO mean life. Although several critical issues remain (such as adapting the fatigue fuse to the environment of a real bridge and conducting tests on a statistically valid sample), the results of this feasibility study indicate that the fuse could be a valuable tool for highway bridge inspection.
Quality Control of Portland Cement Concrete Slabs with Wave Propagation Techniques
Authors: Nazarian Soheil , Yuan Deren , Baker Mark R.
Published: August 2018

Coring is normally done to monitor the thickness and quality of portland cement concrete (PCC) slabs during construction. Because this procedure requires a considerable amount of time, it is done at widely spaced intervals. As a result, the most critical points, in terms of strength or thickness, are sometimes not tested. Their repeatability and extreme sensitivity to the properties of surface layer enable wave propagation techniques to be used for quality control. The main advantage of these techniques is that they are nondestructive. Fortunately, these techniques have been automated in the last few years. Two seismic devices (seismic pavement analyzer and a portable version of it called the Lunch Box) have been used extensively for quality control. With them, slabs can be tested at closely spaced points and at a fraction of the cost and time of coring. The main tests used are the impact echo for determining the thickness of the slab, the ultrasonic body wave for determining the modulus, and the ultrasonic surface wave (an offshoot of the spectral analysis of surface waves method) also for determining the modulus. On the basis of extensive field testing on many types of base and subgrade, the techniques in general—and the two devices in particular—are suitable for many quality-control projects. It was found that the most robust method for determining the modulus is the ultrasonic surface wave. The impact echo also works well, as long as enough contrast exists between the properties of the PCC and the underlying materials.
Analysis of Contractor Pay Adjustment Schedule Using Simulation
Authors: Elliott Robert P. , Qiu Yanjun
Published: August 2018

A common provision in quality control/quality assurance construction contracts is the adjustment of the contractor's pay on the basis of the quality of the construction. The expected impact of the provision on the pay should be examined to ensure that the adjustments are neither unduly severe nor excessively lenient. Most pay adjustment plans have been developed around a quality index by using a percent defective approach. Analyses of these plans are complex but reasonably well defined. Other plans, however, are more complex and do not lend themselves to direct analysis. These plans can be examined by computer simulation. The use of computer simulation to examine a complex pay adjustment provision is demonstrated. The analyses show that simulation can reveal that a pay adjustment schedule behaves differently than it appears on the surface. For example, the schedule examined bases pay solely on averages and appears to ignore construction variability. The analyses, however, demonstrate that the pay adjustments are at least as sensitive to construction variability as they are to construction averages. It is also shown that the simulation process can provide a better, more detailed examination of the pay schedule than is possible by simply determining the expected pay. In particular, the simulation process can provide an indication of the variability of pay at various quality levels and can identify the factors most responsible for pay adjustments.
Quality Assurance Software for Personal Computer
Authors: Weed Richard M.
Published: August 2018

Demonstration Project 89 on Quality Management was created to provide guidance on the use of practical and effective procedures to assure that the level of quality designed into the plans and specifications is actually achieved in the constructed product. One part of this effort is the distribution of a software package consisting of several interactive programs developed for use on the personal computer. These extremely user-friendly programs make it possible to analyze both pass/fail and pay adjustment acceptance procedures, construct operating characteristic curves, plot control charts, experiment with computer simulation, perform statistical comparisons of data sets, demonstrate the unreliability of decisions based on a single test result, and explore the effectiveness of stratified random sampling. This comprehensive software package provides highway engineers with the necessary tools to learn why some statistical procedures are inherently superior to others and how to incorporate this knowledge into fair and effective construction specifications.
Bituminous Pavement Smoothness: Statistically Based Approach to Acceptance
Authors: Budwig Jerry L.
Published: August 2018

Since 1987 the Federal Lands Highway (FLH) Branch of FHWA has been evaluating acceptance of newly constructed bituminous pavements using California-type profilograph measurements. California Test Method 526 and FLH T504, as well as various acceptance plans, have been used in this evaluation. The purpose of this study was threefold: (a) to determine whether operator trace reduction variability was too large for the method to be suitable for acceptance testing; (b) to decide the type of acceptance plan to incorporate into the Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects (FP 92); and (c) to evaluate two commercially available computerized trace reduction systems. The study concludes that when used in conjunction with statistical evaluation procedures, the test method is suitable for acceptance purposes and that computerized trace reduction is superior to manual reduction. Also presented are some fundamentals of statistically based acceptance that are not widely known or understood by highway engineers.
Assessment of in Situ Structural Properties of Lime-Stabilized Clay Subgrades
Authors: Little Dallas N.
Published: August 2018

