The Centre for Transport Studies is pleased to welcome
Dr Ying-en Ge (Dalian University of Technology, China)
to lead a seminar entitled
A Comparison of Dynamic User Optimal States with Zero, Fixed and Variable Tolerances
to be held
Wednesday 20 June 2012 – 16:00
Please join us for presentation and discussion at
Room G08, Chadwick Building, UCL
(Maps and travel directions: http://www.cege.ucl.ac.uk/contact_us/how_to_find_us )
Abstract
Until a few years ago, dynamic user equilibrium (DUE) and dynamic user optimum (DUO) were still interchangeable in investigating the dynamic traffic assignment (DTA) problem. A tolerance-based DUO and DUO with variable tolerance were recently proposed as alternative definitions of DUO, which distinguishes DUO from DUE. The former relies on a pre-chosen fixed tolerance, hence it can be termed DUO with fixed tolerance. At DUO with fixed or variable tolerance, the tolerances reflect the differences in travel costs between used paths of an origin-destination (OD) pair. Because DUE bears no differences in travel costs between used paths of an OD pair, it can be termed DUO with zero tolerance. It is necessary to investigate the relationships between the three concepts and implications for DTA modelling. This seminar first compares the three alternative definitions of DUO and discusses their relationships. Second, the existence conditions of these DUO solutions are compared and discussed by means of three examples. A key conclusion is that DUO with variable tolerance must exist even when the other two may not. In addition, when the tolerances at DUO with fixed or variable tolerances are equal to zero, the solution must be a DUE solution. Furthermore, DUE is a special case of DUO with variable tolerance; because the tolerance in the concept of DUO with variable tolerance is an endogenous variable, if a DUE solution exists, an efficient method for solving for DUO with variable tolerance should find such a DUE solution directly. However, how to model DUO analytically with variable tolerance in a general rather than ad hoc manner, including solving and implementation, seems not to be an easy problem to solve.
About the Speaker
Dr Ying-en Ge obtained his first two degrees in mathematics and then was awarded a PhD in transportation planning and management in 1999 at Tongji University, Shanghai. He then undertook post-doctoral research at the University of California at Davis and then moved to the UK to work at three universities: University of Ulster, Queen's University Belfast, and then Edinburgh Napier University. He also worked as a senior analyst at an urban, regional and transportation planning consulting firm for 1.5 years. He took up a professorship at the Dalian University of Technology in Spring 2010. He has worked on transportation network analysis and applications for more than 10 years and has published nearly 40 scholarly papers, including those in Transportation Science, Transportation Research Part B, and Networks and Spatial Economics.
The next CTS Seminars
Dr Alan Stevens from Transport Research Laboratory (TRL) will be leading a seminar titled “Researching the Benefits and Deployment Opportunities for Vehicle/Roadside cooperative ITS” at Imperial College on Wednesday 27 June @ 16:00
About the CTS Seminar Series
The CTS seminar series aims to facilitate discussion on current research topics in the transport field. Seminars are held jointly with our colleagues in the Centre for Transport Studies at University College London. They are usually held on Wednesday afternoons at Imperial College London or University College London.
Seminars are free of charge and open to all interested parties. Booking is not required.
For further information: [log in to unmask]<mailto:[log in to unmask]>
CTS home: www.imperial.ac.uk/cts<http://www.imperial.ac.uk/cts>
|