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Current Issue | Previous Issues | Subscribe February 2007 - Vol. 5 No. 2

Policy & Planning

Reports examine behaviors and needs of transportation disadvantaged

Reliance on private automobiles and low-density development create mobility challenges for the elderly and the developmentally disabled. Although some in these populations can meet their transportation needs with the existing system, others cannot.

A recent study by Associate Professor David Levinson and research fellow Rania Wasfi, both with the University of Minnesota’s civil engineering department, sought to learn about the transportation needs of members in these specific population groups. The research was supported by Hennepin County, which includes the city of Minneapolis and inner suburbs.

To learn about the elderly, the researchers partnered with area senior centers and service providers to distribute surveys to approximately 8,000 residents of Hennepin County aged 60 to 90 years old. Besides gathering demographic information about the participants, the survey also gauged their attitudes about traveling and asked them to complete a travel diary. 

Responses to a survey of seniors showed that around 77 percent used the automobile as their primary means of travel for shopping. Independence, however, declines steadily with age. Those seniors who were not fully independent were unable to make all the trips they needed or wanted to make (or both) on a given day.

Public transit was the second most-used mode of transportation. Seniors in the sample showed a willingness to use public transit, yet often did not because of a lack of service near their homes or destinations. Although some seniors have a difficult time using public transit (for example, getting up the stairs), a bigger concern was fear of being a victim of a crime; more than half were also concerned about waiting for transit or the length of time of the trip.

In the study exploring the transportation needs of adults with developmental disabilities, the researchers conducted a survey similar to that used for the senior population in partnership with community agencies.  Although many of those surveyed did not live independently, many consider themselves independent travelers, and 70 percent reported that the mode of transportation they used was their choice.     

About half of the trips these adults took were work-related, with recreational and shopping trips cited as well. Walking, public transit, and dial-a-ride were listed as the primary modes of transportation the participants used to meet their transportation needs. Public transit, however, poses challenges for this population; many have difficulty standing, reading transit schedules, or understanding announcements. Many were also concerned with becoming a victim of crime. Fewer than 30 percent ever use public transit services.

The final reports for this research, The Transportation Needs of Seniors and The Transportation Needs of People with Developmental Disabilities, have been published by the Center for Transportation Studies. Copies may be ordered or downloaded from the CTS Web site.

Intelligent Transportation Systems

The less-than-perfect driver: a new model of car-following behavior

Imagine a world where drivers don't make mistakes. Everyone pays perfect attention to the movements of cars around them, and no one takes unnecessary risks like following too closely behind another vehicle. This utopian world really exists—at least in research labs where computer simulations model the movements of virtual vehicles.

But like all utopias, these neat and tidy models are not as perfect as they appear. For researchers like civil engineering professor Panos Michalopoulos and traffic researcher John Hourdos, who are trying to understand how and why vehicle crashes happen and how crashes affect traffic, the behavior of virtual vehicles is frustratingly limited. Joined by civil engineering professor Gary Davis and graduate student Wuping Xin, the researchers set out to develop a more accurate and complete model of car-following behavior.

Understanding the causes and dynamics of vehicle crashes is a goal shared by many ITS researchers at the University of Minnesota, and the search for answers has spurred the development of new tools and techniques. In the case of the Minnesota researchers, the need for more realistic simulations led them to propose a novel model of car-following behavior—one that will give researchers a new insight into the quick and deadly world of traffic collisions. The research was funded by the Intelligent Transportation Systems Institute.

Under the direction of Micholopoulos and Hourdos, Wuping Xin took on the challenge of implementing the research team's conceptual model of driver behavior and vehicle response in the form of computer software that can be interfaced with traffic simulation systems. The model Xin developed is based on a highly flexible conceptual framework that improves its ability to simulate complex interactions between driver perception and response.

The framework divides the driving task into two major components—the external world and the driver-vehicle unit (DVU). Rather than conceiving of the driver and vehicle as a single entity, the DVU comprises three subsystems that work together to govern the movement of the virtual vehicle. A DVU acquires information about the external world through sampling, and compares this information to a target specification or reference input.

