The first categorization, of the available estimation techniques, relates to whether the O-D’s to be estimated are static,
and apply to only one observation time period, or whether estimates are required for a series of linked dynamic time
periods. This paper will focus primarily on the static or single time period problem. The next breakdown relates to whether
the estimation is based on information about the magnitude of trip ends only, or whether information is available on
additional links along the route of each trip. The former problem is commonly referred to as the trip distribution problem in
demand forecasting, while the latter problem is commonly referred to as the synthetic O-D generation problem. This
paper applies to both problems, but will focus on the latter synthetic O-D generation problem. The former is viewed
simply a simpler subset of the former.