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Current Issue | Previous Issues | Subscribe February 2003 - Vol. 4 No. 8

Policy & Planning

U economist says Minnesota receives high rate of return on transportation investment

There's no shortage of debate about the economic benefits of transportation spending in Minnesota, especially during especially during this time of tight budget constraints. Recent research by the University of Minnesota may help shed light on this complex issue.

One of the chapters in the 2002 Economic Report to the Governor, a report prepared by the Minnesota Economic Resource Group, declares that Minnesota receives a high rate of return on its investment in roadway capital. The research for the chapter was conducted by David Anderson, Gerard McCullough, and James West of the Department of Applied Economics and sponsored by Mn/DOT.

In their chapter, Anderson, McCullough, and West examine the extent to which investments in roadway capital--that is, all state, federal, or local streets and highways – contribute to productivity increases. Their main finding is that "a 1.0 percent increase in the amount of roadway capital will lead to a significant increase in the value of goods and services produced in the state," a finding consistent with productivity research in other areas of the country, they say.

The researchers warn, however, that because of data limitations and caveats that apply to this and similar research, the results are not "final or definitive conclusions" but rather offer a basis for discussion, providing evidence that roadway capital contributes significantly to productivity growth in Minnesota. The authors also note that their results do not mean that all new investment in roadways will lead to productivity gains. "Returns to particular projects will differ, and only by investing in the best projects available can the high return be maintained," they write.

The Economic Resource Group is an organization of state research managers formed in 1985 for the purpose of improving economic analysis through interagency cooperation. The 2002 report, the tenth in a series of reports on issues of importance to the Minnesota economy, is the first to include a chapter on the economic contribution of transportation. Tom Stinson, state economist and associate professor in Applied Economics, is a member of the group and wrote the report's introduction. The 2002 report is available at www.minnstats.state.mn.us/2002ERGreport.pdf

"Genetic code of sprawl" encourages suburban-style development, researcher says

A "genetic code of sprawl" is embedded into the designs, planning practices, and policies that encourage conventional, suburban-style development, says Professor Lance Neckar of the Department of Landscape Architecture. He discusses this genetic code in a recently published report, Urban Design and the Environment: Highway 61/Red Rock Corridor. This genetic code, Neckar explains, is embedded into the designs, planning practices, and policies that encourage conventional, suburban-style development and is embedded deeply in the culture of the Twin Cities region.

The report, which is the thirteenth in a series of the Transportation and Regional Growth (TRG) Study, is a combination of two studies (Task 1 and Task 2 and 3) on the Highway 61/Red Rock Commuter Rail Corridor; Red Rock commuter service is proposed to serve communities from Hastings, Minnesota to Minneapolis, with a principal station in St. Paul. The Task 1 portion describes the baseline conditions related to subdivision-scaled growth in the corridor, with particular concentration on Cottage Grove, one of the station sites, and considers current plans for the downtown St. Paul Union Depot.

Task 1 findings illustrate there is a lack of design, planning, and policy integration across transportation, land use, and urban and suburban design in the corridor and the communities served by it. According to Neckar, this lack of integration produces, paradoxically, a homogeneous pattern of dispersed growth or sprawl. This report offers designs for new, alternative patterns of regional growth, both urban and suburban, in broad corridors served by commuter rail service and also demonstrates the designs' effects on two principal problems of sprawl as it relates to the street and highway network: the unstratified, single-mode transportation infrastructure designed for peak demand, and the degradation of environmental resources, especially water.

The Task 2 and 3 study specifically focuses on issues relating to the relationship between transportation and the environment. Also discussed is the need for design and institutional integration of objectives across investments in transit services at a regional scale (such as commuter rail), public space (such as streets and parks), and the long-term value of developed private space, especially in suburbia. Several innovative institutional propositions are raised in the final chapter of this report, all suggestive of greater cooperation across units of government in decisions about infrastructure provision in concert with land use, zoning, and urban design decisions.

This report goes on to explain the critical design and institutional variables that might alter this genetic code of sprawl which has caused exponential growth in vehicle miles traveled (VMT) and has threatened surface and groundwater quality and groundwater quantity. The study findings demonstrate that VMT and water quality could be positively affected by alternative subdivision designs. The designs illustrated in the Task 2/3 study investigate forms of subdivisions different from the current baseline designs shown in Task 1 and pay particular attention to integrating commuter rail, street design and networks, land use, station area design, and hydrological infrastructure. For a copy of the report, call CTS at 612-626-1077.

