Reliability analysis of asphalt structures is of paramount importance for pavement design, which usually aims to ensure a low failure probability. To determine the design strength of pavement against such a low failure probability, well-established probability distribution functions of the strength of asphalt mixtures are needed. While these are relatively easy to determine for asphalt mixtures at normal temperatures, the strength distribution properties for asphalt at low temperatures are more complicated. This presentation shared a research project that aimed to develop a novel method to accurately determine the strength distribution of asphalt mixtures in an indirect manner, instead of relying on the traditional tedious histogram testing. The new method was derived from a rigorous probabilistic mechanics theory and was fully validated by a set of comprehensive experiments on asphalt mixtures.

CTS Seminar Series

10/31/13: Determining the Reliability of Asphalt Structures at Low Temperatures

Intersection safety is a national, state, and local priority. In 2008, approximately 40 percent of crashes that occurred in the United States were intersection-related. However, current methods for assessing intersection safety require either a long history of crash data or subjective observation of traffic conflictsâ€”both of which can be time consuming and expensive. This presentation highlighted a new technique for evaluating intersection safety that overcomes the drawbacks of traditional approaches. The proposed approach uses the massive amount of high-resolution traffic signal event records (including both vehicle-detector actuations and signal phase changes) that has recently become available at a number of MnDOT intersections. The presentation discussed how high-resolution traffic signal data can be used to estimate the number of rear-end and right-angle conflicts and to predict the crash rate at an intersection. The proposed approach could be used to rank the safety performance for intersections within a jurisdiction in a proactive manner, thus helping agencies prioritize the intersections that need improvement.

10/24/13: A New Approach to Evaluating Intersection Safety Using High-Resolution Traffic Data

This presentation shared the results of a project that employed a qualitative approachâ€”primarily in-person interviewsâ€”to better understand the transportation challenges and priorities faced by manufacturers and related industries in MnDOT District 8 and to identify and recommend potential responses to these needs from MnDOT. In cooperation with U of M Extension, MnDOT staff, and local Economic Development Officials, the research team identified and interviewed more than 70 manufacturers and carriers in the district.

10/10/13 - Manufacturers' Perspectives on the Transportation System: A Pilot Study in MnDOT District 8

Information about the use of nonmotorized infrastructure such as bike lanes, trails, and sidewalks is needed for the planning and management of transportation systems. However, state and local transportation officials in Minnesota generally lack information about the use of bicycle and pedestrian facilities. This presentation summarized recent MnDOT-supported research in developing standard approaches for monitoring and modeling nonmotorized traffic in Minnesota. The presentation included summaries of counts taken manually and with automated counters, an assessment of the accuracy of continuous counters, the development of extrapolation factors for estimating annual average daily traffic, and modeling of traffic on streets, sidewalks, and off-street trails. Challenges in establishing a comprehensive monitoring program in Minnesota were also described.

10/3/13 - Monitoring and Modeling Nonmotorized Traffic in Minnesota

The presentation highlighted the Resilient Communities Project (RCP), a new university-community collaboration to advance sustainable and resilient outcomes. The RCP offers a new model of university outreach, organized around a sustained one-year partnership with a single Minnesota community. During the partnership year, RCP staff match between 15-30 locally identified projects with graduate-level courses across the University of Minnesota. The presenters shared information about the RCP program, as well as details about projects completed during last yearâ€™s partnership with the City of Minnetonka and RCPâ€™s new partnership with the City of North St. Paul. Among the diverse range of projects are a number that focus on transportation topics. In addition to offering innovation in outreach, RCP also serves as an important model for advanced cross-disciplinary and experiential learning opportunitiesâ€”both of which are critical for advancing sustainability education.

