Federal Highway Administration

The writers compare the flutter phenomena of the suspension bridge and the airfoil and employ a free-oscillation experimental method to measure model bridge flutter coefficients analogous to airfoil flutter coefficients. They employ the airfoil as a check on the experimental method, both as a theoretical backdrop and to test out the nature of aerodynamic oscillatory forces under exponentially modified motion. A short catalogue of bridge deck flutter coefficients is then experimentally obtained and presented covering a range of bridge deck forms. Detailed results are described to account for a number of phenomena observed in the wind tunnel and in the field.

We apply recent econometric advances to study the distribution of commuters' preferences for speedy and reliable highway travel. Our analysis applies mixed logit to combined revealed and stated preference data on commuter choices of whether to pay a toll for congestion-free express travel. We find that motorists exhibit high values of travel time and reliability, and substantial heterogeneity in those values. We suggest that road pricing policies designed to cater to such varying preferences can improve efficiency and reduce the disparity of welfare impacts compared with recent pricing experiments.

The empirical Bayes (EB) method addresses two problems of safety estimation: it increases the precision of estimates beyond what is possible when one is limited to the use of a 2- to 3-year accident history, and it corrects for the regression-to-mean bias. The increase in precision is important when the usual estimate is too imprecise to be useful. The elimination of the regression-to-mean bias is important whenever the accident history of the entity is in some way connected with the reason why its safety is estimated. The theory of the EB method is well developed. It is now used in the Interactive Highway Safety Design Model and will be used in the Comprehensive Highway Safety Improvement Model. The time has come for the EB method to be the standard and staple of professional practice. The study’s goal is to facilitate the transition from theory into practice.

This study describes experimental and analytical methods to quantify the structure of air voids in asphalt mixes. An x-ray computed tomography system along with image analysis techniques were used to measure air void sizes at different depths within asphalt mix specimens. The statistical analyses performed validated the applicability of the Weibull model for describing the air void distribution. Consequently, the Weibull model was used to quantify the effect of the compaction effort, method of compaction, and aggregate size distribution on air voids. The air void size distribution in Superpave gyratory compacted specimens was found to exhibit a “bathtub” shape, whereby larger voids were present at the top and bottom parts of a specimen. This shape was more pronounced at higher compaction efforts. The method of compaction was significant in influencing the air void size distribution. Specimens prepared using the Superpave gyratory compactor with different aggregate sizes were found to have noticeably different air void sizes.

Cooperative adaptive cruise control (CACC) includes multiple concepts of communication-enabled vehicle following and speed control. Definitions and classifications are presented to help clarify the distinctions between types of automated vehicle-following control that are often conflated with each other. A distinction is made between vehicle-to-vehicle (V2V) CACC, based on vehicle–vehicle cooperation, and infrastructure-to-vehicle CACC, in which the infrastructure provides information or guidance to the CACC system (such as the target set speed value). In V2V CACC, communication provides enhanced information so that vehicles can follow their predecessors with higher accuracy, faster response, and shorter gaps; the result would be enhanced traffic flow stability and possibly improved safety. A further distinction is made between CACC, which uses constant-time-gap vehicle following (forming CACC strings), and automated platooning, which uses tightly coupled, constant-clearance, vehicle-following strategies. Although adaptive cruise control (ACC) and CACC are examples of Level 1 automation as defined by both SAE and NHTSA, the vehicle-following performance that can be achieved under each scenario is representative of the performance that should be expected at higher levels of automation. Implementation of CACC in practice will also require consideration of more than the lowest level of vehicle-following and speed regulation performance. Because CACC requires interactions between adjacent equipped vehicles, strategies are needed such as ad hoc, local, or global coordination to cluster CACC vehicles. Some of the challenges that must be overcome to implement the clustering strategies are discussed as well as strategies for separating CACC clusters as they approach their destinations, as potential traffic improvements from CACC will be negated if the vehicles cannot disperse effectively.

