Stochastic and Deterministic Formulations of Dynamic Traffic Assignment



Stochastic and Deterministic Formulations of Dynamic Traffic Assignment

Authors

HEYDECKER B G and ADDISON J D, University College London, UK

Description

Dynamic traffic assignment is now widely recognised as appropriate for modelling route choice and congestion in urban areas during peak periods, and for the evaluation of tratfic management measures that are intended for them. Various formulations have be

Abstract

Dynamic traffic assignment is now widely recognised as appropriate for modelling route choice and congestion in urban areas during peak periods, and for the evaluation of tratfic management measures that are intended for them. Various formulations have been developed in the literature: in the present paper we consider the within-day dynamics of departure-time and route choice using costs based upon travel times and arrival times. We show how a general formulation of these joint choice processes can accommodate either stochastic or determines" tic user equilibrium principles. The model of traffic flow that is used provides travel times which determine the propagation of traffac through the network and also contribute to the cost of travel. By adopting mechanistic models of traffic movement and hence travel time, we show how temporal departure profiles and route assignments can be calculated according to each of these choice principles and develop cost-throughput relationships for them from this. Detailed comparisons are made between the results according to the various choice models; we show that a good degree of commonality can be identified between them. The results of this are plausible and compare favourably with those in the literature that arise from the use of simple but non-mechanistic travel time models. We conclude that mechanistic travel time models have a fundamental importance for satisfactory dynamic modelling of congestion and of users' response to it, whichever choice model is adopted.

Throughout this analysis, relatively simple models are adopted in the interests of transparency. The consequences of this include clear results that can be taken as indicative of the likely gross response of the transport system to interventions after travellers have adapted their choice behaviour individually.

Publisher

Association for European Transport