User-Equilibrium Class Link Flows and the Condition of Proportionality
David Boyce, P.E., Distinguished Speaker
Adjunct Professor of Civil Engineering Northwestern University
Professor Emeritus, University of Illinois, Chicago
Friday, May 2, 2014
Brickyard (BYENG) 210 [map], Tempe campus
One of the most widely applied methods in transportation network analysis is user-equilibrium traffic assignment. The solution of this method for large-scale urban networks is needed to evaluate alternative system designs and to forecast vehicles emissions for environmental conformity analyses. In practice, this model is often solved for multiple classes of travelers (e.g., cars and trucks), sometimes with as many as ten classes. Curiously, this model is not considered in the few textbooks on travel forecasting models, and is seldom mentioned in journal articles.
The solution of this model is problematic in that the standard solution methods yield only the equilibrium total link flows uniquely. The class link flows are not uniquely determined if all vehicle classes are assumed to minimize the same generalized cost functions (such as travel time). An additional requirement on the solution, called ‘the condition of proportionality,’ can be imposed to determine these class link flows uniquely.
In this seminar David Boyce examines the properties of this important model and reports on three methods for its solution. Computational examples for the Chicago region network will illustrate the results. A recently proposed, but unproven, conjecture on the solution of the model will be described at the end of the seminar. Devising a proof of this conjecture presents a new challenge for network modelers.
David Boyce presently conducts research on urban travel and location forecasting models, transportation network assignment methods, and the history of urban travel forecasting methods and practice. One of his long-term research interests concerns the formulation, implementation, estimation and validation of large-scale, integrated models of urban travel behavior, as an alternative to the multi-step travel forecasting procedures traditionally applied in urban transportation planning practice. In recent years he has experimented with a traffic assignment condition that yields unique route flows and multi-class link flows.
In addition to these primary research themes, Boyce was an early innovator, from 1986-1996, of in-vehicle dynamic route guidance systems, a principal element of the emerging field of Intelligent Transportation Systems. This research culminated in his leading a multi-university team that performed development and evaluation tasks for the ADVANCE Project, a large-scale field test of a prototype route guidance system, in conjunction with Motorola and federal and state transportation departments. In this role he also conducted theoretical and modeling studies of the performance of route guidance systems on urban road networks.
Boyce was a tenured faculty member of the University of Pennsylvania (regional science, 1966-77), the University of Illinois at Urbana-Champaign (civil engineering, 1977-88), and the University of Illinois at Chicago (civil engineering, 1988-2003). Currently he is professor emeritus of Transportation and Regional Science, UIC, and adjunct professor of Civil and Environmental Engineering at Northwestern University.
In 2000 he was awarded the Founder’s Medal of the Regional Science Association International (RSAI) in recognition of his research achievements; in 2002, he was elected a Fellow of the RSAI. In 2003, he received the Emeritus Member award of the Transportation Research Board, the Robert Herman Lifetime Achievement Award of the Transportation Science and Logistics Section of the Institute for Operations Research and the Management Sciences (INFORMS), and the INFORMS Fellows Award in 2003. He received the Fellows Award of the American Society of Civil Engineers in 2009.
Boyce received his B.S. in civil engineering from Northwestern University in 1961, and his Ph.D. in regional science from the University of Pennsylvania in 1965. He also received his Master of City Planning degree from Penn. To date, he has published 210 journal articles, books, book chapters and reports.