CTS Seminar Series

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.

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 conflicts—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.

This presentation shared the results of a project that employed a qualitative approach—primarily in-person interviews—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.

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.

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 year’s partnership with the City of Minnetonka and RCP’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 opportunities—both of which are critical for advancing sustainability education.

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.

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.

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.

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 fences—plantings of trees or shrubs set back from the right-of-way—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.

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 input—a single or double tap on the smartphone's touchscreen—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.