Researchers examine road financing alternatives

The way roads are currently funded is for the most part hidden from users and unrelated to travel. A better way to fund roads would be through new tax policies based on travel and road use, say two University researchers in Road Finance Alternatives: An Analysis of Metro-Area Road Taxes. This recently published report by Barry Ryan and Thomas Stinson of the Department of Applied Economics is the ninth in a series of the Transportation and Regional Growth (TRG) Study.

The report describes how the current tax system uses both fixed fee mechanisms, like the vehicle registration tax, and taxes that vary with system use, like the motor fuels tax, to fund state and local roads. Other important sources of road revenues-property taxes, income, and sales taxes-are hidden from the traveler's perspective. Of all the revenue sources, 71 percent are from fixed or hidden taxes and are unrelated to travel behavior.

The way roads are paid for affects household budgets and creates location incentives, say the authors. To illustrate, they model the budget impacts for a set of representative households, identifying the tax cost from an increasingly longer work commute by moving the households further and further from the central cities. They also explore two alternative road tax policies.

Current tax policy tends to penalize households that travel less and households with lower incomes. Alternatives that are more reliant on variable pricing mechanisms could actually save some households money while encouraging better fuel economy, less pollution, and alternative modes of travel, Ryan and Stinson say.

In addition, while many factors influence housing location decisions, road tax policy can affect development at the urban/rural fringe. Under the proper conditions, more reliance on variable pricing tax policy may slow conversion of the region's farmland to non-farm use.

Giving road users more feedback about incremental travel costs would improve the use of state and local roads. Because variable tax mechanisms send road users a clearer price signal about the true cost of their travel, alternative road taxes, like a vehicle mileage tax or congestion fee, could lead to better travel decisions by factoring weight, distance, or time into the tax price. The authors caution that concerns for improving system efficiency, however, must be balanced with tax fairness and administrative ease.

Ryan and Stinson maintain that policy reforms are needed if road tax revenues are to keep pace over the next 25 years with the rising cost of building and maintaining roads. Between now and 2025, without changing current law, vehicle registration taxes and motor fuel taxes will grow more slowly than the costs of road construction. Motor vehicle sales taxes, on the other hand, will grow much more quickly. A revenue shortfall in these three taxes would lead to additional pressure to pay for roads with property taxes and the state general fund, they say.

As a result of their research, Ryan and Stinson recommend broad public discussion of tax policy choices and their potential economic and social consequences, which could improve understanding of and support for tax reform.

To read or download a copy of the full report, visit the TRG Publications Page or call CTS at 612-626-1077.

Intelligent Transportation Systems

University's "intelligent vehicles" to be featured at ITS America meeting

Participants at the Intelligent Transportation Society of America's 13th Annual Meeting and Exposition will have a chance to ride several "intelligent vehicles" specially equipped with technologies developed and integrated at the University. The outing will be one of the technical tours offered with the national meeting, to be held this year in Minneapolis May 19–22.

The vehicles—including the SAFEPLOW and the TechnoBus—are testbeds used by researchers in the Intelligent Vehicles (IV) Laboratory of the Intelligent Transportation Systems (ITS) Institute at CTS. The IV Laboratory's research is unique in that it uses differential global positioning systems (DGPS) and does not require hardware in the roadway surface. What's more, the technologies are transferable between various transportation modes and work in all low-visibility situations, including snow, fog, smoke, heavy rain, and darkness.

The development and integration of these technologies is the result of a longstanding partnership between the ITS Institute, directed by Professor Max Donath, and the Minnesota Department of Transportation (Mn/DOT). More recent partners include the Federal Highway Administration, the Federal Transit Administration, the Minnesota State Patrol, and a number of Minnesota counties' public works departments.

Led by IV program director Craig Shankwitz, researchers have developed and tested an array of innovative technologies, including centimeter-level DGPS linked with high-accuracy geo-spatial databases for vehicle navigation, guidance, and control, as well as radar and emerging range-sensing technologies combined with head-up displays (HUD's) for collision avoidance. For more about this research, including the SAFEPLOW and the multiyear Intelligent Vehicles Initiative, please see www.its.umn.edu/research/ivifieldtest/index.html.