While the development of the new car-following model was motivated by the research needs of Michalopoulos and Hourdos, future researchers may benefit as well. Implementing the model in such a way that it can interface with standard simulation packages used by traffic researchers makes it a powerful general tool for examining collisions.

Development of the model is ongoing, as the research team plans to improve its accuracy by adding new features such as the ability of a DVU to consider the movements of multiple DVUs ahead of it, if they are visible. This addition would bring DVU decision-making behavior more in line with that of human drivers, who frequently respond to braking or acceleration by cars further ahead in the lane.

Excerpted from the Winter 2006 ITS Institute Sensor newsletter.

Safety & Security

The Center for Excellence in Rural Safety launches Web site

The Center for Excellence in Rural Safety, led by Lee Munnich of the Humphrey Institute of Public Affairs, launched its Web site, www.ruralsafety.umn.edu, featuring detailed information on the organization and its activities.

The new Web site will play a key role in communicating the results of national rural transportation safety research projects to policymakers and the public. The Center’s research activities explore policy, behavior, and technology innovations through projects addressing safety-conscious planning, ITS and rural emergency response, integrated policy approaches, and related human factors, societal trends, and stakeholder needs analysis.

The Center for Excellence in Rural Safety, established by the 2005 federal transportation act, is a joint program between the University of Minnesota's Hubert H. Humphrey Institute of Public Affairs and the Center for Transportation Studies, and sponsored by the Federal Highway Administration, to facilitate citizen-centered research, training, and outreach activities related to rural transportation safety.

SECTTRA adds transportation security researcher

Researcher Vassilios Morellas has joined the University of Minnesota's Security in Transportation Technology Research and Applications (SECTTRA) program, bringing additional expertise in vision-based security systems. He joins a diverse group of researchers drawn from the fields of engineering and computer science and led by professor Nikolaos Papanikolopoulos of the Department of Computer Science and Engineering (CSE).

Before joining the University of Minnesota, Morellas was a senior principal research scientist at Honeywell Corporation's Situation Assessment Technologies Laboratory, where he led research in high-end computerized video surveillance systems and statistical image processing techniques. He now holds the position of program director in CSE.

In 2003, while at Honeywell, Morellas presented his work at an special research seminar, “Advanced Technology for Homeland Security Applications,” sponsored by the Intelligent Transportation Systems Institute. Coverage and a video recording of the seminar is available online at the ITS Institute Web site.

SECTTRA, a joint program of CSE and CTS, collaborates with the ITS Institute and the Safety Security Rescue Research Center (SSR-RC), a cooperative interuniversity research center that coordinates research with a spectrum of large general homeland security contractors, companies with a specific market share, and start-up companies with key enabling technologies.

More information on SECTTRA is available on the program's Web site, www.secttra.umn.edu.

Transportation Infrastructure

New techniques shed light on load limits for horizontally curved steel girder bridges

In today’s increasingly dense urban areas, horizontally curved steel bridges are an essential part of many traffic interchanges. Their graceful curves ensure a free flow of traffic, but their complex geometry has made it difficult for engineers to understand their response traffic loads.

To improve engineers’ ability to determine accurate load ratings for curved steel bridges, Professor Jerome Hajjar and graduate student Dan Krzmarzick carried out a research study incorporating load testing with heavy vehicles and the development of sophisticated computer models of bridge behavior. Their work was funded by the Minnesota Department of Transportation.

Currently, techniques for determining the load rating of curved steel bridges rely on approximate methods of analysis derived from the methods used for individual straight girders. Altering the straight-girder models in an attempt to account for the effects of curvature yields an estimate of load capacity that, combined with conservative assumptions about the behavior of the structure under load, guide the design of the curved bridge.

Hajjar and Krzmarzik carried out both static and dynamic load tests on a five-span steel I-girder bridge using heavily loaded quad-axle dump trucks. Measuring the stresses placed on the bridge by a wide variety of loading configurations provided the researchers with valuable data on the bridge’s response, which they used in developing a finite-element model of the bridge.

