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Current Issue | Previous Issues | Subscribe April 2007 - Vol. 5, No. 4

Policy & Planning

Seminar highlights research on well-designed transportation projects

The benefits of well-designed transportation facilities were at the top of the agenda February 13, at a combined meeting of two CTS Research Councils. The Council on Transportation and the Economy and the Council on Transportation Planning and the Environment met jointly to hear presentations by University researchers involved in ongoing research funded by the American Institute of Architects and coordinated by CTS.

“The Role of Well-Designed Transportation Projects Enhancing Communities” is an interdisciplinary study sponsored by the American Institute of Architects through a grant from the Federal Highway Administration. The study explores three areas: economic development; public health, safety, and the environment; and aesthetic, architectural, and cultural qualities and community planning.

The focus of the research effort, said CTS director Robert Johns, is “not to study how to integrate good design into transportation projects, but to study the benefits of doing it.”

Lance Neckar of the Department of Landscape Architecture provided an overview of the research study outlined the component dealing with transit-oriented development. Neckar is working with a team of researchers examining a number of project settings across the country.

This research is particularly innovative, he said, in that it “requires the researchers to invent a research approach—to figure out what the right metrics are in order to measure these benefits.”

John Adams and Barbara VanDrasek of the Department of Geography are interested in the economic benefits of good design—specifically, how location and context influence the economic benefits of new transportation projects.

“Just because a shiny new project appears does not mean it will have a positive impact,” said Adams. By developing new analytical frameworks that take into account both spatial and temporal factors, the researchers are attempting to understand why some projects create positive effects while others fail to deliver the economic benefits their backers expected.

John Carmody and Virajita Singh of the Center for Sustainable Building Research are focusing their efforts on issues related to the natural environment and the psychological and physical health of human beings. Gary Davis of the Department of Civil Engineering is contributing to this effort, concentrating on public safety impacts such as reducing traffic deaths.

“This is a time of revolution in the way we design buildings and in the field of architecture,” Carmody asserted, citing rapid changes in environmentally friendly and health-conscious building practices over the past ten years.

Although architecture and civil engineering have historically focused on the scale of individual buildings or development projects, Carmody and Singh emphasized the importance of looking across scales and tying together the building, the neighborhood, and the surrounding infrastructure.

Other research projects in this study are being led by Metropolitan Design Center director Ann Forsyth and by Carissa Schively of the Hubert H. Humphrey Institute of Public Affairs.

As commute times increase, research asks why

Commute times across Minnesota, Iowa, and Wisconsin increased by an average of several minutes over the course of the 1990s. Although a few more minutes in the car may not sound all that troublesome, the fact that the increases were measured in every county of the three states—and that these increases overtook historic trends—begs the question of what could be causing widespread increases in commute times.

According to researcher Gary Barnes, many of the “usual suspects” like traffic congestion and urban sprawl appear to have solid alibis for the decade in question. Barnes, a research associate at the University of Minnesota’s Hubert H. Humphrey Institute of Public Affairs, analyzed data on transportation patterns, land use, and economic factors in order to better understand what factors really determine how long it takes to get to and from work. The study was sponsored by the Minnesota Department of Transportation.

Historically, while commute times did increase before the 1990s, the rate of increase was significantly lower. Since 2000, data indicate that the rate of increase has returned to the pre-1990 pace. The “bulge” in commute times during the 1990s was roughly two and a half times the historical average.

Urban sprawl is often cited as a contributor to longer commute times. Barnes found, however, that changes in the geographic distribution of homes and jobs would have added only about 20 seconds to average commute times overall, so sprawl appears not to have been a major contributor to longer commute times. In rural areas, similarly, Barnes found that measured changes in land use and economic factors did not correlate strongly with changes in commute durations.

In the Twin Cities area, while land use changes may not have played a major role in lengthening commute times, the research determined that commute distances did increase; at the same time, average commute speeds decreased. This combination of factors suggests that urban residents chose to travel longer distances to work during the 1990s. This pattern of behavior may be related to increases in average wages, since people who earn more often choose to travel longer distances. Other factors that may have influenced commute times included a strong job market and very low gas prices relative to personal income.

