Transportation Research Circular E-C302: 2nd Conference on Advancing Transportation Equity , from the Transportation Research Board, summarizes the presentations and discussions from this event held July 15–18, 2024, in Baltimore, Maryland.

Asphalt mix design has always been considered a balance of rutting resistance and durability. The conventional Superpave mix design system targets 4% air voids during design and is referred to in this circular as Superpave4. The Superpave5 concept is a modification to the conventional Superpave4 approach. Transportation Research Circular E-C300: Superpave5: How Increasing Air Voids Can Improve Asp...

Asphalt mix design has always been considered a balance of rutting resistance and durability. The conventional Superpave mix design system targets 4% air voids during design and is referred to in this circular as Superpave4. The Superpave5 concept is a modification to the conventional Superpave4 approach. Transportation Research Circular E-C300: Superpave5: How Increasing Air Voids Can Improve Asp...

Simulation has become a crucial tool for evaluating the effectiveness of proposed capital investments aimed at improving transportation system performance. Factors such as persistent congestion, complex facility operations, and the rapid advancement of technologies and transportation systems management strategies have required agencies to invest in developing and utilizing simulation models. TR Ci...

The most inherent advantage of a smooth pavement surface is its reduced noise levels compared to a pavement that is not smooth, but beyond the noise impacts there lies indirect and direct benefits that people gain from a smooth pavement. Transportation Research Circular E-C297: Concrete Pavement Smoothness: 2023 Workshop , from the Transportation Research Board, was developed from presentations ma...

Federal laws and rules require performance standards to be implemented to enhance stewardship of the transportation infrastructure and foster greater innovation in delivering a resilient transportation system, including the life of pavement systems, that supports prosperity and opportunity. Transportation Research Circular E-C296: Foundation Design and Construction for 100-Year Pavement Systems do...

Asphalt pavement stakeholders are working toward a common goal of net-zero emissions by 2050 and incorporating the use of technologies and tools to rationally quantify the environmental impacts of asphalt pavement materials and construction alternatives. Transportation Research Circular E-C295: Day-to-Day Practices to Reduce the Carbon Footprint of Asphalt , from the Transportation Research Board,...

Asphalt mixture mechanical tests (such as Hamburg Wheel-Track, Asphalt Pavement Analyzer, Indirect Tensile Cracking) are growing in use by numerous state departments of transportation (DOTs) as part of their standard material specifications to complement volumetric properties and help ensure satisfactory asphalt mixture performance. Transportation Research Circular E-C294: Adjustment to Asphalt Mi...

The design of asphalt mixtures for use in infrastructure applications has generated significant research and focus over recent years. Recent advancements in mechanical testing of asphalt mixtures, often referred to as "performance tests," brought to the asphalt community the concept of Balanced Mix Design (BMD) and the use of these tests to augment or go beyond volumetric design. TR Circular E-C29...

Monitoring travel on the nation's roadways is crucial for understanding the dynamics of the U.S. transportation system. This involves both broad assessments, such as calculating annual average daily traffic to report on vehicle miles traveled, and detailed analyses, like examining freeway operations on a minute-by-minute basis. TR Circular E-C292: Advancing Highway Traffic Monitoring Through Strat...

The increasing volume of plastic waste generated each year is a global problem—one that has been magnified following the 2017 passing of China’s Operation National Sword policy that ended the import of waste plastics into the country effective January 2018. Rightfully, this action has awakened a renewed effort to reduce and recycle plastic waste and asphalt pavements have been identified as a pote...

Dielectric Profiling Systems and Paver Mounted Thermal Profiling can be used to advance pavement quality measurement of the entire mat from a limited number of random post-construction measurements to near-continuous measurements in real time during construction. TR Circular E-C290: Implementing Dielectric Profiling Systems for Real-Time Quality Control , from the Transportation Research Board, pr...

The community of stakeholders in safe mobility for older adults use technical terms or expressions that can have very specific meanings across disciplines. The variety of different interpretations often leads to miscommunication. Moreover, the terminology continually changes to keep pace with advances in technology, measurement tools and methods, and transportation options. TRB's Transportation Re...

The 4th Innovations in Freight Data Workshop was held September 19–21, 2023, at the Keck Center of the National Academies of Sciences, Engineering and Medicine in Washington, DC. TRB's Transportation Research Circular E-C288: Innovations in Freight Data: 2023 Workshop presents the discussions and presentations from the workshop.

To encourage adoption of performance engineered mixtures (PEM) concepts, the U.S. Federal Highway Administration offered various levels of incentive funding to state agencies to help offset the costs of additional shadow testing, data collection, and reporting. TR Circular E-C287: Using Performance Engineered Mixtures to Improve Pavement Performance and Sustainability: State Experiences presents i...

Traditionally, research and analysis of asphalt pavements have been siloed into pavement structural design, pavement material selection, and pavement service life. In order to achieve a truly perpetual pavement and potentially minimize life-cycle economic costs and environmental impacts, the pavement structural design and material design must also be integrated with pavement preservation and maint...

The recent COVID-19 pandemic highlighted the significant consequences that can result from disruptions in supply chains. The massive disruptions that occurred because of the pandemic were the result of a “perfect storm” from several events. From panic buying to increases in demand for goods and e-commerce from home-bound consumers, to stalled port operations, and labor shortages, disruptions can c...

The deployment of automated vehicles, shared mobility services, and other transformational transportation technologies has the potential to dramatically increase safety, reduce congestion, improve access, enhance sustainability, and spur economic development. However, success in meeting these goals is not assured and there are significant risks that these deployments could cause unintended consequ...

TRB's International Conference on Low-Volume Roads provides a global forum to examine new technologies and new techniques in the planning, design, construction, operation, maintenance, and administration of low-volume roads. The Conference focuses on issues that impact all aspects of life throughout the world, including the first and last mile of the roads where trips by people, produce, and resou...

Building information modeling (BIM) has been used in the vertical construction industry since the 1970s. In the last decade, the worldwide transportation industry has been pushing for the implementation of BIM for bridges and infrastructures. This process revolutionizes the way projects are delivered and, to be successful, it requires the cooperation of all parties involved in the realization of t...

One of several key outcomes of the 2021 Conference on Advancing Transportation Equity (CATE) was the determination that transportation equity can better be achieved by being intentional about facilitating context-specific, people-first practices, policies, and outcomes in the transportation industry. TRB's Transportation Research Circular E-C281: Advancing Transportation Equity: Conference Summary...

The design of asphalt mixtures for use in infrastructure applications is a topic that has generated significant research and focus over recent years. TRB's Transportation Research Circular E-C280: Glossary of Terms for Balanced Design of Asphalt Mixtures provides a reference document for usage of Balanced Mix Design terminology by the asphalt mixtures community in the United States. 

The maritime industry at large has recognized the imperative to reduce localized and global emission impacts on our environment. There are numerous avenues to reducing vessel emissions, with one being the implementation of low- and zero-emission propulsion technology on vessels. TRB's Transportation Research Circular E-C279: Advancing Low- and Zero-Emission Marine Vessel Technology Options Worksho...

The TRB Freight Data Technical Standing Committee initiated the third Innovations in Freight Data workshop to bring together freight data users and decision-makers to learn about and share the latest applications that leverage new and maturing data sources for improving decision-making. TRB's Transportation Research Circular E-C278: Innovations in Freight Data Workshop summarizes the September 202...

During a time of ever-changing dynamics, there is a tremendous amount happening in the world of asset management. The 13th National Conference on Transportation Asset Management featured a variety of topics highlighting best practices in areas such as risk management, life cycle planning, and Transportation Asset Management Plan development. Emerging topics were also featured, addressing subjects ...

Traffic speed deflection devices (TSDDs) are designed to measure pavement deflections or deflection velocities in response to loads applied by trucks moving at or near prevailing traffic speeds. TRB's Transportation Research Circular E-C276: State Departments of Transportation Experiences and Applications with Traffic Speed Deflection Devices details a 2019 workshop, Workshop on the Use of Traffic...

When large-scale events disrupt freight systems, supply chains can fail, and populations are at risk of losing access to basic necessities and to critical goods flows needed to support infrastructure and economic recovery. TRB's Transportation Research Circular E-C275: Measuring and Managing Freight Resilience Workshop summarizes TRB's Measuring and Managing Freight System Resilience Workshop, whi...

There has long been a focus on addressing the need for transportation agencies to incorporate more scientific approaches to developing construction and material specifications. TRB's Transportation Research Circular E-C274: Quality Assurance: Past, Present, and Future provides the synopsis of a workshop held during the TRB Annual Meeting in January 2020 that continued devloping this practice.

There are hundreds if not thousands of variables to consider in foundation design, which require coordination between civil, structural, and geotechnical engineers as well as state departments of transportation (DOTs), environmental planners and other stakeholders, and require knowledge of the many design codes and constantly emerging research and design guidance. The TRB Technical Activity Divisi...

Nearly all state departments of transportation (DOTs) have some level of oversight over local bridges, and different funding mechanisms and approaches are in use in the states. These are among the key takeaways from a best-practices panel sessions in conjunction with the 12th TRB International Conference on Low-Volume Roads. TRB's Transportation Research Circular E-C272: Technology Exchange on Loc...

The aviation industry and federal government are investing significant resources to better understand and minimize the potential environmental impacts related to aviation. In some cases, environmental concerns have become a fundamental constraint to increases in aviation system capacity. Constrained capacity can further exacerbate environmental problems related to noise, local air quality, and oth...

There is a widespread and heightened interest in both taking a hard look at where inequity exists and how to identify ways to address it with actionable solutions. The TRB National Cooperative Highway Research Program's Transportation Research Circular E-C270: Opportunities for Research on Transportation and Equity presents the outcomes of a TRB brainstorming session put forth as a challenge from ...