9/26/13 - Resilient Communities Project: A Model of Community-University Collaborative Engagement

This seminar discussed lab and field tests that were conducted to evaluate the stiffness properties and quantify the contributions of FDR to overall pavement performance. For stabilized FDR, there is no guideline for GE. Some local engineers believe that the GE of FDR material should be greater than 1, especially for stabilized FDR. In addition, little information is available on how seasonal changes affect pavements with a stabilized FDR base. Because stabilized FDR contains less moisture and has higher stiffness than aggregate base, it is believed that stabilized FDR should be less susceptible to spring thawing. This seminar reviewed how lab and field tests were conducted to evaluate the stiffness properties and quantify the contributions of FDR to overall pavement performance. Falling weight deflectometer tests were also used to study the effects of seasonal changes on FDR, especially stabilized FDR. The presentation also highlighted test results, including the finding that all materials had lower stiffness in spring than in summer and fall. Most of the stabilized FDR materials tested, but not all, showed improved seasonal stiffness.

2/25/13 - Lab and Field Evaluation of Pavements with FDR Base

About the Event This presentation will discuss the techniques developed for a 2010 accessibility evaluation of the Twin Cities metropolitan region as part of the interdisciplinary Access to Destinations project. The 2010 accessibility evaluation sought to generate an accurate representation of accessibility in 2010 and to identify data sources, methods, and metrics that can be used in future evaluations. The seminar will include a discussion of the methodology that can be used to implement future evaluations of accessibility, including a discussion of the development and use of software tools created for this evaluation. Study recommendations for the future will also be shared, such as the importance of standardizing data sources and parameters to ensure comparability between multiple evaluations over time. Other highlights include the need for data sources and methodology that provide a good representation of actual conditions, are based on measurements rather than models, and are usable with a minimum of manual processing and technical expertise. Speakers David Levinson is a professor of civil engineering at the University of Minnesota and co-leader of the Access to Destinations study. His current research focuses on understanding the process of network growth, evaluating transportation technology and policy, and modeling travel behavior. Andrew Owen is a graduate student at the University of Minnesota, where he is pursuing master's degrees in civil engineering and urban and regional planning. His research interests include network structure, travel behavior, transit systems, and multimodal accessibility.

2/19/13 - Accessibility Now and in the Future

About the Seminar This presentation highlighted a study that explored intelligent lane control signals (ILCS) and their effectiveness in conveying an intended message to drivers. The study used a driving simulator to present participants with five sets of ILCS, each displaying a different speed limit or lane closure warning message. The lane closure warnings included a variety of merge signs using arrows, words, and chevrons to prompt drivers to move out of a closed lane. The results of the study, which indicate that diagonal merge signs were the most effective, were also be reviewed. Speaker Kathleen Harder is the director of the Center for Design in Health at the University of Minnesota. Her general research interests involve investigating how various systems can be designed to enhance human performance. She has also been involved in several studies focused on designing of safer transportation environments.

2/14/13 - Investigating the Effects of Intelligent Lane Control Signals on Driver Behavior

Blowing and drifting snow are costly realities for transportation agencies in regions with significant snowfall. Large, heavy drifts can require extra snowplow trips or the use of specialized removal equipment to keep roadways passable. Living snow fencesâ€”plantings of trees or shrubs set back from the right-of-wayâ€”can be used to minimize blowing and drifting problems on a roadway. The fences can also decrease travel time and reduce the number and severity of snow-related crashes. In this seminar, Gary Wyatt highlighted a benefit and cost analysis tool developed to help the Minnesota Department of Transportation evaluate its living snow fence program. The tool calculates global and site-specific economic, transportation, and environmental benefits of the fences as well as the costs to landowners. Wyatt also outlined how the tool helps prioritize problem areas and develop landowner payment programs.

