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Current Issue | Previous Issues | Subscribe April 2010 – Vol. 8, No. 4

Policy & Planning

Report tracks changes in accessibility by automobile

In a new report from the Access to Destinations Study, researchers David Levinson, Bernadette Marion, and Michael Iacono of the Department of Civil Engineering describe changes in automobile-based accessibility throughout the Minneapolis-Saint Paul metropolitan region from 1995 to 2005.

Access to Destinations takes a new approach to understanding how people use the transportation system, and how transportation and land use interact. The interdisciplinary research and outreach effort  is coordinated by the Center for Transportation Studies, with support from sponsors  including  the Minnesota Department of Transportation, Hennepin County, the Metropolitan Council, and the McKnight Foundation.

Rather than measuring congestion, the Access to Destinations Study focuses on the concept of accessibility: the ability of people to reach the destinations that they need to visit in order to meet their needs. By focusing on accessibility, the study aims to produce a more complete and meaningful picture of transportation and its role in our lives. Levinson, the Richard P. Braun/CTS Chair in Transportation Engineering and director of the Networks, Economics, and Urban Systems (NEXUS) research group, is a co-director of the study.

The findings of the new report are based on accessibility estimates derived, to the extent possible, from actual observations of network performance throughout the day. The researchers used these data to create a set of cumulative opportunity measures for transportation analysis zones throughout the metropolitan area for 1995, 2000, and 2005. Analysis of the changes in accessibility by location over the period of study reveals that, for the majority of locations in the region, accessibility increased between 1995 and 2005—though the increases were not uniform.

A “flattening” or convergence of levels of accessibility across locations was observed over time, with faster-growing suburban locations gaining the most in terms of employment accessibility. An effort to decompose the causes of changes in accessibility into components related to transportation network structure and land use (opportunity location) reveal that both causes make a contribution to increasing accessibility, though the effects of changes to the transportation network tend to be more location-specific.

Overall, according to the researchers, the findings demonstrate the feasibility and relevance of using accessibility as a key performance measure to describe the regional transportation system.

Access to Destinations Phase 3: Measuring Accessibility by Automobile (Mn/DOT 2010-09) is available from the Access to Destinations Study Web site, along with the other reports in the series and a variety of publications related to the study.

Intelligent Transportation Systems

Researchers featured at ITS Minnesota annual meeting

Showcasing the diversity of intelligent transportation systems (ITS) research at the University of Minnesota, a trio of researchers presented new technologies and recent research results at the ITS Minnesota 16th Annual Meeting & Information Exchange on March 9.

Professor Rajesh Rajamani (mechanical engineering) presented a new type of wireless traffic sensors, under development in his lab, that do not rely on batteries or external power sources. The sensors, based on piezoelectric technology, convert the mechanical energy of vehicles passing over them to electrical energy to power their highly efficient sensing and data-transmission systems. The new sensors offer several advantages compared to traditional pavement-embedded inductive loop detectors, including low cost (projected to be less than $100 per unit), ease of installation, and the added capability of capturing vehicle weight data. Rajamani’s traffic sensor research was highlighted in the Spring 2009 issue of the Sensor, the ITS Institute’s newsletter.

Assistant Professor Xun Yu (electrical and computer engineering, Duluth) outlined the development of an in-vehicle sensor system designed to detect driver drowsiness. Yu’s approach, based on polymer-film sensors mounted on the steering wheel, differs from much of the previous research in drowsiness detection that has relied on cameras to track the driver’s eye movements. The sensors developed by Yu operate on essentially the same principle as Rajamani’s vehicle detectors, albeit on a much smaller scale; the steering wheel sensors detect a driver’s heart rate through their palms and, after filtering out interference from external vibration and variations in grip force, track changes in heart rate that can indicate a transition from waking to sleeping.

Frank Douma, assistant director of the State and Local Policy Program at the Hubert H. Humphrey Institute of Public Affairs, presented recent findings from his investigation of the legal and policy implications of new ITS technology deployments. Because there is no single, comprehensive federal law governing privacy, and because state law can go beyond existing federal regulations to restrict the collection of data, the deployment of automated traffic enforcement systems and data-collection devices is subject to a variety of disparate state laws.

Both Rajamani and Douma are CTS Scholars, a group of leading researchers and educators at the University of Minnesota who work closely with CTS to identify new research opportunities and develop new initiatives for transportation education.

Jan Lucke, CTS manager of research administration, moderated the research session. Linda Preisen, incoming ITS Minnesota chapter president and CTS director of research administration, gave closing remarks.

The event was sponsored by ITS Minnesota in cooperation with CTS and was facilitated by the College of Continuing Education at the University of Minnesota.

CTS is a founding member of ITS Minnesota, the state chapter of the Intelligent Transportation Society of America—a national organization that coordinates the development and deployment of ITS in the United States.

Transportation and the Environment

Engineers probe murky secrets of swirling stormwater

The Saint Anthony Falls Laboratory (SAFL) at the University of Minnesota recently tested hydrodynamic separators to understand how well they perform under a variety of conditions and to determine optimal maintenance schedules. Hydrodynamic separators, which are installed within storm drains, are widely used to remove suspended sediments and floatables from stormwater in urban areas where above-ground space for stormwater management is limited.

Civil engineering graduate students David A. Saddoris and Kurtis D. McIntire joined associate adjunct professor Omid Mohseni and professor John Gulliver on the project, which was sponsored by the Minnesota Department of Transportation and the Minnesota Local Road Research Board.