Lime-stabilized clay subgrades are used almost routinely in Texas to facilitate construction and to provide a foundation for aggregate base courses and hot mix surfaces. Research sponsored by the Texas Department of Transportation demonstrates that the in situ moduli and strength improvements afforded by lime stabilization of these layers are often significant and deserve structural consideration. A study of the range of modulus values determined from falling weight deflec-tometer deflection data and supported by in situ dynamic cone penetrometer data for 40 pavement subgrades indicates that the lime-stabilized subgrades provide a level of stiffness and strength that is similar to that of an unbounded aggregate base. This substantiates previous literature suggesting that properly designed and constructed lime-stabilized subgrades should be assigned AASHTO structural coefficients in the same range as unbound aggregate bases, that is, between 0.10 and 0.14.
Practical Reliability-Based Design Approach for Foundation Engineering
Authors: Phoon Kok Kwang , Kulhawy Fred H.
Published: August 2018

A research study was completed recently that was directed toward the development of practical, reliability-based design (RBD) equations specifically for foundation engineering. Some of the key RBD principles used in the study are presented. The important considerations involved in the development of practical and robust RBD criteria are emphasized. In particular, the selection of an appropriate reliability assessment technique and the careful characterization and compilation of geotechnical variabilities are important because of their central role in the calculation of the probability of failure and the assessment of the target reliability level. An overview of a simplified RBD approach is given, and an application of this approach to the ultimate limit state design of drilled shafts under undrained uplift loading is discussed.
Soil-Foundation-Structure Behavior at the Oakland Outer Harbor Wharf
Authors: Norris G. , Siddharthan R. , Zafir Z. , Abdel-Ghaffar S. , Gowda P.
Published: August 2018

The California Strong Motion Instrumentation Program's Loma Prieta records at Oakland Outer Harbor Wharf maybe used to study the free-field motions, the possible softening of soils surrounding the piles supporting the instrumented wharf, the determination of the motion on the instrumented wharf using free-field motion input and deflection-compatible lateral and vertical pile foundation stiffnesses, and conditions under which a soil-foundation interaction failure or structural failure of the batter piles might have developed.
Aerobic Biodegradation of Petroleum-Contaminated Soil: Simulations from Soil Microcosms
Authors: Ostendorf David W. , Long Sharon C. , Schoenberg Theodore H. , Pollock Samuel J.
Published: August 2018

The capacity of natural bacteria to aerobically degrade hydrocarbon vapors was measured and modeled to assess the potential of bioventing to reduce exhaust vapor treatment requirements at a petroleum spill site. Five sets of aerobic soil microcosms from the vadose zone of a Massachusetts Highway Department contaminated right-of-way were dosed with different initial petroleum vapor standard concentrations, then monitored by gas chromatographic analysis over a 55-day period. The five sets yielded an average maximum reaction rate of 20 μg/m3 (soil gas)-sec, which compared favorably with studies of light hydrocarbon vapor degradation in sandy soils from other sites. The calibrated rate was incorporated into a steady-state bioventing model that simulated the evaporation of 34 000 L of petroleum over a 170-year natural release period and an 8-year accelerated release period for 10-day residence time. Aerobic degradation for a 10-day residence time reduced exhaust vapor concentrations by over 100 percent for natural release rates, with a 13 percent reduction under accelerated conditions.
Using Polyacrylamide Grouts for Permeability Control in Sand
Authors: Khedr Safwan A. , Ahmed Mohamed Salah
Published: August 2018

