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Dynamic traffic assignment approximating the kinematic wave model: system optimum, marginal costs, externalities and tolls

Carey, M (2012) Dynamic traffic assignment approximating the kinematic wave model: system optimum, marginal costs, externalities and tolls. Transportation Research Part B: Methodological. ISSN 0191-2615 (In Press)


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System marginal costs, externalities and optimal congestion tolls for traffic networks are generally derived from system optimizing (SO) traffic assignment models and when these are treated as varying over time they are all referred to as dynamic. In dynamic SO network models the link flows and travel times or costs are generally modelled using so-called ‘whole link’ models. Here we instead develop an SO model that more closely reflects traffic flow theory and derive the marginal costs and externalities from that. The most widely accepted traffic flow model appears to be the LWR (Lighthill, Whitham and Richards) model and a tractable discrete implementation or approximation to that is provided by the cell transmission model (CTM) or a finite difference approximation (FDA). These handles spillbacks, traffic controls and moving queues in a way that is consistent with the LWR model (hence with the kinematic wave model and fluid flow model). An SO formulation using the CTM is already available, assuming a single destination and a trapezoidal flow-density function. We extend the formulation to allow more general nonlinear flow density functions and derive and interpret system marginal costs and externalities. We show that if tolls computed from the DSO solution are imposed on users then the DSO solution would also satisfy the criteria for a dynamic user equilibrium (DUE). We introduce constraints on the link outflow proportions at merges and inflow proportions at diverges. We also extend the model to elastic demands and establish links with previous dynamic traffic assignment (DTA) models.

Item Type: Article
Copyright, Publisher and Additional Information: © 2012 Elsevier. This is an author produced version of a paper accepted for publication in Transportation Research Part B: Methodological. Uploaded in accordance with the publisher's self-archiving policy.
Keywords: cell transmission model, system optimum, dynamic traffic assignment, marginal costs, externalities, optimal tolls
Institution: The University of Leeds
Academic Units: The University of Leeds > Faculty of Environment (Leeds) > Institute for Transport Studies (Leeds)
Depositing User: Symplectic Publications
Date Deposited: 04 Jan 2012 14:13
Last Modified: 01 Jun 2015 16:00
Published Version: http://www.journals.elsevier.com/transportation-re...
Status: In Press
Publisher: Elsevier
Related URLs:
URI: http://eprints.whiterose.ac.uk/id/eprint/43556

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