The Commodity Flow Survey (CFS) provides key data for many state and federal freight planning activities. The CFS is a shipper survey used to gather freight flow information including commodity shipped, origin and destination, value and weight, and mode. TRB's Transportation Research Circular E-C269: 2020 Commodity Flow Survey Workshop summarizes a workshop that provided a platform for discussion ...

In comparison to the levels of public interest and attention, there is little research to help understand the major obstacles and constraints encountered by women travelers and women working in transportation industries. TRB's Transportation Research Circular E-C268: Insights, Inclusion, and Impact: Framing the Future for Women in Transportation details the 2019 Women’s Issues in Transportation Co...

Coronavirus (COVID-19) has proven a formidable adversary worldwide, with tremendous impact on the United States. The transportation system is an essential element of our response to this pandemic but has also been significantly impacted across all modes, both passenger and goods movement. This environment is where research is needed most. TRB's Transportation Research Circular E-C267: Summary of T...

The COVID-19 pandemic has impacted transportation agencies across the U.S. in a variety of ways. On July 15, 2020, TRB's Transportation Asset Management Committee hosted a webinar that featured executives and CEOs from state, regional, and transit agencies. Transportation Research Circular E-C266: Transportation Asset Management in a COVID-19 World captures the details of the discussion on how the...

TRB hosted the Transportation Resilience 2019: 2nd International Conference on Transportation Resilience to Natural Hazards and Extreme Weather Events (TR2019) at the National Academy of Sciences Building in Washington, D.C., November 13–15, 2019. The primary purpose of TR2019 program was to present advancements made in transportation systems resilience to natural hazards, climate change, and impa...

The Conference on Health and Active Transportation brought together leaders from the transportation and health disciplines to chart a course for the future of active transportation. TRB's Transportation Research Circular E-C264: Conference on Health and Active Transportation compiles comments of the plenary sessions and individual breakout sessions.

The use of performance measures and data is informing transportation decision making.  Transportation Research Circular E-C263: Conference on Performance and Data in Transportation Decision Making summarizes many presentations from the conference, which attracted more than 350 professional transportation planners, consultants, industry experts, and academic researchers, from 42 stat...

TRANSED is the International Conference on Mobility and Transport for Older Adults and People with Disabilities. Transportation Research Circular E-C262: TRANSED 2018 is a sample of current research and practice in the field of accessible transportation for older adults and people with disabilities. The research was presented at TRANSED on November 12-15, 2018, in Taipei, Taiwan.

A clear funding and business case –neither of which have yet been clearly articulated – will be important for the success of AVs and shared mobility. Transportation Research Circular E-C261: TRB Forum on Preparing for Automated Vehicles and Shared Mobility: Mini-Workshop on the Economic Implications of Automated Vehicles and Shared Mobility details the roles of government and the public sector as ...

Scaling loose rocks from slopes adjacent to highways is a simple and effective measure for temporarily reducing the risk of rockfall potential on naturally occurring bedrock outcrops and highway rock–soil cuts. However, the current practice in estimating scope of work and contracting rock scaling projects are inconsistent from agency to agency. Many owners and transportation agencies conduct scali...

Transportation Research Circular E-C259: International Transportation and Economic Development Conference 2018 presents the proceedings from the ITED 2018. The report follows the general conference agenda, with presentations by speakers in the four plenary and 12 general sessions summarized. A list of the posters presented in one session is provided in Appendix A and the final program is provided ...

The deployments of automated vehicles, shared mobility services, and other transformational transportation technologies have the potential to dramatically increase safety, reduce congestion, improve access, enhance sustainability, and spur economic development. However, success in meeting these goals is not assured, and there are significant risks that these deployments could cause unintended cons...

Load testing of bridges to assess bridge performance has been in practice since at least 1891 in Switzerland. In times when engineering models were not as accurate and available as today, a critical step in the construction of a bridge was to load test prior to opening or during the opening ceremony of the bridge. Several bridges, including ones in Serbia, Switzerland, and France, collapsed during...

Self-driving cars, rising temperatures and sea levels, increasingly strong weather events, changing citizen preferences, and innovations in technologies that are revolutionizing purchasing behavior, social interaction, financial transactions, communications, and travel—the transportation world is changing very rapidly. Transportation Research Circular E-C256: Managing Transportation Systems in a F...

On April 9–10, 2019, 127 freight community members— including transportation professionals from transportation planning agencies, independent consultants, industry experts, and academic researchers from across North America—participated in the second Innovations in Freight Data Workshop in Irvine, California. Alison Conway from City College of New York chaired the planning committee for this works...

Automated vehicles, shared mobility, and other transformational technologies in transportation provide a unique opportunity to make significant advances in meeting societal goals. TRB's Transportation Research E-Circular 253: Transformational Technologies in Transportation: Impacts on Traditional Research Processes and Programs explores whether and how, in an era of rapidly evolving transformation...

Traditionally, pavement management decision-making has relied on surface cracking as an indicator of structural condition. However, with early-intervention preservation activities to extend the life of pavements, surface cracks no longer are a reliable indicator of structural condition. In the past 15 years, traffic speed deflection devices (TSDDs) have been developed to measure pavement structura...

How do we bring governance into the era of digitization so it can manage demand and supply digitally? At the same time, it is necessary to correct for the existing inequities in our system, working closer with public- and private-sector partners and developing the infrastructure needed to ensure that the transition to shared and autonomous vehicles (SAVs) minimizes the potential challenges and tak...

Information exchanged during the 97th Annual Meeting of the Transportation Research Board in a session titled "Relationship Between Laboratory Cracking Tests and Field Performance of Asphalt Mixtures" is captured in Transportation Research Circular E-C251: Relationship Between Laboratory Cracking Tests and Field Performance of Asphalt Mixtures . The document explores a significant amount of work t...

The emergence of drug-impaired driving, notably marijuana-impaired driving, is a priority concern among road-safety stakeholders. In particular, the availability and potency of marijuana has increased, and the legalization of different forms of marijuana has occurred in many jurisdictions around the world. Of equal concern, in comparison to alcohol, much less is known about marijuana and driving i...

TRB’s Technical Activities Division has released Transportation Research Circular E-C249: Key Elements of Construction Quality Assurance for Implementation, presenting a synopsis of " Quality Assurance: There’s Value in the Basics," held at the 2018 Annual Meeting of the Transportation Research Board. In this session, four speakers with a range of perspectives—the Federal Highway Administration (F...

TRB’s Technical Activities Division has released Transportation Research Circular E-C248: 12th International Conference on Low-Volume Roads, highlighting topics including road surfaces, geotechnology, cold regions and climate change, pavement management, planning and economics, unpaved roads management, geosynthetics in low-volume roads, drainage and stream crossings, climate change resiliency, st...

TRB’s Forum on Preparing for Automated Vehicles and Shared Mobility has released Transportation Research Circular E-C247: TRB Forum on Preparing for Automated Vehicles and Shared Mobility.  The circular provides a summary of a February 2019 mini-workshop on the importance and role of connectivity within the automated vehicles and shared mobility environment. Key takeaways from the workshop su...

TRB's Technical Activities Division has released Transportation Research Circular E-C246: Structural Monitoring as a primer to convey an understanding of how structural monitoring (SM) technology can be used most effectively. The circular is designed to help bridge owners understand the different purposes of structural health monitoring (SHM). Effective use of SHM can help determine the most cost-...

TRB’s Technical Activities Division has released Transportation Research Circular E-C245: Transportation Oral History: State of the Practice and a Path Forward that highlights the availability of more than 1,000 transportation oral histories and includes a proposal for the creation of a guidebook that transportation organizations could use to create their own oral histories. The circular also expl...

The current state of mobility on demand (MOD) is explored in Transportation Research Circular E-C244: Mobility on Demand: A Smart, Sustainable, and Equitable Future. The publication is the synopsis of a January 13, 2019, workshop that examined next steps for preparing for a transition to autonomy, and discussed ways to optimize sustainability and ensure equitability. The workshop emphasized the ro...

TRB's Transportation Research Circular E-C243: SHRP 2 Safety Data Student Paper Competition 2017-2019 contains student papers that were selected from a competition to promote use of the SHRP 2 Safety Data. A call for abstracts was issued in October 2017 to graduate students across the country, soliciting innovative ideas for using the data. The Review Panel for the SHRP 2 Safety Data Student ...

TRB's Transportation Research Circular E-C242: A Literature Review of Rail Trespassing and Suicide Prevention Research reviews and summarizes available research reports and data sources related to the issues of railroad trespassing and suicide, focusing on research from 2013 onwards. This report explores incidences of rail-related trespassing and suicide based on several factors, including lethali...

The notion of an aging and under-funded infrastructure in the United States is widely accepted. Current legislation calls for performance targets to be established to aid not only in the administering of funds, but also to assist states in identifying high-risk practices and roadways within their own networks. In addition to the performance targets, agency officials are looking to design and const...

TRB's E-Circular 240: Workshop on Implementing a Freight Fluidity Performance Measurement System explored emerging tracking and measurement technologies, including blockchain, and examples of multisector data sharing to capture multimodal freight performance as discussed during a September 2018 conference. Performance of the freight transportation system is important to shippers and carriers, plan...

TRB's E-Circular 239: Arterial Roadways Research Needs and Concerns: Informing the Planning, Design, and Operation of Arterial Roadways Considering Public Health explores the planning, design, and operation of arterials considering public health. This report presents a series of descriptive examples where arterials and health concerns appear in practice and identifies how and where health could be...

TRB's E-Circular 238: 2018 National Household Travel Survey Workshop explored users' experiences with the 2017 National Household Travel Survey (NHTS) dataset at an August 2018 workshop in Washington, D.C. Conducted by the Federal Highway Administration (FHWA), the NHTS is the authoritative source on the travel behavior of the American public. It is the only source of national data that allows one...

