SMART’s Distinguished speakers 
Travel Behavior Data Needs for New Mobility:
Is GPS the Ultimate Solution?
Lisa Aultman-Hall
Director, UVM Transportation Center
Professor, UVM School of Engineering
June 11, 2007
SMART Presentation Summary
Traveler route choice behavior is the cornerstone of understanding individual travel needs and decisions. It is an integral part of a newer transportation modeling approach called activity analysis. Yet, we lack data to describe the route decision making undertaken by travelers. This lack of data limits our ability to improve traffic simulation models and regional travel demand planning models. In its place, we assume travelers seek to minimize time, a simplification of complex travel decisions. Actual segment-by-segment travel routes are difficult to collect with paper or phone surveys. While vehicle-mounted and person-mounted Global Positioning Systems (GPS) receivers seem to be a logical means to collect data, very few GPS travel route datasets have been successfully collected and analyzed. Dr. Aultman-Hall’s presentation illustrated some of the reasons why.
With the improved accuracy of GPS devices, it is now feasible to use GPS devices to collect route data, especially passive GPS devices, which are relatively low-cost, do not require additional computerized equipment and are well suited for collecting data for research purposes given their small size and lack of required respondent interaction. Even our cell phones now include GPS devices. However, the application of GPS data is not as straightforward as widely assumed. This is especially true if the data are to be used in route choice behavior directly. When the GPS device is used to collect multiple-day travel data, the post-processing of the data is challenging and yet the complications have received little attention from transportation professionals. Automatic spatial models to identify trip ends and convert point data to link-by-link data are necessary but also extremely time and resource intensive.
This presentation summarized the findings of several recent research projects which address the methodological issues related to GPS use for travel route data:
• Spatial data typology and conversion;
• Map-matching GPS data to underlying road networks; and
• Obtaining comprehensive travel time data for the network to facilitate comparison of alternative routes.
One unique feature of this overall research program is that this methodological analysis included real known route data so that the accuracy of the proposed methods could be measured.
The collection of actual GPS route data “accidentally” led to its use in tailpipe emissions analysis. The presentation concluded with interesting research results related to on-road second-by-second emissions and driving behavior, while questioning whether such detailed analyses answer core transportation policy needs and how planned research at the UVM Transportation Center will address this larger question. Despite GPS’s challenges, its use is planned in all four of the UVM Signature Research projects!
Links
UVM’s Transportation Center website
Biography and CV
Dr. Lisa Aultman-Hall joined the University of Vermont as founding director of the National University Transportation Center in August 2006. Dr. Aultman-Hall is a Professor in the School of Engineering. She had previously served as the director of the Connecticut Transportation Institute, while an Associate Professor of Civil Engineering at the University of Connecticut. She teaches transportation planning and traffic safety. Her research interests include tailpipe emissions, traffic safety (bicyclists, young drivers, old drivers), freight transportation planning, transportation network robustness, and travel behavior, especially route choice. Dr. Aultman-Hall’s work is currently funded by the National Science Foundation, the Connecticut Department of Transportation and the New England University Transportation Center.
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