29 research outputs found
Transfer-Expanded Graphs for On-Demand Multimodal Transit Systems
This paper considers a generalization of the network design problem for
On-Demand Multimodal Transit Systems (ODMTS). An ODMTS consists of a selection
of hubs served by high frequency buses, and passengers are connected to the
hubs by on-demand shuttles which serve the first and last miles. This paper
generalizes prior work by including three additional elements that are critical
in practice. First, different frequencies are allowed throughout the network.
Second, additional modes of transit (e.g., rail) are included. Third, a limit
on the number of transfers per passenger is introduced. Adding a constraint to
limit the number of transfers has a significant negative impact on existing
Benders decomposition approaches as it introduces non-convexity in the
subproblem. Instead, this paper enforces the limit through transfer-expanded
graphs, i.e., layered graphs in which each layer corresponds to a certain
number of transfers. A real-world case study is presented for which the
generalized ODMTS design problem is solved for the city of Atlanta. The results
demonstrate that exploiting the problem structure through transfer-expanded
graphs results in significant computational improvements.Comment: 9 pages, 4 figure
Single-path service network design problem with resource constraints
202304 bckwAccepted ManuscriptRGCOthersNatural Science Foundation of China; Shanghai Education Development Foundation; Shanghai Municipal Education CommissionPublishe
Optimal routing of traffic flows with length restrictions in networks with congestion
When traffic flows are routed through a road network it is desirable to minimize the total road usage. Since a route guidance system can only recommend paths to the drivers, special care has to be taken not to route them over paths they perceive as too long. This leads in a simplified model to a nonlinear multicommodity flow problem with constraints on the available paths. In this article an algorithm for this problem is given, which combines the convex combinations algorithm by Frank and Wolfe with column generation and algorithms for the constrained shortest path problem. Computational results stemming from a cooperation with DaimlerChrysler are presented
Parametric Multiroute Flow and Its Application to Robust Network with Edge Failures
International audienc
Improving the Anytime Behavior of Two-Phase Local Search
Algorithms based on the two-phase local search (TPLS) framework are a powerful method to efficiently tackle multi-objective combinatorial optimization problems. TPLS algorithms solve a sequence of scalarizations, that is, weighted sum aggregations, of the multi-objective problem. Each successive scalarization uses a different weight from a predefined sequence of weights. TPLS requires defining the stopping criterion (the number of weights) a priori, and it does not produce satisfactory results if stopped before completion. Therefore, TPLS has poor "anytime" behavior. This article examines variants of TPLS that improve its "anytime" behavior by adaptively generating the sequence of weights while solving the problem. The aim is to fill the "largest gap" in the current approximation to the Pareto front. The results presented here show that the best adaptive TPLS variants are superior to the "classical" TPLS strategies in terms of anytime behavior, matching, and often surpassing, them in terms of final quality, even if the latter run until completion. © 2011 Springer Science+Business Media B.V.SCOPUS: ar.jinfo:eu-repo/semantics/publishe