Chemical grouting of permeable soils with highly concentrated low-molecular-weight polymeric solutions greatly reduces the permeability. However, a toxicity problem arose from these chemicals. A new process of treating soil with low-concentration cationic and anionic poly-acrylamides with cross-linking aluminum citrate in a cyclic way with particular sequencing is introduced. The new process provides effective control of permeability and eliminates the risk of toxicity. A total of 25 one-dimensional flow laboratory tests were carried out on sand. The effect of three anionic-type polyacrylamides having different molecular weights on the number of cycles required to attain a significant reduction in permeability was investigated. Controlled volumes of chemical flood solutions having four levels of concentration were injected to inspect the impact of concentration on the gel distribution. The effects of water flow and time factor on gel stability were studied. The results of these runs demonstrate the effectiveness of the aluminum citrate cross-linking process between cationic and anionic polyacrylamides in controlling permeability. Partial control of permeability as well as significant seepage cutoff was achieved as a result of gel formation. The spreadability of the gel improved upon increasing the amount of chemical solutions injected. The gel formed endured water pressure of 3 bars for 28 days. Injection with large volumes and low concentrations was found to be equivalent to injection with smaller volumes and higher concentrations. As the molecular weight of the anionic-type polyacrylamide increased, the amount that was required to be injected decreased and, accordingly, the number of cycles needed for blockage under the same conditions also decreased. Toxicological tests run on the solutions used in this research revealed no toxicity to cesarian-originated, barrier-sustained albino rats.
Evaluation of Seasonal Variability in Cohesive Subgrades Using Backcalculation
Authors: Khogali Walaa E. I. , Anderson Kenneth O.
Published: August 2018

Seasonal variation in pavement strength is an important concern for engineers and transportation authorities. In 1990, an investigation was initiated that aimed at quantifying seasonal variations within a typical cohesive subgrade soil in Alberta. The study consisted of two phases: a field investigation phase and a laboratory testing program. The field phase involved instrumenting a pavement section that is representative of the primary highway system in Alberta with thermal conductivity suction sensors. Falling weight deflectometer (FWD) deflection tests were conducted at regular time intervals over a period of 2 years and at various locations within this section. Effective pavement layer moduli were backcalculated using measured deflections, and the results were plotted versus time to quantify seasonal changes occurring in pavement structural strength. Only the research findings obtained from the FWD deflection tests that deal primarily with subgrade moduli are discussed. Remaining field data represent a valuable resource to researchers investigating other pavement structural factors. Use of the backcalculation approach for quantifying seasonal variations in subgrade stiffness seems promising. Following a significant reduction in subgrade stiffness upon thawing, a long period of relatively constant strength prevails. After that a period of gradual recovery and subsequent increase in strength is experienced as freezing approaches. Backcalculated subgrade fill moduli were found to be 65 percent greater than their counterparts in cut areas. Furthermore, the subgrade fill moduli were observed to experience less seasonal fluctuation than the cut moduli. Finally, the backcalculated subgrade moduli were found to be insensitive to asphalt concrete surface temperature influences.
Analysis of Resilient Modulus of Dense- and Open-Graded Aggregates
Authors: Heydinger Andrew G. , Xie Qinglu , Randolph Brian W. , Gupta Jiwan D.
Published: August 2018

The results of analyses of laboratory resilient modulus testing conducted on dense-graded and open-graded aggregates are presented. The testing program included three different aggregate materials (crushed limestone, natural stone, and slag), five different gradation specifications, and three different moisture conditions (dry, moist, and saturated). In addition to the five aggregate specifications, test specimens were prepared so that they would satisfy the lower, central, and upper bounds for the gradations. Resilient modulus tests were conducted as closely as possible according to Strategic Highway Research Program Protocol P-46 (AASHTO T 294-92 I). The test results were analyzed using log-linear regression analysis with two-parameter (bulk stress) and three-parameter (bulk stress and octahedral shear stress) expressions for resilient modulus. The results of the testing indicate that the resilient modulus of aggregates and regression constants vary significantly depending on the type of material and vary less significantly depending on material gradation and moisture condition. The natural stone aggregates had the higher moduli and the slag aggregate had the lowest moduli. The resilient modulus does not vary significantly as the moisture content increases unless the aggregate becomes saturated. The R2 values are consistently higher using a three-parameter expression than a two-parameter expression.
Steady-State Strength, Relative Density, and Fines Content Relationship for Sands
Authors: Thevanayagam S. , Ravishankar K. , Mohan S.
Published: August 2018

The appropriate choice of shear strength of liquefied sands is an important component in seismic slope stability evaluation. Several factors affect the undrained steady-state strength (Sus) of sands. The steady-state strengths of 24 sandy soils were analyzed. It is shown that fines content, relative density, and friction angle play important roles affecting Sus. Fines content was found to be the major factor affecting Sus. This was verified experimentally for one sand. When the Sus. data for sands were grouped into (a) relatively clean sands (<12 percent fines), (b) silty sands (12 to 50 percent fines), and (c) silts or sandy silts (>50 percent fines), at the same relative density, relatively clean sands showed the highest Sus. Silts showed the lowest Sus. Silty sands showed intermediate strengths. Lower-bound Sus-relative density relationships were established for relatively clean sands and silty sands.
Use of Shredded Rubber in Unbound Granular Flexible Pavement Layers
Authors: Speir Richard H. , Witczak Matthew W.
Published: August 2018