In the TechnoBus project, researchers are working to adapt their previous findings to bus operations, particularly for narrow bus rapid-transit (BRT) lanes in the Twin Cities metro area. The TechnoBus project is a partnership of the University, Metro Transit (the Twin Cities transit system), and the Federal Transit Administration. For more about the TechnoBus and BRT research, please see www.its.umn.edu/research/brt/index.html.

ITS America participants will catch the TechnoBus in downtown Minneapolis for a trip to the Minnesota State Fairgrounds and back, during which the driver will demonstrate the automated steering and virtual rumble strip technologies. This feedback system uses DGPS and digital, lane-level road maps to determine position and orientation, and then applies steering-wheel torque feedback, felt by the driver's hands, to "correct" steering and help the driver stay in the lane. The system also vibrates the driver's seat on one side or the other when the vehicle leaves the lane.

At the fairgrounds, the SAFEPLOW and a State Patrol squad car will be part of the technology display. Participants will observe and learn how integrated head-up displays provide drivers of emergency and maintenance vehicles with "roadway" vision during snowstorms and other low-visibility conditions. The custom-designed HUD allows drivers to "see" the road via projected images from a high-accuracy digital road map. Fixed roadside features are also projected on the HUD, as are radar-identified roadway obstacles.

For more information about the IV Lab and its research, please see www.its.umn.edu/labs/ivilab.html.

For more about the ITS America meeting, themed "ITS: Real World, Real Results," see www.itsa.org/annualmeeting.html.

Using machine vision to improve intersection safety

Managing Suburban Intersections through Sensing, a new research report by Harini Veeraraghavan, Osama Masoud, and Nikolaos P. Papanikolopoulos of the University of Minnesota Artificial Intelligence, Robotics, and Vision Laboratory, details the development of a low-cost experimental system to track vehicles and pedestrians using video cameras. Tracking vehicles and pedestrians together will give future intelligent systems the ability to detect hazardous situations and provide necessary warnings to prevent common intersection-related traffic accidents. The full report is available on the CTS Web site at www.cts.umn.edu/pdf/CTS_02-07.pdf.

Ramp meters on trial

Ramp meters in the Twin Cities were the subject of a test of their effectiveness, involving turning them off for eight weeks. University of Minnesota civil engineering assistant professor David Levinson presented his analysis of the results of this test as part of the fall ITS Institute seminar series.

Levinson's research analyzes the results with and without ramp metering for several representative freeways during the afternoon peak period, depending on data availability. Seven performance measures: accessibility, mobility, equity, productivity, consumer surplus, travel time variation and travel demand responses are compared.

It is found that ramp meters are particularly helpful for long trips relative to short trips. On Route 169, trips more than 3 exits in length benefit, while those 3 exits or less are hurt by ramp meters. Ramp metering, while generally beneficial to freeway segments, may not improve trip travel times (including ramp delays). Travel time variation is reduced as another benefit from ramp meters. Non-work trips and work trips do respond to ramp meters, but in different ways. The results are mixed, suggesting a more refined ramp control algorithm which explicitly considers ramp delay is in order. For more information see www.its.umn.edu/seminars/2002/fall/01Levinson.html.

Simulation system to aid in scheduling snowplows

For cities and counties in northern Minnesota, few maintenance operations are as critical – or as unpredictable – as snow removal. Martha Wilson of the University of Minnesota Duluth is working on making snowplow operations more effective by making snowplow scheduling more efficient. 

Differences in snow conditions, temperature, wind, and snowfall duration make snowplowing a challenge for plow drivers, as well as the managers who schedule and direct plows out on the roads. Around the Duluth area, for example, a weather pattern known as a "Colorado low" brings heavy, wet snow into the area, primarily in spring and fall; a wintry Alberta Clipper, on the other hand, brings dry, blowing snow. These different types of storms call for different snowplowing and de-icing techniques to keep the roads open. Add to this the fact that snowplows are owned and operated by entities in different geographic areas, including cities both large and small as well as counties, and you've got the makings of a logistical puzzle.

Snowplow schedulers tasked with keeping the roads open must also worry about reloading plows with sand and de-icing compounds, refueling, and minimizing "deadheading" that occurs when a plow is traveling over plowed roads from one area to another.

Wilson, a professor of industrial engineering, explained that her goal is to develop a decision support tool for managers that will help them deploy their plows in the way that best addresses current weather conditions and system priorities. Analytical techniques, she said, were not suitable for capturing the complexity of plow scheduling operations. Instead, she has chosen to develop a simulation and modeling system to determine optimal plowing methodologies for a range of conditions. The simulation system is designed to capture expert information that currently exists only in the heads of key personnel, such as meteorologists.