Ultrahigh-performance concrete (UHPC) offers significant potential to address a variety of needs in bridge design, construction, and performance enhancement. Bridge owners have shown willingness to embrace novel solutions that could address specific challenges related to the cost, speed of construction, durability, and service life of their projects. There are hundreds of bridges worldwide that, largely in the past decade, have utilized UHPC. These applications range from minor field-cast closures to precast segments for long-span bridges to kilometer-long bridge deck overlays on a signature structure. The objective of this paper is to promote the application of this class of cementitious material in bridge engineering by presenting the progress that has been made in different regions of the world in the past two decades. Today, UHPC is being widely used in Malaysia to design and construct many bridges of different types and spans as they build out their roadway network. In South Korea, the unique characteristics of UHPC are being utilized to advance the state-of-the-art in long-span bridges. The French were early adopters and pioneers in building a strong foundation for using UHPC in a variety of bridge applications. In Switzerland, UHPC is employed to address major bridge rehabilitation needs. The United States bridge sector has embraced UHPC for a variety of field-cast connections. Current research and development efforts are promoting the use of UHPC in major rehabilitation projects and construction of primary bridge components. The adoption of UHPC solutions into the bridge sector is progressing rapidly because of the unique opportunities provided by the strength and durability of the material. It is expected that additional innovations and refinements of solutions will occur as knowledge of the material proliferates.

ABSTRACT The Multi-stress Creep and Recovery (MSCR) Test is currently being considered as a replacement for the Superpave high temperature binder criteria G* sinδ. The MSCR test can distinguish between the rutting properties of both neat binders and polymer modified binders. The test is run on the same dynamic shear rheometer test equipment currently used for the current Superpave binder testing and is easy to run. The validation of the MSCR compliance value Jnr to rutting was done through extensive mix testing using laboratory rut testers, large Accelerated Loading Facilities and actual roadway sections. This paper covers the validation of the MSCR test binder compliance value Jnr to mixture rutting for modified and neat binders. Multiple binders and mix types are included in the validation and it is demonstrated that the MSCR test provides a much better correlation to mixture rutting than the existing Superpave binder criteria.

Routine inspection is the most common form of highway bridge inspection to satisfy the requirements of the National Bridge Inspection Standards. The accuracy and reliability of documentation generated during these inspections are critical to the allocation of Department of Transportation construction, maintenance, and rehabilitation resources. Routine inspections are typically completed using only the visual inspection technique and rely heavily on subjective assessments made by bridge inspectors. In light of this, and given the fact that visual inspection may have other limitations that influence its reliability, the Federal Highway Administration initiated an investigation to examine the reliability of visual inspection as it is currently applied to bridges in the United States. This paper will summarize results from this study related to the accuracy and reliability of routine inspection documentation. A number of important conclusions were developed from the experimental study. Generally, it was found that all structural condition documentation is collected with significant variability. Specifically, 95% of primary element condition ratings for individual bridge components will vary within two rating points of the average and only 68% will vary within one point. Documentation generally collected to support condition ratings also has significant variability as exemplified by the number and types of field notes and photographs taken by inspectors. With respect to the use of element-level inspections, it was found that element usage was generally consistent with the Commonly Recognized Element Guide. However, there is significant variability in the condition state assignments of those elements and in some cases the condition states are not applied correctly to particular elements.

Data collected from the states of Minnesota and Washington on rural two-lane highways are used to build accident models for segments and three-legged and four-legged intersections stop-controlled on the minor legs. The quantity, quality, and variety of data collected, together with the advanced techniques applied in the analysis, make this study of special interest. Variables include traffic, horizontal and vertical alignments, lane and shoulder widths, roadside hazard rating, channelization, and number of driveways. Models are of negative binomial and extended negative binomial form and yield R 2 values from 0.42 to 0.73 and overdispersion parameters from 0.20 to 0.51. A segment model combining both states and including state as a variable, and intersection models derived from Minnesota data, are featured, along with summary statistics, goodness-of-fit measures, and cross-validation between the states. Segment accidents depend significantly on most of the roadway variables collected, while intersection accidents depend primarily on traffic. The study recommends development of adjustment factors for different regions and times and further development of extended negative binomial models.