When determining how large a hydrodynamic separator to install in a particular location, engineers often base their decisions on the volume of runoff produced during relatively frequent storm events, such as a two-year storms. During larger, less-frequent storms, however, the volume of water passing through the separator may greatly exceed design specifications, resulting in previously captured sediments being washed out of the device. The SAFL study aimed to develop methods to determine washout rates under a variety of flow conditions, and to develop maintenance schedules for hydrodynamic separators.

The researchers developed several testing procedures in the laboratory; in all of these, the sump of the tested device was preloaded with commercially available sediments with a relatively narrow particle size distribution, and the device was then subjected to a high flow rate for an extended period of time. Either the volume or the weight of sediments in the sump before and after each test was measured, where the difference between the two during the test period was determined to be the washout rate.

In order to further examine the dynamics of water movement inside hydrodynamic separators, the researchers built and tested two hypothetical scale models of swirl-flow type separators. The results of these tests showed that, in general, swirl-flow hydrodynamic separators are prone to high washout rates due to high flow velocities inside of these devices. In order to reduce the washout rate, the researchers recommend designing devices to either protect the sedimentary deposits or dissipate the energy of the flow.

Hydrodynamic Separator Sediment Retention Testing (Mn/DOT 2010-10) is available from the CTS Web site.

Transit, Bicyling, and Walking

TCRP research publications available online

The federal Transit Cooperative Research Program (TCRP), administered by the Transportation Research Board, provides practical transit research to address technical and operational issues. TCRP emphasizes putting research results into the hands of organizations and individuals that can use them to solve problems.

Recent TCRP publications include:

• Preventive Maintenance Intervals for Transit Buses (TCRP Synthesis 81)
• Guide to Federal Buy America Requirements—2009 Supplement (TCRP Legal Research Results Digest 31)
• Legal Handbook for the New Starts Process (TCRP Legal Research Digest 30)

Transportation Safety

Seminar surveys interagency cooperation in traffic incident management, methods and metrics

At a CTS Research seminar February 25, 2010, Robert Feyen presented an overview of methods and metrics that can be used to evaluate and improve interagency cooperation during traffic incident management. A streaming webcast of the seminar is available online.

Feyen is the director of the Master of Environmental Health and Safety program and an assistant professor in the Department of Mechanical and Industrial Engineering  at the University of Minnesota Duluth. This is one of his first transportation systems projects, conducted in conjunction with Regional Transportation Management Center (RTMC).

Traffic incident management (TIM), Feyen explained, is a coordinated process to detect, respond to, and remove traffic incidents, restoring traffic capacity and ensuring motorist and responder safety. He worked with RTMC to study how emergency services such as police, highway patrol, fire departments, emergency medical services, towing, and media respond to crashes and other incidents in the traffic system. Each group has their own goals during an incident, which can create conflicting objectives. The apparent lack of a uniform goal between TIM agencies can lead to longer response and clearance times, which in turn increases the likelihood of secondary incidents, injuries, and loss of life (responders are particularly vulnerable).

In this seminar, Feyen defined a traffic incident as a non-recurring event that reduces roadway capacity or creates an abnormal increase in demand, and noted that traffic incidents come with a high cost: in terms of money and time, $78 billion and 4.2 billion hours of productivity are lost annually due to delays. Air quality is also affected by excess exhaust and emissions; fuel lost during these delays is equivalent to 58 fully loaded supertankers.

Feyen’s research identified three objectives for interagency cooperation: 1) Identify a common goal (namely, minimizing time dealing with traffic-related incident while maintaining safety); 2) Identify quantitative performance metrics to evaluate TIM performance; and 3) Analyze these metrics to improve interagency coordination and TIM performance.

Using external benchmarking, Feyen surveyed TIM personnel in seven urban areas across the country with similarities to the Minneapolis-Saint Paul metropolitan area: Albany, Austin, Cincinnati, Kansas City, Salt Lake City, San Diego, and Seattle. While no consistent proactive measures were identified, agencies were generally in agreement regarding the need for proactive collaboration, aggressive investigation of long incident durations (such as incidents exceeding 90 minutes), clear understanding and communication of performance with respect to common TIM goals, and agreement on the typical measures used (such as response, clearance, and overall incident duration times). In particular, TIM agencies reported the least success in interagency coordination and consistency in quantitative evaluation of timing metrics—for example, what some agencies call “dispatch time,” others refer to as “response time.”

Feyen discussed four process-based methods as a means of measuring data consistently: 1) Data collection and analysis; 2) Internal benchmarking; 3) Process charting; and 4) Incident simulation. Each of these methods offers potential benefits to transportation and emergency management agencies, though Feyen noted that they all entail challenges in collecting and processing data.

Watch the webcast.

Upcoming Events

May 3-5
ITS America 20th Meeting and Exposition, Houston, TX

May 5-7
Mn/DOT Advanced Flexibility in Design Workshop, Mn/DOT Training and Conference Center, 1900 West County Road I, Shoreview, Minnesota. For more information, contact Norm Plasch at norm.plasch@state.mn.us or 651-336-3301.

May 19-21
TRB 'Transportation Finance: Forging a Sustainable Future - Now!', The Roosevelt New Orleans, New Orleans

June 27-29
Annual Meeting of the Institute of Transportation Engineers Midwestern District,  Minneapolis, MN

July 11-14
TRB Joint Summer Meeting: Planning and Performance Measurement for all Modes, Minneapolis, MN

July 22-23
4th International Symposium on Transportation Network Reliability, McNamara Alumni Center, University of Minnesota