The major objective of the research was to conduct a study into the feasibility of using shredded rubber as a partial replacement for aggregate within conventional base and subbase materials in a flexible pavement system. A graded aggregate base and sand subbase meeting specifications for the Maryland State Highway Administration were used. The rubber used in the study consisted of a shredded product with 60 to 70 percent retained on a 9.5-mm (⅜-in.) sieve. This size was selected because of the relatively inexpensive cost to produce it and because of its adaptability to an aggregate blend. Modified and standard Proctor, California bearing ratio (CBR), and resilient modulus tests were conducted on the base/subbase-rubber blends with up to 15 percent rubber content by weight. The aggregate base blend resulted in significant decreases in both CBR and nonlinear resilient modulus at 15 percent rubber. These significant reductions led the authors to conclude that the use of shredded rubber in a dense-graded aggregate base course is not feasible. In contrast, the sand-subbase blends resulted in insignificant changes to the CBR, friction angle, permeability, and resilient modulus at higher rubber percentages. It was concluded that the sand-rubber sub-base exhibits little change compared with the virgin sand-subbase material. As a result the use of shredded rubber may be a technically feasible alternative in the construction process. Finally, two constitutive models were used in the resilient modulus analysis: the conventional K1, K2 model and a universal model incorporating an octahedral stress term (k1, k2, k3 model). Direct comparisons revealed greatly improved predictability and accuracy with the universal model for assessing the nonlinear behaviors of both aggregate types evaluated.
Cyclic Simple Shear Apparatus for Low-Strain Soil Tests
Authors: Miller Heather J. , de Alba Pedro , Baldwin Kenneth C.
Published: August 2018

A testing system has been developed to study the behavior of saturated sand under low-level cyclic shearing strains. The system has been used to determine threshold shear strain levels for fabric destruction in sand aged for different time periods. The system includes a special soil chamber and a direct simple shear (DSS) machine. To impose very small shearing strains, the DSS machine was designed to apply and measure horizontal deformations as small as 0.0005 mm (2 × 10−5 inches). Data obtained to date support the results of previous investigators who performed triaxial tests on freshly deposited samples, indicating a threshold cyclic shear strain level of approximately 0.01 percent. At strains in excess of those levels, destruction of the sand fabric occurred, as evidenced by a reduction in shear modulus at low strain levels. Subsequent modest increases in shear modulus were observed after the specimens were allowed to recover for 24 hours and then tested again. During the recovery period, drainage valves were left open to allow for dissipation of excess pore pressures and for potential consolidation during the short aging period. The DSS system was found to work well for low strain measurements. Furthermore, since shear strains are measured directly under DSS conditions (as opposed to triaxial conditions), the DSS system shows much promise as a device for studying parameters that may influence threshold shear strain levels and fabric evolution and destruction in sands.
Microdeformations in Sands by Digital Image Processing and Analysis
Authors: Raschke Scott A. , Hryciw Roman D. , Donohoe Gregory W.
Published: August 2018

Laboratory experiments are typically performed on particulate media to study stress-deformation behavior and to verify or calibrate computer models from controlled or measured boundary stresses and displacements. However, such data do not permit the formation of shear bands, displacement fields within flowing granular media, and other small-scale localized deformation phenomena to be identified. Described are two semiautomated computer vision techniques for accurately determining the two-dimensional displacement field in granular soils from video images obtained through a transparent planar viewing window. The techniques described are applicable for studying the behavior of particulate media under plane strain and certain axisymmetric test conditions. Digital image processing and analysis routines are used in two different computer programs, Tracker and Tracer, Tracker uses a graphical user interface that allows individual particles to be selected and tracked through a sequence of digital video images. A contrast edge detection algorithm delineates the two-dimensional projected boundaries of particles. The location of the centroid of each particle selected for tracking is determined from the boundary to quantify the trajectory of each particle. Tracer maps the trace or trajectory of specially dyed fluorescent particles in a sequence of video frames. A thresholding technique segments individual particle trajectories. Together, Tracker and Tracer provide a set of tools for identifying small-scale displacement fields in particulate assemblies deforming under either quasi-static or rapid loading (such as gravity flow).
Analysis of Methods Used in Time Domain Reflectometry Response
Authors: Klemunes John A. , Witczak Matthew W. , López Aramis
Published: August 2018