The first phase of the project is concerned with developing a user interface and simulating a single season's worth of storms. This will allow the correlation of weather conditions with snowplow routes. The end result will be a tool that helps snowplow schedulers determine the best way to deploy their plows to provide maximum mobility and safety to the driving public.

Transit & Alternative Modes

Bus Rapid Transit Lane Assist Technology Systems

Metro Transit and the University of Minnesota's ITS Institute were awarded a contract from the Federal Transit Administration (FTA) to conduct research on Bus Rapid Transit (BRT) Lane-Assist Technology Systems.  Below is more information on the status of this effort.

System Requirements Survey Draft Report

A draft report on the results of a system requirements survey, sent to approximately 95 transit and planning agencies across the United States, includes responses from more than 20 transit agencies, as well as highlights from the May 2002 BRT workshop in Minneapolis. The survey focused on five areas relative to BRT lane-assist systems: operations, narrow lanes/right of way, performance and reliability expectations, deployment issues, and technology applications. The draft report is available on the ITS Institute Web site at: www.its.umn.edu/research/brt/news/reqreport.html.

Human Factors Research Component

The Human Factors team, led by HumanFIRST Program director Nic Ward, has completed its field-testing of bus drivers interacting with lane-assist systems. Drivers were trained in the use of the technologies and were tested under three conditions during rush hour traffic: normal traffic lane without lane-assist technology, shoulder use without lane-assist technology, and shoulder use with lane-assist technology. "On an anecdotal level, drivers appear to like the system, and feel that it represents a potential solution to the narrow lane guidance problem," Ward says. The HumanFIRST team is analyzing the experimental data and plans to release a report on their findings in early 2003.

More information about the BRT lane-assist project can be found online at: www.its.umn.edu/research/brt/index.html.

TCRP research publications available online

The federal Transit Cooperative Research Program, 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. TRCP publications may be viewed at www4.trb.org/trb/crp.nsf.

Here are recent TCRP publications, with associated reference information and summary from the TRB Web site:

• Guidebook for Developing a Transit Performance-Measurement System (TCRP Report 88 -- Project G-06) is intended to assist transit system managers in developing a performance-measurement system that uses traditional and non-traditional measures to address customer-oriented and community issues. It will also be useful to metropolitan planning organizations that desire to add transit-focused performance measures to their planning efforts. An executive summary of the Guidebook is also available.
• Strategies for Increasing the Effectiveness of Commuter Benefits Programs (TCRP Report 87 - Project H-25) is intended to assist transportation agencies to increase the effectiveness of their commuter benefits and outreach programs.
• Support for Fundamental Change in Public Transportation (TCRP Research Results Digest 55 -- Project J-08B) addresses major dimensions of fundamental change in public transportation systems.

Research problem statements solicitation

The Transit Cooperative Research Program welcomes your submission of potential research topics. Submitting a research problem statement is easy. Instructions and the necessary forms may be found at: www.tcrponline.org/whatistcrp_howparticipate.htm. Research problem statements for FY2004 are due June 15, 2003. New projects will be selected in October 2003.

Transportation Infrastructure

Pavement Research Institute established

Crumbling, bumpy roadways. Long traffic backups at construction work zones. And tight transportation budgets. Both locally and nationally, these are common problems crying out for a strong and coordinated investment in pavement research-research that will develop new materials and designs to help pavements last longer, require fewer repairs, and cost less.

To maximize the investment of Minnesota's resources, the University of Minnesota's Department of Civil Engineering (CE) and Center for Transportation Studies (CTS), along with two partners-the Minnesota Department of Transportation (Mn/DOT) Office of Materials and Road Research and the Minnesota Local Road Research Board (LRRB)-have created a Pavement Research Institute. The new institute will leverage the organizations' existing strengths, allow flexibility to respond to research initiatives at the national level, and continue to produce knowledgeable graduates and professionals. "In addition, this new structure will vastly improve our ability to pursue national funding," says John Gulliver, CE department head.

The partners believe that pavement research will be strengthened by pooling the expertise and resources of the organizations that have a deep stake in producing and applying research. "The Institute will strengthen the relationships among faculty, Mn/DOT, and the LRRB, thus ensuring a strong and continuous pavement research effort," says Robert Johns, CTS director. "The Pavement Research Institute will bring together multidisciplinary, collaborative research teams to attract federal and other funds available to academic programs and state agencies," he adds.

