Behavioural micro-dynamics of car ownership and travel in the Seattle Metropolitan Region from 1989 to 2002

In this paper data from 230 households observed in ten different occasions (waves) from 1989 to 2002 in the Puget Sound region are used to explore relationships among number of cars owned, number of trips driving alone, and number of trips sharing cars with household members. Using a mixture latent class Markov model we identify four distinct groups that are a High Mobility group with more cars and car trips, an Average Mobility group with lower car ownership and trips driving alone, a third group with relatively high car ownership but few car sharing trips, and a fourth group of Low Mobility characterized by the low car ownership and trips. Households change behaviour adapting to internal and external changes to their environment but they also anticipate changes and go through a "preparation" stage (e.g., adding another car in their fleet in expectation of adding another employed person). Land use plays a somewhat secondary role. The analysis also reveals three classes (hidden Markov chains) of households underlying behavioural dynamics with increases in the low car ownership categories (zero and one car per household), decreases in the high car ownership (three cars and four or more cars per household) and stable behaviour in the two cars per household group. Household membership in these classes is significantly influenced by householder ratings to parking availability, schedule flexibility, bus transfers, and day-to-day costs of driving. The findings here show attitudes and land use enhance understanding of longitudinal heterogeneity.