Time domain reflectometry (TDR) is a new technique that can be used to measure indirectly the in situ volumetric moisture content of soil. A growing body of research has been conducted in providing a variety of prediction equations to estimate the volumetric moisture content using the dielectric constant calculated from the apparent length obtained from the TDR reader. However, limited research has been conducted to determine which of several available procedures should be used to obtain the apparent length of the TDR response to be used in calculating the dielectric constant. As a result, evaluating which procedure yields the most accurate assessment of the volumetric moisture content of soils is the object of this paper. There are five known methods of analyzing the apparent length of TDR responses. They are the method of tangents, method of peaks, method of diverging lines, alternate method of tangents, and the Campbell scientific method. Twenty-eight soil samples, from the FHWA seasonal monitoring program, were obtained throughout the United States and Canada and used in a laboratory study. Three levels of moisture and five levels of compaction were initially planned for use with each soil sample. A total of 361 data points were eventually obtained and used to analyze each method. The method of tangents proved the most accurate method of estimating the volumetric moisture content. Current studies are ongoing to provide improved multiple regression models to estimate the volumetric moisture content on highway soils.
Innovative Computational Support in Bridge Aesthetics
Authors: Moore C. J. , Miles J. C. , Evans S. N.
Published: August 2018

Bridge aesthetics, an area of great interest to engineers, is recognized as a difficult area to research because of its subjective nature and ill-defined concepts. An innovative computational decision support tool for use in bridge aesthetics is described. The system contains a knowledge base created by using an extensive literature survey and by completing in-depth knowledge elicitation from leading bridge designers in the United Kingdom and with the support of the Department of Transport. To further validate the knowledge base, the rules elicited from the designers were tested against public opinion through a series of questionnaires. This procedure enabled the construction of a knowledge base that supports many aspects of aesthetics for small- to medium-sized span road bridges. This limited domain was chosen because this form of bridge is currently the most commonly constructed in Britain, yet generally receives little attention in terms of aesthetics because of time and economic constraints. The knowledge base has been incorporated into a system aimed at providing interactive advice on comparative bridge design. The system was developed in Visual C + + to run on a personal computer and to operate in a Windows environment. It is currently undergoing prolonged evaluation in practicing bridge design offices. To date, this evaluation has shown that engineers like the system and would find it useful. Therefore, commercial exploitation is currently being explored. The comments received during the evaluation are also being used to further tailor the system to suit practicing engineers' needs.
Public Transportation as Collaborative Art: MetroLink, St. Louis
Authors: Blumenfeld Emily , Yatzeck Tanya
Published: August 2018

MetroLink—the St. Louis region's new 29-km (18-mi), 18-station light-rail system—is a collaborative work of public art. Civic leaders had the foresight to suggest that visual artists collaborate with architects and engineers in designing the infrastructure of the system. The Bi-State Development Agency had the courage to accept this first-of-its-kind initiative. Reaching for design excellence, artists became involved early in the design process of the largest public works project in the region. In January 1988, six visual artists were brought onto the MetroLink design team: Alice Adams (New York), Gary Burnley (New York, formerly St. Louis), Leila Daw (Boston, formerly St. Louis), Michael Jantzen (Los Angeles, formerly St. Louis), Anna Valentina Murch (San Francisco), and Jody Pinto (New York). The results of the MetroLink design team collaboration are evident along the entire alignment. Integration of station design, technical details, and right-of-way to develop a comprehensive look for the system was a consideration from the beginning of the process. Solutions to the design challenges are unique Y-shaped bridge piers and well-designed underground tunnel stations that maintain the character of the historic space. Unconventional passenger shelters for outdoor stations, intimate vehicle interiors, atypical framing of power substations, and preservation of original architectural remnants at some stations are also highlights of the collaboration. Art is integral with design—urban infrastructure is the work of art.
Science, Technology, and Aesthetics: Three Aspects of Design Excellence
Authors: Burke Martin P. , Montoney Jeanette
Published: August 2018