Significant recent advancements in cement-based, fiber-reinforced composite materials have stretched the bounds of concrete into the realm of ultrahigh-performance concrete (UHPC). The durability of a commercially available UHPC was independently evaluated through six standardized durability tests and the results are reported herein. Regardless of the curing treatment applied, this concrete exhibits significantly enhanced durability properties as compared to normal and high performance concretes. The concrete exhibited minimal damage after being subjected to two times the normal number of ASTM C 666 freeze–thaw cycles. It was innocuous to ASTM C 1260 ASR deterioration, to ASTM C 672 scaling deterioration, and to AASHTO T259 chloride penetration. The ASTM C 1202 Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration test result was negligible if any steam-based curing treatment was applied, and was very low otherwise. Steam-based curing treatments significantly enhanced the ASTM C 944 abrasion resistance. The curing treatment applied to this concrete can affect the durability properties, partly due to steam treatment increasing the degree of hydration of the concrete, improving its microstructure, and decreasing its permeability.

The Pontis bridge management system is the predominant bridge management system employed in the United States. The system employs a network optimization model for preservation, formulated as a Markov decision process with a linear program solution procedure. On each bridge, a set of level-of-service standards determines functional needs, whose benefits are calculated according to a user cost model. A multi-year program simulation generates project alternatives by combining preservation and improvement needs on each bridge. The program is optimized within budget constraints by means of an incremental benefit/cost algorithm.The mathematical formulation of each of these components is presented and discussed. Aspects of system development and data management are outlined, along with the current implementation status. California’s experience with the use of Pontis in its funding process is highlighted.

Gender and household life cycle together affect daily travel behavior. Although this makes intuitive sense, transportation planners and policy makers have done little to understand what effect and impact these factors have on daily transportation choices. The 1995 Nationwide Personal Transportation Survey was used to examine trip-chaining behavior of adult men and women traveling Monday through Friday. The data show that women continue to make more trips to perform household-sustaining activities such as shopping and family errands to a greater extent than men. Women, especially with children in the household, are more likely to chain these household-sustaining trips to the trip to and from work. Women’s participation in the labor force is at an all-time high, but women’s patterns in travel to work are different from men’s patterns, and they vary with family and life-cycle status. The type and location of jobs that women take are likely affected by their greater household and family responsibilities. The biggest question for the future is whether and how the changes in women’s status in the workplace, and perhaps the concomitant change in the household dynamics and responsibilities, will affect travel behavior of both men and women. These changes will deeply affect the development of programs related to transit, land-use planning, work schedules, telecommuting, and other programs related to automobile use.

The flexural behavior of an ultrahigh-performance concrete (UHPC) was investigated through the testing and related analysis of a full-scale prestressed I-girder. A 28ksi(193MPa) compressive strength steel fiber reinforced concrete was used to fabricate an 80ft(24.4m) long AASHTO Type II girder containing 26 prestressing strands and no mild steel reinforcement. Intermediate and final behaviors, including cracking, flexural stiffness, and moment capacity, were investigated. Test results are compared to predictions based on standard analytical procedures. A relationship between tensile strain and crack spacing is developed. The uniaxial stress-strain response of UHPC when subjected to flexural stresses in an I-girder is determined and is verified to be representative of both the stress and flexural stiffness behaviors of the girder. A flexural design philosophy for this type of girder is proposed.

OBJECTIVE: To familiarize the reader with the role of electroconvulsive therapy (ECT) in current psychiatric medicine. METHOD: We review clinical indications for ECT, patient selection, contemporary ECT practice, maintenance treatment and ECT in major treatment guidelines. RESULTS: ECT is underutilized largely due to persisting stigma and lack of knowledge about modern ECT technique. CONCLUSION: ECT remains a vital treatment for patients with severe mood disorders, psychotic illness and catatonia.

This paper presents a new holistic vision-based mobile assistive navigation system to help blind and visually impaired people with indoor independent travel. The system detects dynamic obstacles and adjusts path planning in real-time to improve navigation safety. First, we develop an indoor map editor to parse geometric information from architectural models and generate a semantic map consisting of a global 2D traversable grid map layer and context-aware layers. By leveraging the visual positioning service (VPS) within the Google Tango device, we design a map alignment algorithm to bridge the visual area description file (ADF) and semantic map to achieve semantic localization. Using the on-board RGB-D camera, we develop an efficient obstacle detection and avoidance approach based on a time-stamped map Kalman filter (TSM-KF) algorithm. A multi-modal human-machine interface (HMI) is designed with speech-audio interaction and robust haptic interaction through an electronic SmartCane. Finally, field experiments by blindfolded and blind subjects demonstrate that the proposed system provides an effective tool to help blind individuals with indoor navigation and wayfinding.

