An approach to time dependence and reliability in dynamic route guidance

This paper presents a methodology, in order to increase the reliability of the route suggestions in route guidance systems. Based on the A* path finding algorithm and Chen’s link penalty method, the procedure involves penalising links with a high risk of being congested and obtaining a set of reliable route suggestions. Time-dependence of travel times is considered by adapting the Flow Speed Model technique accordingly. Modifications to the structure of the path finding algorithms are also made, so as to account for real road network features. Finally, experiments using simulated travel time and reliability data are carried out on a road network and the results are discussed

A chance-constrained based stochastic dynamic traffic assignment model: Analysis, formulation and solution algorithms

This paper is concerned with the system optimum-dynamic traffic assignment (SO-DTA) problem when the time-dependent demands are random variables with known probability distributions. The model is a stochastic extension of a deterministic linear programming formulation for SO-DTA introduced by Ziliaskopoulos (Ziliaskopoulos, A.K., 2000. A linear programming model for the single destination system optimum dynamic traffic assignment problem, Transportation Science, 34, 1-12). The proposed formulation is chance-constrained based and we demonstrate that it provides a robust SO solution with a user specified level of reliability. The model provides numerous insights and can be a useful tool in producing robust control and management strategies that account for uncertainty in applications where SO-DTA is relevant (e.g. evacuation modeling, computing alternate routes around freeway incidents and establishing lower bounds on network performance). © 2006 Elsevier Ltd. All rights reserved

An extension of labeling techniques for finding shortest path trees

Label setting techniques are all based on Dijkstra's condition of always scanning the node with the minimum label, which guarantees that each node will be scanned exactly once; while this condition is sufficient it is not necessary. In this paper, we discuss less restrictive conditions that allow the scanning of a node that does not have the minimum label, yet still maintaining sufficiency in scanning each node exactly once; various potential shortest path schemes are discussed, based on these conditions. Two approaches, a label setting and a flexible hybrid one are designed and implemented. The performance of the algorithms is assessed both theoretically and computationally. For comparative analysis purposes, three additional shortest path algorithms - the commonly cited in the literature - are coded and tested. The results indicate that the approaches that rely on the less restrictive optimality conditions perform substantially better for a wide range of network topologies. (C) 2008 Elsevier B.V. All rights reserved

A methodology for computing time-dependent alternate routes around freeway incidents

This article introduces an approach that produces dynamic control strategies in the form of alternate routes around freeway incidents in response to the prevailing traffic conditions. The approach consists of a System Optimum Dynamic Traffic Assignment algorithm, a traffic simulator, a heuristic control strategies generation algorithm, and various communication and data processing components. The system is implemented and tested computationally on an example network in a simulated environment under various scenarios of incident severity and congestion levels. The results indicate that the system performs reasonably well for moderately congested networks and severe incidents. Copyright © Taylor and Francis Inc