Transportation Research E-Circular 237: Innovations in Asphalt Mixture Design Procedures explores the fundamentals of asphalt mix design for improved durability and performance. Based off of presentations made at TRB's 95th Annual Meeting, the document examines presentations that cover ways to incorporate more binder into the mix with trials that modify the air void and void in mineral aggregate (...

TRB E-Circular 236: National Academies–TRB Forum on Preparing for Automated Vehicles and Shared Mobility summarizes the deliberations of a TRB forum launched in early 2018 to facilitate evidence-based research needed to deploy automated vehicle technologies in a manner and timeframe that informs policy to meet long-term goals. The deployments of automated vehicles, shared mobility services, and ot...

TRB's E-Circular 235: Glossary of Transportation Construction Quality Assurance Terms: Seventh Edition contains common terms and accepted practice in transportation construction quality assurance terminology. Transportation construction quality assurance (QA), like many other specialized subject areas, has its own unique language containing numerous technical terms or expressions having very speci...

TRB's E-Circular 234: Relationships of Laboratory Mixture Aging to Asphalt Mixture Performance summarizes the results from TRB Session 462: Relationship of Laboratory Mix Aging to Asphalt Mixture Performance, which was held during the 2016 TRB Annual Meeting. This circular includes four papers on addressing laboratory mix aging and explore handling asphalt mixtures at a production facility, varyin...

TRB's E-Circular 233: Applying Census Data for Transportation explores a conference held on November 14-16, 2017, in Kansas City, Missouri that focused on the use of census data for transportation applications. The conference provided a forum for participants to share experiences with the use of Census data, including new techniques for integrating different data sets for use in transportation pla...

TRB's E-Circular 232: Automated Vehicle Symposium 2017: Summary of a Symposium highlights the themes from an event that took place on July 11–13, 2017 in San Francisco, California. The event explored the development, testing, building, and deployment of autonomous vehicles (AVs). The 2017 AVS provided the opportunity for communication, collaboration, and information sharing on a wide range of topi...

TRB's E-Circular 230: Culverts and Soil–Structure Interaction: Fifty Years of Change and a Twenty-Year Projection summarizes the presentations from the TRB 93rd Annual Meeting on January 14, 2014 in Washington, D.C. In the past 40 to 50 years have seen significant changes in the pipe industry in terms of materials used, structure sizes, shapes, and joint capabilities. Design methodologies hav...

TRB's E-Circular 229: 10th SHRP 2 Safety Data Symposium: From Analysis to Results explores the October 6, 2017 symposium that served as a forum for the exchange of ideas about uses and methods for the SHRP 2 Safety Data Program and identified lessons learned from working with the data. This symposium focused on safety data analysis, results, and applications to help researchers and practitioners l...

TRB's E-Circular 228: Rebuilding and Retrofitting the Transportation Infrastructure documents the presentations from a conference of the same name held in Washington, D.C., in September 2017. This meeting was the 11th in a series of Spotlight Conferences funded by the U.S. Department of Transportation’s (DOT) Office of the Assistant Secretary for Research and Technology, University Transportation ...

TRB's E-Circular 227: Advancing Highway Traffic Monitoring Through Strategic Research explores the state of the practice and state of the art in highway traffic monitoring. It explores data acquisition, analysis and reporting tools, quality assurance and quality control techniques, and trends in emerging technologies. It explores how highway traffic data are acquired and used, and will provide the...

TRB's E-Circular 226: Transportation System Resilience: Preparation, Recovery, and Adaptation explores research issues related to implementing transportation systems resilience, and explores themes of a whole system approach to resilience, weather and advances in forecasting, an integrated approach to cyber-physical security for transportation, a European perspective on research for resilient road...

TRB's E-Circular 225: explores the presentations and discussions from a 2007 workshop that provided a forum for researchers, government officials, and private-sector representatives to exchange ideas on how the freight transportation system can be improved. Congestion in ports, on access roads to intermodal facilities, and on the rail system has significant impacts on the productivity and competit...

TRB's E-Circular 224: Eleventh International Bridge and Structures Management Conference summarizes a meeting held on April 26-27, 2017 in Mesa, Arizona that focused on the impacts of the new Federal Transportation Asset Management Rule and proposed federal performance measures. This report summarizes workshops that provided an overview of the federal rules; software implementation to help meet th...

TRB's E-Circular 223: Innovations in Freight Data summarize the presentations and discussions that took place at the Innovations in Freight Data Summit on May 17–18, 2017 in Irvine, California. The conference provided a forum to convene traditional freight-planning stakeholders with data and technology experts to discuss recent advances in the innovative application of these big and emerging data ...

TRB's E-Circular 222: Automated Vehicles Symposium 2016 presents the proceedings from the Automated Vehicle Symposium (AVS) on July 19-21, 2016 in San Francisco, California. The 2016 AVS provided the opportunity for communication, collaboration, and information sharing on a wide range of topics, including potential public policy, safety and security, ethics, and equity concerns, as well as technol...

TRB's E-Circular 221: SHRP 2 Safety Data Student Paper Competition, 2015–2016 contains papers submitted to the first Student Paper Competition featuring applications of safety research from TRB's second Strategic Highway Research Program (SHRP 2). This competition features the use of the SHRP 2 Safety Data to extract new insights and applications of the data. Papers examine such topics as driver d...

TRB's E-Circular 220: First International Roadside Safety Conference: Safer Roads, Saving Lives, Saving Money contains papers and abstracts presented at the TRB First International Roadside Safety Conference: Safer Roads, Saving Lives, Saving Money on June 12-15, 2017 in San Francisco, California. The conference supports and advances global efforts to reduce deaths and serious injuries associated ...

TRB's E-Circular 219: The U.S. Department of Transportation’s Smart City Challenge and the Federal Transit Administration’s Mobility on Demand Sandbox: Advancing Multimodal Mobility and Best Practices Workshop features presentations and dialogue from a January 8, 2017 workshop at the TRB Annual Meeting. The workshop explored the role of public transit, shared mobility, and advanced technology (inc...

TRB's E-Circular 218: Advancing Freeway Operations Through Strategic Research captures the state of affairs in freeway operations and reflects on the known universe of tools, techniques, and trends in emerging technologies in freeway management. From predictive software to electronic surveillance systems, operations have advanced rapidly in the past two decades. This publication will aid transport...

TRB's E-Circular 217: Exploring New Directions for the National Household Travel Survey: Phase Two Report of Activities summarize the status, approach, and expected content of the new National Household Travel Survey data for the user community. The National Household Travel Survey (NHTS), administered by the Federal Highway Administration (FHWA), provided data on personal travel in the United Sta...

TRB's E-Circular 216: International Experience and Perspective of Pavement Texture Measurements and Evaluation includes a synopsis of five presentations at the workshop “International Experience and Perspective of Pavement Texture Measurements and Evaluation” held at TRB's 94th Annual Meeting, January 11-15, 2015, in Washington, D.C. The presentations explore methods used in the United States, Uni...

TRB's E-Circular 215: Roadside Safety Design and Devices: International Workshop summarizes the presentations from a meeting hosted by the International Research Subcommittee of the TRB Roadside Safety Design Committee in Melbourne, Australia, on March 26, 2015. The publication explores assessment practices, work zone safety, safe systems and roadsides, hardware development and testing, and motorc...

TRB E-Circular 214: International Practice in Highway Access Management: A Primer explores the international status of access management through the use of a survey of transportation researchers or professionals from eight countries to document their understanding of access management practices in their country. Authors of each country report were asked to focus on critical issues o...

TRB's E-Circular 213: 13th National Light Rail and Streetcar Conference: Transforming Urban Areas documents the papers and discussions from a conference that took place on November 15–17, 2015 in Minneapolis, Minnesota. The conference focused on how investments in light rail and streetcars may strengthen the entire transit network, contribute to regional mobility, and integrate successfully into t...

TRB E-Circular 212: The Future Locomotive: How to Manage What You Have Today With a View to the Future explores the presentations of a meeting held on July 30-31, 2013 in Omaha, Nebraska that examined locomotive cab design in terms of human machine interface theory and railroad applications. The meeting included perspectives from researchers, unions, locomotive engineers, engine manufacturers, and...

TRB's E-Circular 211: Taxonomy and Terms for Stakeholders in Senior Mobility provides terminology that transportation professionals can use to communicate about senior mobility. The document will help those who encounter older adults with limited mobility, and will assist with communicating potential solutions to preserve and extend safe, independent transportation options for older persons.

TRB's E-Circular 210: Multimobility and Sharing Economy: Shaping the Future Market Through Policy and Research Multimodal explores the results of a workshop that focused on new developments in the shared-mobility sphere, the use of smartphones in pushing the goal of shared mobility forward, and on rural and suburban mobility problems. It also raised the issue of equity for paratransit options in r...

TRB's E-Circular 209: Integrating Asphalt Mixture Design, Structural Design, and Construction Quality Control provides an overview of some of the benefits and issues related to integrating asphalt mixture and structural design under the low-bid process in the United States. The e-circular is grouped into five areas: 1. An overview of the mechanistic–empirical (M-E) structural design process for bo...

TRB's E-Circular 208: Transformational Technologies in Transportation: State of the Activities explores the status and applications of transportation goods, services, and systems that fall under the umbrella of transformational techology. Key transformational technologies include connected and automated vehicles, including shared use services; unmanned aerial systems (drones); Internet of Things (...

TRB's E-Circular 207: Advancing Freight Fluidity Performance Measures: Summary of a Workshop details a December 9–10, 2015 workshop that examined the development and use of freight fluidity performance measures and related analysis techniques to improve the freight transportation system. Participants discussed the opportunities and challenges associated with expanding the use of freight fluidity p...