2/21/12 - Costs and Benefits of Living Snow Fences

People with impaired vision generally have difficulty crossing intersections due to a lack of traffic information. In this seminar, Chen-Fu Liao discussed the development of a Mobile Accessible Pedestrian Signal (MAPS) system to help people with limited or no eyesight cross intersections safely. The system uses Global Positioning System receivers, digital compasses, and wireless networking to provide signal and intersection geometry information to smartphone users at signalized intersections. User interaction is a via a simple tactile inputâ€”a single or double tap on the smartphone's touchscreenâ€”and a text-to-speech interface. Liao also highlighted plans for an upcoming field experiment at a signalized intersection. As part of the test, several visually impaired pedestrians will evaluate the usability and cognitive load of using the MAPS application.

2/15/12 - Signalized Intersection Crossing for the Visually Impaired

In this presentation, Mihai Marasteanu summarized work performed under two national pooled-fund studies that investigated the low-temperature behavior and performance of asphalt pavements. Marasteanu reviewed the development of current performance specifications and discussed the limitations of their parameters. He also highlighted how his team used laboratory and field data to begin the development of a performance-based specification for asphalt mixtures and suggested steps for the successful implementation of such a specification.

2/7/12 - Towards a Low-Temperature Performance Specification for Asphalt Mixtures

Visual accessibilityâ€”how effectively vision can be used to travel safely through or complete activities within a spaceâ€”has an important impact on low-vision mobility. In this seminar, Gordon Legge will describe an empirical approach for studying the visual accessibility of indoor spaces, including experiments on the detection and recognition of steps and ramps. He will also outline the development of a new form of adaptive technologyâ€”the Digital Sign Systemâ€”to assist visually impaired people with indoor navigation.

1/31/12 - The Visual Accessibility of Indoor Spaces

The consideration of vision loss is of growing importance in research, planning, and implementation of travel and transportation needs. There are approximately 12 million people with some form of visual impairment in the United States, and this number is estimated to double in the next 20 years as a consequence of our aging population. To meet the needs of this growing population, far more research is needed to better understand what information is used to support spatial behaviors for people with low (or no) vision. In this seminar, Nicholas Giudice will discuss some practical solutions that can improve information access, safety, and efficient travel for people with vision loss. He will also explain why the failure to consider human perceptual and cognitive factors often leads to poor design decisionsâ€”especially when incorporating auditory, haptic, and other non-visual information into traditional navigation systems and transportation networks.

12/8/11 - Toward Universal Access to Seamless Travel of Indoor and Outdoor Spaces With and Without Vision

Traffic safety comes in several shapes and sizes. Ask a maintenance worker what safety is and you might hear that it's plowing roads when it snows. A transportation designer might say that safety is designing signposts that break away without intruding into a vehicle. A local official might say that installing an interchange or converting a two-lane road to four lanes is safety. Safety has been ingrained in the transportation profession since the time of horse and buggy trails. In this presentation, Brad Estochen will discuss the Minnesota Department of Transportation's diverse approach to roadway safety. He will highlight traditional measures and prioritization processes as well as approaches for addressing safety on a systemic level and using data to help drive Minnesota toward its goal of zero deaths.

12/1/11 - Transportation Safety Issues and Priorities in Minnesota

Cyclopath is a routing and mapping system for bicyclists in the Twin Cities metro area. The system, developed at the University of Minnesota, generates bicycling routes that can be personalized to meet individual cyclists' preferences. Cyclopath is also the world's first full-featured geographic wikiâ€”all users can edit the system's maps of roads and trails. Much information about bike trails and cycling conditions is currently known only to individual cyclists, and Cyclopath allows them to share this key knowledge with each other. Cyclopath is a popular resource for the cycling community and a powerful research platform. In this seminar, Loren Terveen will describe the innovative aspects of the Cyclopath system design, summarize several research studies of Cyclopath users and usage, and describe a few new development and research directions.

11/10/11 - Cyclopath: Personalized Routing and Open Collaboration for Bicyclists

Every year, the Center for Transportation Studies offers a Seminar Series on current transportation research projects at the University of Minnesota. Research projects cover a wide range of disciplines such as mechanical engineering, electrical engineering, human factors, computer science and engineering, planning, and civil engineering.

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CTS Seminar Series

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