Prof. Nikolas Geroliminis

University of Minnesota, USA

January 23, 2009, 15:00, Room GC C3 30 (click here for the map)

Macroscopic modeling and control of traffic in congested cities

Various theories have been proposed to describe vehicular traffic movement in cities on an aggregate level. They fall short to create a macroscopic model with variable inputs and outputs that could describe a rush hour dynamically. This work shows that a Macroscopic Fundamental Diagram (MFD) relating production (the product of average flow and network length) and accumulation (the product of average density and network length) exists for neighborhoods of cities in the order of 5-10km2. It also demonstrates that conditional on accumulation large networks behave predictably and independently of their Origin-Destination tables. These results are based on analysis using simulation of large scale city networks and real data from urban metropolitan areas. The real experiment uses a combination of fixed detectors and floating vehicle probes as sensors. The analysis also reveals a fixed relation between the space-mean flows on the whole network and the trip completion rates, which dynamically measure accessibility. The looking-for-parking phenomenon that extends the average trip length is also integrated in the dynamics of the rush hour. An analytical model based on Variational Theory describes the connection between network structure and a network's MFD for urban neighborhoods controlled at least in part by traffic signals. The MFD is applied to develop control strategies based on neighborhood accumulation and speeds and improve accessibility without the uncertainty inherent in forecast-based approaches.


Dr. Nikolas Geroliminis received his Ph.D. in civil engineering from University of California, Berkeley in 2007. Since then, he has been on the faculty of the Department of Civil Engineering at the University of Minnesota. He is a member of the Transportation Research Board's Traffic Flow Theory Committee. His research interests focus primarily on urban transportation systems, traffic flow theory and control, public transportation and logistics. In summer 2009, he will be an academic visitor at the Chair of Sociology, in particular of Modeling and Simulation, ETH. While a student at Berkeley, he received the University of California "Transportation Student of the Year" award in 2007, and the "Outstanding Graduate Student Instructor Award" in 2006.