01478679

Component

This paper compares two bush-based traffic assignment algorithms, the origin-based algorithm (OBA) and the local user cost equilibrium algorithm (LUCE). The two algorithms are closely related with only one major difference: they solve the decomposed elementary node-based subproblem using different methods. Specifically, LUCE employs a greedy algorithm that is able to solve the subproblem exactly, whereas OBA uses a one-step quasi-Newton method known as gradient projection to solve the subproblem approximately. Therefore, LUCE seems to hold promises to improve OBA because its subproblem solver is presumably faster and more precise. Numerical experiments reported in this paper, however, indicate that LUCE not only provides no obvious computational advantages over OBA, it often fails to converge beyond a certain point. The focus of this paper is to find an answer to this counter-intuitive phenomenon. Our analysis suggests that the greedy method used by LUCE require highly accurate estimation of second-order derivatives. When second-order derivatives are subject to large errors, the greedy method can provide consistently sub-optimal descent direction, which it has no mechanism to fix.

This paper was sponsored by TRB committee ADB30(2) Network Equilibrium Modeling.

01470560

13-5174

English

15p

2013

Transportation Research Board 92nd Annual Meeting

Digital/other

Figures; References; Tables

Algorithms; Equilibrium (Systems); Precision; Traffic assignment

Data and Information Technology; Highways; Planning and Forecasting; I21: Planning of Transport Infrastructure; I70: Traffic and Transport

Transportation Research Board Annual Meeting 2013 Paper #13-5174

PRP, TRIS, TRB, ATRI

Feb 5 2013 12:59PM