Discussed here are the three major aspects of design excellence— science, technology, and aesthetics—with particular emphasis on aesthetics. Although generally applicable to all visible engineered structures, specific comments, descriptions, and illustrations relate to the design and construction of bridges. The study identifies some outstanding books and design manuals on bridge aesthetics that recently have been developed and published by the engineering profession. It also lists a number of primary design guidelines that are recommended by many design authorities and suggests how these guidelines can be used to advantage by those with limited design experience.
Application of Aesthetic Principles to Road Planting in China
Authors: He Peizhuang , Pan Xun
Published: August 2018

This paper deals specifically with the application of aesthetic principles to road planting and its future development. Consideration of such principles will provide a basis for designers to make suitable applications of road planting for both functional and aesthetic purposes. It is expected that the future will see more attention being paid to road planting aesthetics.
Aesthetic Design of Odawara Port Bridge
Authors: Oishi Tsuguo , Inokuma Yasuo
Published: August 2018

The Odawara Port Bridge is located at the mouth of Odawara Port. Selecting a bridge type that symbolized the entire project and blended well with the surrounding area was critical. To achieve this, an extra-dosed prestressed concrete box girder with a main span of 122 m was selected. Construction of this bridge type is the first in the world. Special characteristics of this bridge type are a lower tower height than that of a cable-stayed bridge, the use of a saddle at the top of the towers, and the incorporation of epoxy-coated strands for diagonal cables. The design of the various sections of the bridge was achieved by integrating the characteristic shape of the towers with cable profiles while establishing horizontal continuity with the main girder. As a result of the integration process, the following design objectives were adopted: (a) constant main girder depth; (b) inverted trapezoidal main girder cross section; (c) towers without a connecting beam at the top; (d) a fan-shaped saddle; (e) compact cable vibration dampers; (f) graded metallic coloring of cables; (g) integrated steel railing and road surface lighting; (h) nighttime bridge lighting, and (i) encased drainage pipes.
Simulator Evaluation of Green and Flashing Amber Signal Phasing
Authors: Mussa Renatus N. , Newton Craig J. , Matthias Judson S. , Sadalla Edward K. , Burns Elizabeth K.
Published: August 2018

A research study conducted to evaluate the efficacy of flashing amber signal phasing is reported. Flashing amber, which is set to overlap with the green indication a few seconds before the onset of solid amber, is a form of time reference aid used to warn drivers of an impending onset of amber. The time reference aid is a concept predicated on the principle that driver decisions will be easier and more predictable if drivers have advance information that allows them to predict the onset of amber. The evaluation of the flashing amber method showed that its implementation has the potential to reduce red-light violations, severity of maximum decelerations, and kinematically defined inappropriate stop or cross decisions. However, the data also showed that compared with the regular signal phasing, the flashing amber phasing increased the size of the indecision zone, a mechanism usually responsible for increased rear-end collisions. A measure not previously used in literature was introduced to compare the regular and the experimental signal phasing. This measure, which analyzes first-response time variability in relation to the indecision zone, predicted that increased rear-end collisions might be expected as a result of implementation of the flashing amber signal phasing. Generally, the results suggest that the implementation of a flashing amber signal phasing would not significantly increase intersection safety despite the notion that it would improve driver anticipation of the onset of solid amber.
Motorist Attitudes about Content of Variable-Message Signs
Authors: Benson Brien G.
Published: August 2018

Attitudes regarding the content of messages on variable-message signs (VMSs) are explored. Seven focus groups and a survey of more than 500 motorists in the Washington, D.C., area were carried out. Key findings are as follows. Motorists are evenly divided between those who regularly rely on VMSs and those who do not. Demographic variables have little influence on motorist attitudes about VMSs, except for a few cases involving level of education. Respondents are well disposed to VMS messages that are simple, reliable, and useful. Thus, noting the exact location of accidents, time-tagging traffic information, and posting anti-rubbernecking messages received high levels of support. Proposals failing in any of these regards were met with less interest, including delay time estimates, safety messages, and posting of alternative routes.
Link Flow Evaluation Using Loop Detector Data: Traveler Response to Variable-Message Signs
Authors: Yim Youngbin , Ygnace Jean-Luc
Published: August 2018