Signing the memorandum of understanding that created the Institute were Gulliver and Johns; Patrick Hughes, director, Office of Materials and Road Research, Mn/DOT; Thomas Colbert, chair, LRRB; and Douglas Weiszhaar, then-acting commissioner, Mn/DOT.

Mn/DOT's Office of Materials and Road Research and the LRRB, as sponsors, have each committed funding for a five-year period to support the development of the Pavement Research Institute. As the first step in launching the institute, the University has begun a national search for an institute director.

University seeks director of Pavement Research Institute

The University of Minnesota's Department of Civil Engineering (CE) and Center for Transportation Studies (CTS) are seeking a director for the newly established Pavement Research Institute. The Pavement Research Institute develops and coordinates pavement research activities with the University, the Minnesota Department of Transportation (Mn/DOT), and other funding organizations to further the strong pavement research program.

This position will involve close collaboration and interaction with faculty, staff, and funding organizations to strengthen materials and pavement research, covering topics ranging from pavement mechanics to the characterization of pavement materials, and taking advantage of the Mn/ROAD pavement research facility.

This position is an administrative leadership/development position with a joint appointment in the Department of Civil Engineering and the Center for Transportation Studies. The successful candidate will be expected to:

• Work with the Civil Engineering department head and CTS director to establish a committee of funders and key stakeholders that would help further define the Institute vision and mission. Involve committee members in the development and implementation of a strategic plan and in ongoing meetings and activities to discuss and set directions for the Institute.
• Work with faculty from a variety of disciplines, Mn/DOT, CTS, and the Minnesota Local Road Research Board (LRRB) to develop new ideas that would improve pavement engineering and advocate for research and education programs to pursue those ideas.
• Pursue funding for pavement research from federal and state agencies (for example, FHWA, NSF, Mn/DOT), with a focus on national research that utilizes the Mn/ROAD facility. Lead and assist faculty in the development of research proposals. Work with CTS to develop training and outreach opportunities. Explore participation in research and education consortia with other institutions. Lead the development of budgets and work programs.
• Provide dynamic leadership for the Institute. Represent the Institute in various forums to promote the value of pavement research and education. Strengthen the national role of the Mn/ROAD pavement research facility. Attend national meetings on materials and pavement-related topics, provide leadership and participation in meetings with funding organizations, industry, and professional organizations and associations, make presentations to elected officials and media representatives, and participate in efforts to educate the public and students at all levels.
• Foster a sustainable, joint University/Mn/DOT pavement research program. Coordinate pavement research activities between the University, Mn/DOT, LRRB, and industry. Ensure that the Institute's research meets high standards of academic excellence. Work closely with CTS, Mn/DOT, and local associations in idea development and technology transfer. Work closely with CTS and Mn/DOT in program management.

Qualifications: B.S. in engineering or related discipline plus at least ten years of experience that preferably links academia, government, and industry in pavement research. An advanced degree, Professional Engineering certification, and experience working for or interacting with federal, state, and local transportation agencies are desirable. Other desirable qualifications: Thorough knowledge of the state-of-the-art in pavement engineering, both nationally and internationally. Excellent communication skills, both oral and writing. Ability to work effectively with multiple organizations and individuals. Proven record of leadership and technical accomplishment, including demonstrated ability to lead highly technical researchers and successful experience in managing contracts and budgets.

Salary: Negotiable based on credentials and experience. The University is prepared to offer a salary necessary to attract an experienced research leader. This position is an annually renewable administrative appointment and includes a comprehensive benefits package.

Applications: Send a current resume or curriculum vitae and letter of application specifically addressing your qualifications as they relate to the qualifications outlined above to:
Dr. Joseph Labuz, Chair
Search Committee for Director of Pavement Research Institute
Department of Civil Engineering
University of Minnesota
122 Civil Engineering Building
500 Pillsbury Drive SE
Minneapolis, MN 55455

For a complete position description and posting, contact Jane Govro, 612-625-5522. Applications will be accepted until the position is filled. Review of applications will begin February 28, 2003.

The University of Minnesota is an equal opportunity educator and employer.