TRB E-Circular 206: Trends and Issues in Marine Transportation and the Environment explores urgent and far-reaching research topics pertinent to marine transportation and environmental issues. Subjects explored in this E-Circular include marine emissions and air quality impacts, including alternative fuels, human health impacts, improving marine vessel emission inventory methods, emission reductio...

TRB E-Circular 205: Commodity Flow Survey Workshop highlights an October 29, 2015 workshop that explored the Commodity Flow Survey (CFS), a data source for many freight planning activities. Workshop participants collaborated with the U.S Department of Transportation (DOT) Bureau of Transportation Statistics (BTS) to provide input to the next application of the survey. Input was provided to help in...

TRB's E-Circular 204: Surface Transportation System Resilience to Climate Change and Extreme Weather Events highlights a September 16–18, 2015 conference and live webcast that convened more than 500 experts from across the world to explore state-of-the-art research and emerging practices and policies on adapting surface transportation networks to the potential impacts of climate change and extreme...

TRB’s E-Circular 203: Transportation for Sustainability: An International Conference is the proceedings of a May 2015 conference held in Washington, D.C. that explored ways in which transportation systems can promote sustainability.

TRB E-Circular 202: Transportation Investment for Economic Development: Making the Case explores the presentations made at a peer exchange held August 17–18, 2015, in Detroit, Michigan. The meeting focused on collaboration between state departments of transportation (DOTs) and their state economic development counterparts. This exchange was designed to provide an opportunity for senior state DOT o...

TRB E-Circular 201: Linking the Past to the Future: Lessons from History About Emerging Technology explores the presentations made at a one-day, invitational workshop that took place on June 13, 2014 and was hosted by the Intelligent Transportation Systems Joint Program Office (JPO) of the U.S. Department of Transportation and the History Committee of the Transportation Research Board. The worksho...

TRB E-Circular 200: Transportation Asset Management from Plans to Practice: A Workshop for State Practitioners summarizes the presentations from a May 31, 2015 workshop held in conjunction with the 5th International Transportation Systems Performance Measurement and Data Conference, June 1–2, 2015, in Denver, Colorado. This circular summarizes ideas, experiences, and practices involving transporta...

TRB E-Circular 199: Geotechnical Research Deployment explores how transportation organizations are implementing geotechnical research using new technologies, practices, and policies with the aim of developing and institutionalizing performance standards. The circular summarizes presentations from the 93rd Annual Meeting of the Transportation Research Board, which took place on January 14, 2014 in ...

TRB E-Circular 198: Moisture Damage to Hot-Mix Asphalt Mixtures includes a synopsis of six presentations of the Moisture Damage to Hot-Mix Asphalt Mixtures Workshop conducted at the 91st Annual Meeting of the Transportation Research Board, January 22-26, 2012.

TRB E-Circular 197: Celebrating 50 Years of Traffic Flow Theory explores the presentations that took place at the Standing Committee on Traffic Flow Theory and Characteristics Summer Meeting, August 11–13, 2014 in Portland, Oregon. Presentations covered fundamental diagrams, traffic flow models, traffic control, freeway traffic analysis, calibration, empirical observations of traffic analysis, net...

TRB’s E-Circular 196: Improving Safety Data Programs Through Data Governance and Data Business Planning summarizes the major themes of a peer exchange held on March 3-4, 2015, in Washington, D.C., which explored effective data governance and data business planning solutions for safety applications. Specifically, the conference focused on the business case for data governance, elements of data gove...

TRB’s E-Circular  195: Traffic and Transportation Simulation - Looking Back and Looking Ahead: Celebrating 50 Years of Traffic Flow Theory, a Workshop summarizes a workshop held January 12, 2014 at the TRB 93rd Annual Meeting that focused on traffic and transportation simulation. The workshop provided a means to explore the history, current status, and future of traffic simulation.

TRB E-Circular  194: Literature Searches and Literature Reviews for Transportation Research Projects addresses the necessary steps for producing a high-quality literature review for a transportation research project. The circular explores how to conduct literature searches; where to search for transportation information; how to put it all together as a quality literature review; and what the ...

TRB’s E-Circular  193: Surface Transportation Financing: Innovation, Experimentation, and Exploration summarizes presentations made at the 5th International Conference on Surface Transportation Financing: Innovation, Experimentation, and Exploration on July 9-11, 2014, in Irvine, California. The conference focused on the latest research and practice in transportation finance, with an emphasis...

TRB’s E-Circular  192: Data and Statistics for Valuing Transportation Infrastructure and Transportation's Contribution to the Economy summarizes presentations made at the Workshop on Data and Statistics for Valuing Transportation Infrastructure and Transportation’s Contribution to the Economy on July 23–24, 2014, in Washington, D.C. The workshop initiated a review of methods used to estimate ...

TRB’s E-Circular  191: Aligning Data Systems to Communicate with Decision Makers: A Peer Exchange summarizes a conference held in in Miami, Florida, on April 26–27, 2014, in conjunction with the 10th National Conference on Transportation Asset Management. The peer exchange, organized by TRB, focused on communicating with decision makers on transportation asset management, economic development...

TRB’s E-Circular  190: Innovative Applications of the Highway Capacity Manual 2010 includes seven full technical papers and three extended abstracts focusing on applications of the Highway Capacity Manual 2010 (HCM 2010), as presented at the TRB 93rd Annual Meeting in January 2014.

TRB’s E-Circular  189: Application of Asphalt Mix Performance-Based Specifications contains papers based on presentations made at TRB’s 93rd Annual Meeting in a session titled Application of Asphalt Mix Performance-Based Specifications. The session illustrated performance-based asphalt mix (PBAM) specifications that are being used by various agencies. It provided a review of the concepts behi...

TRB’s E-Circular  188: Application of Reclaimed Asphalt Pavement and Recycled Asphalt Shingles in Hot-Mix Asphalt: National and International Perspectives on Current Practice summarizes papers and presentations presented at a workshop that took place on January 12, 2014 at the TRB 93rd Annual Meeting. The workshop explored material characterization and field validation for short- and long-ter...

TRB’s E-Circular  187: Developing Freight Fluidity Performance Measures summarizes presentations made at a workshop that examined freight fluidity as a measure of overall supply chain performance. The workshop also explored the use of freight fluidity performance measures in managing and improving the performance of the freight system. The Developing Freight Fluidity Performance Measures: Sup...

TRB’s E-Circular  186 contains papers based on a workshop held at the 92nd Annual Meeting, which took place January 13-17, 2013 in Washington, D.C. The workshop focused on enhancing the durability of asphalt pavements, specifically on new design and construction approaches for extending pavement life while also improving their sustainability. The workshop also addressed the use of new materia...

TRB’s E-Circular  185: The Future of TransXML: Workshop Summary is the proceedings of a December 2013 workshop that focused on potential future development and implementation of TransXML. Planning, designing, constructing, and operating transportation systems involve the exchange of large volumes of data. The lack of common data formats to facilitate the exchange of data across different busi...

TRB E-Circular  184: Critical Issues in Aviation and the Environment 2014 explores issues that address the major environmental components affected by aviation activities, sustainable solutions that have evolved and continue to be developed to minimize aviation’s environmental impacts, and key processes that link aviation and the environment. The focus of the e-circular is on the state of scie...

TRB’s E-Circular  183: Monitoring Bicyclist and Pedestrian Travel and Behavior is designed to chronicle the most recent advancements in techniques and technology of active transportation monitoring. The circular identifies a selection of recent advancements in bicycle and pedestrian data monitoring pertaining to both traffic volumes and behavioral data. The circular also introduces a selectio...

TRB E-Circular  182: Progress Toward Performance-Graded Emulsified Asphalt Specifications addresses the current state of practice within the emulsified asphalt industry and examines new test methods that eventually could redefine how the industry determines specifications and performance of emulsified asphalts. This report builds on two e-circulars published in 2006 and 2007, E-C102 : Asphalt...

TRB Transportation Research Circular E-C181: Risk-Based Adaptation Frameworks for Climate Change Planning in the Transportation Sector that explores leading climate change adaptation frameworks and examines the unique aspects of each framework’s development and approach. Recent studies of the climate change adaptation frameworks emerging from the transportation sector show a strong focus on risk. ...

TRB’s Transportation Research Circular E-C180: Motor Vehicle Crashes and Injuries Involving Teenage Drivers summarizes participants' discussions on teenage driving that took place at a workshop in 2008.

TRB’s Transportation Research Circular E-C179: Theory, Explanation, and Prediction in Road Safety summarizes the discussion and describes potential areas of advanced safety research identified by the participants at a November 2008 workshop. The objectives of the workshop were to explore promising future directions in highway crash data modeling and to identify potential areas for advanced researc...

TRB’s Transportation Research Circular E-C178: Exploring New Directions for the National Household Travel Survey summarizes input on the design of the next National Household Travel Survey from the database’s user community.

TRB’s Transportation Research Circular E-C177: Sustaining the Metropolis: Light Rail Transit and Streetcars for Super Cities summarizes the presentations made at a November 2012 conference that focused on introducing the concept of light rail transit (LRT) in North America.

TRB Transportation Research Circular E-C176: Integrating Spatial and Business Data for Improved Decisions is the summary of peer exchange that took place in May 2013 in Boise, Idaho. Attendees at the exchange explore best practices for integrating spatial and business data, and discussed strategies to overcome barriers to implementing solutions. Participants explored both technical and organizatio...

TRB’s Transportation Research Circular E-C175: Strategic Directions on Roadway Departure Crashes contains authored summaries of the presentations and breakout discussions from a August 2012 workshop that explored research needs regarding roadside departure crashes in support of the World Health Organization’s Decade of Action initiative.