Système d'Information Routière Intelligible aux Usagers (SIRIUS) is the largest urban field operational test of the advanced traveler information and automated traffic management system in Europe. With variable-message signs, SIRIUS has been in operation in the Paris region for 3 years. A preliminary investigation of the effectiveness of the SIRIUS system in traffic management is presented. The extent to which drivers respond to real-time traffic information and the consequential changes in link flow under SIRIUS is also presented. Time-series traffic data were analyzed to measure changes in mean flow rates at a selected link. It was found that variable-message signs influence drivers to choose less congested routes when drivers are provided with real-time traffic information, and that a driver's decision to divert is closely associated with the information pertaining to the level of congestion. In the Paris region, drivers received information on the length of the queue at the time of this study. As congestion becomes heavier, drivers are more likely to respond to variable-message signs. According to the data analysis, a queue length of 3 km seems to be a threshold at which a significant number of drivers choose to use an alternative route.
Investigating Effect of Advanced Traveler Information on Commuter Tendency to Use Transit
Authors: Abdel-Aty Mohamed A. , Kitamura Ryuichi , Jovanis Paul P.
Published: August 2018

A study of the effects of advanced transit information on commuter propensity to use transit is described. A computer-aided telephone interview was designed and conducted in Sacramento and San Jose, California. The most important information items that nontransit users seek about the transit services available to them is investigated. Using a customized stated preference choice sets, the likelihood that the commuters will use transit is explored. Commuter perceptions of transit and transit user satisfaction with the information currently available to them are studied. The results indicated that about 38 percent of the respondents who currently do not use transit might consider transit if the appropriate information is available. Analyses using the stated-preference technique and targeting this group of respondents indicated a promising effect of transit information systems in encouraging transit ridership if the desired information is provided. Using binary logit and ordered pro-bit modeling produced results that show the significant effect of several commute and socioeconomic characteristics (such as travel time, car-pooling, and age) on the propensity of using transit.
Application of Relational Data Base Structure for Managing Network Information
Authors: Perincherry Vijay , Evans John E. , Bradstreet Amy
Published: August 2018

Working with transportation networks can be tedious and confusing. Most transportation modeling packages available treat components of a transportation network independently and require coding complete networks for all alternatives. This approach has several weaknesses: it is time consuming, requires duplicate information to be stored for each alternative, and misrepresents the interactive nature of the many network attributes. A relational data base structure in conjunction with effective network management software can be used to capture the interrelationship of network characteristics, facilitate network updates, and maintain all the network scenarios in one data file. The approach, benefits, and implementation of such a system are described.
Sample Weights for Puget Sound Transportation Panel Using Stratification Anchors in Public Use Microdata Sample and Probabilistic Models for Self-Selection
Authors: Ma Jun , Goulias Konstadinos G.
Published: August 2018

The repeated measurement of the same units over time (panel survey) contains many sampling stages such as initial response, sample stratification used as a tool to decrease costs, and panel participation. In all stages, selective (systematic) survey participation needs to be accounted for if panel data are to be used as a tracking device of the population under study. The Puget Sound Transportation Panel (PSTP) offers a unique opportunity to assess the performance of weighting methods because benchmark data, such as the Public Use MICRO DATA Sample data set, are also available. The PSTP weighting scheme contains sequential weighting steps for exogenous and endogenous sampling stratification, missing data, prewave self-selection, and multiwave panel attrition. Statistical comparisons show that weights based on probabilistic models of self-selection succeed in eliminating part of the bias introduced by selective participation.
Vehicle Classification Using Advanced Technologies
Authors: Wei Chien-Hung , Chang Cheng-Chih , Wang Sheng-Shih
Published: August 2018

Applying advanced technologies to existing problem domains is a highly desirable approach in many research areas. Among these techniques, image processing has been shown useful in transportation fields for such tasks as traffic pattern recognition, data collection, accident detection, and pavement evaluation. The integrated model with artificial neural networks (ANNs) has promising potential applications. The image processing and ANN model are combined to explore the feasibility of vehicle classification in real-world situations. Three methods were developed during the research process: ground segmentation, background subtraction, and window segmentation. The first two methods were used to separate the objects of scene and nonscene from the actual traffic image. To reduce the complexity of neural networks, the image was divided into 16 windows and three characteristics (occupation rates of vehicles, of horizontal image lines, and of vertical image lines) of each window were extracted to generate 48 factors as the input units of the neural network. The backpropagation ANN model with one hidden layer is employed. The experiments show that the accurate recognition rates of heavy vehicles, small cars, and motorcycles are 98.5, 96.92, and 91.94 percent, respectively. The result implies the remarkable applicability of the proposed methods in transportation areas.
Review of Methods for Estimating Vehicle Miles Traveled
Authors: Kumapley Robert K. , Fricker Jon D.
Published: August 2018

