Transportation demand models rely on a range of demographic projections to predict future year travel demand. However, these projections themselves are not without error. The accuracy of population projections at the State, regional and suburb level has been quantified previously with comparable results. However, little work has been done to assess the performance of very small area (sub-suburb) projections, typically used in modern travel demand models. This paper summarises the results of previous assessments of the errors associated with small area population projections. Using demographic projections prepared for the Brisbane Statistical Division, the paper goes on to quantify the performance of these projections by comparing them against the 1991 and 1996 ABS Census by (1) demographic variable, (2) projection period and (3) level of detail. The results indicate that average projection error (1) varies between the particular demographic variable being considered, (2) increases with projection period and (3) increases with level of detail. (A)
Abstract