Two-Stage Vehicle Availability Model

It is well accepted that travel forescasting models benefit from the stratification of travel markets by socioeconomic level. The number of vehicles available is a key indicator of that level. Using this variable requiuires that the proportion of households by vehicles available be forecast for each zone. An improved submodel for forecasting vehicle availability by incorporating transit accessibility and land use indicators along with the usual demographic variables is described. This model uses a two-stage approach. The first stage is similar to many other models in current use. In the first step, a lookup table is used to identify an initial estimate of the proportion of 0-vehicle, 1-vehicle, 2-vehicle, and 3 +-vehicle households on the basis of the household's size (1-4 +), number of workers (0-3 +), and income quartile (1-4). This kookup table has 52 cells, with each cell containing the four proportions by vehicles available. Census Public Use Microdata Sample data were used to create this lookup tabl...