Estimates of vehicle miles traveled (VMT) are used extensively in transportation planning for allocating resources, estimating vehicle emissions, computing energy consumption, and assessing traffic impact. The estimates used in these applications usually come from different sources. For an objective comparison of VMT estimates from different methods, the principles and assumptions supporting the methods and the potential sources of error associated with the methods must be clearly understood. Methods of estimating VMT, including those used by the Indiana Department of Transportation (INDOT), are reviewed. Also presented is a comparison of statewide VMT estimates in Indiana from INDOT's traffic count–based method and a non–traffic-data cross-classification VMT estimation model developed for INDOT. The cross-classification model is an independent source of statewide VMT estimates in Indiana to supplement INDOT's traffic count–based estimates. The results of the comparison indicate that INDOT's traffic count–based estimates can be 10 to 20 percent higher than the estimates from the cross-classification VMT estimation model.
Incentives and Rates of Return for Travel Sur veys
Authors: Tooley Melissa S.
Published: August 2018

In recent years, lower rates of return for household-based travel surveys have become a reality. It may be difficult to collect enough data for effective transportation planning. Various incentive methods have been used to induce survey recipients to participate fully. Incentive methods will be described (along with other factors affecting rates of return), and their apparent effect on rates of return discussed. It appears that monetary incentives sent with survey materials are most effective in increasing return rates; nonmonetary incentives offered with survey packets are somewhat less effective. The data are inconclusive regarding monetary and nonmonetary incentives offered as a reward upon completion of surveys.
Retrospective Interviewing and Its Application in Study of Residential Mobility
Authors: Hollingworth Brian J. , Miller Eric J.
Published: August 2018

Recent work in the area of transportation and land use modeling and, more specifically, residential mobility modeling has recognized the need for increased experimentation with dynamic models. Implicitly, dynamic models require longitudinal data, which are time-consuming and expensive to collect. As an alternative to panel studies, a retrospective interviewing technique to collect data for use in a dynamic model of residential mobility is examined. A small retrospective survey of households in Toronto, Canada, was conducted using three data collection methods; mail, telephone, and telephone with mail. Ninety complete observations were obtained. The retrospective survey process and the three data collection methods are assessed and evaluated. Though not without problems, the retrospective survey proved to be a favorable alternative to panel studies. The telephone-with-mail survey method showed the most potential for use in future data collection efforts on the basis of its costs, response rates, and quality of data.
Geographic Information System–Based Transportation Forecast Model for Small Urbanized Areas
Authors: Anderson Michael D. , Souleyrette Reginald R.
Published: August 2018

The geographic information system (GIS) has been demonstrated to be an effective tool for transportation forecasting and scenario analysis. Previous efforts have linked full-function GIS packages with transportation forecasting models. Tools developed to provide a modeling environment more appropriate for the technical knowledge level and budget requirements of small urban or rural areas are described. Specifically, the needs of metropolitan planning organizations and regional planning affiliations in Iowa were considered in the system design. A desktop mapping package, MAPINFO, is integrated with an urban transportation planning model, TRANPLAN, to provide an interface for network analysis. With the system, network modifications and changes representing alternative demand scenarios are made in the GIS environment, and data are exported to the TRANPLAN format, and, after analysis, returned to the GIS for effective presentation of results. User tools were tested and a case study demonstrating alternatives analysis and display capabilities is presented. Although developed and tested for Des Moines, the system can easily be transferred to other agencies to enhance transportation planning capabilities.
Architecture of a Congestion Management System for Controlled-Access Facilities
Authors: Quiroga Cesar A. , Bullock Darcy
Published: August 2018

The architecture of a congestion-management system (CMS) based on global positioning system–geographic information system (GPS-GIS) technology is presented. This CMS is applicable to a road network composed of freeways and principal arterials. The focus is on the CMS structure for controlled-access facilities, which compose the freeway component of the corridor network. The CMS is based on the use of GPS for route identification and traffic monitoring and on GIS for data storage, retrieval, and visualization. A method that allows aggregation of GPS data using highway segments not exceeding 0.32 km (0.2 mi) in length is implemented. Such a method results in considerable savings in data storage needs and provides consistency for analyzing a variety of traffic scenarios. Data collection procedures, data reduction procedures, and data reporting procedures are described.