Transportation Research Record: Journal of the Transportation Research Board vol:2263 pages:19-25
TRB edition:90 location:Washington DC, USA date:24-27 January 2011
In many OD estimation methods a linear relationship expressed by the assignment matrix is chosen. However, this relationship assumes separability of the link flows to the OD flows, which leads to biased results when dealing with congested networks. In the present paper the importance of a theoretically good linear relationship between OD flows and link flows, that takes into account that link flows are non-separable, is demonstrated. Because deriving this relationship is cumbersome in terms of computation time, we propose the use of Marginal Computation, a method that performs a perturbation analysis using Kinematic Wave Theory principles, to derive this relationship. Another cause for biased OD estimation is identified, that is a start OD matrix that produces link flows that are in a different regime than in reality. The presented methodology is tested on a study network and on a real network. In both cases the proposed methodology performs better than traditional approaches, indicating its merit.