TRB’s Transportation Research Circular E-C174: Countermeasures to Address Impaired Driving Offenders provides an overview of the information presented and discussions held during an August 2011 symposium that explored the current state of knowledge about how best to deal with impaired driving offenders.

TRB’s Transportation Research Circular E-C173: Glossary of Transportation Construction Quality Assurance Terms: Sixth Edition is a reference document for usage of transportation construction quality assurance (QA) terminology. The publication is designed to help foster improved communications among those who are involved in transportation construction QA.

TRB Transportation Research Circular E-C172: Roadside Safety Design and Devices: International Workshop is a record of a meeting hosted by the International Research Subcommittee of the Roadside Safety Design Committee in Milan, Italy, on July 17, 2012. The focus of the meeting included assessment practices, safety systems, best practices, and other road safety products and issues.

TRB Transportation Research Circular E-C171: Durability of Concrete: Second Edition provides information on producing durable concrete for transportation structures and pavements. The circular is an update to Transportation Research Circular 494: Durability of Concrete, published in 1999.

TRB Transportation Research Circular E-C170: Nanotechnology in Concrete Materials: A Synopsis explores promising new research and innovations using nanotechnology that have the potential to result in improved mechanical properties, volume change properties, durability, and sustainability in concrete materials.

TRB’s Transportation Research Circular E-C169: Measuring the Transportation System from a Supply Chain Perspective provides a synopsis of the information from a July 2012 workshop that was designed to help to advance the understanding of if and how public-sector decision making could be improved by having better supply chain information. The circular also summarizes initial themes that were identi...

TRB Transportation Research Circular E-C168: Artificial Intelligence Applications to Critical Transportation Issues describes artificial intelligence (AI) applications in transportation and includes opinions on the future of AI by members of the committee that produced the report. The circular also contains 12 individually authored articles that describe five general AI areas: traffic operations, ...

TRB’s Transportation Research Circular E-C167: The Promise of Rural Roads reviews the role of low-volume roads in rural connectivity, poverty reduction, crisis management, and livability. The circular is based on the keynote address at the TRB 10th International Conference on Low-Volume Roads held in 2011 in Florida.

TRB Transportation Research Circular E-C166: Glossary for Regional Transportation Systems Management and Operations Terms: Second Edition is to avoid the frequently occurring misconceptions that arise through the use of different terms for the same meaning. E-C166 is an update of a previous edition published in April 2009 as Transportation Research Circular E-C133: Glossary of Regional Transportat...

TRB’s Transportation Research Circular E-C165: Alternative Binders for Sustainable Asphalt Pavement contains seven technical papers and summaries of presentations made at a January 22, 2012, workshop that explored material characterization and field validation for short- and long-term performance of various sustainable asphalt pavements.

TRB's Transportation Research Circular E-C164: Climate Change and Transportation: Summary of Key Information highlights the key findings of a variety of studies on the subject of climate change and its ramifications for the transportation sector conducted by the National Research Council, the principal operating agency of the National Academy of Sciences and the National Academy of Engineerin...

TRB’s Transportation Research Circular E-C162: Winter Maintenance and Surface Transportation Weather includes papers that were presented at the April 30-May 3, 2012, conference in Coralville, Iowa. Issues addressed by the papers include environmental stewardship and sustainability, road safety under winter conditions, decision support systems, winter surface friction, blowing and drifting snow, wi...

TRB’s Transportation Research Circular E-C161: Applications of Advanced Models to Understand Behavior and Performance of Asphalt Mixtures is a synopsis of information on the applications of advanced models to understand behavior and performance of asphalt mixtures.

TRB’s Transportation Research Circular E-C160: Polyphosphoric Acid Modification of Asphalt Binders: A Workshop documents the research discussed and presentations made at a April 2009 workshop that explored polyphosphoric acid-modified asphalt and its performance. The circular includes presentations made on a survey on polyphosphoric acid use and issues; the why and how of polyphosphoric acid modif...

TRB’s Transportation Research E-Circular E-C159: Teamwork in U.S. Railroad Operations: A Conference is a summary of the proceedings from an April 2009 conference that explored how modern teaming strategies might assist in improving the safety of railroad operations in the United States. The circular includes background papers, presentations, and summaries of breakout sessions held during the confe...

TRB's Transportation Research E-Circular E-C158: Commodity Flow Survey Workshop is the proceedings of a November 2010 workshop that explored the next application of the Commodity Flow Survey (CFS). The CFS is a key data source for a myriad of freight planning activities.

TRB’s Transportation Research Circular E-C157: TRIS Turns 40: Results of a 2007 User Satisfaction Survey on the Transportation Research Information Service (TRIS) documents the results of an online survey of users of the TRIS database. The circular also includes background and information on the history and evolution of TRIS, information on several different versions of TRIS, and a discussion of T...

TRB’s Transportation Research E-Circular E-C156: Automated Imaging Technologies for Pavement Distress Surveys documents state-of-the-art techniques and technologies in the acquisition of pavement surface images, and basic requirements needed to automatically identify and classify pavement surface distresses. The basics of film or magnetic tape–based image acquisition are presented in the circular....

TRB’s Transportation Research E-Circular E-C155: Sensitivity Analyses for Flexible Pavement Design with the Mechanistic–Empirical Pavement Design Guide contains the proceedings of a workshop that was held in conjunctions with the 2010 TRB 89th Annual Meeting. The workshop was developed to provide information for transportation agencies in the process of, or considering the implementation of, ...

TRB Transportation Research E-Circular E-C154: Development of Warranty Programs for Hot-Mix Asphalt is a synopsis of current information for the development of warranty programs for hot-mix asphalt pavements. The opinions expressed in this e-circular are those of the document's author and do not necessarily reflect the views of the Transportation Research Board, the National Academies.

TRB Transportation Research E-Circular E-C153: Dynamic Traffic Assignment: A Primer is designed to help explain the basic concepts and definitions of dynamic traffic assignment (DTA) models and addresses the application, selection, planning, and execution of a DTA model. The report also describes the general DTA modeling procedure and modeling issues that may concern a model user.

TRB Transportation Research E-Circular E-C152: Adapting Transportation to the Impacts of Climate Change: State of the Practice 2011 focuses on transportation adaptation practices that can be implemented to yield potential benefits now and in the longer term. The document highlights what climate change adaptation means for the transportation industry. E-C152 was produced under the auspices of ...

TRB’s Transportation Research E-Circular E-C151: Modeling Operating Speed is a synthesis of existing operating speed models developed in different regions of the world. The models are grouped according to roadway type. Limitations and deficiencies in existing operating speed models and suggestions for future work are also identified. Practitioner perspectives on the potential use of speed predicti...

TRB Transportation Research E-Circular E-C 150: Advancing Regional Transportation Operations: A National Workshop is a summary of the December 2008 workshop held in Washington, D.C. The purpose of the workshop was to advance the state of the practice in regional approaches to managing and operating the transportation system in a multiagency, multimodal, and cross-functional manner with the goal of...

TRB Transportation Research Electronic Circular E-C149: 75 Years of the Fundamental Diagram for Traffic Flow Theory: Greenshields Symposium includes the papers that were presented at a July 2008 conference that explored traffic flow theory’s history, recent developments, technological impacts, current status, and potential research needs.

TRB Transportation Research E-Circular E-C148: Critical Issues in Aviation and the Environment explores the environmental media affected by aviation activities and processes that link aviation and the environment. The circular consists of nine individually authored sections representing the authors' expert opinions on these issues. E-C148 updates and expands upon previous circulars while maintaini...

TRB’s Transportation Research Circular E-C147: Development in Asphalt Binder Specifications includes papers that explore test methods and specifications for high-temperature permanent deformation, fatigue cracking, and low-temperature cracking.

TRB Electronic Circular E-C146: Trucking 101: An Industry Primer is designed to provide a basic picture of the structure of the U.S. trucking industry for public officials, policy makers, engineers, administrators, planners, academic researchers, journalists, and anyone who needs to think about issues affecting, or affected by, trucking. The report emphasizes that many of the distinct parts of the...

TRB’s Transportation Research Circular E-C145: Joint International Light Rail Conference--Growth and Renewal includes 24 peer-reviewed research papers that were presented as part of the April 2009 Joint International Light Rail Conference. Collectively, the papers provide up-to-date information on planning, design, construction, maintenance, and operations involved in running a light rail sys...

TRB’s Transportation Research Circular E-C144: Research Needs Statements for Climate Change and Transportation includes a series of specific research needs statements on climate change and transportation designed as a resource to be used by universities, students, research organizations, government agencies, and other interested parties as they contemplate and fund research in this area.

TRB Transportation Research Circular E-C143: Modal Primer on Greenhouse Gas and Energy Issues for the Transportation Industry is primer designed to provide transportation decision makers with an inclusive, educated, and objective overview of the current state of the transportation industry from a greenhouse gas and energy standpoint.

TRB’s Transportation Research Circular E-C142: Methodology for the Development and Inclusion of Crash Modification Factors in the First Edition of the Highway Safety Manual explores the literature review procedure and inclusion process related to development of Part D—Crash Modification Factors of the Highway Safety Manual (HSM), which is expected to be released later this year. The development of...

TRB Transportation Research Circular E-C141: Colorado's Full-Scale Field Testing of Rockfall Attenuator Systems explores the durability and performance of several currently available mesh and cable net products that can be used to construct rockfall attenuator systems, for which no design guidelines exist.

TRB Transportation Research Circular E-C140: A Review of the Fundamentals of Asphalt Oxidation: Chemical, Physicochemical, Physical Property, and Durability Relationships explores the current physicochemical understanding of the chemistry, kinetics, and mechanisms of asphalt oxidation and its influence on asphalt durability.