A software package dubbed "UMN Program," developed at the University of Minnesota, served as one of the main modeling tools in this research project. The program is designed specifically for linear elastic grillage-based finite-element modeling of curved steel I-girder bridges. The results of the study indicate that grillage analysis can provide accurate load ratings for horizontally curved steel I-beam bridges, potentially reducing the need for load testing to establish load ratings. However, they note that several situations exist in which load testing could be used to complement computational analysis.

Load Rating of Composite Steel Curved I-Girder Bridges through Load Testing with Heavy Trucks (Mn/DOT 2006-40) is available from the Minnesota Department of Transportation Web site.

Transportation & the Environment

Can dry detention ponds mitigate pollution in storm water runoff?

For transportation engineers, controlling storm water runoff from roadways and other transportation facilities is an important part of design and maintenance. Dry detention ponds are often used for temporary storage of runoff, but their use is limited because their ability to safely remove common pollutants has not been demonstrated.

University of Minnesota researchers led by John Gulliver recently evaluated dry detention ponds to find out if these ponds can help reduce pollutant levels in addition to holding excess runoff. Their results have been published in a new research report from the Minnesota Department of Transportation, which funded the study.

Dry detention ponds offer several potential advantages over wet ponds. For example, because they do not need to hold water constantly, they do not serve as breeding grounds for mosquitos, do not produce algal blooms, and are easy to clean. In some cases, portions of dry ponds can be landscaped or used for recreational activities when not filled with water. They are also typically easier and less expensive to construct than wet ponds.

The researchers began with an extensive literature review of research on the pollutant mitigation capabilities of dry detention ponds—an effort aided by the fact that many storm water management organizations have taken the initiative to evaluate the performance of their own systems. Subsequent field research focused on dry detention ponds equipped with under-drains filtered by soil or sand media, having single inflow and outflow locations. Three ponds were selected for the study, and pollutant levels entering and exiting the ponds were monitored.

The dry detention ponds under investigation showed promising results, especially in reducing total suspended solids and total phosphorus. Given the small number of ponds in the study and the high variability of data gathered, it is difficult to generalize the results of this research; however, the preliminary findings lend support to the idea that properly designed dry detention ponds may be suitable for further investigation as tools for storm water runoff control.

Water Quality Performance of Dry Detention Ponds with Under-Drains (Mn/DOT 2006-43) is available from the CTS Web site.

Transit & Alternative Modes

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:

• Smartcard Interoperability Issues for the Transit Industry (TCRP Report 115)
• Methods of Rider Communication (TCRP Synthesis 68)
• Synthesis of Information Related to Transit Problems (TCRP Research Results Digest 80)
• TCRP's Annual Report 2006 (5.6 MB PDF)

Announcements

2006 CTS Annual Report now available

“Creating opportunities for interdisciplinary collaboration within the University of Minnesota and beyond is key to our mission at the Center for Transportation Studies,” notes CTS director Bob Johns in the 2006 CTS Annual Report.

Now available in both printed and electronic formats, the 2006 Annual Report is packed with in-depth coverage of the transportation-related research projects, educational initiatives, and outreach activities that made 2006 a successful year for the Center.

The report highlights new research initiatives begun in 2006, including the launch of the Security in Transportation Technology Research and Applications (SECTTRA) Program and a large study of the effects of well-designed transportation projects on communities, sponsored by the American Institute of Architects.

Visit the Publications area of the CTS Web site to download the 2006 Annual Report as a PDF document, or to request a printed copy.

Upcoming Events

Here are selected events related to transportation research. Visit the CTS Web site, www.cts.umn.edu/events, for more comprehensive event information. You may also subscribe to e-mail event announcements using our subscription form.

February 28
Access to Destinations Workshop, Minneapolis. Contact Stephanie Malinoff, 612-624-8398, malinoff@umn.edu. More

March 1, 2007
Transportation Career Expo, Minneapolis. Contact Mindy Carlson, 612-625-1813, carlson@cts.umn.edu. More

May 1-2, 2007
18th Annual CTS Transportation Research Conference, RiverCentre, St. Paul. Contact Electra Sylva, 612-624-3708, conferences5@cce.umn.edu. More