Seminar

Title: Modeling and Solution of a Linear Optimal Signal Control Problem for Surface Street Networks Using Logic Based MethodsBy Ioannis PavlisPost-doctoral Researcher, University of California, Irvine-----------------------Abstract:The consistent mathematical description of the traffic flow process on surface street (or corridor) networks inevitably includes conditional piece-wise functions. For example, the traffic flow at the approach of a signalized intersection is a piece-wise function whose range depends (is conditional) on the prevailing traffic conditions and the signal indication. Representing this function (or others of similar form) as a set of linear constraints so that the signal control problem is formulated as a mathematical programming problem is a non-trivial task. The practices typically followed regarding the representation of such functions include: 1) approximating them with inexact representations, 2) manipulating them during the solution process, or 3) ignoring them and considering other inconsistent assumptions (e.g., for the aforementioned example a followed practice is to average the outflow during green over the cycle length). Understandably, these approaches result in modeling inconsistencies, solutions of questionable quality due to the involved heuristics, and/or the adoption of a control strategy that is based on the outmoded notion of a single-ring, single-phase, and fixed cycle controller. In recognition of the problems associated with the representation of such functions we have developed, based on analogies from the theory of mathematical logic, two methodological procedures for their transformation into a set of mixed integer linear constraints. The methodologies have been applied in the transformation of virtually every possible conditional piece-wise function that can be found when developing a surface street network model based either on the dispersion-and-store or the cell transmission traffic flow models. The methodologies can also be applied in analyzing the structural properties of existing representations, which can eventually lead to the development of improved representations having lower number of integer variables and/or constraints. Furthermore, in investigating the difficulties associated with solving the optimal signal control problem as a large-scale mixed integer linear programming problem, we have examined the performance of an optimal signal control strategy for an isolated intersection that accommodates eight movements when assuming a dual-ring, 8-phase, variable cycle (and phase) controller under various assumptions regarding the demand pattern and the operational characteristics of the controller. The optimization results show the effectiveness of the control strategy and its potential for real-life applications.Host: Petros Ioannou ** ioannou@usc.eduCENTER FOR ADVANCED TRANSPORTATION TECHNOLOGIES (CATT)

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248

Audiences: Everyone Is Invited

Contact: Irina Strelnik