TRB’s Transportation Research Circular E-C139: Use of Accelerated Pavement Testing to Evaluate Maintenance and Pavement Preservation Treatments explores experiences where accelerated pavement testing (APT) has been successfully used for the assessment of pavement preservation and maintenance strategies. The goal of the report is to motivate future APT research for evaluation of maintenance and pav...

TRB’s Transportation Research Circular E-C138: Critical Issues in Aviation and the Environment 2009 explores the major environmental media affected by aviation activities and the key processes that link aviation and the environment, including climate change, alternative fuels, and sustainability. The circular focuses on the state of science, rather than on policy, and the authors of various portio...

TRB’s Transportation Research Circular E-C137: Glossary of Highway Quality Assurance Terms contains terms of common usage and accepted practice for terminology used in the highway quality assurance field.  The report is designed as a reference document.

TRB Transportation Research Circular E-C136: Implementation Status for Geotechnical LRFD in State DOTs explores various states’ experiences in the practical implementation of Load and Resistance Factor Design (LRFD) in geotechnical and substructure design.

TRB’s Transportation Research Circular E-C135 Maintenance Management includes papers presented at the 12th American Association of State Highway and Transportation Officials–TRB Maintenance Management Conference held in Annapolis, Maryland, July 19-23, 2009. The objective of this series of conferences is to provide a forum every 3 to 4 years for the exchange of new ideas and developments in the ma...

TRB’s Transportation Research Circular E-C134: Influence of Roadway Surface Discontinuities on Safety is designed to help highway engineers evaluate roadway maintenance guidelines and priorities. The report addresses safety issues related to roadway roughness, holes, and bumps; the positive effects of road surface discontinuities; pavement edges; friction variations; water accumulations; surface c...

TRB’s Transportation Research Circular E-C133: Glossary of Regional Transportation Systems Management and Operations Terms is designed to provide clear definitions of terms as they are typically used in the context of regional transportation systems management and operations.

TRB’s Transportation Research Circular E-C132: Young Impaired Drivers provides overview of the information presented and discussions among the participants at a June 3-4, 2008, workshop that explored the risks posed by young impaired drivers and how these risks might be ameliorated.  Background papers prepared for the workshop are also included. The workshop included perspectives on the issue...

Transportation Research Circular E-C131, Transportation Asset Management: Strategic Workshop for Department of Transportation Executives summarizes a workshop held in Washington, D.C., in December 2006 that explored advancements in asset management that have the potential to lead to growth in asset management applications in the United States.  

TRB’s Transportation Research Circular E-C130: Geophysical Methods Commonly Employed for Geotechnical Site Characterization explores how geotechnical, geophysical tools are used to image or characterize the shallow subsurface of the Earth, typically to depths of less than several hundred feet.

TRB’s Transportation Research Circular E-C129: Use of Inclinometers for Geotechnical Instrumentation on Transportation Projects explores the state of the practice and representative applications on the use of inclinometer systems for measuring ground deformation and performance of geotechnical design elements on transportation projects. The report examines inclinometer components and installation ...

TRB’s Transportation Research Circular E-C128 includes papers that were presented at the 10th International Conference on Bridge and Structure Management held on October 20-22, 2008, in Buffalo, New York.  The conference brought together practitioners, administrators, and researchers from around the world to exchange information on the development, implementation, and utilization of effective...

TRB Transportation Research Circular E-C127: Implementation of an Airport Pavement Management System explores the role and data requirements for an Airport Pavement Management System (APMS).  The report also examines the benefits, costs, and common challenges associated with the implementation of an APMS.

TRB Transportation Research Circular E-C126: Surface Transportation Weather and Snow Removal and Ice Control Technology includes papers that were presented at the 4th National Conference on Surface Transportation Weather (June 16–17, 2008), and the 7th International Symposium on Snow and Ice Control (June 17–19, 2008), which were both held in Indianapolis, Indiana.  The E-Circular includes pa...

TRB’s Transportation Research Circular E-C125: Evolving Role of Statewide Transportation Planning in an Era of Regional Funding and Governance reports on a July 7-8, 2006 peer exchange in La Jolla, California that explored this topic.

TRB’s Transportation Research Circular E-C124: Practical Approaches to Hot-Mix Asphalt Mix Design and Production Quality Control Testing explores the state-of-the-practice for Superpave mix design and specification, including a summary of changes made to the Superpave mix design procedure as a result of National Cooperative Highway Research Program research findings, American Association of State ...

TRB’s Transportation Research Circular E-C123, Traffic Safety and Alcohol Regulation: A Symposium provides an overview of the information presented at a June 5-6, 2006, symposium that examined the role of alcohol regulation in traffic safety.  The report explores discussions among symposium participants and includes the background papers prepared for the workshop.

Transportation Research Circular E-C122, Asphalt Emulsion Technology: Review of Asphalt Emulsion Residue Procedures, explores methods used worldwide for the recovery of asphalt emulsion residue and examines new avenues for research and practice on the issue. In January 2014, TRB published Transportation Research Circular E-C182 : Progress Toward Performance-Graded Emulsified Asphalt Specifications...

Transportation Research Circular E-C121, Information Assets to Support Transportation Decision Making: Report of a Peer Exchange of State Transportation Organizations, summarizes discussions at an April 17-18, 2007, peer exchange of state department of transportation officials and other professionals that focused on data and information uses, management strategies, needs, and gaps in their organiz...

Transportation Research Circular E-C120, Traffic Monitoring Data: Successful Strategies in Collection and Analysis summarizes sessions that took place as part of a May 2007 workshop in Washington, D.C., designed as a forum to exchange knowledge about successful strategies in the collection and the analysis of traffic data.  

TRB’s Transportation Research Circular E-C119: North American Freight Transportation Data Workshop summarizes sessions that took place as part of a May 2007 workshop in Washington, D.C., that allowed data users and providers to discuss freight transportation data from a North American perspective.  The workshop highlighted changes in government-supplied data sources and explored data users’ n...

TRB’s Transportation Research Circular E-C118: Lessons Learned from the AASHO Road Test and Performance of the Interstate Highway Systemincludes six papers that reflect on the performance of Interstate Highway System pavements and lessons learned from the American Association of State Highway Officials (AASHO) road test from 1956 to 1961 in Ottawa, Illinois.

TRB’s Transportation Research Circular E-C117: The Domain of Truck and Bus Safety Research explores information and perspectives on truck and bus safety research.  The report is designed to help establish a knowledge base and help identify potential future activities.

TRB’s Transportation Research Circular E-C116, Geotechnical Challenges of the Interstate Highway System: The First 50 Years and a Look Ahead, explores what geotechnical engineers have learned since the construction of the Interstate System and what they see as future challenges for the discipline.  The circular is based on presentations made during a session at the 2006 TRB 85th Annual Meetin...

TRB’s Transportation Research Circular E-C115: Challenges of Data for Performance Measures: A Workshop is the proceedings of a July 8, 2006, workshop in San Diego, California.  The workshop explored ongoing issues and research directions in data management processes for performance measures.  

TRB’s Transportation Research E-Circular 114: Research Opportunities in Radio Frequency Identification Transportation Applications summarizes a conference by the same title that was held October 17 to 18, 2006, in Washington, D.C.  This conference focused on current and future research on radio frequency identification (RFID) technologies in transportation applications, which include the tagg...

TRB has released Transportation Research Circular E-C113, Artificial Intelligence in Transportation: Information for Application includes six articles that explore five general artificial intelligence (AI) areas including knowledge-based systems, neural networks, fuzzy sets, genetic algorithms, and agent-based models.  The circular is designed to serve as an informational resource for transpo...

TRB’s Transportation Research Circular E-C112, Joint International Light Rail Conference: A World of Applications and Opportunities is the proceedings of the Joint International Light Rail (LRT) Conference that was held in St. Louis, Missouri, on April 9-11, 2006.  The conference focused on planning and urban integration, vehicle design and innovation, infrastructure use, security and fare en...

TRB’s Transportation Research Circular E-C111, Integrating Roadway, Traffic, and Crash Data: A Peer Exchange is the proceedings of a November 1-2, 2006, meeting held in Washington, D.C.  The peer exchange was designed to bring both data and highway safety professionals together to share experiences and identify key issues relating to integrating roadway, traffic, and crash data sources used t...

TRB's Transportation Research Circular E-C110: Geometric Design Strategic Research documents efforts leading up to and resulting from the Strategic Geometric Design Research Needs Workshop held in Williamsburg, Virginia, in July 2004. The report also contains research problem statements for possible use as a long-range geometric design research program by organizations such as the American Associa...

TRB’s Transportation Research Circular E-C109: Transportation Information Assets and Impacts: An Assessment of Needs explores the relationship between data, as the raw material, and information as the processed, useful product supporting decisions.  The report also examines the value of information in specific real decisions and outlines an ongoing process designed to help ensure that transpo...

TRB’s Transportation Research Circular E-C108: Geospatial Information Technologies for Asset Management is the proceedings of an October 30-31, 2005, peer exchange held in Kansas City, Missouri.  The peer exchange focused on moving spatial technology applications to the next level by managing change, data integration, and communication.  Participants at the exchange identified research t...

TRB’s Transportation Research Circular E-C107: Control of Cracking in Concrete: State of the Art explores causes of cracking, testing, and ways of minimizing strains and stresses that can cause cracking in transportation structures such as bridge structures, pavements, and footings.    

TRB Transportation Research Circular E-C106: Environmental Geospatial Information for Transportation summarizes a May 3-4, 2006, peer exchange that took place in Washington, D.C.  The peer exchange highlighted several examples of successful collaboration, data sharing, and the effective use of environmental geospatial information systems data in transportation planning.  The report focus...

TRB Transportation Research Circular E-C105: Factors Affecting Compaction of Asphalt Pavements includes invited papers that were presented at a January 2005 workshop that explored asphalt practitioners’ concerns related to specifying and achieving density during hot-mix asphalt (HMA) pavement construction.  Issues covered by the papers include optimizing HMA construction temperatures, advance...

