Matrix estimation techniques are used to modify an origin-destination (OD) table to improve the fit between traffic assignment predictions and observed count data. In many small study area contexts, a 'prior' year base OD matrix and a future year matrix will have been cordoned from a larger matrix obtained with a strategic transport model. The practical question then arises of how any changes in the base year matrix, made by a matrix estimation procedure, should be carried over to the future year matrix. A survey of practitioners confirmed this to be a problem of practical significance but revealed a diverse range of views about how the problem should be addressed analytically. A range of methods was formulated and applied in a practical case study. The results highlight that the assignment results for the future year scenario are sensitive to the updating technique employed to carry forward the matrix estimation adjustments in the base year. While further research is needed to identify superior updating techniques, the results nevertheless provide the basis for formulating guidance for practitioners. (a).
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