Trrl Lr 799

The effects of a number of factors, including incomes and population densities, have been identified. Over riding these effects is a strong tendency for the annual percentage growth rates of car ownership to reduce as the level of ownership rises. The logistic curve model used in previous work is shown not to be suffieciently general; an alternative algebraic form is proposed which helps to reconcile an apparent inconsistency between the recent rapid slowing down of growth in Britain and other evidence that suggests that saturation is still some way off. A range of forecasts of numbers of cars is made on the basis of the new model and of alternative assumptions about future levels of economic growth and of fuel prices. With the middle assumptions, the new forecasts are somewhat lower than those issued previously, at least up to 1985. Thereafter they may be higher or lower, depending on the saturation level chosen.