Generalised equilibrium (GE) modelling offers a modelling framework which has grown out of network-based equilibrium models. In this context, "equilibrium" refers to Wardrop type equilibrium which is well-known in the field of highway assignment modelling. GE modelling considers all modes of travel, not just highways, and may be extended to include non-travel options, such as substituting telecommunications for travel. GE modelling may be contrasted with another framework namely that of logit models, popularly used in transport demand modelling. The logit models typically consider choice by travellers in a hierarchic structure and operate on information about trips and travel costs represented in a matrix domain. GE modelling provides a number of features: it integrates aspects of demand and supply modelling in a single network domain, which is relevant to policies which seek to manage demand and supply together; it enables critical details affecting capacity effects to be represented more readily than in the matrix domain; data requirements focus on costs and perceptions of distributions of costs, rather than preference between choices; attention given to dynamic equilibrium has meant that time variation can be a natural component of the framework. The paper is based on the work to date of an 18 month LINK-based project sponsored by DETR, EPSRC, and ESRC, and which has brought the project partners of MVA, University of York, and University College London together to build on existing streams of work. The paper reports on the mathematical formulation of GE modelling and on the results of the methods used to determine equilibrium solutions.
Samenvatting