TRB’s Transportation Research Circular E-C104, Fifty Years of Interstate Structures: Past, Present, and Future documents some of the key legislation, specifications development, and advances in research, design, and construction for bridges and other highway structures since the signing of the Federal-Aid Highway Act of 1956.

TRB’s Transportation Research Circular E-C103, Concrete: The Sustainable Infrastructure Material for the 21st Century examines some of the research innovations in the 20th century that led to advancements in concrete.  The circular also explores what the future may hold as a result of the continuing advancements in high-performance durable concrete.

TRB Transportation Research Circular E-C102: Asphalt Emulsion Technology includes four papers designed to serve as an overview of the chemistry, production, quality assurance testing, and application of bituminous emulsions.  The papers were produced following a technical session at the 2005 TRB 84th Annual Meeting on bituminous emulsions. In January 2014, TRB published Transportation Researc...

TRB’s Transportation Research Circular E-C101, Driver Education: The Path Ahead includes a series of papers that were presented at a workshop held on September 12–13, 2005, in Washington, D.C.   Issues covered by papers in the circular include novice drivers, content of driver education, instructional methods for young drivers, student competency measures, novice driver training effectiv...

TRB's 100th E-Circular: Linking Transportation and Land Use explores the results from the Land Use Peer Exchange during the summer meeting of the TRB Ports, Waterways, Freight, and International Trade Conference and the Joint Meeting of the TRB Planning, Data, Finance, Administration, Freight, and Management Committees in Boston, Massachusetts, on July 12–13, 2005. The purpose of the peer exchange...

TRB’s Transportation Research Circular E-C099, Statewide Transportation Planning: Making Connections includes the presentations, resource papers, and summaries of views expressed by conference speakers, panelists, and participants at a May 18–20, 2003, conference held in Duck Key, Florida.  The presentations, breakout sessions, and informal discussions held during the conference were oriented...

TRB's Transportation Research Circular E-C098, Maintenance Management 2006: Presentations from the 11th AASHTO–TRB Maintenance Management Conference, contains papers presented at the 11th AASHTO–TRB Maintenance Management Conference held in Charleston, South Carolina, July 16-20, 2006. The report includes papers on outsourcing, pavements, roadside, winter operations, bridges, maintenance managemen...

TRB’s Transportation Research Circular E-C097, International Perspectives on Urban Street Design: Proceedings of the Context-Sensitive Design Workshop includes four papers that were presented during the 2005 TRB 84th Annual Meeting.  The papers explore street design in small European towns; context-sensitive design aspects of arterial streets in Berlin, Germany; and issues relative to histori...

TRB’s Transportation Research Circular E-C096, Drugs and Traffic: A Symposium provides an overview of the information presented and the discussions among the participants, as well as the background papers prepared for a June 20-21, 2005, symposium held in Woods Hole, Massachusetts.  The goal of the symposium was to synthesize and summarize available information on the role of drugs in traffic...

TRB’s Transportation Research Circular E-C095, Operations Data for Planning Applications: Identifying Needs, Opportunities, and Best Practices summarizes a May 4, 2005, Washington, DC, peer exchange that focused on opportunities to improve the linkages between transportation planning and operations.  The report includes a summary of questions addressed by participants about the relationship b...

TRB’s Transportation Research Circular E-C094, Safety Data Analysis and Evaluation: Research Problem Statements contains research problem statements produced by members and friends of TRB’s Safety Data, Research, and Analysis Committee (ANB20).  The committee is concerned with methods of gathering, storing, and, in particular, using the transportation safety data for informed decision making....

TRB’s Transportation Research Circular E-C093: 6th National Conference on Transportation Asset Management summarizes the content of the sessions and presentations from the November 1–3, 2005, conference in Kansas City, Missouri.  The circular includes a summary of each conference session as well as summaries of the individual topics included in the session.  The circular is intended as a...

TRB’s Transportation Research Circular E-C092, Maintenance and Operations of Transportation Facilities: 2005 Strategic Vision explores the major trends that affect maintenance; cites current and emerging innovations in management systems, technology, and intelligent transportation systems; and examines some of the key maintenance challenges of this century.  

TRB Transportation Research Circular E-C091, Innovations in Statewide Planning: A Peer Exchange summarizes a July 2005 peer exchange on innovations in statewide planning.

TRB Transportation Research Circular E-C090, Design–Build: A Quality Process summarizes an all-day workshop that took place at the 2005 TRB 84th Annual Meeting.  The workshop focused on achieving quality on design-build projects from the preparation of the request for proposals, to the actual design, to the use of incentives to achieve desired levels of quality, and to final construction.

TRB’s Transportation Research Circular E-C089: Critical Issues in Aviation and the Environment 2005 updates a 2004 summary of critical issues in aviation and the environment.  The 2005 report identifies priority research that may yield potential benefits to environmental media affected by aviation activities (noise, air quality, and water quality) and processes that link aviation and the envi...

TRB Conference Proceedings E-C088: Commodity Flow Survey Conference is the proceeding from a conference held in on July 8-9, 2005, in Boston, Massachusetts.  The conference examined the commodity flow survey (CFS), reviewed data sources being used to supplement information from the CFS, and explored ideas to improve future iterations of the CFS.

TRB Electronic Circular E-C087: Rubblization of Portland Cement Concrete Pavements includes non-peer reviewed papers that were written based on presentations made during sessions on rubblization of portland cement concrete pavements at the TRB 84 Annual Meeting in January 2005.  Hot-mix asphalt (HMA) overlays can also be considered for application to an existing, deteriorated portland cement ...

TRB Electronic Circular E-C086: Evaluation of Chemical Stabilizers: State-of-the-Practice Report is designed to provide information on practices that agencies have found to be successful and tp provide a reasonable degree of uniformity and standardization in the evaluation of chemical stabilizers used in soil stabilization. The circular is intended to provide the potential users of any chemical st...

TRB Transportation Research Circular E-C085, Railroad Operational Safety: Status and Research Needs summarizes the proceedings of the Midyear Meeting of the Transportation Research Board’s (TRB) Railroad Operational Safety Subcommittee held September 10–12, 2002, in Irvine, California, which examined human factors-related research issues facing the railroad enterprise. The report includes research...

TRB Research Circular E-C084 presents the top 16 pedestrian research problem statements, prioritized from a list of approximately 80 research problem statements by TRB’s Technical Activities Division Committee on Pedestrians.  

TRB Transportation Research Circular E-C083: National Roundabout Conference: 2005 Proceedings includes presentations made during the May 22-25, 2005, conference in Vail, Colorado.  Issues examined during the conference included the range of settings where roundabouts may be used, design elements and criteria, and methods of estimating safety and operations impacts.  The conference also e...

TRB Transportation Research Circular E-C082, Statewide Multimodal Transportation Planning Proceedings: 2004 Peer Exchange focuses on cost estimating for transportation planning and incorporating safety into the transportation planning process.  The report provides an overview of the presentation and roundtable discussions that took place during the peer exchange on July 27-28, 2004, in Park C...

TRB Research Circular E-C081: A Research Program for Improvement of the Highway Capacity Manual describes a research program designed to improve the Highway Capacity Manual (HCM). The proposed program was developed by the members of the TRB Highway Capacity and Quality of Service Committee with the assistance of feedback from users of the HCM.  The program includes 38 research studies that wo...

TRB Electronic Circular E-C080: Freight Data for State Transportation Agencies documents a peer exchange that was held July 11, 2005, in Boston, Massachusetts.  At the peer exchange, participants identified major challenges and issues relating to freight data. Some of those challenges and issues include the determination of data and information needs, logistics and supply chain analysis, frei...

TRB Electronic Circular E-C079: Calibration to Determine Load and Resistance Factors for Geotechnical and Structural Design explores how load and resistance factors are developed.  The circular includes information on how to estimate load and resistance factors where adjustment of these factors is justified based on local experience and data.  The circular also includes criteria for docu...

TRB Electronic Circular E-C078 Roadway Pavement Preservation 2005 contains papers written for the TRB First National Conference on Roadway Preservation held in Kansas City, Missouri, on October 31-November 1, 2005.  The conference addressed all aspects of successfully implemented roadway pavement preservation activities, including management, engineering, economics, the establishment of strat...

TRB’s Electronic Circular 77--Enhancing the Value of Data Programs: A Peer Exchange contains the proceedings of a peer exchange that took place on July 23-24, 2001, in Vail, Colorado.  The purpose of the exchange was to share ideas on raising the awareness of data programs and ensuring that data add value to the operation of state departments of transportation.  The forum examined what s...

TRB Electronic Circular E-C076: Asset Management in Planning and Operations--A Peer Exchange summarizes a September 7–8, 2004, peer exchange that focused on the expanding role of asset management in planning and operations as a comprehensive approach to managing agency resources and transportation systems.  The peer exchange was designed to gather additional information about the state of the...

TRB Electronic Circular E-C075: Statewide Travel Demand Modeling—A Peer Exchange includes presentations made during the September 23–24, 2004, peer exchange and includes comparison of travel demand modeling efforts taking place in select states.

TRB Electronic Circular E-C074: Glossary of Highway Quality Assurance Terms—Third Update contains terms of common usage and accepted practice in the area of highway quality assurance (QA). The report is designed as a reference document that contains common usage of highway QA terminology.

TRB Transportation Research Circular E-C073: Performance Measures to Improve Transportation Planning Practice: A Peer Exchange summarizes the results of a peer review on the use of performance measures to improve transportation planning and its relationship to project programming.  The one-day peer review focused on how state departments of transportation are using performance measures to imp...

