A MODEL OF HOUSEHOLD CAR OWNERSHIP: PART 2

The second part of this paper describes the theory of the techniques used in the regional highway traffic model (rhtm). The authors discuss methods of estimating the unknown parameters, the number of bands and their definition and the fit of the model at zonal level. Details are given of a method using maximum likelihood estimates to investigate the relationship between the proportion of households owning one or two cars and household income. The effects of urbanisation on income/car-ownership relationships is also examined in detail. A sequence of steps is outlined for rapidly fitting the car-ownership model and testing its performance at zonal level. Colour coded zonal maps are used to display the extent and direction of the differences in estimates and observations. Where large errors occurred the model was adjusted to achieve an improved measure of urbanisation. /TRRL/