The Physics of Traffic: Empirical Freeway Pattern Features, Engineering Applications, and Theory , Boris S. Kerner Springer-Verlag, New York, 2004. $139.00 (682 pp.). ISBN 3-540-20716-3 Buy at Amazon

Concrete is in desperate need of revitalisation in the 21st century due to growing durability, maintenance and environmental concerns. Improving the cement within concrete is an essential part of addressing these concerns. While Portland cement manufacture and use can still undergo slight environmental improvements, great opportunities lie in the utilisation of cements based on alternative compositions, binding-phases and green chemistry. This allows cement to be synthesised from a variety of materials including recycled resources and mineral wastes, which reduces the energy demands during production. The present work introduces industrial ecology and the principles of green chemistry as a means of driving the research, development and commercial attractiveness of alternative and sustainable cements. Three promising alternative cements are reviewed (alkali-activated cements, magnesia cements and sulfoaluminate cements) and compared to blended ordinary Portland cements in terms of their chemistry and properties. Emphasis is given to the material properties, durability, performance and applications of the “greener” alternative cements. It is clear that alternative cements have considerable potential in terms of environmental, engineering and economic properties.

The performance of asphalt concrete (AC) mixtures is influenced by its internal structure, which refers to the arrangement of aggregates and their associated air voids. Currently, most of the discussion on the effects of internal structure on AC performance is qualitative. This study proposes computer-automated image analysis procedures to quantify the internal structure of AC. Internal structure is quantified in terms of aggregate orientation, aggregate contacts, and air void distribution. The new procedures are useful tools to describe and compare AC materials produced by different compaction methods and mix designs. The new procedures are used to study the difference in internal structure of AC specimens compacted with the Superpave gyratory compactor (SGC) and the linear kneading compactor (LKC). Specimens compacted with the SGC were found to have aggregates with more preferred orientation and fewer contacts than specimens compacted with the LKC. In addition, SGC specimens were found to have more air voids at the top and bottom, whereas air voids in LKC specimens were found to increase from the top to the bottom.

Congestion is one of the biggest challenges faced by the transportation community; congestion accounted for an estimated $87.2 billion in losses in 2007 alone. Transportation professionals need to go beyond capacity expansion projects and explore novel strategies to mitigate traffic congestion. Automated intersection management is a novel strategy that has the potential to greatly reduce intersection delay and improve safety. Although the implementation of such a system is contingent on the development of automated vehicles, competitions such as the Grand Challenge and Urban Challenge of the Defense Advanced Research Projects Agency have shown that this technology is feasible and will be available. Therefore, the development of the infrastructure and associated control methods required to exploit fully the benefits of such technology at the system level is critical. This research explores one such innovative strategy, an automated intersection control protocol based on a first-come, first-served (FCFS) reservation system. The FCFS reservation system was shown to reduce intersection delay significantly by exploiting the features of autonomous vehicles. Microscopic simulation experimental results showed that the FCFS reservation system significantly outperformed a traditional traffic signal in reducing delay.

Abstract Animal sentience refers to the capacity of animals to feel both positive and negative emotions including that of pain. As veterinary health professionals, we have a medical and ethical duty to mitigate suffering from pain to the best of our ability. In 2014, the first Global Pain Council World Small Animal Veterinary Association (WSAVA) Guidelines for the Recognition, Assessment and Treatment of Pain was published and remains to this day one of the most relevant and widespread documents of its kind. The 2022 WSAVA Global Pain Management Guidelines evolves from the first document with updated scientific information reflecting major advances in veterinary pain medicine in the last decade. This document is designed to provide the user with easy‐to‐implement, core fundamentals on the successful recognition and treatment of pain in the day‐to‐day small animal clinical practice setting. It provides basic and practical information with an extensive reference list to guide those who want to further their knowledge on pain management. The 2022 WSAVA Global Pain Management Guidelines should be easily implemented regardless of practice setting and/or location for the promotion and advance of pain management and animal welfare.