Barnes’ findings are presented in a research report, Reasons for Recent Large Increases in Commute Durations (Mn/DOT 2007-02), available from the CTS Web site.

Transit & Alternative Modes

Hennepin County, U of M form transitway research program

As traffic congestion continues to worsen, transitways—corridors dedicated exclusively to buses or rail—are receiving growing interest. Much is unknown, however, about the economic, travel, and community impacts of transitway corridors in the Twin Cities metropolitan area.

The Transitway Impacts Research Program is intended to answer those questions. Formed last fall, the program is an initiative of the Hennepin County–University Partnership, and is supported by CTS and the Humphrey Institute’s State and Local Policy Program (SLPP). Initial funding is being provided by Hennepin County and the University’s Consortium for Metropolitan Studies.

Members of several University of Minnesota departments and centers participate in the program management team: Tom Scott (Center for Urban and Regional Affairs), John Adams (Metropolitan Studies Consortium), Lee Munnich (SLPP), Kathie Doty (Hennepin-University Partnership), and Robert Johns (CTS).

“The research program will shine a spotlight on transitway issues rather than steering the public debate, which is an appropriate role for the University,” said Johns.

The program will create knowledge and information needed to improve planning and decision making for transitway expansion. It will also help educate legislators, agency leaders and staff, and the University research community about current issues, innovations, and trends pertaining to transitways. In addition, the program can serve as a national model of interjurisdictional collaboration between government and academia for transitway research, education, and outreach.

The program grew out of a previous collaboration between Hennepin County and the University of Minnesota, which resulted in the completion of the Inventory of Data and Research on the Economic and Community Impacts of the Hiawatha LRT (1.4 MB PDF).

The Transitway Impacts Research Program will be featured at the CTS Transportation Research Conference. A conference session will include preliminary results of the before-and-after study for the Hiawatha light-rail transit line as well as news of transitway planning in Hennepin and Ramsey Counties.

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:

• Use of Guard/Girder/Restraining Rail (TCRP Research Results Digest 82)

Intelligent Transportation Systems

“Tags” in the road promise smarter vehicle location systems

What makes intelligent vehicles smart? The ability of a vehicle to “know” where it is at any given moment is one measure of intelligence that enables a host of intelligent transportation systems applications, from basic navigation assistance to automatic collision warning.

Today, the Global Positioning System (GPS), a network of satellites broadcasting navigation signals from geosynchronous orbits, is the backbone of many systems that require constant navigational information. University of Minnesota researchers have developed several advanced driver-assistive systems using GPS technology. But by its very nature, GPS suffers from limitations that keep it from being the ideal single solution to the location needs of intelligent vehicles.

Intelligent Vehicles Laboratory director Craig Shankwitz and graduate student Matthew Bevilacqua are among the researchers developing new technologies that will augment GPS, in order to meet the need for more robust location information in tomorrow’s intelligent vehicles. Recently the researchers have examined the potential use of a technology commonly seen outside of transportation—RFID, or radio frequency identification. The research was supported by the ITS Institute.

Most people today are familiar with RFID through the use of small RFID tags as theft-deterrent devices that must be removed or deactivated before leaving a store. But the technology actually has a long history in transportation: as early as 1973, a prototype system was developed with possible applications including automatic vehicle identification and toll collection.

A passive RFID system works by encoding information on small, unpowered electronic circuits that can be embedded in tags or capsules. When these circuits are close to a specially designed radio transmitter, the power from the transmitter produces a signal from the RFID circuit; these signals can transmit a small amount of unique information that has been encoded within them, such as an identification code. In the system developed by the Minnesota researchers, a transmitter/receiver unit is mounted on the automobile's front bumper; this unit registers proximity to tags embedded in the roadway.