Civil Engineering hires pavement professor

The Department of Civil Engineering announced that Lev Khazanovich has accepted an offer of associate professor. Dr. Khazanovich is well known for his work in concrete pavements and overlays, and was the senior project engineer on the NCHRP 2002 Mechanistic-Empirical Design Guide. Dr. Khazanovich received his doctorate from the University of Illinois at Champaign-Urbana, and has eight years of subsequent industry experience with ERES Consultants, Inc. His current research interests include: pavement analysis, design, and rehabilitation; finite element analysis of soil-structure interaction; using higher order subgrade soil models;and Non-destructive testing of concrete slabs-on-grade.

Members of the search committee, chaired by Professor Henryk Stolarski of CE, were Patrick Hughes, Mn/DOT Materials Research Laboratory; Mike McGray, Progressive Contractors, Inc.; Robert Johns, CTS; and Joseph Labuz and Gary Davis, CE.

Low-volume road research report published

A recent report, Best Practices for the Design and Construction of Low Volume Roads, provides information on methods for design and construction of hot-mix asphalt pavements in Minnesota. Written by researchers Eugene Skok, David Timm, Marcus Brown, and Timothy Clyne of the Department of Civil Engineering, the report recommends using MnPAVE, software developed with information from the Minnesota Road Research Project (Mn/ROAD) test facility, to calculate thickness designs. The report was sponsored by the Minnesota Local Road Research Board.

Currently, hot-mix asphalt pavements in Minnesota are designed using one of three thickness design procedures: the Soil Factor, the R-Value, or the Mechanistic-Empirical Procedure (MnPAVE). The Soil Factor procedure uses two-way Annual Design Average Daily Traffic (AADT) and Heavy Commercial Average Daily Traffic (HCADT) to define loading, while the R-Value and MnPAVE procedures use Equivalent Standard Axle Loads (ESALs) to define traffic loading. It is now recommended that city and county agencies use MnPAVE, in addition to their existing procedure, to calculate thickness designs.

Researchers developed MnPAVE, a software application, with information from the Minnesota Road Research Project (Mn/ROAD) test facility and 40-year-old test sections from around the state. The significant advantage of using a mechanistic-empirical design procedure like MnPAVE is that the properties of various materials and conditions can be entered into the software.

In addition, the report highlights subgrade soils for each thickness design procedure, Mn/DOT's specifications for embankment soil construction and construction of pavement section materials, and best practices for setting up projects most effectively to follow specifications.

For a copy of the report, call Arlene Mathison, CTS librarian, at 612-624-3646, or send e-mail to library@cts.umn.edu. The report (2002-17) is also on the LRRB web site at www.lrrb.gen.mn.us/PDF/200217.pdf.

Improving asphalt could pave the way to cost savings, U researcher says

With more than 90 percent of all paved U.S. highways topped with asphalt each year, research into bituminous materials has never been more important. In fact, University of Minnesota civil engineering assistant professor Mihai Marasteanu estimates that just a 1 percent reduction in costs could save $100 million annually. Marasteanu presented his latest research October 30 as part of the CTS fall faculty seminar series in a lecture titled "Update on Bituminous Materials Characterization."
During the presentation, Marasteanu pointed out that asphalt pavement research has undergone a significant change during the past 12 years, shifting from primarily empirical methods to mechanical-based scientific methods. The goal has been to bring asphalt research to levels similar to those used with other engineering methods, ultimately providing a critical link between basic theories and actual pavement performance.

Many of the changes have been prompted by increases in traffic, changes in the way oil is processed, and significant advancements in computing and other advanced research tools.

Though Marasteanu acknowledges that rutting, fatigue cracking, and low temperature are among the most common "distress mechanisms" for asphalt pavement, he has also found the often-overlooked elements of aging and moisture sensitivity to be just as important. "There are a number of issues that still need a lot of clarification," he said, noting the ever-evolving compositions of asphalt mixtures.

For instance, Marasteanu observed, the properties of asphalt binder, an organic material, irreversibly change when exposed to oxygen, heat, or solar radiation. As a result, the asphalt "ages" as its mechanical properties, adhesion to aggregate, and moisture sensitivity also change.

According to Marasteanu, current research trends are moving in two main directions, modeling fundamental material behavior and developing parameters for pavement design and pavement performance. Future research, he added, needs to examine the interaction between different distress modes (e.g., where does fatigue cracking end and thermal cracking begin?), transition behavior, and asphalt-aggregate interaction fundamentals.

Marasteanu has been the principal investigator on four Mn/DOT projects studying the properties of asphalt mixtures.