TRB’s Electronic Circular 72: Implementing Impaired Driving Countermeasures: Putting Research into Action—A Symposium summarizes a symposium that was held on August 21-22, 2003, in Irvine, California. The circular provides an overview of the information presented and discussions among the participants, as well as the background papers prepared for the symposium.

TRB’s Electronic Circular 71: Data for Understanding Our Nation’s Travel: National Household Travel Survey Conference summarizes a conference held on November 1-2, 2004, in Washington, D.C. The conference was designed to bring together a diverse set of data users who understand the data’s usefulness in order to provide feedback to inform the design of future national travel behavior surveys. ...

TRB's E-Circular 70 - Optimizing the Dissemination and Implementation of Research Results: A Summary of Workshop and Midyear Meeting Activities examines the issues and challenges associated with optimizing the dissemination and implementation of research results. This TRB E-Circular also documents the problem exploration process and the potential priority actions from these efforts.

TRB’s Electronic Circular E-C069: Critical Issues in Aviation and the Environment identifies priority research focused on existing and future environmental impacts of aviation on the environment and the opportunities for mitigating or avoiding those impacts.  This is first in what is planned to be an annual summary of critical issues in aviation and the environment to be developed by TRB’s En...

TRB Circular E-C068: New Simple Performance Test for Asphalt Mixes includes a series of papers that examine practical and reliable laboratory tests that could be considered for ranking the rutting potential of hot-mix asphalt paving mixtures.  The circular also includes a literature review on performance tests.  

TRB’s Transportation Research Circular E-C067: Context-Sensitive Design Around the Country: Some Examples describes Context-Sensitive Design (CSD) projects presented during the 2003 TRB 82nd Annual Meeting.  CSD is defined as a project development process, including geometric design, that attempts to address safety and efficiency while being responsive to or consistent with the road’s natural...

TRB Transportation Research E-Circular 66 is the proceedings of the National Metropolitan Planning Organization Peer Exchange that took place on May 20-21, 2003, in Duck Key, Florida.  The proceedings include information on near-term planning research topics and needs, short-term needs for transportation planning capacity building, and long-term research topics for the TRB Committee on Metrop...

TRB’s Electronic Circular E-C065: Transportation Security Education and Training summarizes the transportation security education and training presentations at the TRB’s 83rd Annual Meeting, January 11–15, 2004, and emphasizes the important security duties transportation professional’ play in protecting against and reacting to security events.

TRB’s Transportation Research Circular E-C064 -- Data Requirements in Transportation Reauthorization Legislation: What Is Included and Impacts on the Data Community highlights a TRB conference held on November, 19, 2003, in Washington, DC, that examined data issues associated with the programmatic proposals being considered for surface transportation reauthorization legislation, including new and ...

TRB Electronic Circular 63: Sixth International Symposium on Snow Removal and Ice Control Technology is the compendium of papers for the June 7-9, 2004, Spokane, Washington symposium.  Issues addressed at the symposium included winter weather (information, models, and data quality); winter maintenance (policy, management, and performance); customers’ perspectives on winter operations; environ...

TRB Transportation Research Circular E-C062: Addressing Fiscal Constraint and Congestion Issues in State Transportation Planning is the proceedings from a peer exchange held on July 14–16, 2002, in Wood’s Hole, Massachusetts.

TRB Transportation Research Circular E-C061: Data Partnerships: Making Connections for Effective Transportation Planning is the proceedings of a peer exchange held on May 21, 2003, in Duck Key, Florida. The meeting addressed some of the benefits and challenges facing the development of transportation data partnerships.

TRB Transportation Research Circular EC060: Using Simulation to Evaluate Impacts of Airport Security -- 2003 Simulation Workshop documents the proceedings of a January 12, 2003, workshop. The primary objective of this workshop was to present, demonstrate, and discuss the passenger and baggage screening simulation techniques used to comply with the Transportation Security Administration’s (TSA) con...

TRB Transportation Research Circular E-C059: Accelerated Highway Construction, Workshop Series Summary summarizes three workshops held in Washington, D.C., Indianapolis, Indiana, and Pittsburgh, Pennsylvania, in 2000-2002. The objective of this workshop series was to provide a forum for the exchange of new ideas and developments in the field of accelerated construction.

TRB Transportation Research Circular E-C058 includes the proceedings of the 9th National Light Rail Transit Conference held November 16-18, 2003, in Portland, Oregon. The ninth national conference focuses on the planning, design, construction, operation, maintenance, and administration of LRT systems.   TABLE OF CONTENTS FRONT MATTER Cover 2003 LRT Conference Planning Committee Forward Conten...

TRB Transportation Research Circular EC057 - The Roadway INFOstructure: What? Why? How? summarizes an August 21-23, 2002, workshop in Irvine, California, which examined the Federal Highway Administration’s vision for a Roadway INFOstructure. The Roadway INFOstructure was designed as the road and highway component of the Integrated Network of Transportation Information.

TRB Transportation Research Circular E-C056: The Future of MEMS: Microelectromechanical Systems in Transportation Engineering introduces microelectromechanical systems (MEMS) into transportation engineering by describing the general concept and the issues related to their development. MEMS are a relatively new innovation in the integrated circuit field. Although there are a few developed applicati...

TRB Transportation Research Circular E-C055: A National Forum on Assessing Historic Significance for Transportation Programs presents the proceedings of a forum held in Washington, D.C., on May 23–25, 1999.

TRB Transportation Research Circular E-C054: Third National Community Impact Assessment Conference includes the proceedings of the conference, which was held in Madison, Wisconsin, on August 19-21, 2002. Community Impact Assessment is an iterative process of understanding potential impacts of proposed transportation activities on affected communities and their sub-populations throughout transporta...

TRB Transportation Research Circular EC053: 9th International Bridge Management Conference Supplement includes two papers that cover Dynamic Load Tests in Bridge Management and Hybrid Knowledge Representation in Bridge Management Systems. This circular is a supplement to Circular E-C049 (http://trb.org/publications/circulars/ec049.pdf) . Papers in both Circulars were presented at the 9th Internati...

TRB Transportation Research Circular EC052: Maintenance Management 2003 contains papers presented at the Tenth AASHTO-TRB Maintenance Management Conference held in Duluth, Minnesota, July 13-17, 2003. The objective of this series of conferences is to provide a forum every three to four years for the exchange of new ideas and developments in the maintenance and operations management of transportati...

TRB Transportation Research Circular E-C051: Future Aviation Activities - 12th International workshop summarizes a September 18-20, 2002 Transportation Research Board and Federal Aviation Administration workshop on forecasting long-term trends and developments in commercial, business, and personal air transport.

TRB Transportation Research Circular EC050: Transportation and Economic Development 2002 summarizes presentations from a May 5-7, 2002, conference that offered transportation, economic development, and planning professionals a broader understanding of the most timely and important issues linking transportation and economic development.

TRB Transportation Research Circular E-C049 contains papers on bridge management concepts, strategies and health indices, asset management, joints, coatings and concrete repair, life - cycle costs, load testing, utilizing the Internet and performance measures, deterioration and reliability, future directions and challenges in bridge management systems, management system implementation, safety and ...

TRB Transportation Research Circular E-C048: Freight Transportation Research Needs Statements identifies critical issues in freight transportation as a resource for researchers in the freight area and serves as a seedbed for further discussion and analysis from a wider cross-section of freight practitioners.

TRB Transportation Research Circular E-C047: Financial Aspects of Equipment Information includes assistance on analyzing various financial acquisition choices and their impacts on budget, total costs, and fleet upgrade factors.

TRB Transportation Research Circular E-C046: Using Spatial Data, Tools, and Technologies to Improve Program Delivery chronicles a peer exchange that focused on optimum use of spatial data, tools, and information to facilitate decision making and to deliver multimodal transportation programs.

TRB Transportation Research Circular E-C045: 2002 California HOV Summit Proceedings The proceedings from TRB's May 3, 2002, California HOV Summit, which examined the latest events and research findings surrounding high-occupancy vehicle lanes, are now available in .

TRB Transportation Research Circular Number E-C044: Bailey Method for Gradation Selection in Hot-Mix Asphalt Mixture Design includes a synopsis of current information on a systematic approach to selecting and adjusting aggregate gradation in hot-mix asphalt design.

TRB Transportation Research Circular E-C043: Significance of Restricted Zone in Superpave Aggregate Gradation Specification presents the historical basis of the restricted zone in hot-mix asphalt (HMA) mixes and summarizes the published research conducted on the restricted zone to determine its significance within the Superpave gradation specification. A characteristic hump in a mix gradation with...

TRB Transportation Research E-Circular Number E-C042: Airport - Airspace Simulations: A New Outlook documents proceedings from a workshop produced by TRB's Committee on Airspace and Airfield Capacity and Delay.

TRB Transportation Research E-Circular 41: Supporting the Establishment of Safety Transportation Networks includes an introduction to safety-conscious planning and a toolkit to organize and conduct a safety-conscious planning forum.

TRB Transportation Research E-Circular E-C040: Aviation Demand Forecasting -- A Survey of Methodologies includes examples of the diversity of techniques used in forecasting aviation system demand and market analyses.

TRB Transportation Research Circular E-C039: Conference on Transportation Improvements: Experiences Among Tribal, Local, State, and Federal Governments is the proceedings from a conference held on October 18–21, 2001 in Albuquerque, New Mexico that focused on the complexity of broad transportation issues of importance for Native American nations.

TRB Transportation Research Circular E-C038: Standards for Testing, Evaluating, and Locating Roadside Safety Features includes presentations by international experts on standards for testing, evaluating, and locating roadside safety features--from a meeting of the TRB Committee on Roadside Safety Features (A2A04) Subcommittee on International Research Activities (A2A04(2)).

TRB Transportation Research Circular E-C037: Glossary of Highway Quality Assurance Terms includes standards for usage of highway quality assurance terminology.