Why use RFID at all? Using satellites gives GPS great advantages, like the ability to cover the entire surface of the planet. But in order to determine a position accurately, GPS receivers require direct line-of-sight signal paths to at least three GPS satellites at all times. For a ship cruising on the open ocean, this is usually no problem, but for a bus navigating urban freeways, many obstacles can interfere with the GPS signal—even passing under a bridge can disrupt the signal, forcing the receiver to spend crucial seconds re-acquiring the satellites in order to compute a new position. Other factors, such as confusing signal reflections from the sides of tall buildings in “urban canyons,” also impede the effectiveness of GPS.

To demonstrate the possible use of RFID-based positioning, the IV Lab researchers implemented a basic collision-avoidance system using the technology. The IV Lab system combines RFID positioning with inter-vehicle communication using the emerging Digital Short-Range Communications (DSRC) standard now under development by a consortium of vehicle manufacturers, researchers, and federal transportation agencies.

Findings from the experimental system are now being applied to the development of a system to assist bus drivers in maintaining position in a narrow shoulder lane when GPS signals are unavailable.

Although the development of RFID-based vehicle positioning systems offers great potential to enhance current positioning technologies, the researchers note that today’s commercial RFID systems may not be adequate for the development of robust solutions. Custom transportation-focused RFID systems could be developed to meet this need; however, the rapid advance of RFID technology may soon make commercially available systems a viable tool for ITS applications.

Safety & Security

Research examines left-turn safety risks

Collisions involving left-turning vehicles at high-speed intersections (where approach speeds exceed 40 mph) are a serious safety concern in many areas—including rural highways. Researcher Gary Davis of the University of Minnesota’s civil engineering department has investigated the safety effects of different types of left-turn traffic signal controls in an effort to understand their safety implications. His findings are now available in a new research report.

Davis analyzed data from intersections across the Minneapolis-St. Paul area in order to develop “crash modification factors”—estimates of the effects of implementing different left-turn controls at each intersection. The Minnesota Department of Transportation supported this research through the Guidestar program.

Confirming the results of other studies, Davis found that changing the type of left-turn control at an intersection changed the types of crashes that could be expected at that intersection. In some cases, an increase in right-angle crashes was accompanied by an increase in the expected number of rear-end collisions.

Davis’s report also includes a description of a simple simulation model for left-turn cross-path crashes, combining a probabilistic model of gap acceptance with a standard braking model for the behavior of oncoming drivers. The model, Davis says, generates collision rates similar to those reported in other research studies of intersection crashes. 

This research is related to the Intersection Decision Support research carried out by the ITS Institute, in which researchers built up a detailed picture of driver behavior at rural through-stop highway intersections. This knowledge is now being used in the design of appropriate countermeasures to reduce intersection collisions.

Safety Effects of Left-Turn Phasing Schemes at High-Speed Intersections (Mn/DOT 2007-03) is available from the CTS Web site.

Transportation Infrastructure

Recycled asphalt pavement makes the (sub) grade

Every aluminum beverage can contains recycled metal, but what happens when you try to recycle a road? Full-depth reclamation is a technique for doing just that: the existing asphalt pavement section and a portion of the underlying aggregate subgrade are uniformly reclaimed and blended to produce a new base course. But how does the resulting base course stack up against traditional materials?

Civil engineering professor Joseph Labuz and graduate student Woosung Kim tested material samples containing various ratios of recycled aggregate pavement (RAP) and aggregate base material. Their objective was to determine the strength and deformation characteristics of these materials.

Potential advantages of full-depth recycling include conserving aggregate material and reducing the cost of reconstruction materials, but performance data have not yet been gathered on a large scale. Labuz and Kim’s research focused on laboratory testing, using a resilient modulus testing protocol specified by the National Cooperative Highway Research Program (NCHRP). The researchers also conducted cyclic triaxial testing to evaluate deformation characteristics.

The researchers found that, when properly compacted, the resilient modulus and strength of mixtures containing various percentages of recycled material were comparable to the measured characteristics of pure aggregate materials. These results should contribute to the growing interest in full-depth recycling for roadway reconstruction—especially in cases where the availability of suitable fresh aggregate materials is limited.

Resilient Modulus and Strength of Base Course with Recycled Bituminous Material (Mn/DOT 2007-05) is available from the CTS Web site.

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.

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